# Fluid Mechanics Ideal Flow Problem

1. Sep 27, 2009

### Wildcat04

1. The problem statement, all variables and given/known data

Calculate flow velocity and magnitude at a point (2,-2)

Sink at origin with strength 20 m2/s
Vortex at (0,2) with strength 25 m2/s
Uniform flow in +x with strength of 10 m/s

3. The attempt at a solution

$$\phi$$ = $$\phi$$1 + $$\phi$$2 + $$\phi$$3

$$\phi$$1 = -Ux = -U r cos($$\theta$$)
$$\phi$$2 = -$$\mu$$s ln r
$$\phi$$3 = $$\mu$$v $$\theta$$

vr = d$$\phi$$/dr
=-U * cos $$\theta$$ - $$\mu$$s * (1/r)
=-10 cos($$\pi$$/4) - 20 / 2.83
=-14.14

v$$\phi$$ = (1/r) d$$\phi$$ / dr
= (1/r) (-14.14)
= -5

u = .5 (14.14) + .5(5) = -9.57
v = -.5(14.14) + .5(5) = 4.57

I know that I have butchered this because the solutions is supposed to be

V = 12.5 m/s
u = 10 m/s
v = 7.5 m/s
$$\alpha$$ = 37 degrees

Could someone please point out the obvious flaw in my logic and point me in the right direction?

Thank you very much in advance!

2. Sep 28, 2009

### Wildcat04

Nevermind! I was making this problem a lot harder than I thought it was. I took a step back and looked at the units that I needed for my solution along with what the correct solution and was able to work it out.