On the nature of jets entering a turbulent flow part b—film cooling performance

The effects of mainstream turbulence intensity between 0.3 percent and 20.6 percent and turbulence scale between 0.06 and 0.33 jet entrance diameters on heated subsonic jets issuing from a row of inclined round holes into a turbulent boundary layer are investigated from the view point of film cooling effectiveness. At low blowing rate the injected jets stay close to the wall and are sensitive to the turbulent mixing resulting in a decrease of centerline effectiveness with an increase of mainstream turbulence intensity. At high blowing rate the centerline effectiveness increases with the mainstream turbulence intensity because of smaller penetration of the injected jets due to the greater mixing with the mainstream and to the thinner boundary layer of the mainstream. At moderate turbulence intensity, the turbulence scale has a significant effect upon the lateral distribution of effectiveness through vortex formation.