Abstract
In this paper, flow through a free triangular orifice is considered. The comparison of two formulas was conducted for discharge calculations: a large orifice formula and a small orifice formula. The results show that, above a certain value of upstream head to orifice height ratio there is no need for small-large formula discrimination. The differences in the outcomes for the two formulas are negligible for upstream head to orifice height ratios greater than 3. This means that a small orifice formula can be used instead of a large orifice formula. Calculations were performed for different variants of triangle orientation (with tip downwards, sidewards and upwards) as well as for different dimensions of orifice (equilateral and isosceles). The calculations also included different submergence levels of the upper edge of the orifice and variable dimensions of the orifice with constant upstream head. Neither of these conditions affect the relative deviation values for small and large orifice formulas.