OBLIQUE IMPINGEMENT OF CIRCULAR TURBULENT JETS

Abstract

The oblique impingement of circular turbulent jets on smooth walls has been studied both experimentally and analytically. This type of flow represents a considerable degree of geometrical generality as the flow is three-dimensional in its main portion. An inductive, semi-empirical method has been developed to predict wall pressures in the impingement region. Wall shear stress in the same region has been measured on the symmetry plane and an analytical method has been presented for its prediction. For prediction of flow properties in the wall jet region, a theory has been developed which is based on boundary-layer approximations of the Reynolds equations of motion and upon the similarity of radial velocity profiles. It is shown that the flow is quasi-axisymmetric, i.e. flow takes place along radial lines with shear stresses between radial planes being very small. The thickness of the wall jet grows linearly on each radial at a universal slope. The local skin friction factor remains constant along radials and moreover it is independent of any other parameter of the problem except R ₀. Further, it is shown that u_m /U ₀α1/(r/d), the proportionality factor being a function of Π and θ. This function was derived semi-empirically and was shown to be a reasonable description of the experiments.