Quantification of the discontinuity of the temperature variance dissipation rate: Wall-resolved les of turbulent channel flow with conjugate heat transfer

Conjugate heat transfer represents the actual thermal coupling between a fluid and a solid part. It is of prime importance in nuclear industrial applications where fluctuating thermal stresses are a concern, e.g. in case of a severe emergency cooling (Pressurized Thermal Shock) or long-term ageing of materials such as thermal striping occurring in T-junctions. For such complex applications, numerical investigations often rely on Reynolds Averaged Navier Stokes (RANS) or wall-modelled Large Eddy Simulation (LES) approaches. RANS models for conjugate heat transfer are relatively recent (Craft et al., [1]). Using Direct Numerical Simulation (DNS), the authors and coworkers have recently established that the dissipation rate (ε_θ) associated with the halved temperature variance (θ’²/2) is discontinuous at the fluid-solid interface in case of conjugate heat transfer (Flageul et al., [2-3]). Actually, there is currently no coupled RANS model for conjugate heat transfer taking this discontinuity into account. As a result, from an industrial perspective, LES remains the best option for thermal fatigue prediction but needs refinement at the wall, which makes it very expensive if not unaffordable, at high Reynolds numbers. In this paper, we will assess the ability of wall-resolved LES to estimate this discontinuity of ε_θ on channel flows ( = 7060, = 0.71) using Code_Saturne, EDF in-house and open-source CFD software.