Q=CLeHe3/2cap Q equals cap C cap L sub e cap H sub e raised to the 3 / 2 power : Discharge coefficient, typically around for ogee crests at design head. Lecap L sub e : Effective length, adjusted for contractions from piers ( Kpcap K sub p ) and abutments ( Kacap K sub a
You pull out your copy of USBR’s Design of Small Dams or EM 1110-2-1603 , flip to the discharge coefficient tables, and start punching numbers into a generic Excel sheet. You spend hours debugging lookup tables for the upstream face slope, fiddling with unit conversions, and praying you didn’t mis-type the design head (H(_d)) relationship.
If you must use Excel because your firm is slow to change, make it by:
An ogee spillway features an S-shaped profile that matches the lower nappe of a freely falling water jet. For a high-quality design or essay, address these core components:
) due to side contractions. The formula to determine this is:
xn=KHdn−1yx to the n-th power equals cap K cap H sub d raised to the n minus 1 power y Where: : Coordinates from the crest apex. Hdcap H sub d : Design head. : Constants determined by the slope of the upstream face. 3. Effective Crest Length ( Lecap L sub e ) Piers and abutments reduce the net crest length (
You can adjust H(_d) and watch the entire crest shape update in real-time. That is a game-changer for parametric studies.