<?xml version="1.0" encoding="UTF-8" ?>
<?xml-stylesheet type="text/xsl" href="https://communities.bentley.com/cfs-file/__key/system/syndication/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/"><channel><title>How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer</link><description /><dc:language>en-US</dc:language><generator>Telligent Community 12</generator><item><title>How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer</link><pubDate>Tue, 24 Sep 2019 15:24:53 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Current Revision posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 9/24/2019 3:24:53 PM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;h1&gt;&lt;br /&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations and is given as:&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;br /&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;br /&gt;d = pipe diameter (m)&lt;br /&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;br /&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;br /&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;Starting with CONNECT Edition Update 2 (version 10.02.02.06) of the water products such as WaterGEMS, WaterCAD and HAMMER, the Modified Hazen-Williams method is now available for analysis.&lt;/p&gt;
&lt;p&gt;Similar to the methods of Hazen-Williams, Darcy Weisbach and Manning&amp;#39;s Equation; the Modified Hazen-Williams formula can be selected in the Calculation Options by navigating to Calculation Options &amp;gt; Friction Method.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " border="0" src="/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-32/8535.Img6.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;When the Modified Hazen-Williams method is chosen as the Friction Method the value of &amp;quot;Cr&amp;quot; or Modified Hazen-Williams factor needs to be entered in the pipe properties. This field is automatically populated based on the material selected. By default it is populated as 1 for the material &amp;quot;Ductile Iron&amp;quot;.&lt;/p&gt;
&lt;p&gt;You can change the change the material from the Engineering Library and the Modified Hazen-Williams factor will be updated accordingly.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/640x480/__key/communityserver-wikis-components-files/00-00-00-00-32/1346.Img8.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;Download the sample model from &lt;a title="here" href="/products/hydraulics___hydrology/m/hydraulics_and_hydrology_gallery/273974" rel="noopener noreferrer" target="_blank"&gt;here&lt;/a&gt; for a preview of using the Modified Hazen-Williams method for network analysis.&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;h2&gt;&lt;span style="font-size:150%;"&gt;Alternative Approach for Older Versions&lt;/span&gt;&lt;/h2&gt;
&lt;p&gt;If you are using a version&amp;nbsp;&lt;strong&gt;below&lt;/strong&gt; 10.02.02.06 (i.e. CONNECT Edition Update 2) which does not have the Modified Hazen-Williams formula available, and you are not able to upgrade, the following workaround can be considered:&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 1&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;&lt;/span&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 2&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 3&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen-Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 4&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 5&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 6&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The&amp;nbsp;above approach is limited to only versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06. For versions &lt;strong&gt;above&lt;/strong&gt; 10.02.02.06 the values for Cr can be directly entered after filtering.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Modified Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
</description></item><item><title>How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer/revision/5</link><pubDate>Tue, 24 Sep 2019 15:22:25 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Revision 5 posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 9/24/2019 3:22:25 PM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;h1&gt;&lt;br /&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations and is given as:&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;br /&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;br /&gt;d = pipe diameter (m)&lt;br /&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;br /&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;br /&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;Starting with CONNECT Edition Update 2 (version 10.02.02.06) of the water products such as WaterGEMS, WaterCAD and HAMMER, the Modified Hazen-Williams method is now available for analysis.&lt;/p&gt;
&lt;p&gt;Similar to the methods of Hazen-Williams, Darcy Weisbach and Manning&amp;#39;s Equation; the Modified Hazen-Williams formula can be selected in the Calculation Options by navigating to Calculation Options &amp;gt; Friction Method.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " border="0" src="/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-32/8535.Img6.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;When the Modified Hazen-Williams method is chosen as the Friction Method the value of &amp;quot;Cr&amp;quot; or Modified Hazen-Williams factor needs to be entered in the pipe properties. This field is automatically populated based on the material selected. By default it is populated as 1 for the material &amp;quot;Ductile Iron&amp;quot;.&lt;/p&gt;
&lt;p&gt;You can change the change the material from the Engineering Library and the Modified Hazen-Williams factor will be updated accordingly.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/640x480/__key/communityserver-wikis-components-files/00-00-00-00-32/1346.Img8.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;Download the sample model from &lt;a title="here" href="/products/hydraulics___hydrology/m/hydraulics_and_hydrology_gallery/273974" rel="noopener noreferrer" target="_blank"&gt;here&lt;/a&gt; for a preview of using the Modified Hazen-Williams method for network analysis.&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;h2&gt;&lt;span style="font-size:150%;"&gt;Alternative Approach for Using Modified Hazen-Williams Formula&amp;nbsp;in Older Versions&lt;/span&gt;&lt;/h2&gt;
