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Models for the study of computational fluid dynamics in vehicles to determine aerodynamic loads usually take into account only the geometry of the body. Several constructive elements such as the wheel geometry or suspension components are disregarded in the computational models. This work presents the study of the aerodynamics of a one-fourth model passenger vehicle, which contains the wheelhouse interior elements. The goal is to identify the aerodynamic loads produced by these components and their effect on the flow dynamics. Wheel and tire set, brake components, suspension and drive shaft are contemplated. Computer simulations were performed to the vehicle speed varying from 0 to 120 km/h and included the rotation of the tire and wheel assembly, considering the tire geometry in dynamic conditions. The computational model is solved by the finite volume method, wherein the computational domain is divided into tetrahedral and hexahedral elements. The turbulence model used is the standard
*k*
−
*ε*.

The numerical study for the calculation of aerodynamic forces arising in a vehicle has become more conventional. The methods usually employed for the analysis of such forces in vehicles are designed after the devise of prototypes in wind tunnels, which are very expensive demanding a large amount of equipment, facilities and skilled labor.

Currently companies have performed three-dimensional construction of their models, thus facilitating pro- cesses of tools construction, assembly interference checking and also allowing the numerical analysis.

Most of the articles related to numerical studies of vehicle aerodynamics aim at the vehicle body [

This article aims to determine the flow influence on a passenger vehicle using a one-fourth model of a complete vehicle as seen in

Many researchers have been trying to understand the complex flow patterns around vehicles, developing measurement techniques in wind tunnels [

The aim of this study is to identify, through numerical simulations, the effects of internal elements of the wheelhouse, the wheelhouse itself, the wheel and tire assembly in drag force of a passenger vehicle, through the modelling of a quarter car.

The finite volume method was used to solve the conservation equations applied to an unstructured mesh. The equations solved for the model are respectively, the mass and the momentum conservation equations. It is used the standard k − ε model [_{in}) of the fluid and the soil (v_{g}) from zero to 33.5 m/s (v_{in} = v_{g}). Mach number (M) for the proposed condition in this analysis is less than 0.3 so the flow can also be considered as incompressible [_{d}) [

A simplification of some elements was adopted for the proposed model given that other geometries exert little influence on the flow. These elements are the hood of the constant velocity joint, wheel bolts case, braking set details, etc. The respective changes can be observed in

The approach presented by Stern and Wilson [

The numerical study was performed in transient regime. In order to demonstrate the highest gradients of the quantities involved, air input speed was chosen to 33.5 m/s (120 km/h). The pressure variation as a function of the model surface is indicated on the color map of _{d}. This section region is protected by the vehicle body which contributes to a small pressure variation against the other variations. The sections in the xz plane,

pressure gradient in the section and on the surface geometry tire/wheel. Also in

In

Vortex structures appeared depending on the geometry of the wheelhouse as shown in

The aerodynamic drag force (F_{a}) according to Fox and McDonald [

where: C_{d}―aerodynamic drag coefficient, ρ―density and A_{f}―frontal area.

The aerodynamic drag coefficient is not constant [

where: L is the is the characteristic length chosen as _{f} perimeter as function of the frontal area.

The respective areas and perimeters for this model can be observed in

The numerical simulations and experimental results reported in the literature indicate that the drag coefficient values vary slightly from a given speed [

For the verification of such feature a graph of velocity versus drag coefficient was built. The vehicle body and the whole vehicle body have different drag coefficients, but show the same trend as shown in

The internal elements of the wheelhouse exert a small influence on the total drag force of the vehicle. It is about 0.4%, so that adopted simplification compared with the order of magnitude of other elements is very much reasonable.

The main conclusions of the study are:

1) It is possible the use of mathematical models for predicting aerodynamic loads;

2) Flow inside the wheelhouse is complex and presents recirculation regions;

3) Mechanical elements within the wheelhouse had simplified geometry and were incorporated into the model; however, the contribution to the drag force of such elements is quantitatively less than that of the wheelhouse and assembly wheel and tire;

4) According to the simulations, presented in paper, neglecting the effects of the box on wheels and wheel tire set is not suitable in aerodynamic vehicle research, except at low speeds where the aerodynamic loads are low for any vehicle.