Fluid Mechanics Ideal Flow Problem

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SUMMARY

The discussion focuses on solving a fluid mechanics problem involving flow velocity and magnitude at the point (2,-2) with a sink at the origin, a vortex at (0,2), and a uniform flow in the +x direction. The user initially miscalculated the velocities using the potential function approach, leading to incorrect values for u and v. Upon reevaluation, the correct solution was identified as V = 12.5 m/s, u = 10 m/s, and v = 7.5 m/s, with an angle α of 37 degrees. The user emphasized the importance of unit consistency in arriving at the correct solution.

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Wildcat04
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Homework Statement



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

The Attempt at a Solution



[tex]\phi[/tex] = [tex]\phi[/tex]1 + [tex]\phi[/tex]2 + [tex]\phi[/tex]3

[tex]\phi[/tex]1 = -Ux = -U r cos([tex]\theta[/tex])
[tex]\phi[/tex]2 = -[tex]\mu[/tex]s ln r
[tex]\phi[/tex]3 = [tex]\mu[/tex]v [tex]\theta[/tex]

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

v[tex]\phi[/tex] = (1/r) d[tex]\phi[/tex] / 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
[tex]\alpha[/tex] = 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!
 
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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.
 

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