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<?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>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f)?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f</link><description /><dc:language>en-US</dc:language><generator>Telligent Community 12</generator><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f)?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f</link><pubDate>Tue, 11 Apr 2023 14:08:16 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Current Revision posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 4/11/2023 2:08:16 PM&lt;br /&gt;
&lt;table style="background-color:#dce5f0;border:#dce5f0 0px solid;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;span style="font-size:medium;"&gt;&lt;b&gt;Applies To&amp;nbsp;&lt;/b&gt;&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&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;HAMMER&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:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Modeling&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&lt;/td&gt;
&lt;/tr&gt;
&lt;/tbody&gt;
&lt;/table&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1 id="mcetoc_1gtoa9sar0"&gt;Problem&lt;/h1&gt;
&lt;p&gt;How does HAMMER compute the Darcy-Weisbach friction factor (f) for each pipe in the model?&lt;/p&gt;
&lt;h1 id="mcetoc_1gtoa9sar1"&gt;Background&lt;/h1&gt;
&lt;p&gt;HAMMER always uses the Darcy-Weisbach friction method during a transient simulation, regardless of the initial conditions friction method. It computes the &amp;quot;f&amp;quot; friction factor based on the initial conditions headloss (total headloss across the pipe including both friction and minor losses). The friction factor &amp;#39;f&amp;#39; is shown in the &amp;quot;PIPE INFORMATION&amp;quot; section of the Transient Analysis Output Log. See more here: &lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/43481/reporting-the-darcy-weisbach-friction-factor-f"&gt;Reporting the Darcy-Weisbach Friction Factor (f)&lt;/a&gt;&lt;/p&gt;
&lt;p&gt;There are a few different variations of the calculation depending on the situation:&lt;/p&gt;
&lt;h1 id="mcetoc_1gtoa9sar2"&gt;Solution - non-zero initial flow&lt;/h1&gt;
&lt;p&gt;For non-zero flow pipes (initial conditions flow above &amp;quot;flow tolerance&amp;quot; transient calculation option) it uses this equation:&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;f = hl / [ (L/D)(V^2/2g) ]&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Where:&lt;/p&gt;
&lt;p&gt;hl = headloss across the pipe (ft, m)&lt;br /&gt;L = pipe length (ft, m)&lt;br /&gt;D = Diameter (ft, m)&lt;br /&gt;V = Velocity (ft/s, m/s)&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;h1 id="mcetoc_1gtoa9sar3"&gt;Solution - Zero initial flow&lt;/h1&gt;
&lt;p&gt;If the initial flow through the pipe is less than the &amp;quot;flow tolerance&amp;quot; transient calculation option, the user-entered friction coefficient will be directly converted to a Darcy-Weisbach &amp;#39;f&amp;#39;.&amp;nbsp;&lt;/p&gt;
&lt;p&gt;In particular if the initial conditions friction method is set to Darcy-Weisbach (with a roughness height &amp;#39;e&amp;#39; entered), it&amp;nbsp;uses the Von Karman equation to compute the friction factor:&lt;br /&gt;&lt;br /&gt;&lt;strong&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1 id="mcetoc_1gtoa9sar4"&gt;See Also&lt;/h1&gt;
&lt;p&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/10619/error-computing-hammer-model-the-darcy-weisbach-friction-coefficient-xxx-is-too-large"&gt;Error computing HAMMER model: &amp;quot;The Darcy-Weisbach friction coefficient xxx is too large.&lt;/a&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: HAMMER, friction method, reviewed2017, Von Karman, Darcy-Weisbach, friction factor&lt;/div&gt;
</description></item><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f)?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f/revision/5</link><pubDate>Tue, 31 Oct 2017 01:08:05 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Revision 5 posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 10/31/2017 1:08:05 AM&lt;br /&gt;
&lt;h1&gt;&lt;/h1&gt;
&lt;table style="background-color:#dce5f0;border:#dce5f0 0px solid;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;span style="font-size:medium;"&gt;&lt;b&gt;Applies To&amp;nbsp;&lt;/b&gt;&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&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;HAMMER&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;10.00.xx.xx, 08.11.xx.xx&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Modeling&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&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 does HAMMER compute the Darcy-Weisbach friction factor (f) for each pipe in the model?&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;HAMMER always uses the Darcy-Weisbach friction method during a transient simulation, regardless of the initial conditions friction method. It computes the &amp;quot;f&amp;quot; friction factor based on the initial conditions headloss. The friction factor &amp;#39;f&amp;#39; is shown in the &amp;quot;PIPE INFORMATION&amp;quot; section of the Transient Analysis Output Log.&lt;/p&gt;
