Flow Visualization and Measurement Techniques in Fluid Flows

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Flow Visualization and Measurement Techniques in
Fluid Flows

• CAOS Presentation
• L.Kiranmayi

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Understanding Fluid Flows

• Dynamics causing the flow (forces)
• Pressure, buoyancy, inertia, viscous forces,
  surface forces. Etc.
• Effects of these forces on the flow (Flow and
  fluid properties)
• Velocity, acceleration, vorticity
• Viscosity, temperature, scalar concentration,
  density . Etc.

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Why Flow Visualization

• Understanding flow phenomenon
• Verifying model or theory results
• Easier measurements for designing
• To get a priori knowledge of solution

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What we need to visualize?

• Stream lines
• a line, tangent to which at any given instant is
  the velocity vector at that point
• Streak lines
• locus of particles which have passed through a
  prescribed point during a specified time interval
• Path lines
• locus of points traversed by a given fluid
  particle during some specified time interval
• Time lines
• line joining different adjacent points at any
  instant of time

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Flow visualization
Leonardo Da Vincis Hand drawings
Naturally occurring flow visualization
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Flow Past a Cylinder
Clouds past a mountain
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Methods of flow visualization

• Gas flows
• Smoke visualization
• Particle
• Shadowgraphs and Schlieren
• Liquid flows
• Dye
• Shadowgraphs and Schlieren
• Particles
• Bubbles
• Fluorescence, phosphorescence

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Some gas flow visualization images
Smoke visualization Top- flow past
aerofoil Side- laminar smoke jet
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Schlieren flow visualization
Shadowgraph
Bullet at supersonic speed
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Liquid flows
Flow over Aerofoil Side particle
visualization Below dye visualization
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Insects walking on water
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Drop falling on liquid surface
Normal laminar flow chain
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Jets and Plumes

• Top left- flow below an ice cube in water
• Top right- near field of a jet
• Side- jet and flame jet

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Buoyant jet in stratified fluid
Tear ducts in wine glass
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Vortex Interactions
Head on collision of vortex rings
Leap-frog movement of vortex rings
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Measurements in Flows

• Velocity
• Conventional methods
• Pitot tubes
• Hotwire anemometers
• Local steady state measurements
• Vane anemometers
• Non intrusive methods
• Laser Doppler Velocimetry
• Particle Image Velocimetry
• Particle Tracking Velocimetry

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Orifice meter for velocity in pipes
Pitot Static tube
Hot wire Anemometer
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Optical Methods
Laser Doppler Velocimetry
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Particle Image Velocimetry
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• Concentration
• Conventional
• Sample analyzers
• Collecting samples by introducing samplers in the
  flow
• Conductivity probes
• Depends on the conductivity of the scalar being
  used
• Optical methods
• PH Sensitive dyes
• Light extinction
• Scattering
• Fluorescence methods.

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If Ie??CL, Where ? Quantum efficiency of
the dye ? Attenuation coefficient L Spatial
extent of illuminated volume under consideration
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Buoyant jet from GFDL, CAOS
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• Pressure
• Pressure transducers
• Pressure Sensitive Paints

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• Temperature
• Thermister probes
• Change in resistance with temperature
• Thermocouples
• Voltage produced at junction of two metals
  depends on temperature
• Temperature Sensitive Paints
• Density
• From Absorption/ scattering/refractive index
• Capacitance/vibrations

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Thank you