Objective Infrared radiation characteristics are one of the most important identifying features of stealth aircraft, and suppressing them can effectively enhance the aircraft’s survivability within enemy defense systems. The exhaust system, as the hottest region of the aircraft, contributes nearly 90% of the total infrared radiation. To reduce the temperature of the exhaust system and thereby suppress its infrared emission, this study adopts a film cooling approach. However, due to the small size and large number of film-cooling holes, traditional modeling methods are difficult to implement efficiently. To address this issue, the source term method is employed to construct virtual holes instead of performing detailed mesh generation for real holes, which significantly improves the modeling efficiency. Based on this method, the study further investigates the suppression effect of film cooling on infrared radiation and verifies its effectiveness. Therefore, the main objective of this research is to develop an efficient film cooling modeling method for aircraft exhaust systems based on the source term approach, and to evaluate its capability in reducing infrared radiation characteristics, thereby improving the simulation efficiency and supporting the engineering application of film cooling technology.

Methods An efficient film cooling modeling method based on the source term approach is established in this study. In this method, source terms are introduced at the exits of film-cooling holes to replace the complex mesh generation required by conventional modeling techniques. First, both single-hole and multi-hole flat-plate models are constructed to compare the computational efficiency and accuracy between the source term method and the traditional method. Then, by varying the total pressure of the cooling air in the source term model, the influence of kidney vortex formation and coolant flow variation on cooling effectiveness and infrared radiation characteristics is analyzed, revealing the variation trend of infrared radiation with respect to the cooling air total pressure. Finally, for the multi-hole flat-plate model, infrared radiation is calculated using both the source term and traditional methods, and the spectral radiation brightness and integrated radiation intensity are compared to demonstrate the suppression effect of film cooling on infrared radiation.

Results and Discussions The simulation results for the single-hole flat-plate model show that, compared with the traditional method, the number of grid cells is reduced from 2.2 million to 180000 and the computation time decreases from 1 hour to 5 minutes, while the mean relative error of the spanwise-averaged cooling effectiveness along the hole centerline is 11.23%, as shown in Fig.8. For the multi-hole flat-plate model, the grid number decreases from 12 million to 2 million and the computation time is shortened from 10 hours to 30 minutes using the source term method, with the root-mean-square relative error and mean relative error of the centerline spanwise-averaged cooling effectiveness being 17.63% and 11.36%, respectively. Compared with experimental point temperatures, the traditional method yields an average relative error of 0.821%, while the source term method yields 1.31%, as shown in Fig.15. These results indicate that the source term method can significantly reduce grid number and computation time while maintaining acceptable accuracy, thus greatly improving computational efficiency. By comparing the spanwise-averaged cooling effectiveness along the hole centerline under different cooling air total pressures, it is observed that as the cooling air total pressure increases, the size of the kidney vortices grows and the coolant flow rate increases, resulting in the cooling effectiveness first increasing and then decreasing, as shown in Fig.9. Furthermore, comparison of infrared radiation in the target region calculated by the source term method and the traditional method shows that the medium-wave integrated radiation intensity decreases by approximately 52%, with a relative error of about 4.64%, demonstrating that film cooling can effectively suppress infrared radiation, as shown in Fig.19. The target region exhibits the minimum infrared radiation intensity at a blowing ratio of 0.4-0.5.

Conclusions The results indicate that, compared with the traditional method, the source term method can significantly reduce the number of grid cells and computation time while maintaining acceptable accuracy, thereby improving computational speed and efficiency and providing an effective solution for the engineering application of film cooling in aircraft exhaust systems. Film cooling can effectively suppress the infrared radiation characteristics of aircraft exhaust systems by reducing their temperature. The cooling air flow has a certain effective range: increasing the total pressure of the cooling air increases the flow rate, but also enlarges the size of kidney vortices, which can inhibit the cooling effectiveness. It is recommended that, when implementing film cooling in exhaust systems, the blowing ratio be maintained within 0.4-0.5, as this range yields the greatest reduction in infrared radiation intensity, thereby achieving optimal cooling performance.