Large Eddy Simulation of Discharge Coefficient and In-Hole Unsteady Flow Field in Laidback Fan-Shaped Hole Under Internal Crossflow Conditions

Abstract Under complex upstream flow conditions, accompanied by modifications in the flow separation and resistance characteristics inside the holes, the heat transfer characteristics will be changed accordingly. To further understand this flow phenomenon, high-resolution simulations are necessary to reveal the pivotal multidimensional vortices within the hole. In the current study, with the aid of large eddy simulations (LES), the discharge coefficient and unsteady flow field within laidback fan-shaped film holes are being investigated under four representative internal crossflow directions. The results indicate that flow separation and the strong shear interactions between high-velocity and low-velocity fluids within the hole are key contributors to flow instability. Different crossflow directions induce distinct flow trajectories, resulting in variations in the extent of flow separation and shifts in the position of the shear layer. Moreover, due to crossflow effects at the hole inlet, the dominant vortex structures inside the hole vary under different crossflow conditions. These vortices form within the cylindrical section, stretch and distort upon entering the expansion section, and eventually dissipate into disordered small-scale vortices. To the best of our knowledge, this is one of the few studies using the LES method to elucidate the underlying correlation between crossflow and its associated effects on the resistance characteristics inside the holes. The aforementioned findings will provide valuable insights to reach accurate predictions of the discharge coefficient of film holes.