Boundary Layer Transition Under High Free-Stream Turbulence and Strong Acceleration Conditions: Part 1—Mean Flow Results

Measurements from heated boundary layers along a concave-curved test wall subject to high (initially 8 percent) free-stream turbulence intensity and strong (K = (ν/U∞2) dU∞/dx) as high as 9 × 10−6) acceleration are presented and discussed. Conditions for the experiments were chosen to roughly simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Mean velocity and temperature profiles as well as skin friction and heat transfer coefficients are presented. The transition zone is of extended length in spite of the high free-stream turbulence level. Transitional values of skin friction coefficients and Stanton numbers drop below flat-plate, low-free-stream-turbulence, turbulent flow correlations, but remain well above laminar flow values. The mean velocity and temperature profiles exhibit clear changes in shape as the flow passes through transition. To the authors’ knowledge, this is the first detailed documentation of a high-free-stream-turbulence boundary layer flow in such a strong acceleration field.