Ground effect interaction problem.

[robinfryer]

Hi again,

Im designing a super streamlined ground vehicle and wanted to come up with an initial design geometry based on mathematically defined curves.

I came accross a method in an SAE technical paper which defined the camberline of a car airfoil shape based on the lift coefficent delta Cz. The problem is i cannot get it to work, or at least reproduce the same results seen in fig 18 of the paper attached. The formula can be found on page 7 section 7 of the paper.Equations 3 and 4 are;

h=ho.exp(integral(Fx)dx) where
Fx=4/b^2 . integral(delta Cz) dx

h=camberline height
ho=inital camberline height (at x=0)
delta Cz=lift coefficent
b=vehicle width

Using there lift distribution shown in fig 18 i cannot reproduce the h value. The main problem i have is that when delta Cz=0 so should Fx and it follows that h=ho for Cz=0. Looking at figure 18, that is clearly not the case as h increases with x.

I know its a long shot but if someone could take a look at this method and see if they can reproduce the same result that would be great! Im sure this method must work somehow but there seems to be some missing information...

Thanks

 

[GregLocock]

e^0=1, so for Cz(x)=0, h(x)=h0, ie you need a flat camberline if the lift is zero.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[robinfryer]

Thanks Greg. You are awesome.