&lt;p&gt;This alternative approach can be adopted for versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06 (i.e. CONNECT Edition Update 2).&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 1&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;&lt;/span&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 2&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 3&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen-Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 4&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 5&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 6&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The&amp;nbsp;above approach is limited to only versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06. For versions &lt;strong&gt;above&lt;/strong&gt; 10.02.02.06 the values for Cr can be directly entered after filtering.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Modified Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
</description></item><item><title>How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer/revision/4</link><pubDate>Tue, 24 Sep 2019 12:10:39 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Yashodhan Joshi</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Revision 4 posted to OpenFlows | Water Infrastructure Wiki by Yashodhan Joshi on 9/24/2019 12:10:39 PM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is given as;&lt;/p&gt;
&lt;p&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;/p&gt;
&lt;p&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;/p&gt;
&lt;p&gt;d = pipe diameter (m)&lt;/p&gt;
&lt;p&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;/p&gt;
&lt;p&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;/p&gt;
&lt;p&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;Starting with CONNECT Edition Update 2 (version 10.02.02.06) of the water products such as WaterGEMS, WaterCAD and HAMMER, the Modified Hazen-Williams method is now available for analysis.&lt;/p&gt;
&lt;p&gt;Similar to the methods of Hazen-Williams, Darcy Weisbach and Manning&amp;#39;s Equation; the Modified Hazen-Williams formula can be selected in the Calculation Options by navigating to Calculation Options &amp;gt; Friction Method.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " border="0" src="/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-32/8535.Img6.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;When the Modified Hazen-Williams method is chosen as the Friction Method the value of &amp;quot;Cr&amp;quot; or Modified Hazen-Williams factor needs to be entered in the pipe properties. This field is automatically populated based on the material selected. By default it is populated as 1 for the material &amp;quot;Ductile Iron&amp;quot;.&lt;/p&gt;
&lt;p&gt;You can change the change the material from the Engineering Library and the Modified Hazen-Williams factor will be updated accordingly.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/640x480/__key/communityserver-wikis-components-files/00-00-00-00-32/1346.Img8.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;Download the sample model from &lt;a title="here" href="/products/hydraulics___hydrology/m/hydraulics_and_hydrology_gallery/273974" rel="noopener noreferrer" target="_blank"&gt;here&lt;/a&gt; for a preview of using the Modified Hazen-Williams method for network analysis.&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Alternative Approach for using Modified Hazen-Williams formula for analysis&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;This alternative approach can be adopted for versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06 (i.e. CONNECT Edition Update 2).&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 1&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;&lt;/span&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 2&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 3&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen-Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 4&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 5&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 6&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The&amp;nbsp;above approach is limited to only versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06. For versions &lt;strong&gt;above&lt;/strong&gt; 10.02.02.06 the values for Cr can be directly entered after filtering.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Modified Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
</description></item><item><title>How to use the Modified Hazen Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer/revision/3</link><pubDate>Tue, 24 Sep 2019 12:06:52 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Yashodhan Joshi</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Revision 3 posted to OpenFlows | Water Infrastructure Wiki by Yashodhan Joshi on 9/24/2019 12:06:52 PM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen-Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is given as;&lt;/p&gt;
&lt;p&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;/p&gt;
&lt;p&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;/p&gt;
&lt;p&gt;d = pipe diameter (m)&lt;/p&gt;
&lt;p&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;/p&gt;
&lt;p&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;/p&gt;
&lt;p&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;Starting with CONNECT Edition Update 2 (version 10.02.02.06) of the water products such as WaterGEMS, WaterCAD and HAMMER, the Modified Hazen-Williams method is now available for analysis.&lt;/p&gt;
