| Bladeless wind turbine is a new type of wind turbine which can capture the wind energy by the vortex-induced oscillation of the energy trap column.The pressure change of the flow field caused by the periodic vortex shedding on both sides of the energy trap column will inevitably affect the sound field.In this paper,the hybrid numerical method combined with the Reynolds average method and the acoustic analogy method is used to investigate the effects of different damping ratios,mass ratios and magnetic recovery torque coefficients on the aerodynamic noise of the vortex-induced swing of the energy capture column.The research work of this paper is as follows:（1）The aerodynamic noise generated by vortex-induced oscillation of the energy trap column with different damping ratios（0.015≤ζ≤0.025）was studied by controlling variable method to keep the mass ratio and magnetic recovery moment coefficient constant.The damping ratio affects the aerodynamic noise emission by affecting the swing amplitude and frequency of the energy trap column.The sound pressure of the monitoring points located at the center of symmetry on both sides of the energy trap column has the same amplitude but the phase difference is 180°,while the sound pressure of the monitoring points located at the same side has the same phase but the farther away from the energy trap column,the smaller the amplitude.The far field noise of the vortex induced swing of the energy trap column is caused by the vibration of the energy trap column and the flow field disturbance caused by the vortex shedding on both sides of the column.The closer the column is to the energy trap,the greater the noise attenuation is.Meanwhile,the far field noise attenuation velocity of the column in the non-locked wind speed is greater than that of the locked wind speed.（2）The aerodynamic noise of vortex-induced oscillations of energy trap columns with different mass ratios(29≤m（9）≤4 9)is studied by keeping the damping ratio and magnetic recovery moment coefficient constant.The peak value of the total sound pressure level of the far-field noise of the energy trap column decreases with the increase of the mass ratio and presents a nonlinear relationship.The more stable the swing of the energy trap column is,the greater the far-field noise will be.At the initial branching stage,the far-field noise pressure is in phase with the lateral swing amplitude and in phase with the lift coefficient,while at the lower branching stage,the phase conversion phenomenon appears.The noise generated by vortex-induced oscillations of energy trap columns with different mass ratios is all low-frequency noise,and the center frequency corresponding to the peak value of the sound pressure level in the octave range at the locked wind speed is obviously larger than that in the non-locked wind speed range.（3）The effects of different magnetic recovery moment coefficients on the aerodynamic noise of the vortex-induced swing of the energy trap column were investigated under the condition that the structural properties and damping ratio of the trap column were unchanged.The locking interval of the energy trap column gradually shifted to the direction of high wind speed with the increase of the magnetic recovery moment value,and the peak value of the transverse swing amplitude increased with the increase of the value,and the increasing value could effectively widen the locking interval.The magnetic recovery moment coefficient does not change the spectrum distribution of far-field noise and the source form of aerodynamic noise.As the lateral swing amplitude is obviously larger than that of the downstream swing,the total sound pressure level of the monitoring point in the cross-flow direction increases greatly,which is obviously larger than that of the downstream.In this paper,the aerodynamic noise of the vortex-induced oscillation of the energy capture column of a bladeless wind turbine is simulated,which can provide guidance for the development of the system parameters of the bladeless wind turbine. |
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