Experimental and Numerical Investigations on the Effect of Rectangular Openings’ Aspect Ratio on Outflow Discharge

Up to now, a few formulas have been suggested by scholars for the amount of discharge from openings, however, the effect of opening's geometry on the amount of discharge has not addressed thoroughly. In this study, to assess the effect of rectangular openings’ aspect ratio on the discharge amount, experimental and numerical investigations have been conducted on the discharge amount from rectangular openings at the bottom of tanks. In the experimental part of the study different water depths have been considered and the amounts of discharge have been measured for openings with identical area, but different aspect ratios. In the numerical part of the study the test results have been compared to those obtained from finite-volume-based numerical simulation. The experimental and numerical results are in good agreement, and both show that there is a trend of increase in the amount of discharge with increase of the opening’s aspect ratio. The amount of this increase is from 13% to 21% for hydraulic head varying between 0.3 to 0.6 meters. On this basis, the conventional orifice formula for calculation of the rectangular opening discharge needs modification.