&lt;p&gt;Similar to the methods of Hazen-Williams, Darcy Weisbach and Manning&amp;#39;s Equation; the Modified Hazen-Williams formula can be selected in the Calculation Options by navigating to Calculation Options &amp;gt; Friction Method.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " border="0" src="/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-32/8535.Img6.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;When the Modified Hazen-Williams method is chosen as the Friction Method the value of &amp;quot;Cr&amp;quot; or Modified Hazen-Williams factor needs to be entered in the pipe properties. This field is automatically populated based on the material selected. By default it is populated as 1 for the material &amp;quot;Ductile Iron&amp;quot;.&lt;/p&gt;
&lt;p&gt;You can change the change the material from the Engineering Library and the Modified Hazen-Williams factor will be updated accordingly.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/640x480/__key/communityserver-wikis-components-files/00-00-00-00-32/1346.Img8.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;Download the sample model from &lt;a title="here" href="/products/hydraulics___hydrology/m/hydraulics_and_hydrology_gallery/273974" rel="noopener noreferrer" target="_blank"&gt;here&lt;/a&gt; for a preview of using the Modified Hazen-Williams method for network analysis.&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Alternative Approach for using Modified Hazen-Williams formula for analysis&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;This alternative approach can be adopted for versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06 (i.e. CONNECT Edition Update 2).&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 1&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;&lt;/span&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 2&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 3&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen-Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 4&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 5&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 6&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The&amp;nbsp;above approach is limited to only versions &lt;strong&gt;below&lt;/strong&gt; 10.02.02.06. For versions &lt;strong&gt;above&lt;/strong&gt; 10.02.02.06 the values for Cr can be directly entered after filtering.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Modified Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
</description></item><item><title>How to use the Modified Hazen Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer/revision/2</link><pubDate>Fri, 07 Sep 2018 07:24:21 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Yashodhan Joshi</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Revision 2 posted to OpenFlows | Water Infrastructure Wiki by Yashodhan Joshi on 9/7/2018 7:24:21 AM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is given as;&lt;/p&gt;
&lt;p&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;/p&gt;
&lt;p&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;/p&gt;
&lt;p&gt;d = pipe diameter (m)&lt;/p&gt;
&lt;p&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;/p&gt;
&lt;p&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;/p&gt;
&lt;p&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;The numerical solver in WaterGEMS and WaterCAD does not use the Modified Hazen-Williams formula directly in the analysis of water networks like the Hazen-Williams or Darcy-Weisbach equations. However, it is possible to transform the Modified C factors to standard Hazen-Williams C factors for use in WaterGEMS or WaterCAD.&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 1&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;&lt;/span&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 2&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 3&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 4&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 5&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;span style="font-size:150%;"&gt;Step 6&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
</description></item><item><title>How to use the Modified Hazen Williams formula for analysis in WaterGEMS / WaterCAD / HAMMER?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer/revision/1</link><pubDate>Fri, 07 Sep 2018 07:20:15 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:3420f20f-623f-4989-b9df-7c99953f5668</guid><dc:creator>Yashodhan Joshi</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39605/how-to-use-the-modified-hazen-williams-formula-for-analysis-in-watergems-watercad-hammer#comments</comments><description>Revision 1 posted to OpenFlows | Water Infrastructure Wiki by Yashodhan Joshi on 9/7/2018 7:20:15 AM&lt;br /&gt;

&lt;table style="background-color:#dce5f0;border:0px solid #dce5f0;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;WaterGEMS, WaterCAD&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;CONNECT Edition, V8i&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Calculations&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;How to use the Modified Hazen Williams formula for analysis in WaterGEMS / WaterCAD?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;In some parts of the world the Modified Hazen-Williams formula is used in analysis of water supply and distribution networks.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is derived from the Darcy-Weisbach and Colebrook-White equations.&lt;/p&gt;
&lt;p&gt;The Modified Hazen-Williams formula is given as;&lt;/p&gt;
&lt;p&gt;V = 3.83C&lt;sub&gt;R&lt;/sub&gt;d&lt;sup&gt;0.6575&lt;/sup&gt;(g.s)&lt;sup&gt;0.5525&lt;/sup&gt; / v&lt;sup&gt;0.105&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;Where,&lt;/p&gt;
&lt;p&gt;C&lt;sub&gt;R&lt;/sub&gt; = dimensionless coefficient of roughness&lt;/p&gt;
&lt;p&gt;d = pipe diameter (m)&lt;/p&gt;
&lt;p&gt;g = acceleration due to gravity (9.81 m/s&lt;sup&gt;2&lt;/sup&gt;)&lt;/p&gt;
&lt;p&gt;s = friction slope (H&lt;sub&gt;L&lt;/sub&gt; / L)&lt;/p&gt;
&lt;p&gt;v = viscosity of the fluid&lt;/p&gt;
&lt;p&gt;For a circular pipe, using v = 10-6 m&lt;sup&gt;2&lt;/sup&gt;/s (for water at 20&amp;deg; C) and g = 9.81 m/s&lt;sup&gt;2&lt;/sup&gt;, the headloss equation becomes;&lt;/p&gt;
