Large Eddy Simulation of Turbulent Flow in a T-Junction

Abstract

A large eddy simulation at the conditions of experiments by Vattenfall [1] was performed in order to investigate the phenomenon of turbulent mixing affecting the thermal fatigue in a T-junction. In the present LES based on the dynamic Vreman model, mean velocity, turbulence intensity, and Reynolds shear stress profiles show good agreement with those measured in the Vattenfall experiment. With the present LES results verified, the characteristics of vortical structures in terms of turbulent mixing resulting in thermal fatigue was investigated. The energy spectra are shown to have a dominant frequency of around St = 0.5 agreeing with the value reported in experiments. On the other hand, the dominant frequency near the wall is different from that reported at the centerline (St ∼ 1), meaning that the thermal fatigue may not result from the wake structure, and is affected by the vortical structures existing near the wall. This result is consistent with one stated by Muramatsu [2] that the frequency characteristics near the wall are closely associated with arched vortices. In addition, the present LES results are used to provide useful insights in predicting this kind of flow using RANS computations.

Acknowledgments

This work was supported by the Nuclear Research & Development Program of Nuclear Research and Development Program of the NRF (National Research Foundation of Korea) grant funded by the MEST (Ministry of Education, Science and Technology) of the Korean government (grant code: M20702040002-08M0204-00210).