Where does this equation come from?
Where does this equation come from?
(OP)
Hi,
In a text book I found an equation for the volumetric flow rate of air through a channel (tube). I can't find from where the equation is coming, someone an idea?
The equation which I mean is: Q = - pi*d^4/(128*viscosity)* dp/dx
I know that Q = A*v = pi*d^2/4 *v
Also from the simplified equation of motion 'v' can be calculated as:
dp/dx = viscosity * ddv/ddy (dd = second derivative)
from this equation v = ?? if I fill v in, in Q = pi*d^2/4 *v will this give Q = - pi*d^4/(128*viscosity)* dp/dx ??
In a text book I found an equation for the volumetric flow rate of air through a channel (tube). I can't find from where the equation is coming, someone an idea?
The equation which I mean is: Q = - pi*d^4/(128*viscosity)* dp/dx
I know that Q = A*v = pi*d^2/4 *v
Also from the simplified equation of motion 'v' can be calculated as:
dp/dx = viscosity * ddv/ddy (dd = second derivative)
from this equation v = ?? if I fill v in, in Q = pi*d^2/4 *v will this give Q = - pi*d^4/(128*viscosity)* dp/dx ??





RE: Where does this equation come from?
It could be the formula is a derivation of the famous Hagen-Poiseuille law for friction dissipation in a horizontal pipe:
Replacing r = D/2, one gets:
RE: Where does this equation come from?
Cheresources.com devotes a lot of attention to flow problems using this handbook.
This is a book you need to own if this is more than a passing interest in flow.
JMW
www.ViscoAnalyser.com
RE: Where does this equation come from?