Large eddy simulations of flow past an inclined circular cylinder: Insights into the three-dimensional effect

The flow past an inclined cylinder is simulated using large eddy simulations to study the three-dimensional wake flow effects on the forces on the cylinder at Re = 3900. Four inclination angles of alpha = 0 degrees, 30 degrees, 45 degrees, and 60 degrees are considered. The validity of the independence principle (IP) at the four investigated angles is examined. The results suggest that IP can predict the vortex shedding frequency at 0 degrees <= alpha <= 60 degrees, while it fails to predict the drag, lift, and pressure coefficients variations because the three-dimensional effect is neglected for IP. A comprehensive analysis is performed to provide insights into the three-dimensional effects on the drag and lift forces caused by alpha. The flow velocities, the Reynolds stress, and the spanwise characteristic length of the flow structures are discussed in detail. It is found that the recirculation length reaches its maximum at alpha = 45 degrees, which results in the smallest drag coefficient and lift force amplitudes. The spanwise characteristic lengths of the vortices are similar for all cases, while spanwise traveling patterns are observed only for alpha > 0 degrees. A force partitioning analysis is performed to quantify the correlations between the forces and the spanwise and cross-spanwise vortices. It reveals that for alpha = 30 degrees, the drag force becomes dominated by the cross-spanwise vorticity. With the increasing alpha, the dominant contribution gradually changes from the cross-spanwise to the spanwise vorticity, and the cross-spanwise vorticity contribution to the drag force further becomes negative at alpha = 60 degrees.