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negative pressure gradient in cone-shaped pipe

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Old   April 29, 2017, 15:16
Default negative pressure gradient in cone-shaped pipe
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Hello,

I was wondering (and also calculating) if it's possible to create a pipe which gives you no pressure (static pressure) drop, or give you higher pressure at the outlet.
I'm prette sure this is basic fluid mechanics stuff (separation occurs, due to negative pressure gradient right?) but anyway, wanted to ask you guys. So, we have two effects:
-pressure drop due to friction (Darcy law)
-pressure raise due to conversion from velocity to static head (Bernoulli equation)

So, we have one equation (loss)
dp_l=lmb*L/D*rho*u(L).^2./2 (negative value)
and we have gain:
dp_g=rho/2(u0.^2-u(L).^2) (positive value)

soooo, is it possible to create a pipe which gives you u(L) function that makes those two equal, or gain higher than loss?

why couldn't we create a pipe that gives you like infinite static pressure?
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