Expert: Paul Soderman - 3/20/2010

Question
hi,
i'm student of chem engineering.
currently me and my team is building a wind tunnel.
i'm responsible for the part of contraction cone.
i would like to ask is there any formula to calculate
the angle of the bending curve on the contraction cone part.
the opening end is 42"x42" while the other opening  is 12"x12".

thx u

Answer
If this is a close circuit wind tunnel, the contraction should be an S shape with cubics at each
end. The inflection point should be much closer (1/4-1/3 of the length)
to the inlet than the exit.  The following guides will help.

Rouse, Hunter and Hassan, M. M.: "Cavitation-Free Inlets and
Contractions". Mechanical Engineering, Vol. 71, March 1949, pp 213-216.

The same guides are also given in NASA TN D-8243.

Paul