Measuring drag coefficient experimentally

bermet

Hello, everyone!

Any ideas how to measure drag or drag coefficient on a body of simple shape? We should conduct an experiment without use of sophisticated equipment.

Thank you!

elegysix

I'd say support the object by a string attached to a scale or force sensor. zero it while letting it hang and then place your fan under it. Measure the difference in weight/force and solve your equation for the coefficient. you can place it inside a tube if you want to make air flow fairly uniform.

Keep in mind that the coefficient is going to depend on the orientation of the object with respect to the direction of air flow.

AlephZero

Measuring the force is the easy part. Getting a uniform flow of fluid and measuring its velocity is harder, if the fluid is air.

It may be easier to do experiments in water, since you will get larger forces at slower speeds. "Towing" something along the length of a bath, with a spring balance to measure the force and a timer to measure the speed, would be about as simple as you can get.

bermet

Thanks, but have will we meausre the force with which we are pulling the object, because we also apply some force to tow it?

AlephZero

That's why I said "with a spring balance". Or you could use a falling weight, with some arrangement of pulleys so the tow-line is pulling in the right direction.