# What is a Car Diffuser?

For more information, visit https://www.airshaper.com ---------------------------------------------------------------------------------------- Link to sample report: https://airshaper.com/assets/reports/aquilo.pdf ---------------------------------------------------------------------------------------- In this video, we will be discussing car diffusers. How do they work? Why do car designers install them? How can you make one for your design? Theory - the Bernoulli effect The Bernoulli effect states that if you follow an air particle along its path within a flow the energy density remains constant. This means that if one term goes up, another must go down. This means that for example, if the velocity increases, the pressure has to go down. Relation to the car underbody The car underbody is the bottom side of a car. At the front of the car, you have high pressure because the air collides with the front of the car. At the back of the car, the pressure is lower because the wake wants to pull the car backward. This pressure difference between front and back of the car is the driving force of the airflow beneath the car which is called the car underbody or car underbody aerodynamics. Down force Because this section is quite narrow, the air has to speed up and this is where the Bernuit effect comes in: higher velocity, lower pressure, creating a suction effect pulling the car downwards. For a sports car that's fantastic, it means more grip. Diffuser This effect of accelerating the air below the car can be much improved by shaping the rear of the car underbody, by giving it a slight upward angle. This improves the transition to the normal velocity of the surrounding air and it helps to fill the wake behind the car. The result is an even bigger acceleration underneath the car with more downforce as a result. Design So if you want to design a diffuser, the question is, how large should the angle be? Too low and the effect will be too limited. Too high and the air will separate and not follow the geometry of the diffuser. So much depends on local dimensions and aspect ratios. An angle between 7 and 10° is considered quite a good starting point for your design. ----------------------------------------------------------------------------------------------------------- Wouter Remmerie Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week! For more information, visit: www.airshaper.com www.facebook.com/AirShaper www.linkedin.com/company/airshaper #AirShaper #CarDiffuser #SportsCarDesign