From Physics debate to prototype vehicle
While it’s possible for sail boats to travel many times the speed of the local winds by using Bernoulli’s principle, is it possible to have a land based vehicle do the same? “Wait,” you say? “How can a sail boat travel faster than wind when it is only wind powered?” Simple, by traveling at an angle to the downwind direction, you can force more air to travel over the curved section of the sail, creating a pressure difference between the front & back of the sails. This provides your thrust.
This equation is important when considering how the thrust of the fan is produced. Here is the equation for fluids at constant depth.
So… how does it work?
Since the propellers are designed to be more like a fan (pushing air backwards), the test vehicle is able to travel directly downwind and acclerate. The downwind speed is, say, 10mph. The vehicle is initially pushed upto wind speed from pressure hitting the vehicle from behind. The driver then adjusts the pitch of the propellers such that the kinetic energy from the wheels creates thrust pushing more air behind the vehicle. While the wind on both sides of the vehicle is still 10mph, the wind speed directly behind the fan is, say, 8mph as the net difference reduces the pressure behind the fan, but increases it before the fan. As long as there are air particles to push backwards, the fan will continue to accellerate the vehicle. Cool, huh? Of course, this also requires minimum resistance on the gearing and the wheels to continue forward travel. Physics is fun. 🎡🎆