Fernando Birck really enjoys racing simulators -- so much so, that he runs Fergotech, a company specializing in racing simulation hardware and tools.
Recently Birck shared a really easy way to add a wind simulator to your home setup. The goal is to be able to have a variable amount of wind blowing in your face, getting stronger as you accelerate. He pulled it off pretty well and shared all his code and schematics so you could follow along.
As you can see in the video, thanks to his amazingly technical and advanced method of displaying the fan speed (a piece of paper), it seems to be quite effective. As his car accelerates on the screen, the fan smoothly also accelerates to supply more air movement. Yes, he points out that the windshield on his vehicle would stop the wind, but the effect is quite nice anyway.
How he's doing it is as follows. First, there's a piece of software installed on the computer that reads the speed of the car in the game. This data is then sent out to an Arduino, which is simply controlling a 12V DC computer fan via PWM (pulse width modulation). Fernando acknowledges that these fans aren't really made to run with PWM, so its life might be shortened, but they're cheap so he's not too concerned at this point in prototyping.
The schematic is extremely simple, requiring only a single transistor to handle the 12V power to the fan. He actually points out that if you were to go with a 5V fan, you wouldn't even need a transistor. You can download the Arduino code as well as the client piece of software from his web page if you'd like to try this out for yourself.
This kind of addition would be absolutely perfect not only for the kind of racing simulation in the video, but also for virtual reality setups like the occulus rift.