Abstract: Film cooling is a widely applied thermal protection technique in aero-engines, and trenched hole configurations have been demonstrated to provide superior cooling performance. In this study, a control-point-based trench profile design methodology is proposed and applied to optimize the downstream trench geometry. In addition, an absolute-cosine curvature-modulated trench configuration is developed to systematically investigate the influence of the trench leading-edge curvature on cooling performance. A total of 21 trench configurations are evaluated. The trenched holes are arranged on a flat-plate model with cylindrical injection holes of 30° inclination embedded within the trench. Adiabatic cooling effectiveness is measured using Pressure-Sensitive Paint experiments, and the associated flow field characteristics are examined through numerical simulations. The results demonstrate that the control-point-based design approach offers greater geometric flexibility and yields the highest cooling effectiveness. The optimized configuration is characterized by a protruding leading edge and relatively gentle sidewalls. The optimized configuration promotes the lateral spreading of coolant within the trench, alters the generation and transport of corner vortices, effectively weakens the counter-rotating vortex pair, and enables the coolant to remain closer to the wall while achieving a wider lateral coverage. Compared with the baseline straight trench, the optimized design achieves a maximum improvement in cooling effectiveness of up to 42.4%. Sensitivity analysis further reveals that the trench profile within the outlet width region of the cylindrical hole exerts the strongest influence on cooling effectiveness, and that the optimal leading-edge curvature radius associated with the cylindrical jet is approximately 0.70 times the hole diameter.

Key words: film cooling, trenched hole, pressure sensitive paint, structural optimization, trench curvature