Flow and surface pressure field measurements on a circular cylinder with impingement of turbulent round jet

Abstract

When the circular jet impinges onto a cylinder, the three-dimensional (3D) curved wall jet was attached to the wall due to the Coanda effect and the flow separation was delayed with increasing Reynolds number and impinging angle. These interesting phenomena can be studied in depth through a variety of parameters and measurement methods. Time-resolved stereo PIV measurement was conducted to investigate the 3D flow characteristics with instantaneous velocity and vorticity fields. Pressure sensitive paint (PSP) method was used to examine the pressure distribution on the cylinder surface when a circular jet impinges on it. The effects of the impingement angle, Reynolds number, and diameter ratio between the jet nozzle and the cylinder (d/D) were examined at a fixed nozzle to wall distance ratio of two (H/d = 2). Experimental results show that the pressure gradient in the flow direction decreases and the separation is delayed when the Reynolds number and impingement angle are increased at the same distance ratio. As the diameter ratio decreases with the same impingement angle and Reynolds number, the maximum suction pressure increases, and the pressure gradient in the wall jet flow direction increases. The three-dimensional nature of the surface pressure distribution changes with the flow parameters, which are well explained with three-dimensional flow field measurements in the curved 3D wall jet due to the Coanda effect.