# Ball in pipe turbulant problem

1. Oct 30, 2011

### ytcat

Hello

I have a vertical pipe with floating ping pong ball in it.

I have fan at the bottom that that push the ball up.

The pipe parameters:
D=45mm
L=1.07m

Ball parameters:
D=40mm
M=2.7g

I tried to change fan speed to move the ball but becouse turbulance the ball is not steady, and so I can not control ball hight with fan speed.

I installed step motor at the top to open and close the hatch, it seems to be working.

I have now problem to calculate all of it.

If I look at the ball that floats in the air (inside the pipe) , the forces that I believe are effecting the ball are:
fg-weight force (down)
fd-drag force (up)
fb-buoyant force (up)

And I believe that there is a some turbulance force that pulls the ball down.

I cant use stocks equations becouse Re number is more than 2300 and I cant use bernoulli equations also becouse I have turbulance.

Eventually I need somehow to calculate the pressures ratio between two sides of the ball,

and develop formula for ball's hight.