18 Questions
What is the Reynolds number equation for falling films?
Re = 4S(vz)p/p
At what Reynolds number does the flow regime become irregular and chaotic?
Re > 1500
What characterizes the flow regime with Reynolds numbers less than about 20?
Long and slow ripples
Who is the dimensionless group named after?
Osbome ~ e ~ n b l (1842-1912)
What happens to ripple growth as the Reynolds number increases above 20?
Ripple growth increases rapidly
Which regime is the analysis mentioned in the text valid for?
Laminar flow with negligible rippling
What is the formula for the Reynolds number (Re) in fluid flow?
Re = 2R(1 - v)p/p
What is the Reynolds number defined as for circular tubes?
$D \times V / \nu$
In which neighborhood does the transition from laminar to turbulent flow occur?
Re = 2000
What is the significance of Re = 2000 in fluid flow?
It marks the start of laminar flow.
What condition must be met for flow to be considered laminar?
Reynolds number ($Re$) must be less than about 2100.
How is the Reynolds number (Re) calculated for fluid flow?
Re = (po - p)vL/p
Which assumption is NOT made when obtaining the Hagen-Poiseuille equation?
The fluid is non-Newtonian.
What determines the momentum-flux and velocity distributions in fluid flow?
Pressure gradient
What correction is needed for the buildup to the parabolic profile after the tube entrance?
$L, = 0.035D Re$
When does the flow become turbulent in a system?
When Reynolds number exceeds about 2100.
Why are the equations derived above valid only for laminar flow?
As a result of a smooth and planar interface
What effect is neglected in the flow assumptions for obtaining the Hagen-Poiseuille equation?
End effects
Test your knowledge on the three flow regimes observed in falling films and how they are classified based on the Reynolds number. Learn about laminar flow with negligible rippling, laminar flow with pronounced rippling, and turbulent flow. Explore the analysis limitations of the first regime.
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