基于大涡模拟分析气膜冷却的湍流场

Analysis of turbulence field of film cooling based on large eddy simulation

用大涡模拟考察了单孔平板气膜冷却的湍流场,气膜孔沿流向倾斜30°,气膜出流的雷诺数为2600,吹风比为0.5.计算结果表明:①气膜孔内的流动分离增加了湍流动能,导致气膜冷却效率的降低,在设计中要尽量避免或减少流动分离;②与射流侧向扩展有关的涡黏性系数在气膜孔两侧存在峰值,而采用各向同性的湍流模型预测气膜冷却时,涡黏性系数的峰值出现在射流与主流的剪切区,因此会高估射流的垂直穿透而低估射流的侧向扩展;③可以用大涡模拟辅助建立各向异性的湍流模型,以便提高湍流模型的预测精度.

Large eddy simulation of film cooling over flat plate with 30° streamwise inclined cylinder hole was performed to investigate the turbulence field of film cooling.The Reynolds number at the jet exit was 2 600,and the blowing ratio was 0.5.Numerical results show that flow separation in the hole increases the turbulence kinetic energy and results in the decrease of film cooling effectiveness,which should be avoided as much as possible in design of coolant supply plenum.Eddy viscosity coefficient relevant to the lateral diffusion of film has peak on both sides of the hole,while the peak predicted by isotropic eddy viscosity model is in the shear layer between mainflow and jet.This results in the overprediction of vertical penetration and underprediction of lateral spread of the jet.Large eddy simulation can be used to construct anisotropic turbulence model in order to improve the accuracy of turbulence model.