The thermal performance of a novel film-cooling scheme for a high temperature gas turbine application is introduced. The new jet, with both forward and laterally diffused exit, enables the coolant to spread wider and more uniform over the downstream surface, when compared with the traditional circular hole. As a result, the coolant momentum is reduced in the normal direction, and thus the occurrence of jet lift-off is avoided. This novel film-cooling scheme is superior to traditional cooling scheme since less amount of coolant can provide the same protection under the same conditions, making more efficient use of the coolant air. Systematic simulations have been carried out on two benchmark cases. The performances of different turbulence models as well as different wall treatments have been isolated and evaluated. Turbulence was modeled using four classes of turbulence models, namely k-[varepsilon] (including its 3 variants), k-?, Reynolds-Stress, and Spalart-Allmaras. Three-dimensional simulations were carried out by numerically solving the Reynolds-averaged Navier-Stokes equations. For the first time, to the best of author's knowledge, the jet lift-off effect is clearly captured in the simulations at high blowing ratios, and the results are in excellent agreement with experimental data. The new methodology established in the two benchmark cases has been applied to the new scheme. (Abstract shortened by UMI.).