Measurements were made of the distributions of mean velocity, turbulence intensities, and turbulent shear stress in a turbulent boundary layer downstream from a hemispherical cap attached onto the plane rigid wall. The eddy viscosity, when computed in the classical way according to Boussinesq's concept from the lateral gradient of the mean velocity and the turbulence shear-stress, showed a very strong nonuniform lateral distribution across the outer region of the boundary layer. Moreover, the nondimensional values of the eddy viscosity, using the wall friction velocity and the boundary layer thickness as the velocity scale and length scale respectively, were higher than those for the boundary layer when not disturbed by the wake of the spherical cap. When account is taken of an axial memory effect of the stream-wise variation of the lateral gradient of the mean velocity, the values of the nondimensional eddy viscosity are close to those for the undisturbed boundary layer. (Author)
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