Measuring wind in a vertical wind tunnel

In summary, the vertical wind tunnel is made of stovepipe and powered by a leaf blower. The goal of this experiment is to find the terminal velocity of different shapes. However, the wind tunnel is turbulent and measurement will be a challenge. A simple anemometer is cheap to build, but the accuracy of the measurement is unknown.
  • #1
merce1
3
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.
 
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  • #2
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.
 
  • #3
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.
 
  • #4
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.
 
  • #5
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.
 
  • #6
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.
 
  • #7
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.
 
  • #8
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.
 
  • #9
tanks guys. mender's cheap anemometer sounds the easiest, but i should probably try the manomater as well
 

1. How is wind speed measured in a vertical wind tunnel?

Wind speed in a vertical wind tunnel is measured using an anemometer. This device consists of four or more cups mounted on a central axis, which rotate as the wind blows. The rotation speed is then converted into a measurement of wind speed in miles per hour, meters per second, or other units.

2. What is the purpose of measuring wind in a vertical wind tunnel?

Measuring wind in a vertical wind tunnel allows researchers and engineers to study and test the aerodynamics of objects, such as airplanes or cars, in a controlled environment. This can help improve the design and performance of these objects in real-world conditions.

3. How is wind direction determined in a vertical wind tunnel?

Wind direction in a vertical wind tunnel is determined using a wind vane. This instrument consists of a flat surface that is aligned with the direction of the wind. As the wind changes direction, the vane rotates and points in the direction of the wind.

4. What factors can affect wind measurements in a vertical wind tunnel?

Several factors can affect wind measurements in a vertical wind tunnel, including the shape and size of the object being tested, the speed of the wind, and any obstructions or turbulence within the tunnel. It is important to control these factors to ensure accurate and consistent measurements.

5. How are wind measurements in a vertical wind tunnel used in real-world applications?

Wind measurements in a vertical wind tunnel are used in a variety of real-world applications, including the design and testing of aircraft and vehicles, the development of new wind energy technologies, and the study of wind patterns and their effects on structures and the environment. These measurements help engineers and scientists make more informed decisions and improve the performance and safety of various technologies and structures.

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