Reducing the drag force has become one of the most important concerns in the automotive industry. This study concentrated on reducing drag through use of some external modifications of passive flow control, such as vortex generators, rear under body diffuser slices and a rear wing spoiler. The study was performed at inlet velocity (V= 10,20,30,40 m/s) which correspond to an incompressible car model length Reynolds numbers (Re=2.62×10~5, 5.23×10~5, 7.85×10~5 and 10.46×10~5), respectively and we studied their effect on the drag force. We also present a theoretical study finite volume method (FVM) of solving Reynolds-averaged Navier-Stokes equations (RANS) using a realizable k-epsilon (k-ε) turbulence model, conducted on a car, model KIA Pride, which is popular in Iraq and Iran. All computational analysis and modifications were carried out using the ANSYS Fluent 19 computational fluid dynamics (CFD) software and SOLID WORKS 2018 modeller. The drag coefficient of the analysed car was found to be 0.34 and the results show that the drag can be reduced up tol.73% using vortex generators, up to 3.05% using a rear wing spoiler and up to 2.47% using rear under-body diffuser slices modifications, whereas it may be reduced up to 3.8% using all previous modifications together.
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机译：减少阻力力已成为汽车行业最重要的问题之一。本研究集中在通过使用无源流量控制的一些外部修改，例如涡流发生器，后部漫射器切片和后翼扰流板的一些外部修改来降低拖曳。该研究在入口速度（v = 10,20,30,40 m / s）上进行，该速度对应于不可压缩的汽车模型长度雷诺数（RE = 2.62×10〜5，5.23×10〜5,7.85×10〜分别为5和10.46×10〜5），我们研究了对拖曳力的影响。我们还使用可实现的K-EPSILON（K-EPSILON（K-EPSILON（K-EPS）湍流模型来介绍求解Reynolds平均的Navier-Stokes方程（RAN）的理论研究有限体积法（FVM），该湍流模型是在汽车中进行的，模型Kia Pride，这是流行的在伊拉克和伊朗。所有计算分析和修改都是使用ANSYS FLUENT 19计算流体动力学（CFD）软件和SOLD WORK 2018 MODELLER进行的所有计算分析和修改。发现分析的汽车的拖曳系数为0.34，结果表明，使用涡流发生器可以减少阻力，使用后翼扰流板高达3.05％，使用后部底部持续3.05％扩散器切片修改，而且可以使用先前的修改在一起降低至3.8％。
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