A numerical investigation on hydrodynamic characteristics of the circulating water channel

A Circulating Water Channel (CWC) generates a stable flow field for prolonged experiments. The main challenge in common CWC design lies in how to achieve the flow field uniformity and the free surface flatness in the test section. In this paper, a thorough investigation on the hydrodynamic performance of the CWC is reported using numerical methods with test validations. Flow rate measurement and steady wave measurement are conducted in the CWC. A numerical CWC, based on the RANS method, is established to simulate the flow field and the free surface. The Moving Reference Frame (MRF) method and the Volume of Fluid (VOF) method are applied to simulate the impeller rotation and capture the free surface, respectively. The accuracy of the numerical results is verified by comparing them with the experimental data. According to the numerical results, the numerical CWC reproduces the same high-quality flow field as the physical one. The relationship between the impeller rotation and the incoming flow velocity in the observation section is established. As for surface flow characteristics, the wavelength of steady waves varies with the incoming flow velocity, while the steady wave height can be significantly reduced by slightly adjusting the water level in the test section. The rotor type surface flow accelerator obviously improves the surface flow velocity. Moreover, the detailed flow field inside the numerical CWC is extracted to show the effect of each rectifying section. Honeycombs strongly straighten swirling flows with the result that the flow uniformity downstream of the porous plate is significantly improved. In addition, without a honeycomb downstream of the diffusion section, the residual rectifying section is sufficient for the test section to obtain a high-quality flow field. Based on the above analysis, the whole domain of CWC simulations can evaluate comprehensive hydrodynamic performances and then set the stage for subsequent optimizations.