Abstract

A series of large-scale parallel simulations of flat-plate film cooling are performed to uncover the qualitative and quantitative relationship between coherent structure dynamics and heat-transfer features. The near-wall flow dynamics and heat-transfer features at five inclination angles of ${15}^{\circ },$ ${30}^{\circ },$ ${45}^{\circ },$ ${60}^{\circ }$ and ${90}^{\circ }$ are also analyzed in detail. Hybrid thermal lattice Boltzmann method and multiple graphic processing units are used to fulfill the simulation efficiently. The detailed coherent structure dynamics are captured by the high-resolution simulation. The results show that large vertical size of coherent structure and great intensity of negative spanwise vorticity indicate prominent coolant-jet detachment leading to bad cooling performance. Meanwhile, the value of area-averaged film cooling effectiveness is proportional to 4th power of area-averaged non-dimensional turbulent kinetic energy. This quantitative relationship is first proposed to make further understanding of film-cooing mixing mechanism. On the other hand, inclination angle has a complicated impact on flow dynamics and heat-transfer features. The vertical size of coherent structure becomes large and the strength of negative spanwise vorticity is strengthened in the case of large inclination angle, resulting in poor cooling performance. The influence of inclination angle is less remarkable in large-inclination-angle case than that of small inclination angle.

摘要

对平板薄膜冷却进行了一系列大规模并行模拟，以揭示相干结构动力学与传热特征之间的定性和定量关系。五个倾角下的近壁流动动力学和传热特征${15}^{\circ },$ ${30}^{\circ },$ ${45}^{\circ },$ ${60}^{\circ }$和${90}^{\circ }$也进行了详细的分析。混合热格子玻尔兹曼方法和多个图形处理单元用于有效地完成模拟。高分辨率模拟捕获了详细的相干结构动力学。结果表明，大的共格结构垂直尺寸和较大的负展向涡度表明冷却剂射流分离明显，导致冷却性能差。同时，面积平均薄膜冷却效率的值与面积平均无量纲湍动能的 4 次方成正比。首次提出这种定量关系是为了进一步了解薄膜冷却混合机制。另一方面，倾角对流动动力学和传热特性有复杂的影响。大倾角情况下共格结构垂向尺寸变大，展向负涡量强度增强，导致冷却性能变差。大倾角情况下倾角的影响不如小倾角情况下显着。