Aero Efficiency

[m3_lover]

What is Aero Efficiency? Does anybody have pictures showing this and a explanation?

[manchild]

In order to cause smallest amount of drag car is being designed as aerodynamically efficient as possible. So aero efficiency is term usually used with good or bad, increased or decreased... - aero efficiency.

More drag = decreased, bad... - aero efficiency
Less drag = increased, good... - aero efficiency

http://www.f1technical.net/articles/10

[kilcoo316]

Uhh,

Aero efficiency is defined as the lift to drag ratio. L/D.


For a formula 1 car it would be negative, and the more negative it is, the better.

[Reca]

As kilcoo said aerodynamic efficiency is by definition the ratio between lift and drag. So when you hear that a F1 car has an aerodynamic efficiency of 3 (just an example, I don’t know the actual number), that means that while generating 3 N of downforce it also generates 1 N of drag. When on the contrary you hear that car A is more efficient than car B, it means that car A generates less drag for a given level of downforce, or, alternatively, more downforce for the same drag.

As a reference, the efficiency of a small airplane, like a small Cessna for example, is in the order of 10-15, the efficiency of the best gliders can even be in the order of 100. For a glider it’s obviously particularly important since they don’t have the engine and it also gives you an immediate indication of how many meters of altitude it will lose while flying, efficiency = 100 means that it will lose 1 m altitude every 100 meters horizontal.

Notice that the efficiency for an airplane isn’t a fixed number, it depends by the angle of attack and obviously by the configuration (flaps reduce it drastically), the airfoil used etc etc.
In the same way for a f1 car it depends by the aerodynamic setup. But it also depends by car attitude (rake, ground clearance, yaw angle etc etc) and also considering the huge influence vortices have in current designs, I wouldn’t exclude that efficiency could also slightly change with speed. And that without talking about flexing parts that everybody uses.
In slow and twisty tracks like Monaco they certainly sacrifice a lot of efficiency to increase downforce while on the contrary in Monza they possibly sacrifice a bit (not much) efficiency to decrease drag, hence I would look at configurations like for example Canada to find a setup were efficiency is the highest.
Comparing 2005 with 2006 then, in 2005 it was crucial in term of aero design to generate as much downforce as possible, to compensate the, relative, lack of grip from tyres and with less concerns about drag because there was lot of power for it. This year drag reduction is lot more important because there’s less power and you also have lot of grip from tyres, hence aero efficiency is more important than last year was.

[superstirl]

so we know that aerodynamic efficiency is lower drag for higher downforce. Any F1 team then also needs to make sure that the airflow after the front wing doesn't create futher drag on the parts of the car behind the wing.

Here's my question: what create's more downforce for less drag; an angled flat (i.e /) panel, an upside down airplane wing shaped panel, or a curved flat panel (like over the rear tires of an F1 car)?

[manchild]

so we know that aerodynamic efficiency is lower drag for higher downforce.

Only in racing cars - not in general aerodynamics where downforce is not needed at all.

Here's my question: what create's more downforce for less drag; an angled flat (i.e /) panel, an upside down airplane wing shaped panel, or a curved flat panel (like over the rear tires of an F1 car)?

an upside down airplane wing

[kilcoo316]

Here's my question: what create's more downforce for less drag; an angled flat (i.e /) panel, an upside down airplane wing shaped panel, or a curved flat panel (like over the rear tires of an F1 car)?

Depends where you put it in the airstream.

Neglecting upstream effects, away from the ground, its the standard aerofoil shape, but close to the ground, undoubtedly the curved flat panel (ground effect).

[NickT]

Another point is that all the figures change at different points in the speed range. The primary goals of the aerodynamicist are to produce an effiencent design that:

* Generates a good negative lift to drag ratio accross the entire speed range of the car.

* Is stable during changes in ride height, pitch, roll, yaw and any combination of these.

* Has enough range of tuneability for the driver to balance the car to his liking and the team to balance the car to the circuit.

Simple realy, in theory but in practice

[DaveKillens]

As Reca pointed out, aero efficiency is lift versus drag. It's that simple, and easy to define. But there are many factors that affect that ratio, and it can change depending on variables. There is no perfect shape that gives optimal values, just optimal shapes for different variables. For instance, an aircraft wing that generates great lift to drag at 300 kph may just plain suck at 3000 kph. And vice versa.
And when you visualize how air is influenced and generates drag and lift, there are basically two different laws of physics that are relevant. Bernouilli's theorem, where an increase in velocity produces lower pressure, and Newton's third law, "For every action, there is an equal and opposite reaction." A simple kite is a very good example of this third law in action. It's just basically a flat plate, placed at an angle to the relative wind. The air molecules strike the flat object, and are forced in one direction. Because the flat object is forcing the air in one direction, the flat object is being forced in the opposite direction. And if you've ever flown a kite and hung on to the string, you know that it generates tremendous drag, which is very inefficient.
So when you visualize an object, it is influenced by the sum of these two forces. A wing at zero degrees angle of attack to the air has very low drag, yet generates lift. But as soon as youy turn it on an angle to the wind, Newton's third law kicks in and more lift is generated, but much more drag too. Crank in more angle of attack, and the lift to drag ratio skyrockets, giving more lift, but much increased drag. There comes a point where the air starts to separate and shed from the skin of the object, and then it becomes incredibly inefficient. Drag skyrockets, and lift drops. In aircraft, this is the stall region, and that's when planes can fall out of the sky.
Also, in a racing car, the aero is heavily influenced by the interaction between itself and the ground. It's very complex, and that is why all the major teams have wind tunnels that have a moving road surface, so they can study this.
In a racing car with wings, you can generate as much downforce as you want, just keep cranking in more wing angle. But drag increases, so you suddenly find that top speed and acceleration suffers. The trick is to find the balance between getting enough downforce to get through the corners as quick as possible, yet remain fast enough down the straights so you don't get passed.
http://www.grc.nasa.gov/WWW/K-12/airplane/bga.html

[kilcoo316]

Dave, I would say they cannot get enough downforce on the cars presently.

Circuits like Monaco, Hungary, Imola, Nurburgring and Melbourne would see the teams at their maximum downforce levels I would suspect.

I would say the V-8s have increased the impact of L/D as opposed to pure downforce levels in the past.