Numerical Simulation Of The Flow Channel Wall Obstructions Around

Large eddy simulations (LES) were performed on a channel flow with two rectangle cylinder mounted on its bottom wall. Our results agree well with relative experimental and numerical simulation results, which validate the possibility of LES to simulate the 3-D compressible flow pass over multiple cylinders.Based on the practical background, the influences of the cylinder height on the channel flow have been simulated. Our numerical results showed that with the increase of cylinder height, the cylinder wake becomes instable, and results in a complex flowfield, the vortex diffusion and separation increase. When the height of the cylinder large than a threshold value, no large vortex occurs. Moreover, when the distance between two cylinders is small compared to their height, the wake of the upstream cylinder will shed even before it growing up. On the other hand, the drag coefficient of upstream cylinder is positive and raises quickly with the increase of its height, however, the drag of second cylinder is negative and its oscillation amplitude augments with the increase of its height. To improve the drag force of second cylinder, it may keep the upstream cylinder height constant and increase the height of the second one. Our calculated results display that with the increase of its height, the drag coefficient raises also, and when the height become h2=1H/6, its average value fluctuates at around -0.05, therefore, it is possible to improve their drag coefficient with the adjust of the height of second cylinder.In this theisis, the influcenes of a variation of distance between two cylinders were also simulated numerically, and our results disclosed that, with a small distance compared to the height of the cylinder height, there is no obvious vortex shedding at the rear of the upstream cylinder. However, with the increase of the distance, a vortex shedding occurs, and the vortex sheds when its size become large. The sheded vortex interacts with the downstream vortexes from the second cylinder, which make the flow complex. When the distance become large, the vortex interaction between two cylinders decreases, but the flow is still complicated. The drag coefficient of upstream cylinder raises slowly with the increase of the distance and the drag coefficient of the second cylinder decreases.