I've just been revising fluid mechanics, and noticed a glaring error on the Wikipedia page for the Reynolds number. The person has obtained the Navier Stokes equations using primed dimensionless coordinates and divided by a factor to obtain the Reynolds number R, but has not included S which also should be obtained in front of the partial time derivative of velocity. S is called the Stround, or Stronal number, I'm not sure which. Does anyone know what it's called?

 

That's actually the reason I tried searching on the net in the 1st place! Also, for future reference, how is it one can edit Wikipedia? is it an harder than ordinary Latex?

The Wiki syntax takes a bit of getting used to. There's a guide here. Anything in the <math> tags should be ordinary LaTeX, AFAIK.

Would you mind giving us a link to the error?

 

The start of the page about the Reynolds number (Re) seems fine.

 

I did find a part called "Where does it come from" (same wikipedia page). Could you point out where you have a problem? The formulas are not the same as in my book, and the whole trick with making the entire Navier-Stokes equation dimensionless and then changing some stuff about it is unknown to me. However, when checking the top and bottom formula of the "where does it come from" section, I find it weird that the [math]-\nabla{p}[/math] term is not changed, while all other terms seem to lose the density [math]\rho[/math]. Dimensionless these kinds of tricks might be acceptable, but once the primes are dropped (for ease of reading? what kind of reason is that?), the dimensions don't seem to match anymore.

 

Regarding some "S" number, all I know are the Schmidt (Sc), Sherwood (Sh) and Stanton (St) numbers...

Edited April 22, 200916 yr by CaptainPanic