What is the solution for a venturi tube with water flow and pressure changes?

In summary, the conversation discusses a question involving a venturi tube and the determination of flow rate, channel height, and pressure needed at different sections. The necessary equations and solution steps are also mentioned.
  • #1
Workingitout
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Homework Statement


I have a question involving a venturi tube - Air flows through the channel of a venturi of constant width 0.06m. Compressibility and viscous effects are negligible.

a) Determine the flowrate when water is drawn up 0.10m in a small tube attached to the static pressure tap at the throat where the channel height is 0.02m

b) Determine the channel height, h2, at section (2) where, for the same flowrate as in part (a), the water is drawn up 0.05m

c) Determine the pressure needed at section (1) to produce this flow

(Other information shown in attched picture)

Homework Equations


v = (sqrt) (2(P1 - P2)/[itex]\rho[/itex])

The pressure change (P1 - P2) is usually calculated using
P1 - P2 = h x Pw x g
Where h is the height difference between the two points (No picture attached, but if you can imagine the two pressure points being connected using a 'U' shaped pipe with liquid at the bottom), Pw is the density of water and g is the gravity constant

The Attempt at a Solution


I am having a considerable amount of diffuculty due to the fact that I haven't encountered this type of problem before. I have seen similar ones where the 2 pressure points are connected, but not in this way - with an independant "straws" setup.

I intend on calculating 'v' to use it in Q=vA - Am I doing this right? As in, do I do this problem using these formulas? If so, do I use 'h' differently in this example?

Any help would be appreciated, and a link to a site that can guide me through would also be welcome.

If I'm being unclear, please tell me. Thanks in advance
 

Attachments

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  • #2
Isn't this case simpler than having U-shaped tube?

(Here starting from left of the venturi I have considered junction above the first straw as point 2 and one above straw right to previous as point 3.)

Q = v2*a2 = v3*a3
p2-p3 = density* (v2^2 - v3^2)

Solve these equations which gives solution to Q and then v2 and v3 and then everything falls in the place.

I hope this helps.
 

1. What is a Venturi tube and how does it work?

A Venturi tube is a device used to measure the flow rate of a fluid in a closed system. It consists of a constricted section in the middle with a gradual taper on both sides. As the fluid flows through the constricted section, the velocity increases and the pressure decreases, according to Bernoulli's principle. This pressure difference can then be used to calculate the flow rate.

2. What are the main applications of Venturi tubes?

Venturi tubes are commonly used in industries such as aviation, oil and gas, and water treatment. They are also used in medical devices, such as oxygen masks, to accurately measure the flow rate of gases.

3. How accurate is a Venturi tube in measuring pressure?

A Venturi tube is considered to be a highly accurate instrument for measuring pressure. It has an accuracy of within 1%, making it a reliable choice for various industries.

4. Can a Venturi tube be used for measuring both liquids and gases?

Yes, a Venturi tube can be used for measuring the flow of both liquids and gases. However, the design and calculations may differ slightly depending on the properties of the fluid being measured.

5. Are there any limitations to using a Venturi tube for pressure measurement?

One limitation of using a Venturi tube is that it can only measure flow rates within a certain range. If the flow rate is too low, the pressure difference will be too small to accurately measure. Additionally, the fluid being measured must be clean and free from particles, as they can affect the accuracy of the readings.

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