Deck_3_Stability_and_downforce_crosswind_diffuser_ground_effect

Question 1

What 3 types of rears effect both front and rear Axle lift.

And how are they effected, and why does that matter

Answer 1

Notchback, fastback, squareback

These effect the lift coefficients and therefore the higher the Cl the worse the handling

Question 2

How can body style (fastback vs squareback) affect cross-wind behaviour?

Answer 2

Different rear shapes promote different attachment/separation patterns under yaw, which changes the magnitude/trend of side force and yawing moment (stability sensitivity).

Question 3

What do cross winds and transient conditions affect.

Answer 3

Effect of side wind on front and rear lift is important for vehicle stability/handling

Question 4

In a cross-wind, what two aerodynamic “extra loads” are highlighted

Answer 4

Side force coefficient, Cs
and yawing moment coefficient, Cym
increase with yaw and depend on rear shape/flow separation behaviour.

Question 5

What is a Diffuser and what is it designed to do?

Answer 5

A rear diffuser is the rising underbody section at the back of the car.

It’s designed to:
keep the underbody flow fast. and
then recover pressure smoothly at the exit.

Question 6

What does an underbody diffuser do to drag and rear lift as diffuser angle increases?

And what can its effectivenes depend on

Answer 6

Increasing diffuser angle generally reduces rear lift (can create rear downforce).

drag Cd typically decreases only up to an optimum angle; beyond that​ Cd rises because diffuser flow separates.

Diffuser effectiveness also depends on ride height and body style (fastback vs squareback)

Question 7

What is ground effect in vehicle aerodynamics?

Answer 7

Using the underbody + proximity to the ground to accelerate underbody flow, reducing static pressure under the car and generating downforce.

Question 8

Why do racing cars use flexible skirts with ground effect?

Answer 8

To seal the sides and reduce pressure leakage under the car, helping maintain a strong low-pressure region and more consistent downforce.

Question 9

What does a negative Cp
under the car indicate?

Answer 9

Pressure under the car is below freestream (suction), contributing to downforce when integrated over area.

Question 10

What is the purpose of a front air dam (road car)?

Answer 10

To control/restrict underbody inflow and help establish a lower-pressure, higher-speed underbody region (reducing lift / improving stability).