In order to deeply understand the influence of porous media parameters on the cylindrical flow and its mechanism, based on the microscopic pore scale of porous media, the flow around the cylinder covered with a Reynolds number of 150 is numerically simulated based on the microscopic pore scale of the porous medium, and the flow characteristics of the cylinder under different porosity and different structures are analyzed. After the cylinder is covered with porous media, the original fluid flow characteristics of the cylinder are changed, and the wake stability characteristics increase first and then decrease with the porosity after the structure of the porous medium is changed. However, with the complexity of the structure, the delay degree of the cylindrical tail shedding vortex decreases, while the marginalization degree of the tail vortex is basically the same, and the fluid flowing out of the porous medium will re-enter the porous medium, so that the vortex adheres to the surface of the porous medium. Under the same structure, when the porosity is 0.992, the periodic shedding delay and marginalization of the tail vortex of the porous medium are the largest. Due to the existence of small-scale flow in the porous medium, multiple separation and shear flow occur when passing through the small cylinder. When the fluid flows out more in the tail of the porous medium, the resulting shear flow forms a thick shear layer at the trailing edge of the porous medium, resulting in the elongation of the vortex detachment of the cylindrical tail. As the structure becomes more complex, the fluid flowing into the porous medium will flow out close to the tail of the porous medium, increasing the thickness of the shear layer on the upper and lower surfaces of the porous medium. The flow behavior of the fluid in the pore scale of porous media plays a key role in the influence of cylindrical flow, and this study can provide theoretical guidance for the effective control of flow and noise in porous media in engineering.

Based on the LBM-LES method, aeroacoustic of the NACA0012 airfoil at medium Reynolds numbers was directly simulated. The flow field and aeroacoustic field under acoustic vortex interaction were obtained, and the hydrodynamic characteristics in the shear layer were analyzed. The results show that in the shear layer near the airfoil surface, the T-S wave turns into the K-H instability after the flow separation, and the K-H instability plays an important role in the growth of the disturbance. Turbulence intensity in the separation bubble increases significantly until transition to turbulence, but the turbulence intensity decreases again after the flow reattachment. The large-scale vortex structure of 750 Hz is formed and developed into a stable structure inside the separation bubble, while the vortex structures corresponding to the 2nd and 3rd harmonics are formed after the transition, and developed into stable structures outside the separation bubble. It suggests that the generation mechanism of the 2nd and 3rd harmonic tonal noise is different from that of the 750 Hz fundamental one.