Numerical Simulation And PIV Experimental Study On The Flow Past The Rotating Cylinder

Flow past a rotating cylindrical has always been a very basic and important realm of fluid mechanics research. Compared with flow past a static cylinder, the rotating cylinder could obviously change the structure of the flow field and make the flow pattern more complex. Periodic vortex shedding occurred in the leeward of static cylinder, and lift force fluctuating periodically had an effect on the static cylinder,while for rotating cylinder vortex shedding pattern, frequency and lift force had apparent variation. Rotating cylinder flow field was distinct from the static cylinder.Expendable current profiler(XCP) was a typical example of flow past the rotating cylinder,when working which rotated at a certain speed in ocean current. In this paper,the flow field past a rotating circular cylinder was studied by numerical simulation and PIV experiment, and the influence of different rotating speed of the cylinder on the flow field was discussed.Computational Fluid Dynamics Software STAR-CCM+ was used to simulate flow past the rotating cylinder. In the simulation, the geometry models of cylinder and flow field were built, and the polyhedral mesh was used when the software enforced calculation. For better description of turbulent flow, detached eddy simulation(DES)which was more precise than RANS was chosen for the turbulence model. With Re=1000 and angular speed of rotating cylinder increasing, flow field at different angular speeds was acquired, then lift force curve, vorticity field and vortex shedding frequency were extracted from calculation results. In terms of these experiment data,it could be made clear that the influence law of rotating speed ratio on the lift force,vortex shedding frequency and vortex motion change.Experimental study of flow past the rotating cylinder was conducted in medium-sized low speed circulated water channel with PIV used for sampling flow fields information. Similarly, flow field with Re=1000 in different spin rate of the cylinder was acquired. Flow fields were processed by Proper Orthogonal Decomposition(POD) and Dynamic Mode Decomposition. With the help of POD, the change law of spatial scale and energy distribution with the rotating speed ratio was analyzed. DMD could acquire dynamic information of flow fields and extract main structure and frequency, so the change law of frequency as rotating speed ratio was acquired.Comparing numerical simulation results and experimental results, following conclusions could be draw:(1) when rotating speed ratio was lower ? ???0.20?cylinder rotation made vortex shedding frequency increase.(2) when rotating speed ratio was beyond 2.0, vortex shedding was suppressed.(3) when rotating speed ratio was larger than 2.0, energy of flow field was redistributed.