Wolff reveals Red Bull's NEW and effective car trick! Mercedes to copy?!https://www.youtube.com/watch?v=AuLZwzXynC4The reason why Redbull RB18 is faster than Mercedes W13 is that Redbull RB18’s shape makes it move in an “aerodynamic envelop” whilst Mercedes moves on an “aerodynamic plane”. The reason is the bottleneck formed by the side pods on the Redbull RB18 and on other cars.
Assuming that models of Redbull RB18 and Mercedes W13 were made of slippery/soapy material, it would be impossible to lift the Mercedes around the side pods due to its triangular cross-section; but one would easily lift the Redbull RB18 below the side pods. This is what aerodynamic flow at high speeds does. Whereas the Mercedes is just pressed down by air but lifted up by mechanical suspension springs. The aerodynamic envelope around the Redbull RB18 gets more effective the faster the car moves, and as such dampens the tendency to porpoise. Thus, the body is pressed down and lifted up by the same aerodynamic flow - but different in magnitudes down and up. The resultant effect is that the car body moves in an aerodynamic equilibrium, shaped like the letter - C - turned over by 90°. If one imagines the way an umbrella can be flipped over in stormy weather, then one can reckon that the aerodynamic envelope around Redbull RB18’s side pods stabilizes the car body to such an extent that porpoising is fully attenuated. The fact that aerodynamic loads pressing the car down and lifting it up around the side pods increase or decrease in equilibrium, engineers simply have to make fine adjustments to get maximum downforce without porpoising. Redbull RB18’s mechanical suspension therefore only dampens the usual track surface vibration and does not cause any oscillatory movement - porpoising. Even if it were to porpoise slightly, the aerodynamic “envelope-” would counteract by proportionately damping the tendency; Mercedes, on the other hand, is simply pressed down 100% aerodynamically but lifted up 100% mechanically – thus the cause of porpoising. Mercedes has no choice but to emulate Redbull RB18 by using the side-pod bottleneck. One cannot go around physics by a “trial and error” approach; one must have an objective that is economically, legally, scientifically, and technically viable.
Exactly, the RB 18 pods have a bottleneck (undercut) that helps lift the body just enough to avoid stalling of ground effect airflow. At those speeds, airflow makes the difference in 10ths of a second. Put your hand out of a car at 130kph, any difference in shape you form with your hand moves it up or down or sideways.
"Aerodynamic plane" means the aerodynamic loads act only downwards; "aerodynamic envelope" means some loads act downwards and some upwards. Redbull moves like a suspended train on an overhead rail, where the rail is the air flowing past the car at high velocity, but with wheels contacting the track. Where Mercedes has 100% downforce, Redbull has (100-X) %, where X is the share of upward lift. When you lift something with two fingers, the two fingers make a C-cross-section, flipped through 90° thus hooking the object. If you measured the forces acting through the suspension spring on Redbull and on Mercedes, you would see that the forces in Redbull springs are less than those in Mercedes springs because the aerodynamic envelope modulates the magnitude of forces that the springs experience.
Decisive is not only the side pods, but the undercut; they lift the car like the wings on an airplane do, just enough to make the desired difference. Newey knew this, that is why RedBull first complained about Mercedes's new side pods, but soon backed down. If Newey does not complain about or copy your design variation, then you have an aerodynamic problem.