This paper, as Part II of the study on wake-disturbed boundary layer, is aimed at investigation of the effects of free-stream turbulence on wake-induced transition of the boundary layer under a favorable pressure gradient. Hot-wire probe measurements are also made on the wake-disturbed boundary layer to obtain ensemble-averaged shape factor contours on the distance-time diagrams. These data are then used to examine how the favorable pressure gradient and the free-stream turbulence affects time-resolved behaviors of the boundary layer subjected to periodic wakes. In addition, likewise in Part I, the heat transfer data are compared with the transition model proposed by Funazaki (1996) in order to check the capability of the model under the favorable pressure gradient as well as the free-stream turbulence.

The objective of this study is to investigate effects of favorable pressure gradient as well as free-stream turbulence upon wake-induced boundary layer transition on a flat plate. Likewise in the previous study by Funazaki (1996), a spoked-wheel type wake generator is employed in this study. Two identical flat plates with sharp edge are used as test model. One of them is for measurement of boundary layers over the test plate by use of a single hot-wire probe, and the other is provided with thin stainless-steel foils on the surface to measure wake-affected heat transfer along the surface. Free-stream turbulence intensities are controlled with several types of turbulence grids. Pressure gradients over the test surface are adjusted by changing an inclination angle of the plate located opposite to the test model. In Part I, transition models proposed by Mayle and Dullenkopf (1990b) and Funazaki (1996a, 1996b) are compared with the experimental data obtained in this study to examine how such a model succeeds or fails in predicting the wake-induced boundary layer transition under the influences of favorable pressure gradient with a low free-stream turbulence.

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