An Experimental Investigation of Variations of Pressure Distribution with Reynolds Number and Surface Roughness in C?rcular Wall Jet

摘要

An experimental study is carried out to investigate the coefficient of pressure distribution after emerging a circular wall jet over smooth and rough flat surfaces. The effects of the systematic variations of the range of jet exit Reynolds numbers and of relative roughnesses of the surface are carefully observed. The Jet exit Reynolds numbers ranges of 8799 - 18804 and the relative surface roughnesses of smooth ranging from 0.01371 to 0.01613 were considered for this investigation. A converging nozzle of diameter 6.2 mm was taken for the jet issuing while the length of the flow straightener tube was 320 mm, sufficiently larger than hydraulic diameter (120mm ID) to ensure fully developed flow. Dial gauge indicator and Pitot tube were used to measure the surface roughness and the velocity of flow respectively. It was observed that the overall co-efficient of pressure, Cp decreases with the increase of both jet exit Reynolds number and surface roughness. Since the fluid moving with higher kinetic energy initially and decays along the length of the surface due to viscous effect, the coefficient of pressure with higher value at starting point decreases with the increase of jet exit Reynolds number. The same trend also holds well with the increase of relative surface roughness because of the enhancement of frictional effect. The co-efficient of pressure remains more or less steady after a particular distance along the axial length of the surface.