Physics of turbulence

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Physics of turbulence
muna Al_khaswneh Dr.Ahmad Al-salaymeh
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Introduction

• Turbulence cannot exist by itself, however it
  requires a continuous supply of energy changes
  in velocity direction .

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Objective

• The Definition of turbulence
• Examples of turbulence
• Boundary layer
• Study Reynolds numbers
• Study the differential continuity equation
• Study Navier-Stocks equation
• Kolmogorov theory
• Laminar-turbulent transition
• Problems of turbulence

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Definition properties

• It is a flow with disordered in time space .
• 1-three-dimensionality.
• 2-Unsteadiness.
• 3-strong vorticity.
• 4-Unpredictability.
• 5-Broad spectrum.

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Reynolds number

• 1. inertia forces
  2. viscous forces
• 1. ? u2 , ? fluid density ,u fluid speed
• 2. µ u , µ viscous fluid , d diameter
  fluid d

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Re inertia forces viscous forces
? d u µ
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So that Reynolds number depend on fluid
properties as speed , pipe diameter ,viscosity
density .
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Random pipe
Re
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Boundary layer
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Laminar-turbulent transition

• .
• Linear stability theory .
• Primary instability of free shear flow .
• Later stage of transition in free shear flows .

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Continuity equation
The conservation of mass principle is applied to
the control volume
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Continuity equation

• For three dimension (our interest )

z
?z
y
?y
?x
x
uxî uy? uz?
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Continuity equation
or
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Navier-stokes equation

• the momentum translate with tow ways tow forces
• ways
• Convection transition
• Molecular transition
• forces
• 1.Gravity force
• 2.Pressure force

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Forces

• 1.Gravity force
• Pressure force

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Convection transition
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Molecular transition

• Shear stress

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Molecular transition
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For x direction
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Navier-stokes equation
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Newtonian equation
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stocks equation
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Kolmogorov theory

• The physics of turbulence is the same in all
  turbulent system .
• It is independent of large scale forcing small
  scale dissipative
• Fluctuation occur in an incompressible
  medium-density
• 4.Energy flows from large scales to small scales
  .

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laminar
flow (average speed)
turbulent
pressure (drop)
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Primary instability of free shear flow
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Primary instability of free shear flow
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Later stage of transition in free shear flows .
Some vorticity remains between the vortices , we
will call it secondary instability .
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Problems
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The endThank you