Problem Definition & Objectives

PROBLEM DEFINITION & OBJECTIVES Problem Definition: To perform the aerodynamic analysis of the body of a car currently available in Indian Market (Maruti 800). Objectives: (1)

To prepare the surface or solid model of the car body with proportionate dimensions using IDEAS.

(2)

To find out the aerodynamic drag force, and pressure distribution on the car body in case of front and side winds at the most common city speeds using CFD (Computational Fluid Dynamics) software ANSYS-CFX.

(3)

To find out the Drag Coefficient of the car body and compare it with theoretical prescribed values for good aerodynamic behavior.

(4)

To suggest methods/modifications to improve the aerodynamic behavior of the car body under study.

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LINE OF ACTION The 3-D model of the car body is generated in IDEAS. To ensure accuracy, the outline curves of the car body are traced from real time photographs of side and back views. The coordinates of the curves are modified by a scale factor to generate a model of approximately actual dimensions. When the modeling is complete, the IDEAS file has been converted into an IGES file and the IGES file is then imported into ICEM CFD 5.1 for creating a wind tunnel around the car body and meshing. For accuracy, the mesh should be as fine as possible. After meshing, the model is then imported into CFX-Pre where appropriate boundary conditions are applied. The boundary conditions involve both straight wind and combined straight and side winds. After applying boundary conditions, the problem is send to CFX-Solve which performs the necessary numerical calculations and generates the results file, which is then opened into CFX-Post for visualization of results. After comparing the results with the theoretical prescribed ones, the model is modified and results are compared with initial ones to validate the modifications. In chapter 1, as stated above, introduction and statement of the problem has been discussed. In chapter 2, under the title literature review, theory of vehicle aerodynamics, importance and basics of CFD are explained. In chapter 3, project methodology is explained. In this chapter, detailed method with different boundary conditions, turbulence models, mesh sizes etc. is explained. In chapter 4, the results are discussed and are compared to the theory. In chapter 5, the modifications performed along with results, and other possible modifications are explained. In chapter 6, the conclusions obtained from original model test results, and those obtained from modifications are explained, which is followed by further scope of studies on the topic discussed.

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