Effect of orifice thickness-to-diameter ratio on turbulent orifice flow: An experimental and numerical investigation

This paper reports a study on the effect of orifice thickness-to-diameter ratio (tau/d) on the turbulent flow through an orifice plate. Details of the flow characteristics downstream of the orifice are investigated both experimentally and numerically for a Reynolds number of 25, 000. For this purpose, seven orifice plates are manufactured with tau/d ranging between 0.27 and 1.37. Particle Image Velocimetry (PIV) is used to experimentally study the flow patterns downstream of the orifices, with particular focus on instantaneous and time-averaged velocity distributions, streamline patterns, turbulent kinetic energy, Reynolds shear stress, and out-of-plane vorticity. Results show that, with increasing tau/d, the location of the vena contracta moves closer to the orifice plate, and eventually inside for tau/d > 0.55. Increasing tau/d also results in decreasing turbulent kinetic energy and Reynolds shear stress. For the selected tau/d range, experimental and numerical results are in good agreement with the thick and thin orifice classification available in the literature.