&lt;p&gt;There are a few different variations of the calculation depending on the situation:&lt;/p&gt;
&lt;h1&gt;Solution - non-zero initial flow&lt;/h1&gt;
&lt;p&gt;For non-zero flow pipes (flow above &amp;quot;flow tolerance&amp;quot; transient calculation option) it uses this equation:&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;p&gt;f = hl / [ (L/D)(V^2/2g) ]&lt;/p&gt;
&lt;p&gt;Where:&lt;/p&gt;
&lt;p&gt;hl = headloss across the pipe (ft, m)&lt;br /&gt;L = pipe length (ft, m)&lt;br /&gt;D = Diameter (ft, m)&lt;br /&gt;V = Velocity (ft/s, m/s)&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;h1&gt;Solution - Zero initial flow&lt;/h1&gt;
&lt;p&gt;If the initial flow through the pipe is less than the &amp;quot;flow tolerance&amp;quot; transient calculation option, the user-entered friction coefficient will be directly converted to a Darcy-Weisbach &amp;#39;f&amp;#39;.&amp;nbsp;&lt;/p&gt;
&lt;p&gt;In particular if the initial conditions friction method is set to Darcy-Weisbach (with a roughness height &amp;#39;e&amp;#39; entered), it&amp;nbsp;uses the Von Karman equation:&lt;br /&gt;&lt;br /&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/10619/error-computing-hammer-model-the-darcy-weisbach-friction-coefficient-xxx-is-too-large"&gt;Error computing HAMMER model: &amp;quot;The Darcy-Weisbach friction coefficient xxx is too large.&lt;/a&gt;&lt;/p&gt;
&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: HAMMER, friction method, reviewed2017, Von Karman, Darcy-Weisbach, friction factor&lt;/div&gt;
</description></item><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f)?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f/revision/4</link><pubDate>Tue, 15 Aug 2017 19:17:13 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Revision 4 posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 8/15/2017 7:17:13 PM&lt;br /&gt;
&lt;h1&gt;&lt;/h1&gt;
&lt;table style="background-color:#dce5f0;border:#dce5f0 0px solid;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;span style="font-size:medium;"&gt;&lt;b&gt;Applies To&amp;nbsp;&lt;/b&gt;&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&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;HAMMER&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;10.00.xx.xx, 08.11.xx.xx&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Modeling&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&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 does HAMMER compute the Darcy-Weisbach friction factor (f) for each pipe in the model?&lt;/p&gt;
&lt;p&gt;a pipe with zero initial flow and the Darcy Weisbach friction method (or when the initial flow below the &amp;quot;Flow Tolerance&amp;quot; calculation option).&lt;/p&gt;
&lt;h1&gt;Background&lt;/h1&gt;
&lt;p&gt;HAMMER always uses the Darcy-Weisbach friction method during a transient simulation, regardless of the initial conditions friction method. It computes the &amp;quot;f&amp;quot; friction factor based on the initial conditions headloss. There are a few different variations depending on the situation:&lt;/p&gt;
&lt;h1&gt;Solution - non-zero initial flow&lt;/h1&gt;
&lt;p&gt;For non-zero flow pipes (flow above flow tolerance calculation option) it uses this equation:&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;p&gt;f = hl / [ (L/D)(V^2/2g) ]&lt;/p&gt;
&lt;p&gt;Where:&lt;/p&gt;
&lt;p&gt;hl = headloss across the pipe (ft, m)&lt;br /&gt;L = pipe length (ft, m)&lt;br /&gt;D = Diameter (ft, m)&lt;br /&gt;V = Velocity (ft/s, m/s)&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;
&lt;h1&gt;Solution - Zero initial flow&lt;/h1&gt;
&lt;p&gt;If the initial flow through the pipe is less than the &amp;quot;flow tolerance&amp;quot; transient calculation option, the user-entered friction coefficient will be directly converted to a Darcy-Weisbach &amp;#39;f&amp;#39;.&amp;nbsp;&lt;/p&gt;
&lt;p&gt;In particular if the initial conditions friction method is set to Darcy-Weisbach (with a roughness height &amp;#39;e&amp;#39; entered), it&amp;nbsp;uses the Von Karman equation:&lt;br /&gt;&lt;br /&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: HAMMER, friction method, reviewed2017, Von Karman, Darcy-Weisbach, friction factor&lt;/div&gt;
</description></item><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method?</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f/revision/3</link><pubDate>Tue, 25 Apr 2017 12:29:41 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Scott Kampa</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Revision 3 posted to OpenFlows | Water Infrastructure Wiki by Scott Kampa on 4/25/2017 12:29:41 PM&lt;br /&gt;
&lt;h1&gt;&lt;/h1&gt;
