On the Need for Higher Order Interpolation with Overset Grid Methods

Overset methods, by overlapping several grids, allow large and arbitrary motion of bodies. First developed for the aerospace industry (Benek et al., 1985), it is now used for a wider range of applications like maritime ones (Carrica et al., 2013). At the fringes of each grid, the coupling is done by interpolating field variables. This interpolation step is key in any overset computations since the choice of the interpolation scheme directly influences the accuracy of the solution and the performance. Most overset implementations done for unstructured CFD codes uses 1st or at most 2nd order interpolation schemes (Gatin et al., 2018, Völkner et al., 2017, Chandar et al., 2018) but higher order interpolation schemes (3rd or 4th) are not often studied (Chandar, 2019). This paper evaluates the use of higher order (higher than 2nd order) interpolation schemes for the overset method by comparing the accuracy of different interpolation schemes on a Poiseuille flow test case, no performance study is however conducted here. The overset implementation used in this study is a coupling between the CFD solver ReFRESCO and the overset library Suggar++ (Noack and Boger, 2009). The paper is organised as follows: section 2 presents the overset approach and the different interpolation schemes used in this study. Section 3 discusses the robustness of Least Squares interpolation scheme. Section 4 describes the test cases ran for the study as well as the computational setup. Results are presented in section 5 and finally concluding remarks are given in section 6.