Quote:
Originally Posted by hat_man
I'm willing to learn something here but I'm going to need some guidance.
Is the lift of the Dream created by the attached airflow over the top of the profile or because the design of the underside creates more pressure on the underside than is created on the top (underside pressure >topside pressure. Lift created by a specific design.) or us the lift created by the basic shape resembling an airfoil and adds as such (Bernoulii ?) because it is positioned high enough off the road that it acts as a "wing" (not a specific underside design to create lift, but placement of a basic design in relation to the road to create lift)
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1) there's a bunch of different Dream vehicles, so we'd want to discuss a particular version.
2) that said, lift will be caused by less pressure on top than on the bottom.
3) the contour determines the pressure, as it also determines the velocity, which are always dance partners.
4) all the cars are light for their dimensions, however, I believe the real issue is with crosswind and especially with gust.
5) If an Australian land train gust reaches the wheel fairings, they may act like a weathervane, turning the entire car sideways, where it takes on a much larger aspect ratio ( longer wingspan ) in relation to the car going straight forwards ( very little wingspan ). For the weight of car and driver, the coefficient of lift may be great enough, such that the lifting force exceeds the static load of the racer, and it must takeoff!
6) GM feared this in 1987, and removed the entire wheel fairing package as a palliative. Cd rose from 0.125, to Cd 0.147. In the documentary film, 'Who Killed The Electric Car,' there's a brief section filmed inside GM's wind tunnel, with Dr. Paul MacCready using a pitot-tube as a stethoscope to ascertain the limits of the boundary layer thickness. He's also responsible for calculating the 400-mpg Sunraycer would yield as an ICE vehicle.An inspiration for my projects.