Recently, Deng et al. have developed Weighted Compact Nonlinear Scheme, WCNS, that achieves high order spatial accuracy with less stencils. Because WCNS shows monotone shock capturing capability, we suppose the scheme is able to apply Implicit LES. In this study, Implicit LES of the Burgers turbulence using WCNS is carried out to obtain energy spectrum. It is found that the energy spectrum of Implicit LES using WCNS is in fair agreement with DNS whereas the result of LES shows non-physical bump in the highest wavenumber region.

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In this paper, advanced drag prediction methods based on the momentum conservation theorem were applied to CFD computational results. These methods can decompose total drag into drag components such as wave, profile and induced drag as well as spurious drag which is due to the effect of numerical diffusions. The computational results showed that the advanced methods had the good capability of the drag prediction and meaningful drag decomposition. It was also confirmed that the predicted physical drag values were almost independent of the mesh resolution. Moreover, the meaningful investigation of the drag reduction mechanisms was conducted by the use of these methods.

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One of the major concerns for diesel engines is that the exhaust gas has more particulate matters (PM) including soot. As one of the key technologies, a diesel particulate filter (DPF) has been developed to reduce PM in the after-treatment of exhaust gas. In this study, we simulate soot deposition in simplified porous media by the Lattice Boltzmann method. Results show that the flow pattern is largely changed when the soot is accumulated. Resultantly, the pressure drop is largely increased, and the surface area where the soot can be attached is expanded. When the soot concentration is higher at the inlet, the accumulated soot is expectedly increased.

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Spatial direct numerical simulations are performed to study the formation and development of three-dimensional structures in a compressible flat plate boundary layer, where the freestream Mach number is 0.5 and the Reynolds number at the inlet based on the displacement thickness 1000. A pair of neutral/stable oblique modes and a TS wave are superimposed on the laminar profile at the inlet plane of the boundary layer computational box. The magnitudes of the TS and oblique waves are chosen to be 1% of the freestream velocity, respectively. After saturation of the T-S wave, the growth of the oblique modes produces peak-valley splitting downstream and hairpin vortices (hairpin packets) on the low speed streak are observed further downstream. The oblique subharmonic mode leads to sooner transition to turbulence downstream in the boundary layer. Numerical results show the evolution of hairpin vortices into a large-scale structure, in which fine-scale vortical structures with low-/high-speed streaks develop near the wall.

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