Tsunami-like flow induced forces on the structure: Dependence of the hydrodynamic force coefficients on Froude number and flow channel width in quasi-steady flow phase

During the tsunami landfall, the structures near the coast perform like a wall of certain obstruction, b/W (b = structure width, W = available flow channel width) to the incoming flow due to abutting adjacent structures. In the previous paper (Harish et al., 2021), the generalized semi-analytical equation for the horizontal forces using the free flow parameter during the quasi-steady flow is provided. The emphasis was on understanding flow characteristics at the structure front. However, the quantitative dependence of the hydrodynamic drag force coefficient (Cd) on the influence of b/W and Froude number (Fr) are not investigated in detail. In the present paper, from the experimental analysis, in addition to show Cd as a function of b/W and Fr, the influence of Fr in Cd variation for various b/W is brought out. Based on this, a generalized empirical equation for Cd is proposed. The experimental analysis on the vertical force shows that the hydrodynamic uplift force (Fu) can be explicitly estimated based on the average water depth at the structure front and backside from the buoyancy force equation (Fub). Further, Fu/Fub is found to be independent of Fr and b/W, unlike the horizontal force. From the practical design perspective, these two explicit expressions are essential, and the physical process involved in obtaining this expression has been discussed in this paper.