Aerodynamic Devices - Part 1

Another Sunday , that means another post from Explaining Engineering. Before starting this weeks topic , I would like to thank everyone for your over whelming responses. Coming to this week topic , as I told before we are going to look into aerodynamic devices , but to understand them a little science is required. Let us first get into science part of today's topic.

Source : Autosport.com

I have mentioned air tends to follow the surface of the car , but a question is raised on me, why air tends to follow the surface. Answer is simple , molecular adhesion and friction. Air tends to attach to the surface with the help of static friction. between air and molecules and air. This adhesion of air and surface is really very helpful in getting some downforce ,also known as negative lift in terms of SAE. There are number of ways to create downforce , but the main and maximum amount of downforce is produced with the help rear wings. Thanks to Bernoulli.

To understand how rear wings work . We need to understand a very important topic of fluid dynamics called Bernoulli Principle. Bernoulli's principle states the following, Bernoulli's principle: Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed.

This can be used in the favour of us to produce downforce which is achieved by a special shape called aerofoil. Below image shows how it looks like.





The advantage of using a aerofoil shape is it can transfer the air attached to the surface in different speeds. When a horizontal layer of air hits the the aerofoil , they tends to follow the surface of the shape. But when your look at the bottom path , the steep of the curve doesn't allow efficient transmission of fluids ,as a result a vacant low pressure zone is created and that pullout the surrounding air making a laminar flow of air. (Laminar flow , type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular fluctuations and mixing.)






Since, the air flowing at the bottom is faster than the air at the top . The pressure is less at the bottom compared to top. Like said before , fluids move from higher pressure to lower pressure. Which applies a force down the car.



Above image shows how downforce is created.

This downforce can be increased by increasing the frontal area or slanting the aerofoil. but this may end up like climbing half well and falling. This is because , as the slant angle is increased , now the vacant area is high and molecular adhesion forces between gasses are weak enough to attract the next layer of air that is loacated far. Which may end up creating more pressure difference between the front and rear part of aerofoil as a result more drag is created without getting paid off (downforce). So Engineers have to be very careful in choosing the frontal area and slant angle of this aerofoil , because if u didnt work on it well. You are going to end up getting a useless trade called drag. This also rises to turbulent force.






It is not the tone I always end right?.. When there is a problem , our Formula 1 engineers comes with a solutions. Yes , there are ways to overcome these negative points to. Thanks to Modern Engineers. This is where the importance of vortices came. Vortices are the flow of air in spiral shape . Vortices do not allow air from outside to come in or air from inside to go out. This Vortices traps the air inside it , so the vacant zone is now filled with these laminar flowing air molecules. Which again create more and efficient downforce.

Vortices trapping the air inside it so the vacant areas are filled.

This vortices are generated by vortice generators which we will look into further blogs. Another main way of producing downforce is with the help of monocoque shape.






Back in 2011 the F1 have introduces a top nose design rule. This rule helped the engineers to produce a better and good amount of downforce compared to the past with less ground effect ( Will make a detailed post on ground effect in further weeks). This monocoque with nose at the top worked on the principle of venturi effect. Thanks again to Bernoulli .




Venturi is a shape similar to the above one. Suppose a fluid of certain volume is passing through this venturi on the wide mouth side , as the cross section area is decreasing , the amount of fluid passing through the area is limited , since the air flowing inside is continuous , the air tends to move at higher velocity in the small cross section area. Therefore less pressure is created. Now I am splitting the venturi into half.






Now compare this shape to the monocoque of the car. You will get the answer.


Since the cross section area is less at that point ( usually found on same axis of Center of gravity) . The velocity off air in that point is high , that means low pressure as a result , a huge amount of downforce is created . But due to the safety and drivers facing difficulty is analyzing tracks at slopes . This concept is then changed to low nose concept which looks like the one below .

Source : F1.com

The void is available in this car also which acts as venturi , but this wont be as effective as the top noce concept used before , because of the less incoming air in to the bottom part.


That's , it for today's weeks , we will look into other simple and tertiary aerodynamic devices in upcoming post.