- The effect of high free-stream turbulence on turbulent boundary layer heat transfer is investigated experimentally. The high free-stream turbulence is produced by a wind tunnel with a biplanar, square-mesh, round-tube grid with uniform jet injection. Injection air is oriented to blow in either a counterflow or coflow direction with a controllable flow rate. The effects of length scale and low Reynolds number on the surface Stanton number are also discussed. More measurements are required in order to conclude the combined effects of turbulence intensity, length scale, and Reynolds number on turbulent boundary layer heat transfer.