Venturi tube help needed in determining pressure difference

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Homework Help Overview

The discussion revolves around a fluid dynamics problem involving a venturi tube through which water flows. The original poster presents a scenario with specific flow rates, diameters, and density, seeking to determine the pressure difference between two points in the tube, while also considering head loss.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of Bernoulli's equation and the continuity equation in the context of the problem. The original poster attempts to calculate velocities and head differences but expresses uncertainty about the correctness of their approach. Questions arise regarding the need to transpose equations to isolate pressure.

Discussion Status

The discussion is ongoing, with participants providing feedback and prompting the original poster to clarify their calculations. There is an exploration of different equations and methods, but no consensus has been reached on the correct approach yet.

Contextual Notes

The original poster mentions that they have been provided with numerous equations to choose from, indicating a structured homework assignment with specific constraints. There is also a suggestion that the initial equation selected may not be appropriate for the problem at hand.

timothy1875
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Homework Statement



Water flows through venturi tube at 0.3 litres/s. Diameter of venturi tube is 32mm to 20mm to 32mm and the water density is 1000kg/m^3.


Homework Equations



a) Assuming head loss is neglible, what is pressure difference between 1 and 2.

b) If pressure head difference between these is 45mm what is head loss.


The Attempt at a Solution




So far I have V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

delta H 1/2 = H1 - H2 = 1/2g (V2^2-V1^2))
delta H 1/2 = 39.3mm

Where do I go from here, if this is even correct ?

Thanks a lot for your help.
 
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welcome to pf!

hi timothy1875! welcome to pf! :smile:

(try using the X2 and X2 icons just above the Reply box :wink:)

i don't follow you :confused:

use the fact that the volume per time is constant, and Bernoulli's equation :wink:
 
Hi Tim,

Thanks for getting back to me.I am trying to answer the question but think I may be going about it the wrong way.

Using the Bernoulli equation do I need to transpose to find P ?
 
show us what you have so far :smile:
 
V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

delta H 1/2 = H1 - H2 = 1/2g (V22-V12)
delta H 1/2 = 39.3mm

This where I have got to so far, :(
 
timothy1875 said:
V2 = P1A1V1/P2A2 = 0.9548

what does this mean? :confused:

where does it come from?
 
Basically we have been set this question and there are numerous equations on the back that we have to pick from. I take it from your response I have selected the wrong equation initially. Should it be 1/2g (V22 - V1 2) ??
 

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