Experimental modification of the internal solitary wave force exerted on a horizontal transverse cylinder due to wave-flow and vortex shedding

Based on the experimental measurements of the ISW force on a horizontal transverse cylinder in a gravitationally stratified fluid flume, the modification formulas of the empirical coefficients in the ISW force calculations are proposed by use of parameter optimization methods such as the least square method and wavelet transform. The time series and spatial characteristics of various forces exerted on a horizontal transverse cylinder by an ISW, including the wave force, the reduced gravity and the vortex shedding force, were obtained, and their description precision was improved. It is shown that those forces exerted on a horizontal transverse cylinder involve the empirical coefficients, including the inertial force coefficient Cm and the drag force coefficient Cd in the Morison formula, and the vortex shedding lift coefficient Cl in virtue of the vortex shedding frequency omega s, in which the fitting modification formulae of the empirical coefficients and vortex shedding frequency with the Reynolds number Re (1000-3000) by use of experimental data are approximated to the exponential function and the polynomial function, respectively. The calculation accuracy of the ISW force with modified coefficients is significantly improved compared with those forces having constant coefficients, in which the average relative errors of the horizontal force and the vertical vortex shedding lift with modifications are reduced by approxi-mately 71% and 46%, respectively. In addition, some characteristic descriptions closer to the actual processes are obtained, including the time series variation of various forces, its contribution to the horizontal pushing or pulling force, and to the vertical downward drag or the 'double peak' force, and to its spatial variation with varying cylinder submerged depth, which further improves the understanding of the temporal and spatial fea-tures of the ISW acting on structural objects.

Automated summary

Based on experimental measurements, the modification formulas of empirical coefficients in ISW force calculations are proposed using parameter optimization methods. Various forces exerted on a horizontal transverse cylinder by an ISW and their description precision are obtained. The calculation accuracy of the ISW force is significantly improved using modified coefficients compared with constant coefficients, and some characteristic descriptions closer to the actual processes are achieved, further improving the understanding of the temporal and spatial features of the ISW acting on structural objects.