A versatile immersed boundary method for high-fidelity simulation of Conjugate Heat Transfer

Abstract

A numerical strategy based on an immersed boundary method (IBM) is presented for performing high-fidelity simulation of thermal hydraulics while including Conjugate Heat Transfer (CHT). The well documented pipe flow is considered which, despite its academic nature, can be seen as a prototype of complex geometry in the sense that the computational mesh, only regular and Cartesian, is not in any way designed to fit the wall. An original strategy is proposed to impose Neumann boundary conditions in this generic situation where the wall geometry is disconnected from the mesh organization. As a first validation step, the technique is used in the context of heat transfer in pipe flow with isoflux conditions (IF). The actual order of accuracy is assessed in laminar regime and then direct numerical simulation (DNS) results are compared to turbulent data of reference, including first- and second-order one-point statistics, as well as budgets of temperature variance for a Reynolds number Re=5300 and two Prandtl numbers Pr=0.025,0.71. The technique is then used to develop a versatile methodology for CHT simulations, where the coupling between fluid and solid thermal solution is performed by an immersed boundary technique that translates the information from the normal and tangential surface directions into the Cartesian grid directions. Consistent results are presented in laminar and turbulent regimes, through the check of the accuracy order for the former and the analysis of turbulent statistics for the latter, including the assessment of the discontinuity of the temperature variance dissipation across the fluid-solid interface.