With the changes to the regulations this year in F1, some aerodynamic effects known as porpoising were seen. This is where the aerodynamic characteristics of the vehicle, combined with the mechanical properties, cause the vehicle motion to oscillate in an undamped manner. This is usually initiated by aerodynamic behaviour that is inconsistent with changes to ride height. Endurance series, such as LMP1 and LMP2, have suffered from this in the past and race engineers have to find a balance to mitigate the issue. Stalled front wings and vortex bursts, particularly at low ride heights, are often the cause of the excitation.
“With hysteresis in the aerodynamics, dynamic motion gives you vastly different results to a series of static simulations”
Aerodynamic development is usually carried out at multiple but fixed attitudes due to computational or experimental constraints. However, it is possible to carry out dynamic simulations, where the vehicle attitude is oscillated at a given frequency and amplitude. This is slightly different to reality where the aerodynamics initiate the motion, but it can help pin point causes of the unsteady aerodynamics.
The video, shows the dynamic motion of an F1 car drawn by Ryan Vella, to meet the current regulations. Although it is relatively underdeveloped, it gives you an insight into what can be seen by this approach. The surfaces of the car are coloured by static pressure contours. The simulation was carried out by Catesby Projects, using a DES based transient solver with mesh motion.
We hope to follow up with more posts to give additional insight into how this type of simulation can be useful in aerodynamic design, development and trouble shooting.