Supersonic film cooling in an aero-engine nozzle with a Coanda-driven expansion hole design

Film cooling is essential for thermal protection in aero-engine nozzles, but its effectiveness is limited by shock waves, vortical structures, jet detachment, and coolant-mainstream mixing induced by discrete coolant injection. To improve film attachment and cooling performance, a Coanda-driven expansion (CDE) hole is proposed and evaluated for nozzle film cooling at a mainstream Mach number of 2. A Roe-informed scheme coupled with large eddy simulations is developed based on the OpenFOAM framework to capture shock waves, vortical structures, and heat transfer. Adaptive mesh refinement and dynamic load balancing are incorporated to improve computational efficiency by more than 24%. The aerodynamic and thermal performances of the proposed CDE hole are systematically compared with those of an inclined cylindrical hole and a 7-7-7 hole at blowing ratios ( M ) of 0.5 and 1.0. The results show that, despite its smaller area ratio than the 7-7-7 hole (2.22 compared with 2.50), the CDE hole weakens the jet induced shock and expansion wave system, suppresses the upward lift of vortical structures, reduces mixing between the jet and mainstream, and sustains coolant coverage along the wall farther downstream. The CDE hole increases the laterally averaged adiabatic cooling effectiveness relative to the cylindrical baseline by 0.04–0.10 at M = 0.5 and up to 0.12 at M = 1.0. In addition, a higher blowing ratio enhances attachment near the hole and lateral coverage, but accelerates downstream mixing and the decay of cooling effectiveness. These findings suggest that the CDE hole could become a highly competitive candidate for aero-engine nozzle film cooling design to promote coolant attachment.