The Turbulence Characteristics of Two-Dimensional Wall-Jet and Wall-Wake Flows

Abstract

Measurements of mean and fluctuating hydrodynamic properties of two-dimensional, constant property, wall-jet and wall-wake flows are reported. The mean properties include static pressure, velocity and wall shear stress; the fluctuating properties include the three fluctuating components of velocity, the local turbulent shear stress, uv , and u-spectra. The measurements were carried out for four values of the velocity ratio, U C /UG , viz. 0.75, 0.91, 1.33, and 2.3; for values of the ratio of lip thickness to slot height, t/yC , of 0.126 and 1.14; and for values of nondimensional distance, x/yC , between zero and 150. The results demonstrate the difficulties involved in deriving a satisfactory prediction procedure for flows of this type. In the upstream region, normal pressure gradients and separated flow regimes imply the need for elliptic equations. Also in the upstream region, the u-spectra measurements reveal preferred frequencies although the energy contained at the preferred frequency is never more than 25 percent of the total energy. Prandtl mixing length and the Prandtl-Kolmogorov turbulence length scale are deduced from measurements and shown to be very nonsimilar for all values of x/yC . The measurements are reported in sufficient detail to permit the detailed testing of prediction procedures.