External Aerodynamic: Introduction, And External Aerodynamics

1.Introduction

1.1Aerodynamics

Aerodynamics is a branch of fluid mechanics which deals with motion of moving air over the object. It is related to gas dynamics but the difference is being that gas dynamics is related to all gasses. When air is moving around the vehicle it enables to calculate the forces and moments acting around the vehicle(often called the flow field). Typical properties of flow field include velocity,pressure,density and temperature as a function of time and position. The equations for the conservation of mass, momentum, and energy can be solved by defining the control volume around the field. Aerodynamics is generally divided into two categories namely internal aerodynamics and external aerodynamics. External aerodynamics

The best approach to minimize fuel consumption is improving the aerodynamic performance of vehicle. This can be achieved by reducing the drag on vehicle. This maintains the vehicle capacity and comfort which leads in the improvement of aerodynamics which will not effect the shape of the vehicle.

Due to the rapid increase of price and scarcity of the fuel, the technological world has focused on alternative for energy saving. Most of the automobiles consumes decent percentage of fossil fuels for their working, so they has to be improved. Automobiles include electronic vehicles, Hybrid Vehicles and Human Powered Vehicles are developing to consume a large mileage per gallon. Instead of finding alternatives for fossil fuel, Designers are trying to improve the vehicle performance by manipulating different parameters of vehicles like engine parameters, Weight, Rolling Resistance and Aerodynamic Drag.

1.1.3 Aerodynamic

It forms vertices at the rear side of the vehicle while traveling . The vertices in turn caused by the aerodynamic lift.

c) Friction drag force:- It contributes about 10% of the aerodynamic drag and is caused by the friction force between boundary layer and the body surface.

d) Interference drag:- It contributes 15% percent of the total drag. It includes such elements as projecting door handles, mirrors badges which projects out of the normal surface of vehicle body.

e) Cooling and ventilation drag:- It contributes 10% of the total drag with careful attention to the design of ducting in the vehicle ,it should be possible to reduce this value considerably for past vehicle and in theory to use the energy given to air flow by the radiator to secure a positive forward force. The drag can be calculated from FD = CDAρ /2 Where, CD is coefficient of drag ,A is characteristic area of the body which is the largest projected area of body on a plane perpendicular to the direction of the air, ρ /2 is called the dynamic pressure of the flowing