The objective of this CFD study was to set up a methodology for the simulation of non-linear loads that appear during cargo/mother ship separation. To this end, a reference case was studied. The case consisted of the vertical motion of a cylindrical body tested in several towing tank tests.

High-quality unstructured meshes were generated using NUMECA's HEXPRESS™ software. The meshes ranged in size from 2.5 million cells to 7 million cells, depending on the type of calculation. Unsteady 3D Navier-Stokes and Euler calculations were run using the FINE™/Marine software suite. The motion of the cylinder was sinusoidal and several frequencies were computed. The free surface between air and water was computed by the solver.

Post-processing included the time evolution of 2D streamlines and hydrodynamic pressure inside several cutting planes through the cylinder, as well as the time evolution of the vertical force acting on the body. At the end, the results were compared to available experimental data.

The movie above presents the time evolution of the hydrodynamic pressure in a cutting plane.

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