Abstract
Tangential oscillation of thermal stratification is a new finding in previous investigations on thermal-mixing pipe-flow at mixing tee. Due to this phenomenon, regular temperature changes can be created on the pipeline inner surface and lead to material damage caused by the degradation mechanism of thermal fatigue, which has been frequently reported as a reason for incidents on piping systems of nuclear power plants. Currently, numerical simulations have been performed to reconstruct this phenomenon by using LES (Large-Eddy Simulation) methods. The tangential oscillation can be recognized from the animation of spatial temperature distributions but is still difficult to present in writing form.
In this work, principal component analysis (PCA) has been applied to identify and analyze the tangential oscillation of thermal stratification. Time-dependent temperature data in the vertical cross-sections of stratified pipe-flow has been extracted from the previous LES calculation. The characteristics of the spatial temperature distributions has been estimated with the PCA method. The results show the angular shift of the temperature distribution and its periodical change with the physical time in the simulation. It proves that the PCA method is effective in presenting the tangential oscillation of thermal stratification and can be applied in the further investigation of this phenomenon.
