Fluid flow and momentum equation. Do I have the right equation?

AI Thread Summary
The discussion focuses on the fluid flow and momentum equations, questioning the validity of the equations presented. The user highlights a potential error in combining pressure and area due to differing units, emphasizing the need for clarity in labeling forces and resultants in the diagram. The equations for resultant forces Rx and Ry are proposed, but their correctness is debated based on unit consistency. Additionally, the user mentions modifying the direction of forces based on external resources. Overall, the conversation underscores the importance of accurate unit handling and clear diagram labeling in fluid dynamics equations.
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http://img89.imageshack.us/img89/3914/unled23g.png F1x+F3x = density x Q(Vx2 – Vx1)
F1x = -Rx
F3x= (pressure 1 x area 1) + (Pressure 2 x area 2) (Cos B)
F1y+F3y = density x Q(Vy2 – Vy1)
F1y = -Ry
F3y = (Pressure 2 + Area 2)(Cos B)
So is it:
Rx= (pressure 1 x area 1) + (Pressure 2 x area 2) (Cos B) - density x Q(Vx2 – Vx1)
Ry = (Pressure 2 + Area 2)(Cos B) - PQ(Vy2 – Vy1)
 
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For starters, I see that in two cases you are adding area to pressure. This cannot be done because units are different. You should label your diagram as to what is F and what is R.
 
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