Numerical Simulation Of The Vortex Wave Flow In Two-dimensional Channels

The study of vortex wave is one of the fields of unsteady flow and vortices. The vortex wave could generate effective mixing at low Reynolds number. The vortex wave flow is studied using the methods of numerical simulation. And the focuses in this paper are the study of influence factors to the vortex wave flow, such as inlet velocity, scale of channels, Reynolds number, and Strouhal number. The flow mechanism and corresponding parameters are analyzed in this paper.The results are drawn as follows:Whether the vortex flow can generate is intensively influented by the velocity inlet. The vortex wave flow can be taking on both as the oscillating flow inlets and as the oscillating inflow superposing small mean flow, whereas they bring on different flow structure. Unilateralism intermission pulse flow can generate vortex wave at half period.Vortex wave flow can perform in channels with right angle, 45-degree angle and arc angle with similar moving structure, whereas there is a little difference in 45-degree angle to in other two. According the simulation, in the right angle channels, the vortex wave can perform at expansion ratios from 1:1.4 to 1:2.8.Reynolds number and Strouhal number are the important factors. At a fixed Reynolds number, as the Strouhal number is increased, the quantity, the size and the moving distance of vortices decrease and the wavelength of mainstream shortens, and the length of channels should be shortened, too. At a fixed Strouhal number, as the Reynolds number is increased, the quantity and the size of vortices change little, while the wavelength of mainstream shortens a little.The flow parameters of the vortex wave are studied in this paper, too. The vortices in the vortex wave flow have particular moving structure, they develop downstream first, stay at the point for a short time, then move upstream. Vorticity at the expansion field periodically waves. At a fixed Reyonlds number, as the Strouhal number is increased, vorticity waving range minishes; at a fixed Strouhal number, as the Reyonlds number is increased, vorticity increases linearly. The tendency of shearrate is similar to that of vorticity. With the study of vortex wave flow, the conclusion is drawn that decelerating phase of inlet velocity is the key factor of the vortex wave.In the end, the flow mechanism of vortex wave is analyzed. The conclusions drawn from this paper provide the basal theory for further studies and applications of vortex wave.