Research On The Aerodynamic Drag Reduction Efficiency Of MIRA Model With Non-smooth Surface Based On Flow Disturbance

Reducing air resistance is an important effort to improve the car’s performance of its power and fuel consumption. Energy consumption and positively related to drag, and drag reduction means saving. Currently, only the streamlined car body design are insufficient to satisfy to the aerodynamic drag. This paper carried out drag reduction experiments and simulation studies on the car body covered with non-smooth surface, in order to seek the effectiveness of non-smooth surface and design criteria.In this paper, the classical model of vehicle—MIRA is used in Fluent fluid dynamics software for aerodynamic wind tunnel simulation, calculate its drag coefficient Cd, in order to testify the reliability of the simulation methods, MIRA model is manufactured and tested in Zhejiang University wind tunnel lab with the same test conditions in experimental. Simulated values obtained 1.39% of the error. Where the use of wind tunnel testing and computational fluid dynamics simulation method of combining to raise support deduction interference, then the test data and the level of blockage ratio effect correction proposed for automotive aerodynamic drag coefficient of Zhejiang University wind tunnel correction method.Based on the analysis of the automotive aerodynamic fairing (vortex generators, spoiler and spoiler) air disturbance on the mechanism to carry out the study of non-smooth surface MIRA car model unit drag performance. From the mining of non-smooth surface geometry (concave, scale, groove) and perturbation mechanism outflow car starting field to study the characteristics of non-smooth surface coating.Using orthogonal test of concave surfaces on MIRA model, the simulation results showed that the model primary and secondary factors affecting the aerodynamic drag of the order of concave depth, concave depth to diameter ratio; simulation results for the non-smooth units in different locations showed that the optimal drag reduction model front and hood position arranged non-smooth unit was only 1.47% and -0.227%, while in the model as well as the back cover layout when the concave set drag rate reached 5.99% and 6.39%; simulation for non-smooth unit showed different geometries, when arranged in the top model of non-smooth unit, scale-shaped unit reached 8.03% of aerodynamic drag reduction,trench concave drag reduction rate was 4.30%; in the model of non-smooth unit back layout, scale-shaped non-smooth unit rate reached 7.86 percent drag reduction, trench concave drag reduction rate 3.52%.Non-smooth surface has the best aerodynamic drag coefficient of drag reduction mechanism were analyzed to draw relevant CFD software images:(1)The MIRA surface pressure distribution and symmetric surface pressure distribution, analysis of the impact of the pressure resistance; (2)The distribution and direction to the flow direction of the vector velocity perpendicular to the flow direction in the model front, top and tail of the velocity distribution and vector analyzing eddy effects;(3) Analysis of turbulent kinetic energy dissipation, turbulent kinetic energy diagram on different sections, and take the turbulent kinetic energy curve plotted.Results of this study can guide non-smooth coating design and optimization, film is set in different locations of different geometries for automotive surfaces, but also for more areas (high-speed train, F1 Formula racing, etc.) more turbulence control objectives provide a theoretical basis.