Framepersonnalwork Concrete production Realised by : Duyck Maxime & Compagnon Frédéric
THEME : Formula 1 ‘s aerodynamism Problematic : Why do aerodynamism and performances are so closely linked in case of Formula 1 ?
SUMMARY Introduction -History of Cx I / Some notions -The driving force -The resistance -The aerodynamic support
-The bearing pressure -The Bernouilli ‘s principle II / Presentation of experiences -The aim -Experimental protocols * First experience * Second experience
III / Runnings and results of experiences -The speed -The oil consumption -The security -Results Conclusion
Introduction The CX owes its name to the excellent drag coefficient (Cx) which it had when it came out in 1974. Compared to the DS the SCX (surface X coefficient of form) is improved of 11 percent. The CX replaced the next Citröen car. But why was this coefficient so important? Is that just for design? No, it isn’t. Let us take the example of formula 1, why would they seek to have a Cx also evolved if the purpose of they are only the performances? It’s in fact because Cx acts on them but how? As many questions which brought us to the following reflexion that is our problematic: Why aerodynamism and performances are so closely dependent, linked? case of formula 1.
I / Some notions -The resistance The resistance is a horizontal force . It’s the opposite of the driving car , the movement so it is negative for performances of the car . It is calulated with this formula : T=Cx.S.1/2.P.V² T : resistance (in Newton) S : frontal surface (or the surface wich resist to the wind)(in m²) V : the speed of the fluid upstream from the car (in m/s) P : density of air Cx : resistance coefficient We can see an exemple of a frontal surface of a Formula 1
-The driving force The driving force is the force which propel the car , it is in the movement direction .Generally , it uses about 70 percent of his force to fight against rubbings and the resistance . -The aerodynamic support This force is called « the grip » by aerodynamic engineers. It’s a force which give grip to the car . To increase this force , engineers add some ailerons (front , back) Engineers use this vertical force to make up for the bearing pressure and stick the car on the road . Indeed , Formula 1 must wheel on a circuit with a lot of bends . So a minimum of grip is necessary to negotiate bends at high speed and keep the control of the car, without skids.
-The bearing pressure We meet this notion more generally with the plane , it’s a vertical force , but his direction is opposes of the grip direction and so it’s negative for cars . It is created by an air depression -The Bernouilli ‘s principle This principle recreate the principle of the bearing pressure. When the boy blow the fluid speed increase and it is created a depression on the paper and a surpression under the paper , so the paper go up . Demonstration of the Bernouilli’s principle with a paper .
II /Presentation of experiences -The aim We do two experiences to justify what we say . With these ones , we can do better explainations , and for all people it’s more interesting than some abstract explainations . -Experimental protocols * First experience This first experience consists to calculate the aerodynamic coefficient (cx) of two cars . We use the same car but in the second part of the experience , it is covered by paper to obtain two different cx from two cars which have the same weights , and frontal surfaces . And to do that , we use the « Pitot tube » to measure
the speed of the fluid upstream from the car (in m/s) , a blow machine to produce wind , and a dynamometer to measure the resistance force (in Newton). Dynanometer car Pitot tube Blow machine
* Second experience For this second experience , we use cars model (one normally , one covered by paper), and a spring system . At the first time , we do the experience an we measure the distance and we do the same thing with the second car . After we compare the two distances and normally, we note that the car with the best cx go further than the other car ( covered by paper) Tthe spring system Car : formula 1
III / Runnings and results of experiences The aerodynamism coefficient (cx) have an effect on three important car performances . -The speed The first is the speed of the Formula one because with an improved cx , the resistance and rubbings are less important ( T=Cx.S.1/2.P.V² ) and so the motor or the driving force fights less against these ones and propels faster the car
-The oil consumption We can deduce the second which is the oil consumption from the first because if the motor work less for a better or the same Formula one speed then the motor consume less oil , it is very important for all people ( in Formula one of course but for citizen too because it is cheaper and more ecologistic ). -The security The third and the last is the security of the car because at high speed and with an improved cx , the car have a lot of grip . And a car with an good cx is less sensitive to lateral wind and to turbulences because the frontal surface is less important .
-Results * First experience The 1st one is without a paper and the 2nd one is with one. Weight of a sheet: 5.033g; its surface: 0.05643 m; weight of the sheet that was used as the frontal surface:0.36g; 5033 g 0.05643 m 0.36 g ? surface of the sheet: Fs2 = (0.05643*0.36)/5.033 = 0.0062 m We found then: U = 18 meters per second; Fx1 = 0.025 Newton; Fx2 = 0.05 Newton; Fs2 = 0.01591 m. Cx formula is: Cx = Fx / (1/2 * Poo * Uoo * Fs) However:* U is the wind speed they were produced by the same machine which has just one regulated speed; then U are equal; ·
P is the mass for a air volume we can say that it was the same in the two cases; To have comparison of Cx1 and Cx2, we can just have it: Fx and Fs . To don’t write an error 1/ (½ * Poo * Uoo) is replaced by K. Cx1 = K * Fx1 / Fs1Cx2 = K * Fx2 / Fs2 Cx1 = K * 0.025 / 0.0062 Cx2 = K * 0.05 / 0.0062 Cx1 =4.03 K Cx2 = 8.06 K Then: with Fx1 < Fx2, we obtain Cx1 < Cx2.
* Second experience D1 : 70 cm and D2 : 58cm D1> D2 We found a bigger distance for the first car (without paper) than the second car . And there is the same force at the begining from the spring system. So with a an improved Cx , performances are better
Conclusion We needed two different ways to achieve our objective. At first there’s the theoretical study, necessary to know the aerodynamism basis, its functionment and how to calculate it. Secondly, there’s the study on an experimental basis ,its the center of every F.P.W. This second part permits to apply all what we’ve learned with making our testings a reality. Then, thank’s to them, we’ve discovered that a car with a better ( a smaller) Cx or aerodynamism goes farther in the same conditions. Of course, the internal conditions were the same because the two parts were realized with the same car but as far as the externals, they were incorrect because it didn’t happen in a laboratory: our experiments weren’t qualitative but significant.
To traduce the calculations in english, a bigger Cx generates a bigger resistance force. However, more the resistance is significant and because of the fact that it is a horizontal force which is opposed to the movement, it slowed down the racing car. This resistance requires more oil, the weight is increased. The support, depend on the mass of the object that is moving and which is the whole of frictions on the ground, is also increased.