@champboy1990 Re is defined slightly differently as the geometry of flow changes. I am using one for flow in an infinitely wide channel. A Re eqn for flow in a pipe (the Moody chart) uses diameter rather than depth, and pipes have more friction per volume of flow. The Re eqn for pipes defines the transition from laminar to transitional at a different Re rather than including the geometry differences in the equation. The key universal point is that the flow is laminar close to solid surfaces.
If Re < 1, the flow is laminar and reversible. There's a great video of reversible flow in corn syrup, posted by catwebster. Paste this text in after youtube... watch?v=p08_KlTKP50
More questions!!! Is the laminar sublayer the same as the boundary layer (sorry my questions are more related to aerodynamics) If so then how is it possible to have turbulent boundary layers (at higher Re numbers). Thanks
The boundary layer is the zone where the boundary influences the flow speed and includes, but is larger than the laminar sublayer. It consists of the zone from the base of the flow to the depth where the average flow speed is reached in my drawing. The boundary layer is transitional to turbulent for most of it's thickness. The laminar sublayer becomes very thin to non-existent as Re gets very high (especially in air which has low viscosity).
Does the thickness of the laminar sublayer change with speed?.... Because at higher speeds the distance l (in the equation) will have to be of a lower value in order for Re to be 500......??? Also, how would the thickness of the laminar sublayer differ with different fluids (e.g. water and air at same speed)? thanks.
Excellent questions! You are right - the laminar sublayer is thinner at higher flow speeds and it is different in different fluids because the viscosity and density of fluids varies. Your use of Re to guide your thoughts is right-on.
Sono una studentessa del terzo anno di geologia a Torino e sono entusiasta di vedere questi argomenti su youtube!!!Li scarichèrò tutti e i tuoi studenti devono essere fieri di te!
i thought the boundary between laminar flow and transitional flow gave a Re of around 2000? that's according to the moody diagram..
champboy1990 9 months ago
@champboy1990 Re is defined slightly differently as the geometry of flow changes. I am using one for flow in an infinitely wide channel. A Re eqn for flow in a pipe (the Moody chart) uses diameter rather than depth, and pipes have more friction per volume of flow. The Re eqn for pipes defines the transition from laminar to transitional at a different Re rather than including the geometry differences in the equation. The key universal point is that the flow is laminar close to solid surfaces.
sumnerd 9 months ago
thank you so much for such a compact and all-in-one video.
emreturkoz 1 year ago
thank you
i think the origin of reynolds number is very mysterious
kghrib 2 years ago
I just got a 47/100 on my sed rocks test. I hope this thing can help me
MRburitz 3 years ago
if the reynolds number is <1, there's a reversible flow, but what characteristiques has that kind of flow?
kiben7 3 years ago
If Re < 1, the flow is laminar and reversible. There's a great video of reversible flow in corn syrup, posted by catwebster. Paste this text in after youtube... watch?v=p08_KlTKP50
sumnerd 3 years ago
More questions!!! Is the laminar sublayer the same as the boundary layer (sorry my questions are more related to aerodynamics) If so then how is it possible to have turbulent boundary layers (at higher Re numbers). Thanks
limewaveZ 3 years ago
The boundary layer is the zone where the boundary influences the flow speed and includes, but is larger than the laminar sublayer. It consists of the zone from the base of the flow to the depth where the average flow speed is reached in my drawing. The boundary layer is transitional to turbulent for most of it's thickness. The laminar sublayer becomes very thin to non-existent as Re gets very high (especially in air which has low viscosity).
sumnerd 3 years ago
Makes sense! Thanks for clarifying.
limewaveZ 3 years ago
Does the thickness of the laminar sublayer change with speed?.... Because at higher speeds the distance l (in the equation) will have to be of a lower value in order for Re to be 500......??? Also, how would the thickness of the laminar sublayer differ with different fluids (e.g. water and air at same speed)? thanks.
limewaveZ 3 years ago
Excellent questions! You are right - the laminar sublayer is thinner at higher flow speeds and it is different in different fluids because the viscosity and density of fluids varies. Your use of Re to guide your thoughts is right-on.
sumnerd 3 years ago
Sono una studentessa del terzo anno di geologia a Torino e sono entusiasta di vedere questi argomenti su youtube!!!Li scarichèrò tutti e i tuoi studenti devono essere fieri di te!
THANKYOU THANKYOU THANKYOU!!!!!
VIVIANA
skiana86 4 years ago
mamma mia come cazzo stai messa male.....
giogio147 3 years ago