Science Buddies: "Ask an Expert"

hi i am a student of mechanical engineering and i got a project of making a small wind tunnel(open circuit) i just don't want to use sensors to measure drag and lift i including my friends can't bear the expenses of using sensors ! is there any other way of measuring drag and lift?kindly answer me because all the work has been done......i mean we have complete our all homework about what we do in the manufacturing phase but.....we can't use sensors....and only cause of that......we haven't enter in the fabrication phase....?please do help me!!! thanx in advance

Hi,

Here are some ideas to consider:

http://video.google.com/videoplay?docid ... 2106078468#

http://www.morpheus.umd.edu/research/fi ... -dist.html

http://www.freepatentsonline.com/6055869.pdf

http://www.globalspec.com/reference/312 ... ic-Systems

http://ctr.stanford.edu/Summer06/kitsios.pdf

http://www3.interscience.wiley.com/jour ... 1&SRETRY=0

http://www.iop.org/EJ/abstract/0957-0233/17/10/022

http://www.wipo.int/pctdb/ja/ia.jsp?ia= ... SPLAY=DESC

http://pages.slu.edu/faculty/gbramesf/LowRe.pdf

http://www.interactiveinstruments.com/e ... jetstream/

http://books.google.com/books?id=hV3b6J ... er&f=false

Look at this project:

http://www.ceeo.tufts.edu/robolabatceeo ... bpages.pdf

http://www.ceeo.tufts.edu/robolabatceeo ... al_asm.pdf

And this thesis:

http://scholar.lib.vt.edu/theses/availa ... sis_r2.pdf

The bad news here is I think you will have to use sensors to measure lift and drag. The good news is they may not have to be expensive. The customary method seems to use strain gauges and A/D computer interface using a wheatstone bridge circuit

The only thing I know that is responsive to your question is attaching a string to the wing to act as a stall indicator..

I hope this helps, even though it is not the kind of answer you were looking for.

Best regards,

Barrett L. Tomlinson

Seems like you may be able to use a spring as a sensorless way to measure lift. Somehow you'd have to measure how much the spring is stretched (or compressed, depending on where it's located) and then use the spring constant to determine the force.
Mike

Measuring lift and drag in a home-made wind tunnel is not difficult, nor expensive.

I designed a system for our local junior school that uses inexpensive postage scales that you can purchase at any office supply store, or even Target. They're usually less than $20.

To measure lift, you attach your model to a slender, light weight rod, which pokes through the bottom of your test section. You attach a weight to the end, which is heavier than your test specimen plus the amount of lift you expect it to develop. You put this on the postage scale. Note the weight. As your test specimen lifts, subtract the resulting weight from the initial weight.

You can measure drag the same way, but you'll need a bell crank mechanism to convert the horizontal force into a vertical force. Being a mechanical engineering student, you should be able to manage that easily.

Good luck.

thnx guyz u helped me alot!