Investigation of flow over an inclination pile under a Reynolds number of 3900 by numerical simulation

Flow over an inclination pile was studied numerically by solving the Navier-Stokes equations with large eddy simulation closure under a Reynolds number of 3900, and the inclination angles were in the range of -45 degrees <= theta <= 45 degrees. First, flow over a finite-length vertical pile with symmetric boundary conditions at both the upper and lower boundaries is used for verification, and the results are in good agreement with the previous results. Then, the lower boundary is set as a no-slip wall to simulate a rigid seabed, and 19 different inclination angles are numerically simulated to investigate the effects of the rigid seabed on the hydrodynamic characteristics and the wake structure of the cylindrical wake with different inclination angles. It is found that there is a significant difference between the forces on the piles, which were inclined forward and backward due to the end boundary conditions. When the pile is inclined forward, the force on the pile and the frequency of vortex shedding are lower than that of a vertical pile, which is more conducive to the stability of the structure. When the pile is inclined backward, the lower sidewall induces a strong spiral upward flow of the fluid at the lower end around the pile, which leads to the shedding of the wake vortex at a very close position to the pile. The return zone tightening phenomenon occurs at inclination angles greater than 25 degrees backward, and this phenomenon leads to a sharp increase in the forces on the pile. Backward inclination angles greater than 30 degrees are extremely unfavorable for structural forces.