# Homework Help: Pipe Flow Drag

1. Oct 9, 2008

### Spimon

Hey everyone! I'm having difficulty and wondering if someone would be kind enough to help me figure out how to approach this problem. I'm a mechanical engineering student and reasonably new to fluid mechanics, and quite confused.
Thanks for any help anyone can give me

1. The problem statement, all variables and given/known data
http://img522.imageshack.us/img522/6383/pipedg4.jpg [Broken]
http://g.imageshack.us/img522/pipedg4.jpg/1/ [Broken]

An incompressible fluid enters a horizontal circular pipe (at inlet 1) with uniform velocity, Uo, as shown. Pipe radius R. At some distance downstream (section 2), the fluid velocity becomes parabolic as per the equation below.

Q.Obtain an expression for the drag force by the flowing fluid on the pipe wall over the length 1-2 in terms of pressure at sections 1 and 2, fluid density p, pipe radius R and inlet velcity, Uo.

2. Relevant equations
Fluid Velocity @ 2.
U = U(centre) [1-(r/R)^2]
where U is the velocity at radial distance r, and U(centre) is the velocity along the centre line.

From the mention of pressure and velocity, I would guess Bernoulli's equations is needed.

3. The attempt at a solution
I'm not sure how to approach this problem. If someone could give me some pointers I'll attempt it, but at the moment I'm very lost.

Last edited by a moderator: May 3, 2017