Flow Rate

[vivatix]

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I know that there are 2 equations for flow rate but I am confused about which one to use for which type of problems.

A1v1 = A2v2

Q = P/R

For example, Q. If the radius of the blood vessel increases by a factor of 2, what happens to flow rate?

Why can't I use Q = A x v equation?
Area of blood vessel would be pi x r^2
Q = pi x r^2 x v

If r x 2, then Q x 4

Can someone go over the difference between the 2 equations and when to use which one?

 

[bee17]

You need to check out Poiseuille's equation. Flow rate is proportional to r^4, so increasing the radius by a factor of 2 would increase flow rate by a factor of 16.

 

[vivatix]

I know Poiseuille's equation but I am confused on when to use which equation.

For example, Questions: If the radius of the blood vessel increases by a factor of 2, what happens to flow rate?

Why can't I use Q = A x v equation?

 

[bee17]

You might find this thread helpful:
http://forums.studentdoctor.net/thr...-when-to-use-the-continuity-equation.1148776/

 

[vivatix]

Thanks, that was helpful 🙂