Numerical simulation and experimental study of hydraulic performance of circular crested normal weirs

Abstract EN

Weirs are simple control structures usually built across channels for water storage and measurement of flow rates.

The main target of the present study is to numerically simulate and experimentally study the hydraulic performance of circular crested normal weirs.

For numerical simulation, the commercial package ANSYS CFX is utilized adopting tetrahedrons mesh with a maximum total number of 1932301 elements, while, for the experimental study nine physical models are manufactured and tested having different crest diameters and various weir heights.

Numerical simulation results demonstrated that the ANSYS CFX software is highly capable for simulating circular crested normal weirs showing quite good agreements in water surface profiles and 4.3% mean percentage error in upstream head above crest, while, the software showed 6.8% mean percentage error in estimating discharge coefficient.

A simple empirical expression is obtained for the estimation of coefficient of discharge in terms of ratio of upstream head to weir height and the ratio of upstream head to crest diameter with a coefficient of correlation = 0.88.

The flow rate magnification is found increasing with the increase of upstream relative head and the best performance of the weir is found when the ratio of crest diameter to weir height = 0.33 at which the highest increase in flow rate is observed ranging between 25.41% and 32.14% compared with sharp crested weirs having the same height and the same length of crest