Large eddy simulation of film cooling flow from round and trenched holes

• Published in: International journal of heat and mass transfer 2019-12, Vol.144, p.118631, Article 118631
• Main Authors: Hou, Rui, Wen, Fengbo, Luo, Yuxi, Tang, Xiaolei, Wang, Songtao
• Format: Article
• Language: English
• Subjects: Blowing; Computational fluid dynamics; Computer simulation; Cooling; Cooling effects; Cooling flows (astrophysics); Film cooling; Fluid flow; Horseshoe vortices; Large eddy simulation; Plates (structural members); Variation; Vortices
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2019.118631

•LES model is used to simulate trenched-hole film cooling.•The differences of vortex structures for round and trenched holes are clarified.•The origination of downstream CVP is summarized for round and trenched holes.•Flow fields at different blowing ratios are obtained for trenched holes. The thermal and flow fields of round and trenched holes in the flat-plate model are investigated using large eddy simulation (LES) after validated against the experimental results. The focus is on understanding the influence of the trenched hole on downstream vortex structures at blowing ratios M = 0.5 and 1.0, which may benefit its effective application in cooling design. At M = 1.0, the transverse trench increases turbulent fluctuations and augments the complexity of vortex structures. Dynamic mode decomposition analysis is employed to extract the primary vortex structures. The dominant vortices of the trenched hole include K-H vortices and hairpin-like vortices near the centerline. This series of hairpin-like vortices present a larger spatial size than the hairpin vortex downstream of the round hole. Besides, they correspond to the downstream counter-rotating vortex pair in the mean flow field, which is detrimental to the local film cooling effectiveness. At lower blowing ratio M = 0.5, the previous spatially large hairpin-like vortices are replaced by a smaller one which alternatively appears on both sides of the centerline. In the mean flow field, each branch of the CVP is caught between two anti-CVPs. The suppression of adjacent vortices guarantees the attachment of coolant to the surface.