Sunday, July 11, 2010

Laser aerodynamics

One of the intentions of the new technical regulations introduced for the 2009 F1 season, was to exclude the existence of bargeboards between the trailing edge of the front tyres, and the leading edge of the sidepods. A crucial function of these devices was to guide the turbulent air from the front wing and front wheels, away from the vital airflow underneath the car, that ultimately feeds the diffuser.

Now, the teams responded to this with typical ingenuity, by shortening the sidepods, and installing mini-bargeboards in the newly created region of space. Nevertheless, the regulations were successful here in eliminating full-length bargeboards. When an item is banned in F1, however, the engineering tradition is to find some other means of achieving the same effect, so let us see if we can do just that. Note, however, that what follows is not intended to be a serious short-term practical recommendation, more an attempt to demonstrate the art of the possible.

Bargeboards were solid, 2-dimensional surfaces. When a solid is introduced into a viscous airflow, the surface of the solid provides a new boundary component, along which the airflow velocity must be zero. In the case of a bargeboard, this creates a stagnation point at the leading edge, and boundary layers down the inner and outer flanks of the boards. The stagnation point at the leading edge forces the streamlines of the airflow to go either side, hence the stagnation point functions as a branching point in the airflow. Thus, a solid, 2-dimensional surface is a hugely convenient device for enforcing the separation of airflow.

However, with bargeboards now banned, the question is whether there are other means of enforcing the separation of airflow in the region of space between the trailing edge of the front tyres and the leading edge of the sidepods. The rules prohibit solid substances in this region, so what else could we use?

Well, in principle we could use a plasma, but confining the plasma would be rather tricky, and would require the use of magnetic fields generated by superconducting magnets, which in turn would need to be cooled by liquid helium. That would be rather challenging to package.

So how about electromagnetic radiation? The regulations only prohibit the presence of solid substances in that sensitive region of space behind the front wheels. The space all around the car is already filled with natural and artificially generated radiation, so banning the presence of radiation would be very difficult. If electromagnetic radiation is permitted in the space between the front wheels and the sidepods, then it follows that coherent radiation, or laser light, is also permitted, and it may be that we can create virtual bargeboards out of laser light.

For aerodynamic purposes, the crucial property of radiation is that it is capable of applying and transferring pressure. Lasers provide the capability to inject pressure into an airflow at very precise locations, and could therefore be used, amongst other things, to create stagnation points in the airflow, and narrow high-pressure layers of air. By this means, lasers could, in principle, be used in F1 to replicate the function of bargeboards in achieving airflow separation.

Needless to say, this would not be the work of a moment. The radiation pressure would create high air temperatures as well as pressures, and the injection of heat energy into the airflow just in front of the sidepods is not necessarily ideal. There is also, of course, the question of laser energy consumption. One might wish to power F1 lasers with the energy stored by kinetic energy recovery systems (KERS), and such an aspiration will be assisted both by the gradual decrease in laser energy requirements over time, and the gradual increase in the energy harvested by KERS.

Nevertheless, given the heat energy injected into the airflow by lasers, it is perhaps at the rear of the car where they could most usefully be employed. Red Bull, of course, have re-introduced exhaust-blown diffusers to the sport this year, and the point about these is that they ultimately use heat energy generated within the engine for aerodynamic purposes. Craig Scarborough explains how Red Bull may be using retarded ignition in qualifying this year to maintain the flow of exhaust gases even when the driver is off the throttle. Perhaps a single KERS-powered laser inserted into the exhaust tract of the engine could achieve the same effect here...

4 comments:

Hasala said...

That is a very interesting idea, but how exactly would you create a curved profile using a laser beam? I mean, a laser beam would be a straight, continuous line right? so wouldnt you be forced to have a straight line which affects aiflow rather than a curved, aero-friendly profile?

Gordon McCabe said...

Indeed, a curved profile would be tricky! But a simple diagonal bargeboard would still be useful.

Neutrino said...

If we consider article 3.15 of the F1 Technical Regulations:

3.15 Aerodynamic influence :
With the exception of the cover described in Article 6.5.2 (when used in the pit lane), the driver adjustable bodywork described in Article 3.18 and the ducts described in Article 11.4, any specific part of the car influencing its aerodynamic performance :
- must comply with the rules relating to bodywork ;
- must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom) ;
- must remain immobile in relation to the sprung part of the car.

Now the photons eminating from the laser are definately not immobile in relation to the sprung part of the car and definately influencing the aerodynamics of the car, but are they "a specific part of the car"?
An interesting question for Charlie Whiting!

It is rather like the blown diffuser question - the exhaust gasses influence the aerodynamics and they are moving. One might take this particular argument further and say that they are expelled by a moving piston which is definately a specific part of the car..........

Gordon McCabe said...

Indeed, good point Pat, and one could argue that there's no difference in principle between an exhaust-blown diffuser and Gordon Murray's Brabham fan-car.

An F1 car already emits numerous photons for measurement, telemetry, timing and communication purposes, all of which move with respect to the sprung part of the car. Their legality is currently uncontroversial because there is no suggestion that they perform an aerodynamic function. But would it always be possible to distinguish between these different functions? Might one, for example, use a laser for aerodynamic purposes, but claim that it is a tyre-temperature sensor?