The figure below shows the effect of vehicle ride height on lift and drag. Notice that the drag is insensitive to ride height, yet the lower ride height generates an increase in download over the vehicle. This can be explained quite simply by using Bernoulli’s famous theorem, which states that, due to the principle of conservation of energy, the total energy of a lump of fluid moving with the flow must remain constant. If compressibility of the air effects are ignored, this implies that, as the fluid accelerates to pass through the tight space under BLOODHOUND, the corresponding increase in kinetic energy must be compensated for by a decrease in some other form of energy, in this case, pressure. The implication is that the lower the car is to the ground, the faster the flow must accelerate to ‘squeeze’ underneath, the lower the pressure experienced by the base of the car, and hence the greater the suction effect pulling it towards the ground. A bit of download is good, too much is not (at 1000 mph we can generate huge forces!), so we are using this data to find the ideal ride height.
http://www.bloodhoundssc.com/_db/_im...1212014023.jpg
Although the designed maximum speed ofBLOODHOUND is 1050mph, the aerodynamic response of the car has to be such that it is safe and drivable right from its initial roll all the way up to this top speed. This makes the design loop for optimisation of the geometry an extremely complex activity especially since as BLOODHOUND accelerates and decelerates through the ‘transonic’ regime (just below fully supersonic) when parts of the flowfield are supersonic, and parts remain subsonic, conditions (such as positions of shock waves) are changing rapidly. All in all, this makes working on the BLOODHOUND aerodynamics both a massive privilege and challenge!
Not sure what it all means but it was taken from here http://www.bloodhoundssc.com/car/aerodynanics.cfm Also I doubt the ZS will be exceeding the speed of sound! |
