Experimental Study And Numerical Simulation Of Vortex Generator Tailing Vortex Characteristics

Taking the vortex generator in hydrodynamics as the research object,Firstly,the single blade vortex generator with different wedge angle,different lower edge height ratio and different inflow angle of attack is simulated.The position of the trailing vortex is described by the height of the vortex center and the deviation of the vortex center.The strength of the trailing vortex is described by the turbulent kinetic energy on the back center line and the vorticity of the vortex.The velocity of a point in the flow field behind the blade is monitored and recorded.The frequency of the vortex shedding is described by Fourier transform.Based on the principle that the higher the vortex height,the better the deviation,the stronger the vortex intensity and the larger the vortex shedding frequency,the better the optimal geometric parameters of the vortex generator are selected.Through simulation and analysis,the optimum wedge angle,the optimum lower edge height ratio and the optimum inflow angle of attack of vortex generator are 53 degrees.2 and 20 degrees respectively.After determining the optimum geometric parameters of single blade vortex generator,the parallel double blade vortex current generator installed with counter-vortex is studied and analyzed.Finally,the optimum installation distance is determined to be four times the height of the vortex generator.Secondly,the rectangular vortex generator is taken as the research object to verify the applicability of large eddy simulation in the flow field around blades.PIV experiments were carried out on a single blade rectangular eddy current generator with blade widths of 2,3 and 4 cm at different angles of attack.The experimental results were compared with the results of large eddy simulation.In the experimental study of two blades,PIV experiments were carried out with two vortex generators with 2 cm blade width,and the experimental results were compared with the results of large eddy simulation.Through comparison,it is found that large eddy simulation is suitable for both single blade and double blade flows.Finally,four different size vortex generators with blade lower edge length of 2,3.4 and 5 cm are selected.The other geometric dimensions are determined according to wedge angle of 53 degrees and height ratio of lower edge of 2.The angle of attack is 20 degrees,Four vortex generators are installed in the actual draft tube by inverse vortex installation method.By calculating,the efficiency of draft tube can be improved by nearly 7 percentage points when the length of the lower edge is 4 cm,which verifies the effectiveness of the vortex generator.