| Non-dimensional iterative formulas for computing water depth at vena contraction are derived from the basic equations of water depth at vena contraction in parabola form cross section through proper mathematic-exchange.According to hydraulic characteristics,the astringency of these iteration formulas has been testified,and five approximate formulas for computing water depth at vena contraction have been obtained by using four methods.Through error analysis and a case history computed by using these formulas we can obtain the easiest formula.In the practical area of engineering,the maximum error of the water depth is not greater than 0.48 percent.These formulas are qualified,short-cut and correct,and can be widely used.They overcome the shortage of graphic chart and trial computation methods widely used in the past-time. |