Round incompressible jets with asymmetric initial velocity distributions

Abstract

THE near-field development of turbulent air jets with asymmetric initial velocity distributions is investigated experimentally. The jets emerge from pipes of circular cross section into a still environment. The level of asymmetry of the exit plane mean velocity distribution is controlled by the angle of pipe bend upstream of the exit. Jets with two levels of initial streamwise velocity asymmetry are studied in addition to an axisymmetric jet emerging from a straight pipe. The-Reynolds number based on exit bulk velocity and pipe diameter is 13,500. Streamwise velocity measurements, using hot-wire anemometry, indicate that the near-field turbulence structure is significantly modified by the skewed velocity distribution. On the plane of symmetry, higher levels of initial velocity skewness lead to increased disparity of turbulence intensity and unequal rate of growth on the two sides of the jet. Furthermore, higher rates of maximum velocity decay and jet growth are attained with the initially asymmetric jets. The increase in jet spread rate on the symmetry plane is found to distort the initially round cross-sectional shape of the jets beyond 10 pipe diameters from the exit plane.