The proposed research aims to develop and apply advanced computational methods of handling the near-wall region of the fluid flow within the Large Eddy Simulation technique, which is increasingly being adopted by industrial researchers in safety studies of nuclear energy plants and other applications. Despite the fact that Large Eddy Simulation (LES) offers an extremely accurate resolution of free unbounded fluid flows, the near-wall regions that drastically affect heat transfer rates impose a great challenge for LES, due to the very high computational cost of resolving the small turbulent eddies which occur there. Therefore in the vicinity of walls LES often employs wall functions, which are used to evaluate the resistance of the near-wall viscous layer to heat and mass transfer. Unfortunately, the conventional wall functions, which are employed in LES, have considerable limitations in terms of accuracy due to inherent assumptions that are built into them.
New wall functions (referred to as AWF), have recently been developed by applicant for use within Reynolds-averaged simulations, and these have proved to be widely applicable since they are based on the analytical solution of Reynolds equations and are not dependent on the prescribed velocity profiles. This allows the AWF to account for many important physical effects that take place at near-wall flows. To date this strategy has been developed and applied to a significant range of flows within a Reynolds Averaged Navier-Stokes (RANS) framework. The main objective of the research project will be to extend and validate the AWF treatment within an LES methodology. Given the improved physics embedded within the AWF, this will equip academic and industrial researchers with a powerful and affordable tool in resolving heat and fluid flow problems.
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