Vortex shedding critical velocity.HELP!!

[Someone11]

How is the new critical velocity calculated after the term in the square root is found negative. As far as i know,normally the second critical velocity is taken as 6.25 times the first one. But here the result is different. Can anybody guide me through this?

 

[Champ58]

Maybe some conversion factor is involved in this. I too couldn't get any reference regarding this step.

 

[hacksaw]

There are a number of design standards addressing your (OP's) question.

The reponses can only help if you clearly identify what you are trying to accomplish.

 

[JStephen]

Vcrit in that last equation is ft/sec, as opposed to mph in the first equation. It's the same speed, not the second critical speed.