Experimental investigation of conical wall jets

Abstract

The investigations described here pertain to the determination of the flowfields of different conical wall jet systems. The flow configuration is obtained by pushing a cone-frustum with a flow guide attached to its leading edge into a diffuser having the same included angle as the cone, creating a uniform gap. Air is blown through this gap along the conical surface to form a conical wall jet. A radial or cylindrical wall jet would occur if the apex angle a of the cone becomes 90 or 0 deg. A plane wall jet would occur if the radius of the cylinder becomes infinity for the case of a = 0. The experimental results show that the dimensionless velocity profiles and the rate of jet spread follow patterns similar to those reported for a radial, plane, or cylindrical wall jet. Based upon available skin friction data for wall jets, the velocity profiles have been satisfactorily expressed in terms of variables in the law of the wall and the defect law. No effect of transverse curvature is observed. An analytical model based upon conservation of momentum in the axial direction has been developed to predict the longitudinal decay of the maximum velocity. The experimental data conform to the trends of the predictions.