Numerical Simulation Of Aeroelastic Problems For The Fairing Of Commercial Vehicles

With dwindling oil resources and the development of automotive technology,energy conservation and emission reduction and reduction of fuel consumption have become the constant pursuit goals of the entire automotive industry.The fairing is a very important pneumatic drag reduction accessory for commercial vehicles and is increasingly being used in models of major auto brands.There are many excitation sources that cause deformation or vibration of the fairing,including the excitation of the road conditions,the excitation of the engine,and the excitation of the airflow.At present,automotive engineers often neglect the influence of aerodynamic loads in engineering practice.However,with the development of lightmass,the mass of auto parts is getting smaller and smaller,the reduction in mass reduces the stiffness of the fairing,and the vehicle travels at higher speeds,resulting in more sensitive for aerodynamic loads.Therefore,it is necessary to use fluid-structure interaction method to study the Aeroelastic Problems.The research content of this article mainly includes the following three parts:Firstly,the data exchange between Star-ccm+ and ABAQUS based on the ALE method is implemented using the CSE data engine,and the two-way coupling simulation is successfully implemented.The vortex-induced vibration of the flat plate was studied.The "Carmen vortex street" was observed in the wakes under different Reynolds number conditions.Periodically shed vortices cause periodic changes in plate surface pressure and plate torque.Compared with the rigid plate,the vortex shedding frequency and the Strouhal number of the elastic plate are larger due to the coupling effect.When the vortex shedding frequency is equal to the second natural frequency,that is,the frequency of the change of the torque is equal to the second natural frequency of the plate,resonance occurs,the amplitude increases dramatically.Secondly,the aeroelastic deformation of the side fairing under different speed conditions in 0° yaw angle situation was studied.As the wind speed increases,the deformation of the structure increases.Vibration is mainly induced by the turbulent on the surface of the structure,and the final convergence of vibration amplitude is small,no regular.In order to reduce the structure deformation and improve the NVH performance,the influence of the shape of the structure on the elastic deformation was studied.Four different shape structure schemes were constructed.The results showed that the “15mm” scheme,“tip_middle” scheme,and “round_corner” schemes significantly reduced the deformation.In order to continue to reduce the amount of deformation,two schemes of “Groove type side fairing” and “Reinforced rib side fairing” were constructed.The simulation results show that these two schemes significantly reduce the structure elastic deformation.Thirdly,the aeroelastic deformation of the top fairing under different speed conditions in 0° yaw angle situation was studied.The flow field was studied using traditional CFD method and the two-way FSI method respectively.There is no significant difference in the pressure distribution cloud diagram of the flow field,and the trend of the numerical curve of the pressure monitoring point is basically the same,with slight differences in values.This shows that the top shroud surface pressure distribution is insensitive to the fluid-structure interaction effect.This is mainly because the structural response is small under the action of aerodynamic forces,and the structural deformation has little effect on the flow field.The steady-state response of the structure was obtained using the one-way FSI method,and the difference between the average value of the instantaneous response and the steady-state response result was compared.The differences under the three speed conditions were 0.33%,0.43%,and 0.57%,respectively.For small deformation problems,the one-way FSI method is sufficient to guarantee a higher accuracy of results.The pressure distribution on the inner and outer surfaces of the top fairing is loaded and input into the finite element model.Then the sickness of the structure is optimized,and the mass of the top fairing is reduced on the premise of satisfying the stiffness performance.The thickness of the structure is reduced from 20 mm to 11.17 mm,and the mass of the structure is reduced from 98 kg to 54.8kg.This balanced the properties of lightweight,stiffness,and modality.