The imposition of mean flow three dimensionality on a turbulent boundary layer has usually been coupled with relatively strong streamwise pressure gradients in previous experiments. Such pressure gradients can cause reductions in the vertical turbulent mixing usually attributed to three dimensionality. Control experiments in which the same streamwise pressure gradient is applied to both a 2D and a 3D turbulent boundary layer are not available. The goal of this work is to develop a three dimensional turbulent boundary layer (3DTBL) experiment which has an obvious 2DTBL analog. The geometry chosen is the flow over a surface mounted bump swept at a 45 degree angle. The analog, of course, is an unswept bump with the same streamwise cross-sectional profile. Mean velocity and turbulent stress profiles were measured at several locations above and downstream of the bump. The relative effects due to surface curvature, streamwise pressure gradient, and mean cross-flow are compared for the two cases. Of particular interest is the vertical turbulent mixing and relative alignment of the shear stress and strain rate vectors. Also of interest is the effect of Reynolds number on a 3DTBL. An unique wind tunnel design allowing Re to be varied by an order of magnitude will be presented.
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