Flow measurement mechanism and hydraulic characteristics analysis of the airfoil weir-orifice facility in a rectangular channel

ABSTRACT Experimental studies and numerical simulations are conducted on the airfoil weir-orifice facilities to find a flow measurement and control device with a stable combined outflow form and good hydraulic performance. The orifice height under the weir is changed by adjusting the chord length and rotation angle of the weir. This paper uses three airfoil weir-orifice facilities for comparative study. The facilities have three flow forms under different rotation angles and flow conditions. Orifice discharge in combined outflow form is related to weir crest height but not upstream water depth. Flow formulas for three discharge forms are derived using dimensional analysis and incomplete self-similarity theory. The results show that the relative error of the formula is within ±6.34%. The Froude number is less than 0.4 under all working conditions; the critical submerged range is between 0.7 and 0.95; and under the premise of the unified weir crest height, the head loss decreases with the increased orifice height. The hydraulic jump location analysis yields the airfoil weir-orifice facility under the combined outflow as a submerged orifice outflow, and the hydraulic jump energy cancelation efficiency under the same flow condition is consistent with the upstream water depth change trend.