Comparing Methods of Deforming and Overlapping Meshes to Simulate the Motion of Bodies on a Free Surface

Two methods of accounting for the motion of the bodies—the deforming mesh method and the method of overlapping meshes (or overset mesh method)—are compared using problems with floating bodies, which are typical for the shipbuilding industry. Three problems are considered: oscillation of the cylinder on the water surface, movement of the box under the influence of waves, and heaving and pitching of the ship model in head waves. Numerical computations are carried out in the LOGOS software package, the simulation methodology used is based on the solution of a system of Reynolds-averaged Navier‒Stokes equations, and the Volume of fluid (VOF) method to take into account the free surface. In all problems, the characteristics of the movement of bodies are evaluated; the resistance force of the ship model is also determined in the third problem; control values obtained using two methods of accounting for moving bodies are compared with the available experimental data. The results of numerical simulation have shown that both methods predict body movement parameters well; the accuracy in determining the resistance force in the task of streamlining the ship’s hull is also comparable: the difference between the maximum deviations of the resistance coefficient in the computations with deformation and overlapping computation meshes is 0.5%. In the case of computations of the three-dimensional problem, the time spent when using the mesh-deformation method turned out to be 10% more; therefore, the method of overlapping meshes can be considered more optimal when solving such shipbuilding tasks as self-propelled tests and streamlining the ship’s hull with and without wind and wave loads.