The near field structure of initially asymmetric jets

The structure of turbulent jets with asymmetric initial velocity distributions is investigated experimentally. Jets with two different levels of initial streamwise velocity asymmetry were considered. For reference, measurements were also made in an axisymmetric jet In all three cases, the jet Reynolds number, based on the exit bulk velocity, was 13,500. The jets exited from pipes of circular cross-sections and the level of asymmetry of the initial velocity distribution was controlled by the angle of pipe bend upstream of the exit Hot-wire anemometry was used to measure streamwise and transverse velocity and the measurements extended to twelve jet diameters from the exit The near field turbulence structure is significantly modified by the initial skeweness (asymmetry) of the mean streamwise velocity distribution. On the plane of symmetry, higher levels of velocity skewness lead to increased disparity of turbulence intensity and Reynolds shear stress on the two sides of the jet and thus, unequal growth rates of the two sides. The average turbulence levels are higher for the asymmetric jets leading to higher overall rates of jet growth and maximum mean velocity decay.