Conjugate heat transfer in spatial laminar-turbulent transitional channel flow

Abstract

In the present work the simulation of Conjugate Heat Transfer (CHT) in a spatial laminar-turbulent transitional channel flow for Re = 3420 and Pr = 0.71 is carried out using Direct Numerical Simulation. This is achieved employing the Incompact3d code to solve the fluid field, a 3D module to solve the conduction equation in the solid field and the stability analysis to promote the transition. Present results are compared with those obtained employing the standard Uniform Heat Flux (UHF) boundary condition and with fully developed turbulent reference values. It is found that the temperature and first-order parameters are not significantly influenced by the modeling of solid walls. However, the modeling of solid walls in the heat transfer process significantly affects the wall temperature variance all along the transition. We show that the use of UHF largely overestimates this quantity respect to CHT. For both boundary conditions, and all along the transition, temperature fluctuations at the fluid boundary show a strong similarity with the dynamics of the velocity field in the viscous layer. Finally, fluctuations within the solid walls are also computed. These data can be employed to improve turbulencemodeling in applications where fluctuating thermal stresses are a concern.