为了研究非定常气膜冷却的强化冷却机理，利用大涡模拟对非定常圆孔气膜冷却进行数值模拟，研究了4种不同脉动频率下（St=0，0.2，0.3，0.5）的涡结构与气膜冷却效率，并利用动态模态分解对计算结果进行分析，研究流场与换热的耦合机理。结果表明：脉动频率对非定常射流气膜冷却效率的影响较大，当St=0.2时气膜冷却效率与稳态射流相似，当St=0.3时气膜冷却效率比稳态高，而当St=0.5时气膜冷却效率反而会降低；当St=0.3时非定常射流能抑制下游发卡涡的生成并加速其破碎，从而提高气膜冷却效率；射流脉动产生了很多次生涡结构，这些涡结构促进了在流向方向上射流与主流的掺混，但是抑制了展向上的射流与主流掺混。

To study the enhancement cooling mechanism of the unsteady film cooling, the large eddy simulation (LES) was used to numerically simulate the unsteady film cooling in circular hole and study the eddy structure and film cooling efficiency under four different pulsation frequencies of 0, 0.2, 0.3 and 0.5. Then the dynamic modal decomposition (DMD) was used to analyze the calculated results and study the coupling relationship between the flow field and heat transfer. Results show that the pulsation frequency has great influence on unsteady jet film cooling efficiency. The film cooling efficiency at St=02 is similar to that of steady state jet; the film cooling efficiency at St=0.3 is higher than that of the steady state jet, while the efficiency at St=0.5 is much lower than that of the steady state jet. The unsteady jet at St=0.3 can inhibit the generation of the downstream hairpin vortex and promote the fragmentation of the hairpin vortex, so that the film cooling efficiency can be enhanced; the pulsating jet causes a lot of secondary vortex structures, which promote the mixing of the jet and the main stream in the flow direction, but inhibit the mixing of the jet and the main stream in the spanwise direction.

TK221

国家自然科学基金(12172242)；山西省面上基金(202203021211122)；机械制造系统工程国家重点实验室课题(sklms2021015）