2023 technical regulations change

 Hello and welcome to my 4th article on the Formula OverAnalysed blog! Today I will be talking about the minor 2023 technical regulations change. 

 During every session of 2022 pre-season testing and most of the opening few races, one word, in particular, was oft-repeated: porpoising. As I briefed over in my previous article while talking about the W13, it refers to the verticle oscillation or bouncing of the car on the straights, which are occasionally quite frequent. As this was impacting the spine health of many drivers due to how brutal porpoising presented itself along with being an effect that hindered the ability of the car, the FIA decided to raise the bottommost tip of the floor by 15 millimetres. But, how does porpoising actually take place? How does raising the floor aid in counteracting this?

This is where a little bit of fluid dynamics is to be known; specifically, Bernoulli's principle.

In simple terms, Bernoulli's principle states that the faster a fluid moves, the lower the pressure it exerts on the surrounding bodies. In practice, this can be seen by passing air or water over a Venturi tube. A Venturi tube is a tube which has a region of constriction, where the area of that region of the tube is smaller than the 2 other, equal parts of the tube. While it is a digital image, the picture below shows how the pressure change occurs in a Venturi tube: note that in the constricted region, the velocity of the air increases, and its pressure decreases.

This then begs the question: how is this related to F1 at all? Well, given the new general regulations regarding the floors of the cars, the floor itself can be seen as a semi-circular version of the Venturi tube: the front part is the air inlet, the constriction lengthened on either end, such that the region of high velocity is relatively small, and the diffuser can be the rear part of the tube .

(See summarised labelled picture below)

Hence, when the car is accelerating on the straights, the air passing under the flow gets constricted, then moves at a velocity greater than that of the car, and then decreases the pressure of the floor acting on the underside of the car relative to that over the floor. It is then that the floor gets pushed closer to the road. When the car gets pushed too close to the floor, the pressure of the diffuser itself drops so much that the diffuser 'stalls' as it is no longer receiving a sufficient amount of air for it to work efficiently. As more air is collected at the mouth of the diffuser than is 'dissipated' by it due to the car running so low, the air under the car itself now exerts a pressure on the floor greater than the air above it, causing the floor to rise. The car rises so much that the air is again constricted, and the whole cycle is repeated.

Since the cars themselves reach tremendous speeds of over 280 kph on the straights, the frequency of the phenomenon above -known commonly as porpoising- was too much for comfort initially; figuratively and literally. (Lewis Hamilton once complained about his back hurting pretty badly after the out-of-hand porpoising in his W13.) This could be easily negated by decreasing the constriction of the floor from its top edge, but this would make the car slower around the corners due to the lesser amount of downforce generated through ground effect.

Some may then ask:  Why was this not a big issue in the past? Venturi tunnels are not a new concept, and were around in the 70s, so why is it only now that we see this issue so prominently? The simple answer to such a question is that there were solutions that were permitted then but not so, under the 2022 regulations.

The cars of the past had something that was called a 'skirt' that ran the length of the sidepod. The aerodynamicists of the teams of yesteryear like Lotus' Colin Chapman were able to predict porpoising early, and hence added a rubber-ended thin sheet of aluminium to the outer edge of the side pod. The skirt itself would prevent the car from getting too close on the straight, such that the diffuser would stall and cause porpoising.

It was able to do so despite being relatively small, thin and short (heightwise) as those cars didn't have a floor that we are all now familiar with, and since the cars were much shorter and lighter than those of today, the relatively low wear and tear would allow the skirts to be durable for at least a session of a race weekend. An example of a skirt that Lotus ran in 1979 for their Lotus 79 is pictured below

Such a device is not possible as the FIA pretty much have it outlawed as of their 2022 and 2023 regulations. However, the FIA do acknowledge porpoising as a serious threat to racing and health, and has since stepped in to update the initial regulations, which will be implemented in 2023:  the bottommost tip of the floor can now be 15 millimetres further away from the ground/road/reference place than before. This means that while the ground effect itself is present, it will not be to the extent of the initial few races and sessions of 2022, allowing for lesser porpoising and better racing.