| Automotive aerodynamics is an important program applying in automotive engineering technology. Vehicles with excellent aerodynamic characteristics have a good fuel economy. This has a sufficiently significant to the whole world. So, it is wise for China to carry out aerodynamics research to improve our vehicle researching and developing capability.Wind tunnel is essential equipment for the aerodynamics research. Aerodynamics research in China could not do well without automotive wind tunnel.In China, the automotive wind tunnel was built late. Jilin University Automotive Wind Tunnel started in 2002 and completed in 2008. At the end of 2005, Tongji University Automotive Wind Tunnel started and it completed in 2009. These two automotive wind tunnels were both equipped with rolling road ground effect simulation systems.The research of automotive aerodynamics in China went into one new stage.After automotive wind tunnel completed, more research should be done to improve automotive wind tunnel technologies. The first thing is the correction of automotive wind tunnel. But now there is little experience, method and test data for reference in China.For above reasons, supported by National Natural Science Foundation of China and State Key Laboratory of Automobile Dynamic Simulation, some researches work of correction to Jilin University Automotive Wind tunnel have been done based on numerical simulation and test.(1)In this paper, the development of automotive wind tunnel were summarized , five different characteristics from aeronautic wind tunnel were summed up. From the two aspects of wind tunnel,its testing technology and automotive aerodynamics, its numerical simulation, domestic and foreign corresponding studies were reviewed.It was pointed out the background and necessity of the automotive wind tunnel correction. This article identifies the method based on simulation and experiment to correct the automotive wind tunnel and the research contents.(2)In this paper, automotive wind tunnel simulation method was studied, on the basis of mathematical description of fluid flow, by comparing the advantage and disadvantage of all kind of turbulent models, numerical simulation using commercial CFD code were adopted. In this article, we used standard k ?εturbulent model, standard wall function and meshes of tetrahedron and prism to simulate.The car models are MIRA and SAE reference car model. Based on traditional virtual wind tunnel simulation, the new virtual wind tunnel reconstruction of Jilin Universtiy Automotive Wind tunnel was improved.(3)In this passage, we concluded test rule and some requirements of wind tunnel test, and introducted the aerodynamic drag measurement. Meanwhile, we improved the pressure scanning technology on vehicle body using a new slice scanning device. The PIV (Particle Image Velometer) is used in the study on automotive aerodynamics. One new method of using ribbon to show the streamline was applied in this paper. That method could overcome the shortage of smoke stramline.(4)After summarizing different test sections, supports and balances in foreign wind tunnel, we analysed the layout of Jilin University Automotive Wind tunnel and pointed out the advantage and disadvantage. According to aeronautic wind tuunel test, it was put forward the technologies on eliminating support aerodynamic drag, correcting support interference and wall blockage using numerical simulation and wind tunnel test. This paper developed the general method to correct the automotive wind tunnel. We made two half-scale clay models of MIRA and SAE reference models. It was introduced the wind tunnel test plan of eliminating support drag, pressure measurement, numerical simulation of big domain and virtual automotive wind tunnel.(5)According to the corrections of support interference of wind tunnel of Jilin University, some numerical and wind tunnel test had been done. By the wind tunnel test of car and support, the aerodynamic drag of car model, support and their interferences were measured. After separating the car model and support, fixing car model on floor, we measured the drag of support and the interference from car model to support. The difference of two measured drag is the car aerodynamic drag including the interference from support to car model. Using virtual wind tunnel simulation, we simulated the above wind tunnel test. By comparing the results of simulation and test, analysing the flow field, we consider that the way of eliminating the support drag is reasonable.(6)After the wind tunnel was completed, we could not test with different test section parameters. High blockage ratio in open jet wind tunnel would result in experiment error. Using virtual wind tunnel simulation, the research on the effect of test section parameters to the test result had been done. That parmaters include nozzle area, collector area, test section length and chamber. According to the results, some rules were concluded that the geometrical parameters of the wind tunnel test section affect on experiment results. The simulations show that the nozzle area, collector aera, test section length affect the results large but the chamber little. These conclusions have important reference value to the correction of open jet wind tunnel and estimate the open wind tunnel test results exactly.(7)To correct the support interference of the wind tunnel test, one new correction method was brought forward based on numerical simulation in virtual wind tunnel with only car and no support. By simulation, the interference of support to car model was got. After considering traditional wind tunnel correction theory, we corrected the data using semi-experience correction method. By comparing the result of simulation and test, we analysed the pressure coefficients and flow field. Results show that the simulation and the correction are right and reliable.The main innovations in this paper are:(1)Based on the experience of automotive aerodynamic numerical simulation, we studied on the automotive wind tunnel numerical simulation and improved the virtual automotive wind tunnel. The practice in this paper shows that virtual automotive wind tunnel could get the same accurate results with the wind tunnel test.(2)Automotive wind tunnel test rules and some requirements were concluded. We improved the pressure scanning technology on vehicle body using a new slice scanning device. The PIV (Particle Image Velometer) was used to show flow velocity field aroud car in the study on automotive aerodynamics.One new method of using ribbon to show the streamline was applied in this paper. That method could overcome the shortage of smoke stramline.(3)After analysing the layout of foreign wind tunnel, we pointed out the advantage and disadvantage of Jilin University Automotive Wind tunnel. According to the aeronautic wind tuunel test, it was put forward the technologies on eliminating support aerodynamic drag, correcting support interference and wall blockage by numerical simulation and wind tunnel test.(4)By virtual wind tunnel simulation, the research on the effect of test section parameters to the test result had been done. The parmaters include nozzle area, collector area, test section length and chamber. According the results, some rules are concluded that the geometrical parameters of the wind tunnel test section affect on experiment results. The study will help us to do the correction and build new wind tunnel. (5)To correct the Jilin University Automotive Wind Tunnel, one general correction method was brought forward. That got the car model drag and the interference of support to model by two special wind tunnel tests. That corrected the interference of support to car model by virtual automotive wind tunnel and corrected the wind tunnel blockage using on sime-expericenc croecction method.In this paper, to study on Jilin University Automotive Wind Tunnel, some technolgies about wind tunnel test, virtual wind tunnel simulation and wind tunnel correction were brought forward based on numerical simulation and test. We used this technologes to solve the key problem of automotive wind tunnel correction. All of these show that the method of correction is accurate, feasible, reasonable and reliable, could meet the enginnering needs. |
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