Measuring wind in a vertical wind tunnel

Click For Summary

Discussion Overview

The discussion revolves around designing a vertical wind tunnel for a physics project, specifically focusing on measuring wind speed accurately without incurring high costs. Participants explore various methods and tools for measuring airflow within the tunnel, considering both theoretical and practical aspects of their designs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes their project involving a vertical wind tunnel made from stovepipe and powered by a leaf blower, seeking affordable methods to measure wind speed.
  • Another participant suggests using a simple anemometer, noting the challenges of turbulence in the tunnel and the need for calibration.
  • A follow-up response mentions that the wind tunnel's small diameter may limit the effectiveness of a homemade anemometer and requests recommendations for small, inexpensive commercial options.
  • One participant proposes building a pitostatic tube and manometer as a low-cost solution, providing a brief description of the construction process and referencing Bernoulli's equation for velocity calculations.
  • Another participant supports the pitot tube suggestion, emphasizing its accuracy under reasonably laminar flow conditions and recommending specific suppliers for materials.
  • A different viewpoint argues that laminar flow is not a strict requirement for using a pitot tube, as long as flow straighteners are employed and measurements are taken in a fully developed flow section.
  • One participant shares their experience with a specific model of an anemometer, suggesting it as a viable option if its specifications meet the project's needs.
  • The original poster expresses gratitude for the suggestions and considers trying both the anemometer and the manometer for their project.

Areas of Agreement / Disagreement

Participants generally agree on the potential effectiveness of both the pitot tube and anemometer for measuring wind speed, but there are differing opinions on the necessity of laminar flow and the best approach to measurement. The discussion remains unresolved regarding the optimal solution for the specific conditions of the wind tunnel.

Contextual Notes

Participants mention challenges related to turbulence and the small size of the wind tunnel, which may affect the accuracy of measurements. There are also references to the need for calibration and ensuring fully developed flow for accurate readings.

merce1
Messages
3
Reaction score
0
for a physics project i am designing a vertical wind tunnel made out of stovepipe and powered by a leaf blower. this experiment is designed to find the terminal velocity of different shapes. We already have a way to vary the wind speed, but what we don't have is an accurate way to measure this inside the wind tunnel without buying expensive gear.

if anyone has any ideas, please post them.
 
Physics news on Phys.org
merce1 said:
for a physics project i am designing a vertical wind tunnel made out of stovepipe and powered by a leaf blower. this experiment is designed to find the terminal velocity of different shapes. We already have a way to vary the wind speed, but what we don't have is an accurate way to measure this inside the wind tunnel without buying expensive gear.

if anyone has any ideas, please post them.

Well, you probably already know you're got a turbulent tunnel and measurement is going to be a challenge. But, assuming you can straighten some of that out, a simple anemometer is very cheap. A piece of plastic or metal free to rotate on a rod will show the air speed if (I probably should say if) you can calibrate it.
 
TVP45 said:
Well, you probably already know you're got a turbulent tunnel and measurement is going to be a challenge. But, assuming you can straighten some of that out, a simple anemometer is very cheap. A piece of plastic or metal free to rotate on a rod will show the air speed if (I probably should say if) you can calibrate it.


we have a setup that does straighten out the airflow, but the wind tunnel is only six inches across so we need something small and I'm not sure if a home made anemometer will do the job. if you know somewhere where i can get a small one for cheap(< $30), please post it.
 
You can build yourself a pitostatic tube and manometer for about $10 - I did it when I was in high school...

Take a piece of brass tubing and bend it at a 90 degree angle. Take another straight piece and mount the two pieces through the wall of the wind tunnel. Connect them to opposite sides of a u-tube manometer (u-shaped piece of clear tubing with a ruler behind it). Use Bernoulli's equation to calculate the velocity.
 
Yes, follow Russ's advice. If you have $30 and reasonably laminar flow, the pitot tube is accurate and easy. You might check McMaster-Carr and Grainger for some low cost materials.
 
There's no restriction to having laminar flow when using a pitot tube. If there are flow straighteners (highly recommended) then the rotational flow should be minimized. The only thing left to do is to make sure that the measurement is taken in a section with fully developed flow. That way you don't have to do a traverse and integrate to get an semi accurate measurement since a fully developed turbulent velocity profile is pretty flat.

The best way to do it is to separate the static pressure measurement from the dynamic pressure measurement. Take the dynamic measurement via the pitot tube. Do not have the static ports on the tube itself. Take the static readings via static ports on the wall of the tunnel. This does assume that you've done a decent job at flow straightening and are fully developed.
 
TVP45 said:
Yes, follow Russ's advice. If you have $30 and reasonably laminar flow, the pitot tube is accurate and easy. You might check McMaster-Carr and Grainger for some low cost materials.
They actually sell the stuff itself:
http://www.mcmaster.com/#pitot-tubes/=16q343

'bout $110 for a pre-made pitostatic tube and a manometer.
 
I have a La Crosse anemometer #EA-3010U that usually sells in the $30 range but it has a max air speed of 67 mph (30 m/s). If that is enough a quick search on e-bay will show a few suppliers.
 
tanks guys. mender's cheap anemometer sounds the easiest, but i should probably try the manomater as well
 

Similar threads

  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 10 ·
Replies
10
Views
4K
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 69 ·
3
Replies
69
Views
17K
Replies
9
Views
8K
  • · Replies 4 ·
Replies
4
Views
3K