CFD study of oscillatory flow through 90º bends of thermoacoustic devices

Numerical simulation is performed to investigate oscillatory flow through 90º bends of a thermoacoustic system. Bends are often used in thermoacoustic systems as parts of acoustic networks. In the feedback loop, geometrical changes can cause system losses and it is often important to find optimal bend curvature radius that keeps the losses to the minimum. This paper investigates the effects of radius of curvature on the properties of the acoustic wave propagating through 90º bends, using 3D Computational Fluid Dynamics (CFD) simulation approach. Oscillatory flow phenomena are investigated using RANS method with SST k-ω turbulent model. Two curvature radii are considered with the drive ratio of acoustic excitation up to 0.65%. The simulation results are analysed with respect to the acoustic Dean Number and the associated flow phenomena causing losses in the bend are described. The results suggest an interesting lead that is worthy of further investigation.