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ON THE ACCURACY OF THE PRESSURE FLUCTUATIONS CALCULATED FROM AN LBM SIMULATION OF TURBULENT CHANNEL FLOW

Dustin J. Bespalko
Department of Mechanical and Materials Engineering Queen's University Kingston, Ontario, Canada K7L 3N6

Andrew Pollard
Department of Mechanical and Materials Engineering, Queen's University, Kingston, Ontario Canada K7L 3N6

Mesbah Uddin
Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, K7L 3N6, Canada; Department of Mechanical Engineering and Engineering Science The University of North Carolina at Charlotte Charlotte, North Carolina, USA 28223-0001

Аннотация

In this paper the pressure fluctuations from a simulation of turbulent channel flow computed with the D3Q19 athermal lattice Boltzmann method (LBM) are compared to those calculated by the spectral simulation of Moser et al. (1999). Special care was taken to ensure that the computational domains used in each simulation were the same in order to eliminate the effect of the domain size on the turbulence statistics. It was found that the LBM over-predicts the variance of the pressure fluctuations by as much as 7%. A number of possible causes for this over-prediction were investigated, and it was concluded that the over-prediction is most likely caused by compressibility effects since the Mach number of the LBM simulation was 0.2 while the spectral simulation was incompressible. The compressibility of the LBM was examined further by comparing the LBM results to a fully-compressible discontinuous Galerkin simulation with the same Mach number. It was determined that, while the effect of the compressibility on the pressure fluctuations was similar, the density and temperature fluctuations were very different. This is because the D3Q19 LBM does not have enough degrees of freedom to allow the temperature to vary. For this reason, it is not recommended that this LBM be used for simulations in which the effect of compressibility is thought to be important.