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The resolution and efficiency of the finite-difference lattice Boltzmann method (FDLBM) is improved to deal with wall-bounded turbulence, which is characterized by the strong shear and anisotropy. FDLBM puts the merit of LBM, which is the explicit and non-iterative algorithm, into practice on the body-fitted coordinate in the conventional solvers based on Navier-Stokes equation of motion. Thus the performance of FDLBM is mostly affected by the finite-difference scheme for the advection terms of LBM, which has to be an upwind one from a stand point of numerical stability. Particularly in this study, the influences of the the order of accuracy and upwind method are assessed by the direct numerical simulation of fully-developed turbulent flow in a plane channel. We introduce a discretization method with numerical flux similar to the finite-volume method, and a nonlinear scheme which localizes the effect of the numerical diffusion. Our method successfully reproduced the mean velocity and turbulence statistics in comparison with standard database. We confirmed that the nonlinear scheme improved the resolution. Increase of reproducibility with the higher order scheme surpassed increment of its computational cost. The 7th-order scheme, for example, provided a comparable result to that by the 3rd-order scheme using 4 times finer grid, though the calculation time increases just 20 % at the same resolution. This higher-order nonlinear scheme proposed in this study, by reducing the requirement of computational resources, can extend the applicability of LBM for DNS and LES of turbulent flows.

We studied sound generated by a diagonally arranged fin in a uniform flow. We set 2-dimensional computational model which neglected spanwise effect of the fins, and performed direct simulation of aerodynamic sound for two types of fins whose difference is the width of the back section with the finite-difference lattice Boltzmann method. Conditions of numerical results in which strong resonance occurred consisted with experimental results and Parker type resonance appeared. When the resonance occurred, the frequency of Kármán vortex shedding from the trailing edges of the fins agreed with the natural frequency of air columns which correspond the space between neighbouring fins. The phase differences between the neighbouring columns were completely “anti-phase” and the same was true for the vortex shedding. We also show the temporal and spacial variations in far sound field which are caused by the asymmetric arrangement of the fins. We also noted that the radiations of sounds of two different frequency existed for high speed flow range.