An experimental and LES comparison of water- and air-based swirling flow test rigs in vertical and horizontal configurations

A 2D PIV experiment was carried out on the confined swirling flow and compared with simulation results. Simulations were performed using Star CCM+ commercial software. The LES WALE method of air and water was used to investigate the effect of working fluid on the swirling flow field. A second comparison was conducted to study the gravitational effects on the swirling flow. Velocity analyses were performed by extracting the mean velocity data, and FFT analysis was conducted on the instantaneous flow field of axial and pressure distribution. In general, good agreements were obtained using the experimental data; interestingly, the air simulation showed relatively higher performance in terms of predicting the asymmetric behavior of the flow. Energy cascade was studied at two different points, which indicated a similar tendency between air and water, with a slight shift of 0.1 Strouhal number in terms of dominant frequencies. The discrepancy of the CRZ and CTRZ formation was found to be of minor degree due to changes in the working fluid or the gravitational effect. Thus, a conclusion was made regarding whether applying water instead of air or altering the vertical test rigs affects the structure of the flow.