Contracted Rectangular Weir Flow Calculator
The first page of the Excel template for contracted rectangular weir flow calculations is shown at the left and a second page is shown at the right. For a contracted rectangular weir, L < B, so in addition to the three input values needed for the suppressed rectangular weir (P, B, and H), a value for the weir length, L, must be entered.
The Excel formulas in this spreadsheet template will then calculate (B - L)/4H, P/H, and H/L. If (B -L)/4H and P/H are greater than 1 and H/L < 0.33, then the simpler equation, Q = 3.33(L - 0.2H)H3/2, can be used.
If any of the three conditions are not met, then the equation to use is:
Q = (C1(H/P) + C2)(L - 0.003)(H + kb)3/2
If any of the three conditions are not met, you will need to use the value of L/B calculated by the spreadsheet, together with the graph and table on the second page, to obtain values for C1, C2, and kb, and enter them in the indicated cells. The Excel formula built in the spreadsheet template will then calculate Q using the above equation.
Click here to download this Excel template.