&lt;p&gt;H&lt;sub&gt;L&lt;/sub&gt; = L(Q/C&lt;sub&gt;R&lt;/sub&gt;)&lt;sup&gt;1.81&lt;/sup&gt; / 994.62 d&lt;sup&gt;4.81&lt;/sup&gt;&lt;/p&gt;
&lt;p&gt;The coefficient of roughness for the Modified Hazen-Williams formula is &amp;ldquo;1&amp;rdquo; for very smooth pipes and reduces for rougher pipes. The coefficient will also reduce for higher design periods.&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;The numerical solver in WaterGEMS and WaterCAD does not use the Modified Hazen-Williams formula directly in the analysis of water networks like the Hazen-Williams or Darcy-Weisbach equations. However, it is possible to transform the Modified C factors to standard Hazen-Williams C factors for use in WaterGEMS or WaterCAD.&lt;/p&gt;
&lt;p&gt;1. Define a new &lt;a title="User Data Extension" href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/39391/how-to-create-custom-fields-using-user-data-extensions" rel="noopener noreferrer" target="_blank"&gt;User Data Extension&lt;/a&gt; (Tools &amp;gt; User Data Extensions) for Pipe. Setup the UDX as follows;&lt;/p&gt;
&lt;table&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Label&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Modified C (you can put your own custom label)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Data Type&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Real&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Dimension&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;No Units&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Storage Unit&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;&amp;ldquo;Blank&amp;rdquo; (keep this field blank)&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;&lt;span&gt;Numeric Formatter&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;span&gt;Roughness &amp;ndash; Hazen Williams&lt;/span&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;The newly created User Data Extension would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/6646.Img1.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;2. Check the pipe Flex Table and add the newly created &amp;ldquo;Modified C&amp;rdquo; column to the existing columns;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/3583.Img2.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;3. Enter Modified Hazen-Williams C factors. (Setting display precision to 2 is best). Do not modify the order of the rows after this point. The below image represents what the you would see before modifying the Hazen-Williams C factors.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/8078.Img3.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Note: The Modified Hazen-Williams C factors are entered depending on the smoothness of the pipe. For very smooth or new pipes the C factor would be &amp;ldquo;1&amp;rdquo;. For old pipes for which roughness has increased, the C factor would reduce.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The Modified Hazen Williams C factors must be obtained separately for all the pipes in the network.&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;4. Export this table to Excel using either Export to File or Copy with Headers and Paste In Excel, create a new column like New HW C.&lt;/p&gt;
&lt;p&gt;Decide on what value of the traditional Hazen-Williams C corresponds to the value of 1.00 for the Modified Hazen-Williams C (i.e. the smooth pipe C). Here we are considering the value to be 150.&lt;/p&gt;
&lt;p&gt;Calculate the new C values by multiply the Modified C values by the smooth pipe C.&lt;/p&gt;
&lt;p&gt;For this case;&lt;/p&gt;
&lt;p&gt;New HW C = Modified C * 150&lt;/p&gt;
&lt;p&gt;New HW C = 0.9 * 150 = 135&lt;/p&gt;
&lt;p&gt;The table in Excel would look like this;&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0160.Img4.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;5. Copy the column New HW C into the Hazen-Williams C column in the Flex Table.&lt;/p&gt;
&lt;p&gt;&lt;img alt=" " src="/resized-image/__size/1040x0/__key/communityserver-wikis-components-files/00-00-00-00-32/0638.Img5.jpg" /&gt;&lt;/p&gt;
&lt;p&gt;6. Save the file with the new Hazen Williams C factors.&lt;/p&gt;
&lt;h1&gt;FAQ&amp;#39;s&lt;/h1&gt;
&lt;p&gt;&lt;strong&gt;The Modified Hazen-Williams C factors change as per diameter. How to modify the existing C factors for multiple diameters?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;In some cases (where diameters vary widely), the value of the smooth pipe C-factor can be function of diameter. In that case, the flex table can be filtered by diameter and the above steps can be repeated for each diameter.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Does viscosity affect the headloss in the Modified Hazen-Williams formula?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The effect of viscosity changes is slight, and it would take a very large change in temperature to have any effect of hydraulic results.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;What are the differences in headloss computed by Modified Hazen-Williams equation and Hazen-Williams or Darcy-Weisbach equations?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The differences depend on the range of roughness. For smooth pipes the differences are small while for very rough pipes they can be larger. However, if there are differences, the Darcy Weisbach equation is generally considered more accurate.&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;WaterGEMS Help topic &amp;quot;Hazen-Williams Equation&amp;quot;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;WaterGEMS Help topic &amp;quot;Darcy-Weisbach&amp;nbsp;Equation&amp;quot;&lt;/span&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Roughness, Hazen Williams C factor, Hazen-Williams friction coefficient, Modified C factor, Modified Hazen-Williams, C factor, Darcy-Weisbach, WaterGEMS, Darcy-Weisbach friction factor, User Data Extensions, WaterCAD, roughness coefficient, Hazen-Williams, Headloss Coefficient, headloss&lt;/div&gt;
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