فهرست نشریات علمی دسترسی آزاد ایران

Abstract To determine the free surface flow characteristics over a triangular broad crested (crump or hump) weir with different with different upstream and downstream slopes, a series of experiments were conducted in hydraulics laboratory using a 5 m long flume. The experiments were simulated by a numerical model, Flow-3D, in order to study the flow characteristics such as free surface elevation (water surface profile), Froude number, discharge coefficient and specially  the  location of critical flow state in different head ratios and ramp slopes. To investigate the hydrodynamic field over the weir, the computational results, included different turbulence models: two-equation k–ε, renormalized group (RNG), and large eddy simulation (LES).  A nested mesh with higher resolution around the weir was employed and the computatinal results showed a close agreement with experimental data. Finally, according to the results it was found that when steeper ramp slope faces upstream, the critical flow occurs exactly at the crest of the weir, while milder ramp facing upstream makes the critical flow move backward just before the crest. The critical state location showed no sensetivity to different head ratios. Moreover, discharge coefficients were calculated and it is concluded that Cd equales 0.95 and 1.30 respectively for steep slope and mild slope facing upstream. It is worth mentioning that identification the accuracy of turbulence models’ functionality among different ones offered by Flow-3D in such experiments, requires employing an additional criterion besides water surface elevation.