Getting our priorities straight...

[GasSavers_mattW]

I was just looking over my notes from a course I did at uni about solar car design. I came across these nine rules for minimising drag. Its no so much the rules that are interesting, its more the priority given to each rule. They are given in order so changes affecting the rules lower down the list should only be made if they don't compromise the top ones. Trying to get these priorities right might help in making decisions about aero-mods. NB: this list is specifically for very aerodynamic and streamlined solar cars, the priorities might be different for normal cars.

1. Ensure attached flow over every surface of the vehicle.

2. Minimise wetted Area (i.e. surface Area exposed to air flow).

3. Maximise laminar (non-turbulent) flow over as much of the vehicle as possible.

4. Surface finish should be as high a quality as possible (especially ahead of the transition point to turbulent flow).

5. Minimise lift/down force.

6. Minimise wing tip drag (i.e. where two flowing streams of air come together).

7. Decrease frontal area (this is pretty far down the list because it generally compromises the other 6 rules).

8. Minimise interference drag (drag caused by the combination of boundary layers when two shapes meet).

9. Minimise ventilation drag.

It might be good for some of the more well informed aero-dudes to edit the order of this list for conventional cars. I'm sure things like wing tip drag are less of an issue and laminar flow is virtually impossible to maintain but as I said above, getting our priorities straight would help a lot in making aero-mods.