Numerical method for simulation of fluid flow and heat transfer in geometrically disturbed rod bundles

This paper describes briefly the computational algorithm that includes proc edures to obtain finite-difference form of governing convection-diffusion e quations, to generate an orthogonal mesh system for complex regions and to solve the finite-difference equation system, and several results of numeric al simulation in comparison with experiment. The Reynolds and energy conservation equations for steady-state fully devel oped turbulent incompressible hows are discretized by the Efficient Finite Difference (EFD) scheme. Here secondary flow components are neglected. In t he averaged energy conservation equation, anisotropic turbulent conductivit y coefficients are employed based on the axial velocity distribution. An or thogonal mesh generation system has been developed that allows us to model the rod bundle geometry by assembling elementary mesh components generated for every typical sub-domain inside the flow channels. This procedure has b een made efficient with a help of object-oriented programming techniques. B y solving the derived equations on the boundary-fitted coordinates, good co mparisons between calculation and measurement are presented in general for detailed distributions of the local shear stress, axial velocity and wall t emperature in a hexagonal rod bundle in the presence of a dislocated rod. D iscussion is also made on a discrepancy of the calculated wall shear stress from the experimental data near the narrowest gap position in this "geomet rically disturbed" region.