Fluid mechanics - flow through pipe

Click For Summary

Discussion Overview

The discussion revolves around fluid mechanics, specifically the flow through a pipe involving multiple inlets and outlets with differing densities. Participants are analyzing the conservation of mass flow and the implications of mixing immiscible fluids in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a calculation for flow rates and seeks validation from others, asserting that the total flow rate is 2700 gal/min.
  • Another participant expresses uncertainty about the assumption of conserved volume flow rate, questioning whether the differing densities at the inlets and outlet affect this assumption.
  • A participant references the conservation of mass flow equation, indicating that the equation requires equal densities for the inlets and outlet to simplify to a volume flow rate equation.
  • Concerns are raised about the problem's consistency, particularly regarding the mixing of immiscible fluids and how this affects the concept of a "mixture."
  • One participant draws an analogy with oil and vinegar to illustrate that while two immiscible liquids can coexist, their individual volumes are conserved in the flow context.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions regarding density and flow conservation, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are limitations regarding the assumptions made about density and the implications of immiscibility in the context of the problem, which remain unresolved.

Who May Find This Useful

This discussion may be of interest to those studying fluid mechanics, particularly in contexts involving multiple fluid types and conservation principles.

charlies1902
Messages
162
Reaction score
0
Please see attached. I'm pretty sure i did the problem right, but I'd like to check with the great minds of physicsforums.

Summing up flow rates and inlet and outlet gives:
1500+1200=2700 gal/min

2700gal/min= area at exit *Velocity at exit
2700 gal/min * (1ft^3 / 7.48 gal) ( 1min / 60 s) = Area at exit * 30 ft/2
Area=0.2 ft^3 or 1.5 gallons
 

Attachments

  • Untitled.png
    Untitled.png
    24.2 KB · Views: 617
Physics news on Phys.org
You are correct but my mind is not a great one.
 
I'm second guessing myself. The way I did the problem is assuming that the volume flow rate is conserved, but can I really assume that? What I basically said is that the densities at the 2 inlets and outlet are the same.

The densities given aren't the same tho.I.Ep1*V1*A1+p2*V2*A2=p3*V3*A3
where p=density
V=velocity
A=area

That is the conservation of mass flow equation.
To get from that equation to the
Q1+Q2=Qout equation, the densities have to cancel. If they cancel, that means the densities are the same for both inlets and outlets, but that is not the case since they give different specific gravities for the 2 inlets, thus different densities.

It seems the problem contradicts itself by saying "volume flow is conserved" and giving 2 different SGs.
 
Last edited:
UGHHH the more i read this problem the more I get confused.

Read the 1st sentence. imiscible=not mixable
How can 2 not mixable liquids be mixed?
How can there be a "mixture" that exists, if it's not mixable?
 
"How can 2 not mixable liquids be mixed?"
Have you ever mixed salad dressing..oil and vinegar? Vinegar and oil do not mix but each still maintains its unique volume when combined. Each is incompressible. Therefore flow volume per unit time is conserved.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
2
Views
2K
  • · Replies 12 ·
Replies
12
Views
5K
  • · Replies 38 ·
2
Replies
38
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K