NUMERICAL IMPLEMENTATION OF A 3-D THERMAL-HYDRAULIC MODEL USING THE IMMERSED BOUNDARY METHOD IN THE "KORSAR/CFD" CODE
Yu. V. Yudov, S. S. Chepilko, I. G. Danilov
VANT. Ser.: Mat. Mod. Fiz. Proc 2018. Вып.4. С. 46-56.
A numerical implementation of a CFD module based on the immersed boundary method included in the KORSAR/CFD code using the semi-implicit scheme is described. The KORSAR/CFD code has been developed from the KORSAR/GP thermal-hydraulic system code certified by the ROSTECHNADZOR (Federal Environmental, Industrial and Nuclear Supervision Service of Russia) in 2009 for the numerical safety analysis of VVER reactors. The CFD module is intended for representing three-dimensional effects in the reactor lower plenum and used in spatial simulations of coupled thermal-hydraulic (in the sub-channel analysis approach) and neutronic processes in the reactor core during asymmetrical loop operation. The module is based on the immersed boundary method and Cartesian cut cell approach. To improve the numerical scheme stability, small cut-cells are merged with appropriate large neighboring cells. The diffusion and convection terms in conservation equations are approximated on the collocated grid with the second order accuracy using the central difference scheme and the bounded continuously differentiable SDPUS-C1 scheme, respectively. The time integration of the conservation equations is implicitly performed by the second-order Kim-Choi scheme. The Poisson equation for pressure is solved with the geometric multigrid method. Results of testing the method on the Karman vortex street problem, where a uniform laminar stream flows over a circular cylinder, are presented. Keywords: CFD-module, immersed boundary method, multigrid method, Karman vortex street.
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