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Falling Film Flow Regimes and Reynolds Number Quiz

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Questions and Answers

What is the Reynolds number equation for falling films?

Re = 4S(vz)p
Re = S(vz)p/p
Re = 4S(p/vz)p
Re = 4S(vz)p/p (correct)

At what Reynolds number does the flow regime become irregular and chaotic?

20 < Re < 1500
Re = 1500
Re < 20
Re > 1500 (correct)

What characterizes the flow regime with Reynolds numbers less than about 20?

Pronounced rippling
Short and fast ripples
Long and slow ripples (correct)
Negligible rippling

Who is the dimensionless group named after?

Osbome ~ e ~ n b l (1842-1912) (D) Signup and view all the answers

What happens to ripple growth as the Reynolds number increases above 20?

Ripple growth increases rapidly (D) Signup and view all the answers

Which regime is the analysis mentioned in the text valid for?

Laminar flow with negligible rippling (A) Signup and view all the answers

What is the formula for the Reynolds number (Re) in fluid flow?

Re = 2R(1 - v)p/p (A), Re = 2R(1 - v)p/p (B), Re = 2R(1 - v)p/p (C), Re = 2R(1 - v)p/p (D) Signup and view all the answers

What is the Reynolds number defined as for circular tubes?

$D \times V / \nu$ (D) Signup and view all the answers

In which neighborhood does the transition from laminar to turbulent flow occur?

Re = 2000 (D) Signup and view all the answers

What is the significance of Re = 2000 in fluid flow?

It marks the start of laminar flow. (C) Signup and view all the answers

What condition must be met for flow to be considered laminar?

Reynolds number ($Re$) must be less than about 2100. (C) Signup and view all the answers

How is the Reynolds number (Re) calculated for fluid flow?

Re = (po - p)vL/p (B) Signup and view all the answers

Which assumption is NOT made when obtaining the Hagen-Poiseuille equation?

The fluid is non-Newtonian. (B) Signup and view all the answers

What determines the momentum-flux and velocity distributions in fluid flow?

Pressure gradient (A) Signup and view all the answers

What correction is needed for the buildup to the parabolic profile after the tube entrance?

$L, = 0.035D Re$ (B) Signup and view all the answers

When does the flow become turbulent in a system?

When Reynolds number exceeds about 2100. (D) Signup and view all the answers

Why are the equations derived above valid only for laminar flow?

As a result of a smooth and planar interface (B) Signup and view all the answers

What effect is neglected in the flow assumptions for obtaining the Hagen-Poiseuille equation?

End effects (D) Signup and view all the answers

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