| With the increasing energy consumption and environmental pollution caused by traditional energy sources,as well as the increasing demand for convenient travel,countries have been researching new energy-efficient means of transportation since the last century to cope with the growing energy depletion challenges.Since the successful application of the internal combustion engine,it has brought epoch-making convenience to people’s travel,production and transportation,but at the same time,the energy consumption of human social activities has increased rapidly.Various countries and research institutions have started to explore new energy-efficient transportation as early as last century,but the huge energy consumption of traditional wheeled vehicles is one of the bottlenecks limiting their further development.Therefore,technically developed countries have started to research new clean energy high-speed trains since they recognized the energy problem.Maglev trains are one of the earliest new trains developed by countries around the world,but they gradually withdrew from the world stage due to their low efficiency.The concept of Aero-train was pioneered by Professor Yasuaki Kohama of Tohoku University.Aero-train is an efficient high-speed transportation vehicle utilizing ground effect,and its energy efficiency ratio even exceeds that of commercial airliners,Aero-train is powered by clean energy(wind and solar).The levitation principle of Aero-train is to utilize the wing-in-ground effect to lift the car into the air.The wing-in-ground effect,also known as the ground effect,is a phenomenon that increases the lift-to-drag ratio significantly as the wing approaches a wall or water surface due to the formation of a high pressure area under the wing.Compared with watercraft based on the wing-in-ground effect,Aero-trains are safer because watercraft experience medium changes in the water-air during the takeoff and landing phase,while Aero-trains operate more smoothly because the entire process is carried out in a U-shaped land track.This study is divided into two parts,the first part investigates the aerodynamic noise generation and propagation characteristics of the annular wing of the new Aero-train under the ground effect,obtains the influence law of ground clearance on the aerodynamic noise of the wing through analysis,explores the aerodynamic noise frequency components and sound pressure level intensity generated by different flow structures,and makes a more accurate positioning of the sound source.The results show that when the ground clearance is lower,the aerodynamic performance will be better and the lift-to-drag ratio will be increased,but at the same time,the aerodynamic noise will be enhanced sharply.This is due to the strong aerodynamic noise caused by wall-bound vortices when the ground clearance is small.In addition,the aerodynamic noise caused by the wingtip vortices is also strong.In the second part,based on the results of the first part,the main contributing sound sources are targeted and the flow field is actively controlled by arranging plasma exciters to induce jets to destroy the flow structure that generates strong aerodynamic noise.At the same time,this paper further analyzes the principle of the plasma jet destroying the flow structure to obtain the noise reduction effect by using the POD method,and briefly explains the basic principle of this noise reduction method.The results show that the plasma jet exciter at the airflow separation point and trailing edge can achieve good noise reduction effect.The plasma jet is often used for the optimization of the aerodynamic performance of the transportation under low speed conditions,and the results show that through a reasonable arrangement,the plasma exciter is still effective in the field of aerodynamic noise reduction under high speed conditions,and can achieve a relatively good noise reduction effect at the cost of less energy consumption,which provides an important reference for the noise control of Aero-train. |
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