The Influence of Guide Vanes on Flow Characteristics in the O-Tube

Fully enclosed circulating water channels, such as the large O-tube flumes located at the University of Western Australia and at Dalian University of Technology, are a kind of advanced experimental facilities that combines the capabilities of conventional open channel flumes in simulating steady currents and the U-tubes in simulating oscillatory flows. The O-tube facilitates the study of the flow-structure-seabed interactions at near full-scale conditions. Despite its capabilities, the O-tube flume has two minor flaws that could be optimized. The first one, the turbulence intensity at the central height of the O-tube ranges from 3% to 5%, which can hardly be further reduced without introducing physical control equipment. The second one, the flow velocity close to two sidewalls are not strictly symmetric at a given cross section of the flume due to different turning radii at the O-tube corner. Trying to address these issues, we introduce additional guide vanes at two ends of the working sections, and numerically investigate their influence on the flow. In this paper, a simplified geometry of O-tube and kinds of guide vanes with lengths and numbers are adopted. The flow inside the O-tube is simulated using the open-source software OpenFOAM, and the Improved Delayed Detached Eddy Simulation (IDDES) models are utilized. The numerical results indicate that well-designed guide vanes can significantly reduce turbulence intensity in the central area of the flume and slightly improve the flow asymmetry at two side walls.