Application And Research Of Plasma Active Jet In Vehicle Wake Control

Surface dielectric barrier discharge(SDBD)plasma,as a new active flow control technology,has gradually become one of the hot research directions in the field of flow control due to its simple actuator structure,rapid response,low power consumption,and easy layout.Simultaneously,due to the depletion of global energy and the increasingly serious "greenhouse effect",people have put forward higher requirements for automobile fuel economy and exhaust emission standards.In this paper,the surface dielectric barrier discharge plasma active flow control technology is applied to the vehicle wake flow control.By comparing the changes of aerodynamic force and wake flow field before and after flow control,the control mechanism and law of plasma active flow control on the flow field in the tail of the Ahemd model are explained.Firstly,the plasma phenomenological model proposed by Suzen et al.was verified by numerical simulation in still air,and the induced flow velocity and flow field structure obtained are consistent with the experimental results.Because some of the empirical parameters in the model are only for a certain actuation parameter,it cannot meet our research needs.Therefore,we have modified the existing plasma model parameters based on the distribution of charge density generated by plasma discharge under different actuation voltages and the velocity characteristics of the ion wind given in the relevant literature.This lays the data foundation for the subsequent study of the influence of changes in plasma actuator parameters on the wake flow control of the Ahemd model.Secondly,A single linear plasma actuator was used to study the flow control of the tail flow of the Ahemd model with an oblique back angle of 25.By analyzing the influence of the position of the actuator,the actuation voltage,and the incoming flow velocity on the wake flow control effect,we found that placing the actuator on the top of the slope near the flow separation point has the best flow control effect.Through increasing the airflow velocity in the boundary layer near the flow separation point,it makes the normal velocity distribution in the boundary layer more full and enhances the ability of the boundary layer to resist the reverse pressure gradient,thereby inhibiting the generation of separation bubbles on the slope of the model tail.Although the local pressure drops due to the acceleration of the gas flow near the application of plasma actuation,the suppression of the separated bubbles brings the pressure of the entire slope to rise,so the aerodynamic drag is reduced.At the same time,increasing the actuation voltage can improve the plasma flow control effect.When the flow separation bubbles are completely suppressed,and then increase the actuation voltage,the drag reduction effect is no longer obvious,but will increase the power consumption of the actuator.The current type of actuator has limited flow control ability,so its control effect is very weak under high incoming Reynolds number.Finally,a combination of multiple linear plasma actuators was used to study the flow control of the model tail flow at a relatively high incoming flow velocity.Through the analysis of the results,it is found that compared with a single actuator,multiple actuators working at the same time are beneficial to improve its flow control effect,but from the perspective of energy conversion rate,this solution is not very economical.In this paper,the plasma active flow control technology is applied to automobile drag reduction through numerical simulation methods,which promotes its development in the field of automobile aerodynamics,and accumulates experience and data foundation for the practical application of this technology to automobile aerodynamics.