The cause of overprediction of cooling efficiency by unsteady Reynolds averaged simulations of turbine blade trailing edge cooling flow is investigated. This is due to the deficiency in the level of unsteady coherent energy very near to the wall. Farther from the wall, the Reynolds averaged simulation produces the correct level of mixing. Eddy simulations of the instantaneous turbulent eddying produce a close agreement to data on film effectiveness. In particular, they reproduce the reduction in cooling effectiveness toward the trailing edge that has been seen in experiments. The scale adaptive simulation model of Menter and Egorov (2005, "A Scale-Adaptive Simulation Modeling Using Two-Equation Models," AIAA Paper No. 2005-1095) is invoked for the eddy simulations.