Forces On Bodies Exerted By Internal Waves In Stratified Fluids.

In recent years, the studies on internal waves generated by the moving bodies and drag increment caused by the stratification, and of forces and loading of cylinders exerted by the internal waves are paid considerable attention by physical, engineering and military oceanographer. In the present paper, the significant problems described above are investigated in full length.First, the resistance (or drag) of a horizontal moving body in a stratified fluid is studied, and a theory on the drag is given for different moving velocity (or Froude number) of ellipsoids with different ratios of length to diameter (RLD) in a uniformly stratified fluid. Asymptotic curves of the wave-drag are found theoretically. A towed experiment is carried out in the 3D internal wave and stratified flow tank in Physical Oceanography Laboratory (POL) in OUC. Horizontal drags of models are measured by the forced measured system, and then the curves on the drag-increments are given by means of an averaged method. And the experimental and theoretical result is in good agreement. From the experimental results, it is shown that drag-coefficients increase with the increase of Froude number at its small end, and decrease with the increase of Froude number at its large end and approach to zero as Froude number approaches to infinity. There exists a maximum drag-coefficient in the drag curves corresponding to a critical Froude number. And the critical Froude number increases with increasing of RLD.