A new approach for handling body motion by combining a grid deformation method and an overset grids technique. (1st October 2020)

• Record Type: Journal Article
• Authors: Ohashi, Kunihide
• Is Part Of: Ocean engineering. Volume 213(2020)
• Publication Date: 2020-10-01
• Subjects: Grid deformation -- Overset grids method -- RANS; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2020.107836
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: A new approach for handling body motion by combining the grid deformation and the overset grids methods is proposed. The present approach can completely avoid the computational load of the dynamic overset grids method. The regions where the overset relations are composed move with the body motion, maintaining the geometrical relation to determine for the weight of the overset interpolation. The present approach is applied to the cases with 2D single and multiple cylinders with motion. The scaled-Jacobian before and after the grid deformation is examined. The values of the scaled-Jacobian maintain at least 0.35 after the grid deformation, and the velocity and vorticity contour lines are smoothly connected on the computational grids, thus, the effectiveness of the present approach is revealed. Additionally, the verification using the computational grids with three different resolutions is performed on the case with the single cylinder. The present method which combines the grid deformation and overset grids methods succeeds to reduce the CPU time approximately from 40% to 65% of the time using the dynamic overset grids method. Next, the present approach is applied to the computation of the flow around a ship with an appendage, including ship motion in regular head waves with a high Reynolds number condition. The present method reproduces the impact pressure when points on the hull surface enter the water and the difference in the peak values of the pressure at different positions. The present method succeeds in reducing the CPU time to 40% of the case using the dynamic overset grids method at the case with the ship motions in the regular waves. Highlights: A new approach handling body motions is developed. Present approach can completely avoid the computational load due to the dynamic overset grids method. The body motions are predicted by the present approach combining the grid deformation and the overset grids methods.