Implementation and Verification of an Explicit Overset Grid Method

The design of modern ships capable of achieving complex manoeuvres and handle dynamic ocean environment requires a precise understanding of the flow around hulls, propellers and control surfaces. Computational fluid dynamics already allows complex simulations to be performed thanks to conventional mesh techniques. Moving, sliding and deforming grids allow for some dynamic simulation of moving bodies (Toxopeus and Bhawsinka, 2016). However, when considering more complex motions, e.g. 6 degrees of freedom of several bodies, the combination of previously mentioned conventional techniques is at its limit. The overset grid method (or overlapping grid method), allows large and arbitrary relative motion of bodies by overlapping several meshes. The overset method was first designed for the aerospace industry (Benek et al., 1985) but is now also used for maritime applications like ship motions (Carrica et al., 2013), submarine maneuvers (Martin et al., 2015), etc.

This paper presents an initial implementation of overset using the two libraries Suggar++ and DiRTlib to compute the domain connectivity information (DCI). Manufactured solutions and analytical solutions are used in order to quantitatively assess the discretisation errors.

The paper is organised as follows: section 2 presents the overset approach and its nomenclature. Details of the implementation are introduced in section 3. Section 4 describes the test cases used for the study. Results are presented in section 5 and conclusions are given in section 6.