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Why does the weir coefficient field for a v-notch weir have units on it?Shouldn't it be unitless?What is the difference between the weir coefficient with a v-notchversus other weir types?What typical values are expected for a v-notch weir coefficient?Product: SewerCAD V8i, SewerGEMS Sanitary V8iVersion: 08.11.02.46Area: Settings/Attributes, Problem ID#: 47628, PROBLEMSOLVINGInternal Reference Number: 61661
There is a known issue in version 08.11.02.46 that incorrectly causesunits to display for the weir coefficient field when using a v-notchweir. V-notch weirs use a discharge coefficient similar to orifices,which is different from the weir coefficient used for other weir types.It is unitless and is multiplied by (2g)^0.5 for use in thecalculations.Therefore a typical value when using a v-notch weir is around 0.6,whereas a typical value when using other weir types is 3.0However, due to this known issue, the value that you enter for thev-notch weir coefficient field will be converted to US units first, thenused in the calculations. Therefore if you're using metric units forthat field, the coefficient used in the calculations will not becorrect. In this case, there are two solutions:1) Change the units on the weir coefficient to US, by right clicking thefield, choosing "units and formatting", then choosing ft^(1/2)/s. Then,enter the correct value again (~0.6)2) Download and apply the latest cumulative patch set for SewerCAD08.11.02.46, for a partial fix. The field will then be unitless andcorrectly accept the normal coefficient of discharge value such as 0.6.If you apply the latest cumulative patch set for SewerCAD 08.11.02.46,please note the following:1) The default value for this field will still remain 3.0. A betterdefault value for future versions would be 0.58.2) If you are in metric units and you set the weir coefficient when theweir type is inline and change it to V-notch, the value presented willchange. It will show the converted US value. This is because theunderlying schema the field has a storage unit. Be sure to correct thevalue as needed.3) If you had a file with a V-Notch weir with units in Metric, when youopen the file after installing the patch the coefficient presented willbe different. Be sure to correct as needed.
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