Adaptive diffusive time-step in conjugate heat transfer interface conditions for thermal-barrier-coated applications

Abstract

Abstract High pressure turbines are subjected to high temperature flow exiting the combustion chamber. This paper presents a reliable method for a conjugate heat transfer (CHT) procedure using different interface treatments. Indeed, a coupled approach is used to properly capture the transient heat load variations at the interface and have a better estimation of the conduction within the solid. The numerical methods developed in this paper are derived from a 1D CHT model problem in which the thermal properties of each domain drive the numerical stability. Thus, from this model, two fundamental parameters are introduced: a “numerical” Biot number, B i ν , and an optimal coefficient. Even if the optimal coefficient is theoretically unconditionally stable, the stability zone is drastically reduced when the Biot number increases. In this paper, a unified approach applicable to a wide range of Biot numbers is proposed for the case of multiple materials involved in a coupling process. In order to properly estimate the transient variation, an adaptive diffusive time-step has been developed based on physical thermal properties. This time-step is able to capture the transient effects inside the thermal boundary layer. Coupled results demonstrate a fast and steady converging behavior. Special attention is given to properly define the variable relaxation parameter used in this algorithm. The gain in using an adaptive optimal coefficient is discussed.