AERODYNAMICS IN AUTOMOBILES

What is Aerodynamics ?

As the name suggests , " Aero "  "dynamics" i.e. Dynamics of Air. This means that Aerodynamics is that branch of engineering that deals with the study on Forces by Air in layman language.

How to study Aerodynamics ?

One of the most difficult problems that students face while beginning there study on aerodynamics is ,            " Where to start from".

Aerodynamics is in itself so wide a branch , that one may find it difficult to gallop the elephant at once.

Thus , it has to be cut in pieces and eaten accordingly. One must classify his/her branch eg.    Aeronautical /Automobile and should pick up specific studies.

Another problem that students face is that at times the subject can be really boring. Unlike other divisions in automobile engineering , Aerodynamics does not present itself with visuals . So, this might result in the boredom of students.

                               However, I have tried to make sure that the same boredom is not felt by the readers of this blog . The scope of this blog does not go beyond the section of automobile aerodynamics.

Aerodynamic Forces

Aerodynamic forces can be classified into 3 forces

• Drag
• Lift
• Downforce

Considering the movement of the automobile in the left direction , The force acting in the upward direction is the Lift . The force in the downward direction is the downforce and the force in the rightward direction in the  drag

DRAG

Drag is the force that opposes the motion of the vehicle , as can be seen from the figure.

 Now , the question arises that how is drag formed. Drag is produced, when air comes into contact with the surface of the automobile . when any fluid comes into contact with any solid surface , it leads to the formation of a boundary layer.

         What is Boundary Layer ?

Considering a streamline fluid flow ,when fluid comes into contact with a solid , its lowermost layer moves at the same speed as that of the moving solid body while the speed differs in the subsequent layers.Then a layer is encountered, whose speed is 0.99 times the speed of the free fluid . The thickness between the point of contact of the solid and this point is called the boundary layer thickness and this layer is called the boundary layer . The fluid flow in the boundary layer is laminar. Here , Laminar is that kind of flow in which the fluid particles move in streamlines.

Now, coming back to  Drag , the saperation of this boundary layer , induces backwar surface force on the vehicle , and this force ic known as drag.

The mathematical formula through which drag is calculate is given below :-

Drag = 0.5*d*C*A*V^2

here

d = density of air

C = coefficient of Drag

A = vehicle frontal area

V = velocity of the vehicle

The Drag due to the boundary layer is far less than the drag due to the fluid flowing above it

Thus, the saperation of boundary layer from the vehicle is considered to be a cause of high drag .

We can thus successfully claim that the lesser is the coefficient of drag , the more aerodynamic the car is .

REVOLUTIONARY ATTEMPTS TO REDUCE DRAG

In the past many designers and and engineers made attempts to design a perfectly aerodynamic automobile some of them are below mentioned .

• The first car that was created keeping aerodynamics in mind was the Chrysler Airflow(1930) .
• Another was the Rumpler Trepfenauto , manufactured in Germany . I was designed keeping in mind the most aerodynamic object ( a tear drop ).The coefficient of this car is 0.27

A Chrysler Airflow (1930)(left)

                                                    A Rumpler Trepfenauto (right)
                                                     








SOME INTERESTING FACTS

• Cars of 80s had coefficient of drag equal to 0.36 on an average .
• Volvo S80 Sedan has coefficient of drag equal to 0.28

                                                                                                             

                                                                                                                         A Volvo S80 Sedan

• Most Cars Nowadays have coefficient of drag equal to 0.3
• SUVs have coefficient of drag equal to 0.3-0.4
• TOYOTA PRIUS has coefficient of drag equal to 0.26

                                                                                                                             A Toyota Prius

FORMULA 1  AND AN UNDESIRABLE ANOMALY

As we know, Formula 1 cars have to travel at very high speeds and they also have to face huge cornering stresses . Due to these forces there are some adverse effects on an F1 car . At high speeds these cars have the tendency to go airborne just like a plane , thus there are some measures that are taken to counter these forces which will be discussed in the forthcoming sections .

LIFT

Lift is that force which acts in the opposite direction to the weight of the automobile .The formula for calculating lift is ,

LIFT = 0.5*C*d*A*V^2

C= coefficient of Lift

d = density of air

A= frontal cross section area

V= velocity of Automobile relative to air

The formula in itself gives an idea that why a car tends to fly at high speeds .

this force can lead to disastrous accidents an lifeloss . A simillar incident happened with a Mercedes Driver , Peter Dumbreck in 1999

                                                           Accident of Peter Dumbreck            

HOW LIFT IS PRODUCED ?

coming soon .........