Abstract:
A comprehensive low-speed experiment on a three-dimensional turbulent boundary layer is described and the results are presented in detail. The flow caused by an obstruction placed in a thick two-dimensional boundary layer is investigated at a free-stream velocity of 200 ft/s. The boundary-layer momentum-thickness Reynolds numbers are approximately 50,000. The investigation is reported in two parts. This part is concerned with the area of the flow directly up-stream of the obstruction, which includes the axis of symmetry of the flow and extends down-stream as far as the saddle separation point and the adjacent boundary-layer separation lines. Part 2 is concerned with the flow to one side of the obstruction and the main characteristic of this region is that it contains a free-stream inflexion. Referring to the area of the flow investigated in this part, it is shown that polar plots of the velocity vector through the boundary layer are well represented by Johnston's triangular model. The extension of the law of the wall to three dimensions is discussed. Simple extensions to three dimensions of existing methods of representing two-dimensional profiles, using Cole's wake function and Thompson's weighting function, are shown not to fit the data.
