Numerical Analysis of Free Surface Flow over a Submerged Rectangular Bridge Deck

This study integrates a large eddy simulation model to investigate the effect of a submerged rectangular cylinder on the hydrodynamics of free surface flows. The simulation results are validated by the results of flume experiments. Then the numerical model is utilized to examine the influences of Reynolds number, Froude number, and blockage ratio on the flow field and the force coefficients of the deck. The simulation results reveal that the drag coefficient is dependent on the deck’s Froude number and blockage ratio of the bridge deck, rather than the Reynolds number. For both subcritical and transcritical flows, the drag coefficient increases as the blockage ratio increases. However, due to the wave-induced drag, the drag coefficient of the cylinder in transcritical flows is greater than that in subcritical flows with the same blockage ratio. On the other hand, the lift coefficient is a function of the submergence ratio and the deck’s Froude number. The separation shear flow on the upper side of the cylinder is constrained by the water surface when the submergence ratio h*<2.0, and resulting in an asymmetric pressure distribution on the upper and lower sides of the deck, which subsequently generates a downward force on the bridge deck.