&lt;table style="background-color:#dce5f0;border:#dce5f0 0px solid;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;span style="font-size:medium;"&gt;&lt;b&gt;Applies To&amp;nbsp;&lt;/b&gt;&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&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;HAMMER&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;10.00.xx.xx, 08.11.xx.xx&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Modeling&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&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;What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method (or when the initial flow below the &amp;quot;Flow Tolerance&amp;quot; calculation option).&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;It uses the Von Karman equation, based on the Roughness height and diameter:&lt;br /&gt;&lt;br /&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: HAMMER, friction method, reviewed2017, friction factor&lt;/div&gt;
</description></item><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method? (Solution 500000070006)</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f/revision/2</link><pubDate>Fri, 06 Mar 2015 20:21:06 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Scott Kampa</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Revision 2 posted to OpenFlows | Water Infrastructure Wiki by Scott Kampa on 3/6/2015 8:21:06 PM&lt;br /&gt;
&lt;h1&gt;&lt;b&gt;&lt;img style="border-width:0px;" alt=" " src="/cfs-file.ashx/__key/communityserver-components-sitefiles/TSG-Logo.png" width="189" height="60" /&gt;&lt;/b&gt;&lt;/h1&gt;
&lt;table style="width:500px;background-color:#dce5f0;border:#dce5f0 0px solid;" border="0"&gt;
&lt;tbody&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;b&gt;&amp;nbsp;&lt;/b&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;b&gt;&amp;nbsp;&lt;/b&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;b&gt;&amp;nbsp;&lt;/b&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;span style="font-size:medium;"&gt;&lt;b&gt;Applies To&amp;nbsp;&lt;/b&gt;&lt;/span&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Bentley HAMMER&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Version(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;08.11.xx.xx&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Environment:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;N\A&lt;/td&gt;
&lt;td&gt;&lt;/td&gt;
&lt;/tr&gt;
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&lt;td style="text-align:right;"&gt;&lt;strong&gt;&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td style="text-align:right;"&gt;&lt;strong&gt;Area:&amp;nbsp;&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Modeling&lt;/td&gt;
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&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&lt;/td&gt;
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&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method (or when the initial flow below the &amp;quot;Flow Tolerance&amp;quot; calculation option).&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;It uses the Von Karman equation, based on the Roughness height and diameter:&lt;br /&gt;&lt;br /&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;
&lt;p&gt;&lt;a href="/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Migrated, SELECTsupport&lt;/div&gt;
</description></item><item><title>What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method? (Solution 500000070006)</title><link>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f/revision/1</link><pubDate>Fri, 06 Mar 2015 20:19:01 GMT</pubDate><guid isPermaLink="false">6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:84973860-6524-4654-8247-a6191a1c407f</guid><dc:creator>Jesse Dringoli</dc:creator><comments>https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19847/what-equation-does-hammer-use-to-compute-the-darcy-weisbach-friction-factor-f#comments</comments><description>Revision 1 posted to OpenFlows | Water Infrastructure Wiki by Jesse Dringoli on 3/6/2015 8:19:01 PM&lt;br /&gt;
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&lt;td style="text-align:right;"&gt;&lt;strong&gt;Product(s):&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Bentley HAMMER&lt;/td&gt;
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&lt;td&gt;08.11.01.32&lt;/td&gt;
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&lt;td style="text-align:right;"&gt;&lt;strong&gt;Original Author:&lt;/strong&gt;&lt;/td&gt;
&lt;td&gt;Jesse Dringoli, Bentley Technical Support Group&lt;/td&gt;
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&lt;p&gt;&lt;/p&gt;
&lt;h1&gt;Problem&lt;/h1&gt;
&lt;p&gt;What equation does HAMMER use to compute the Darcy-Weisbach friction factor (f) for a pipe with zero initial flow and the Darcy Weisbach friction method (or when the initial flow below the &amp;quot;Flow Tolerance&amp;quot; calculation option).&lt;br /&gt;&lt;/p&gt;
&lt;h1&gt;Solution&lt;/h1&gt;
&lt;p&gt;It uses the Von Karman equation, based on the Roughness height and diameter:&lt;br /&gt;&lt;br /&gt;DW f = (1.0 / (2.0 * Log10(Diameter / roughness height) + 1.14)^2&lt;br /&gt;&lt;/p&gt;
&lt;h1&gt;See Also&lt;/h1&gt;&lt;a href="http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/8597.unexpected-results-seen-in-pipes-with-zero-initial-flow"&gt;Unexpected results seen in pipes with zero initial flow&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;

&lt;div style="font-size: 90%;"&gt;Tags: Migrated, SELECTsupport&lt;/div&gt;
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