Numerical study on compressible flow arounda circular cylinder in proximity to the wall

In the present study, the compressible flow around a circular cylinder in proximity to the wall is investigated. By using direct numerical simulation approach, the flow behavior with the Reynolds number 100 and the Mach numbers 0.1 - 0.6 are examined. The numerical result shows that the compressibility effect would enhance the flow stability, whereas the strength of shedding vortices, the shedding frequency, and the fluctuation of aerodynamic force are reduced by increasing the Mach number. Through the examination of signed enstrophy and shear steepness in the cylinder boundary layer, it is found that the vortices shedding from the free-stream side and the wall side are concurrently inhibited by the wall when the cylinder is fully embedded in the wall boundary layer, and the strength of the wall-side vortices is relatively weaker. This imbalance would be intensified when the cylinder gets closer to the wall, and thus a reduction in the shedding frequency is produced. Based on this effect of wall proximity on frequency, the flow behavior is divided into three regimes, i.e., high-frequency, low-frequency, and completely suppression regimes. Finally, from the observation of mean forces, the trend of mean drag and lift force coefficients with regard to the Mach number and gap ratio is described as the scaling behavior in terms of two piecewise functions.

Automated summary

This study investigates the compressible flow around a circular cylinder near a wall using direct numerical simulation. The results show that compressibility enhances flow stability but reduces the strength, shedding frequency, and fluctuation of shedding vortices with increasing Mach number. The wall inhibits vortices shedding from both the free-stream side and the wall side, with the wall-side vortices being weaker. This imbalance is intensified as the cylinder approaches the wall, leading to a decrease in shedding frequency. Based on the effect of wall proximity on frequency, the flow behavior is divided into three regimes: high-frequency, low-frequency, and completely suppression regimes. The trend of mean drag and lift force coefficients with Mach number and gap ratio is described as a scaling behavior with two piecewise functions.