Double-hole film cooling on a turbine blade under varying blowing ratios and turbulence intensities: A numerical study

This paper presents a numerical investigation of double-hole (DH) film cooling on the suction surface of a C3X turbine blade, with single-hole (SH) configurations used as reference cases for comparison. Reynolds-Averaged Navier–Stokes (RANS) simulations are performed using the realizable k–ε turbulence model with enhanced near-wall treatment and a refined mesh (y + < 5). The study considers four blowing ratios (MR = 0.5, 0.7, 1.0, and 1.4) under low and high freestream turbulence intensities (0.02% and 12%), representative of turbine operating conditions. Film-cooling performance is evaluated using temperature fields, effectiveness distributions, and flow visualizations. The results show that DH configurations consistently improve film-cooling performance compared to SH cases, particularly at moderate blowing ratios and elevated turbulence levels. The enhancement is reflected in improved surface coverage and more stable downstream cooling behavior. Overall, the findings indicate that the effectiveness of double-hole injection is strongly dependent on operating conditions, with the most favorable performance observed at moderate-to-high blowing ratios under high turbulence intensity. The results provide design-oriented insight into optimizing hole multiplicity for improved thermal protection and operational robustness in turbine blade cooling applications.