Experimental investigation of boundary layer behavior in a simulated low pressure turbine

A detailed investigation of the flow physics occurring on the suction side of a simulated low pressure turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT blade onto a flat plate. The experiments were carried out at Reynolds n umber of 100,000 and 250,000 with three levels of freestream turbulence. Th e main emphasis in this paper is placed on flow field surveys performed at a Reynolds number of 100,000 with levels of freestream turbulence ranging f rom 0.8 percent to 8 percent. Smoke-wire flow visualization data were used to confirm that the boundary layer was separated and formed a bubble. The t ransition process over the separated flow region is observed to be similar to a laminar free shear layer flow with the formation of a large coherent e ddy structure. For each condition, the locations defining the separation bu bble were determined by careful examination of pressure and mean velocity p rofile data. Transition onset location and length determined from intermitt ency and height of the laminar separation bubble were observed to be invers ely proportional to the levels of freestream turbulence. [S0098-2202(00)007 01-X].