Why Re is diff for external and internal flow?
 

We know that Reynold's no is different for internal flow and external flow? I wonder why does it happen? Is it the charecteristic length, which is different in both and so Re is different in both?

Re: Why Re is diff for external and internal flow?
 

If you are talking about critical Re, then it's really because of characteristic length. To compare them directly you'll need to use boundary layer thickness for external flow, instead of body size