Analysis of the performance of flow field modes around double round-ended piers

Because of the interaction between the flow and piers, the velocity of coherent turbulent flow around tandem double round-ended piers becomes complicated, proposing a threat to the navigation in the bridge area. This paper numerically investigates the flow velocity performance around tandem double round-ended piers by performing a flow field model and moving ship model. Flow velocity performance was analyzed under different inflow velocities in the four flow modes: single mode, attachment mode, transitional vortex detachment mode (TVDM), and independent vortex detachment mode. The yaw moment was employed to verify the performance from the perspective of the force on the ship. In each mode, the flow velocity in x axis ( v_x ) and y axis ( v_y ) behind the downstream pier are similar, the difference mainly occurs between the two piers. In TVDM, the spacing ratio (L/D = 6) is close to the critical spacing ratio (L/D)c which is significantly affected by the inflow velocity. Under high inflow velocity, v_x and v_y are greater, K P and critical spacing ratio are smaller, and the formation of the Karman vortex street is closer to the pier. Verification of flow velocity performance by yaw moment has high reliability. The extreme values of yaw moment mostly appear in the sections where v_y increases and v_x appears to be negative. The research on the flow velocity around the piers in various modes provides a reference in studying on turbulence width and improving navigation safety in the bridge area.