Numerical study of turbulence related to vortex shedding structures of an oscillatory flow in thermoacoustic energy system

Abstract

Thermoacoustic system is a system that provides green technology for power and energy devices. Fluid dynamics of flow inside the system, that could influence system’s performance, is less understood. In this paper, turbulence in oscillatory flow condition inside thermoacoustic environment is studied numerically using a validated two-dimensional computational fluid dynamics model. A new investigation of the effect of flow frequency is presented. The model was solved for two flow frequencies; 13.1 Hz and 23.1 Hz. Detail description on vortex formation and changes as fluid flows in cyclic manner is presented. For stack of plates that is 200 mm long, turbulence seems to start at a drive ratio of 1% as the velocity prediction deviates from the laminar theory. Visualization of vortex contours indicated that as flow reverses the returning vortex alters the boundary layer condition within the channel of the plates. Therefore, the flow needs to be modelled as turbulence flow. The volatility of vortex structures at the end of plate seems weaker as the flow frequency increases. This study indicates that turbulence need to be carefully considered in modelling/designing thermoacoustic systems especially if better ‘thermoacoustic effect’ that represents performance of the energy system is required.