The discussion revolves around the characteristics of fluid flow over a plate, specifically addressing whether a turbulent flow region must always be preceded by laminar and transitional regions. Participants explore the implications of Reynolds number and critical lengths in this context.
Participants express differing views on whether a laminar region must always exist before turbulence, with some arguing for its necessity and others questioning this assumption based on flow conditions and Reynolds number calculations. The discussion remains unresolved.
Participants reference the critical Reynolds number and its dependence on distance along the plate, but there are no definitive conclusions about the existence of laminar flow in all scenarios. The discussion includes assumptions about flow conditions and the applicability of results at various velocities.
SteamKing said:That is going to depend on the flow velocity or however you are calculating Reynold's number for the plate.
pyroknife said: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.
Thanks.Chestermiller said: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.