Laminar, transition, turbulent flow question

1. Mar 21, 2013

pyroknife

If we're considering fluid flow over a plate and found that at one location the flow is turbulent. Is it always the case that there is also a transition and laminar region before that turbulent region on the plate?

2. Mar 21, 2013

SteamKing

Staff Emeritus
That is going to depend on the flow velocity or however you are calculating Reynold's number for the plate.

3. Mar 21, 2013

pyroknife

Even if the flow velocity is gigantic, wouldn't there always be a laminar region, even if it is infinitesimally small?

Like for example let's say Velocity=speed of light.
Re=velocity*length/(kinematic viscosity)
Depending on what you classify the critical reynold's # as, you can always solve for a critical length (even if it's miniscule) and anything before that critical length is laminar flow.

4. Mar 22, 2013

Staff: Mentor

If the reynolds number is defined in terms of distance along the plate, then there will always be a critical length at which the transition occurs. You are working in terms of dimensionless parameters, which is a good thing to do. Incidentally, please stay away from velocities approaching the speed of light until you have had some experience with special relativity. Your results will certainly always apply at values of the dimensionless group v/c much less than unity, which includes all the situations you are likely to ever run into in practice.

5. Mar 22, 2013

pyroknife

Thanks.

I was just using the speed of light as an exaggerated example.

I'm not sure if anyone's ever used Incropera's "Fundamentals of Heat and Mass Transfer Textbook." But this question was mainly due to the table at the end of chapter 7 in that book. If anyone's used it, I can explain further what caused my concern from that chapter,.