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?

    <p>Osbome ~ e ~ n b l (1842-1912)</p> Signup and view all the answers

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

    <p>Ripple growth increases rapidly</p> Signup and view all the answers

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

    <p>Laminar flow with negligible rippling</p> Signup and view all the answers

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

    <p>Re = 2R(1 - v)p/p</p> Signup and view all the answers

    What is the Reynolds number defined as for circular tubes?

    <p>$D \times V / \nu$</p> Signup and view all the answers

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

    <p>Re = 2000</p> Signup and view all the answers

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

    <p>It marks the start of laminar flow.</p> Signup and view all the answers

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

    <p>Reynolds number ($Re$) must be less than about 2100.</p> Signup and view all the answers

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

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

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

    <p>The fluid is non-Newtonian.</p> Signup and view all the answers

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

    <p>Pressure gradient</p> Signup and view all the answers

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

    <p>$L, = 0.035D Re$</p> Signup and view all the answers

    When does the flow become turbulent in a system?

    <p>When Reynolds number exceeds about 2100.</p> Signup and view all the answers

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

    <p>As a result of a smooth and planar interface</p> Signup and view all the answers

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

    <p>End effects</p> Signup and view all the answers

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