WALL STATIC PRESSURE DISTRIBUTION DUE TO CONFINED IMPINGING CIRCULAR AIR JET

Abstract

The wall static pressure of confined air jet, impinging normally onto a flat plate has been experimentally investigated. The mean velocities, and wall static pressures were measured for Reynolds numbers ranging from 18,000 to 40,000 and the nozzle-to-plate spacing’s in range of 0.25–4. The effects of Reynolds number, nozzle-to-plate spacing and flow confinement on the pressure coefficient are reported. The pressure distributions are independent of the Reynolds number and depend on nozzle-to-plate spacing only. The maximum pressure occurs at the stagnation point (r/d=0) for the all nozzle-to-plate spacing’s studied and as r/d increases, the pressure decreases. At very low spacing (z/d=0.25) stagnation pressure is rather larger than those of the other spacing’s due to rapidly decreasing of axial velocity in the deflection zone. It is concluded that a sub atmospheric region occurs on the impingement plate for the nozzle-to-plate spacing’s up to one for all the Reynolds number; however, there is no evidence of the sub atmospheric region in confined jet For the nozzle-to-plate spacing’s greater than one.