Why Re is different 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 different for external and internal
 

Reynolds number depends on velocity magnitude and viscosity. If the length is different with the same flow rate (and same fluid) the Reynolds is different.

Re: Why Re is different for external and internal
 

I am not sure what you are asking. The Re is defined the same for every flow. I think what you are asking is why the Re for transition is different for external versus internal flow?

Re: Why Re is different for external and internal
 

Me too... What do you mean exactly by internal and external flow ?