numerical analysis of film cooling flow dynamics and thermodynamics for perfect and imperfect cooling holes

Film cooling protects high-temperature components and generates complex vortex structures through the interaction between the mainstream flow and the injected coolant. additionally, the process of applying thermal barrier coatings introduces imperfect cooling holes. a numerical simulation study is conducted on two geometric configurations: inclined perfect and imperfect holes arranged in a single row on a flat plate to investigate the effects of flow field vortex structures and hole imperfections. the k-epsilon turbulent model is employed to analyse the impact of varying blowing ratios and defect positions on flow field structure and cooling efficiency, with vortex dynamics providing explanatory insights. as the blowing ratio increases, the kidney vortex associated with the perfect holes progressively detaches from the wall, reducing film cooling efficiency. the kidney vortex originates from the shear interaction between the mainstream and the impinging jet, predominantly influenced by the vortex stretching component. imperfect holes influence the distribution state of the kidney vortex, with weakened roll-up phenomena observed at the it4 defect location. consequently, a noticeable enhancement in film cooling effectiveness is achieved near the proximal end of the hole.