BreezyRacer wrote:speedsense wrote:
I would argue that wings are the only creation of downforce. Tunnels, diffusors only stop/reduce the creation of lift. In simple terms, once a gap to the ground is increased these devices stop functioning. As per your example of ground separation. A wing has the opposite effect, get it too close to the ground and it will stop it's function, however every other position it will produce forces.
So is it (a wing) the only true producer of downforce? All the other devices are constrainted by their enviroment and only work when in one perticular postion...
With DDD, diffusors that have a second chamber above the diffusor, encased in it's own chamber, how is it that an enclosed space, similar to an air for the engine intake, can produce downforce? My thinking is that it is designed to replaced the missing wing close proximity (2009 wing height rules) and the creation of vortices to model the wings addition to "drawing" air out the exit of the diffusor is the function.
Speedsense, you might be confusing exactly how an undertray/diffuser setup works. In a well designed undertray, the DF is created in front of the diffuser, not in the diffuser. How well the diffuser operates with ride height changes, curbing, chassis roll, etc is part of making an effective design. And as with a wing, if you get too close to the ground the undertray too will stall. However with the 50 mm step rule that problem is taken care of, and I would argue that the step even enhances the undertray's abilities. A big difference between undertrays and wings however is that in contrast to a wing, undertrays create very little drag to go with the downforce.
Think of the double decker diffuser design as simply a way to share an even lower pressure area of the car with the undertray. Without close interaction with the lower wings the double decker exit design double deckers wouldn't be all that useful.
Instead of thinking in terms of specific components used to create DF, such as splitters, wings, endplates, diffusers, gurneys, etc it might be helpful to see how each of these components work to create DF. Then instead of looking at a particular component you can track/visualize the airflow along the car and thus the interaction of the entire vehicle as a whole. That's the way I tend to look at the designs, anyways.
In my world, I do look at a race car as a "whole" package. Also in my world, I see things, like high pressure introduction into gaps along the sidepods, between the wheels and because of the wheels, the car in front and the irregular surfaces that cars run over. These uncontrollable enviroments, dislodge the strict (or not so strict, depending on which side of the fence your on) aero "rules" and throw literal wrenches into the reasons why the perticular devices function as they do. You can look and analyze them individual, and define their existance, but ultimately you have to run it in it's intended enviroment and it will change the reason for it's use and it's operation.
We actually agree in how the diffuser works, in that the forces are because of what the pressures are around the diffuser and not so much in it. Though I would argue that down ward forces are not created there. Much like a boat in water will not sink, no matter how aero it's bow is.
Were you to design a similar bow to a flat bottom/ diffuser and place it exactly as close to the bottom as an F1 car, and flow water passed it at a comparable speed, would it create a downward force? Not until there is a downward force from above the boat (with air speed equal to water speed) and some device that is actually creating the downward force.
As an arguement for the semenatics, if this device were a wing on the upper boat surface, it would produce downforce even if the bottom of the boat, were a regular boat bow. It would however have greater force of forcing the boat to the bottom, if it had the F1 style bottom.
And to further the agrument, turn it upside down, the only thing creating constant lift would be the wing, unless we add a roof (for the bottom to start working) to the whole contraption. Spoilers, windshields etc. would cause lift as well, thought the only device capable of lifting the boat out the water and maintianing flight would be large enough wings.
Though I don't agree with a "closed" compartment, like the second tier of a diffuser as a low pressure area that has added any forces. A look at the outlets and forms of the Hungry Mclaren diffuser and the Brawns, all reflect vortex generation. They seem to be larger and wider vortices that are trying to be created. These are to further enhance the counter rotating vortices created by the "slats" dividing the inside of the diffuser. Much like the bottom of the wing, that is no longer in the same area.
If it was that the low pressure "compartment" is the reason, why not create similar low pressure compartments through out the car, in the side pods and nose?
Unless a ground effect device, or a flat bottom, is sealed to the ground, the intervening air plugging the gaps along it and around it, will continue to introduce alternating pressures to a device that in theory, should only have a lower pressure associated with it. I still contest that removal of the existing higher pressure areas and lowering them is a scavenging (>sic?<) device and an attributing factor to enhance devices that create downforce (wings and spoilers above on the body).
BTW, laying the diffuser on the ground, with a stepped bottom, will not stall the diffuser, but will actually make it more efficent. You have to completely prevent air from getting to it, from the sides as well to stall it. The sides of the diffuser exposed to the stepped floor will generate higher velocities within the diffuser. Unless there was some way to pitch the front of the car through the ground. IMHO
"Driving a car as fast as possible (in a race) is all about maintaining the highest possible acceleration level in the appropriate direction." Peter Wright,Techical Director, Team Lotus
