Quote:
Originally Posted by kach22i
You mean to straighten out the air flow off a swirling fan?
I looked at a couple of PDF's and a website on the subject, not sure that you mean exactly.
I have cardboard, mirrors, drinking straws and cigars.......................maybe I should blow some smoke?  |
With a closed test section,a boundary layer builds up on the floor,walls,and ceiling,which thickens as you progress further and further into the tunnel.
This boundary layer,unless it is blown,or suctioned,can effectively choke down the cross-sectional area of the test section,increasing the local velocity.
Also,a boundary layer is forming and growing on the test vehicle itself,aggravating the situation.
And as a rule,anything tested,should not have a frontal area which exceeds 5% of the test sections cross-sectional area.
This is one reason why Cds can vary,from tunnel to tunnel.