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Abstract: Numerical investigation has been performed for flows past an inclined square cylinder in the range of Re≤300 to elucidate the characteristics of the laminar three-dimensional wake behind the cylinder depending upon Reynolds number and angle of incidence (θ). An immersed boundary method was used for implementation of the cylinder on a Cartesian grid system. Both Floquet stability analysis and full three-dimensional simulation were employed to detect the onset of the secondary instability leading to three-dimensional flow, and to provide quantitative flow data. It was revealed that mode A becomes more unstable for “symmetric” flow configuration, while mode C is dominant for asymmetric flows in the range of 10°≤θ≤25°. The most unstable three-dimensional modes predicted by the Floquet stability analysis were well confirmed by the full 3D simulations which were conducted at Re=150, 200, 250, and 300, with varying angle of incidence. The full 3D simulations also provided the key flow characteristics such as mean flow-induced force/moment coefficients and Strouhal number of vortex shedding. It was seen that they are sensitive to slight inclination of the square cylinder, and the Re effects are insignificant except for mean lift coefficient. Vortical structures in the wake, taken from the results of the Floquet stability analysis and the full 3D simulations, respectively, were visualized by Q-contours, revealing good agreement between the two. [Copyright &y& Elsevier]

Detached Eddy Simulation (DES) has been used to investigate the effect of the Reynolds number on the wake of a high-speed train in the range from 5.2 ​× ​105 to 2.2 ​× ​107. Then, the characteristics of vortex structure, streamlines distribution, velocity characteristics, and pressure characteristics in the wake region of the high-speed train at five Reynolds numbers are studied. The results show that with the increase of the Reynolds number, some small-scale vortices emerge in the wake region of the high-speed train, which increases the complexity of the wake vortex structure, but the large-scale vortex structure has not changed significantly. The separation lines and vortices distributed on the train surface, and the characteristics of the pressure distribution in the wake region do not change considerably at different Reynolds numbers. The frequency of the vortex shedding from the train based on Strouhal number is approximately a constant at five Reynolds numbers, and the phenomenon and mechanism of the flow in the wake region are almost the same within the range of Reynolds number selected in this study. With the increase of the Reynolds number, the fluctuation degree of the velocity and pressure, and the vorticity in the wake region increase substantially. • DES has been used to investigate the wake characteristics of a high-speed train at five Reynolds numbers. • With the increase of Re , small-scale vortices emerge, but the large-scale vortex structure has not changed significantly. • The separation lines and vortices distributed on the train surface do not change considerably at different Re. • The phenomenon and mechanism of the flow in wake region is almost same within the range of Re from 5.2 × 105 to 2.2 × 107. • With the increase of Re , the fluctuation degree of velocity and pressure, and the vorticity in the wake region increase. [ABSTRACT FROM AUTHOR]