flow visualization and measurement techniques in fluid flows l.
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Flow Visualization and Measurement Techniques in Fluid Flows. CAOS Presentation L.Kiranmayi. 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)

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Presentation Transcript
understanding fluid flows
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.
why flow visualization
Why Flow Visualization
  • Understanding flow phenomenon
  • Verifying model or theory results
  • Easier measurements for designing
  • To get a priori knowledge of solution
slide4

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
flow visualization
Flow visualization

Leonardo Da Vinci’s Hand drawings

Naturally occurring flow visualization

slide7

Flow Past a Cylinder

Clouds past a mountain

methods of flow visualization
Methods of flow visualization
  • Gas flows
    • Smoke visualization
    • Particle
    • Shadowgraphs and Schlieren
  • Liquid flows
    • Dye
    • Shadowgraphs and Schlieren
    • Particles
    • Bubbles
    • Fluorescence, phosphorescence
some gas flow visualization images
Some gas flow visualization images

Smoke visualization

Top- flow past aerofoil

Side- laminar smoke jet

slide10

Shadowgraph

Schlieren flow visualization

Bullet at supersonic speed

slide11

Liquid flows

Flow over Aerofoil

Side –particle visualization

Below –dye visualization

slide13

Drop falling on liquid surface

Normal laminar flow chain

slide14

Jets and Plumes

  • Top left- flow below an ice cube in water
  • Top right- near field of a jet
  • Side- jet and flame jet
slide15

Buoyant jet in stratified fluid

Tear ducts in wine glass

slide16

Vortex Interactions

Head on collision of vortex rings

Leap-frog movement of vortex rings

measurements in flows
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
slide18

Orifice meter for velocity in pipes

Pitot Static tube

Hot wire Anemometer

slide19

Optical Methods

Laser Doppler Velocimetry

slide23
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.
slide24

If = IeCL,

Where  = Quantum efficiency of the dye

 = Attenuation coefficient

L =Spatial extent of illuminated volume under consideration

slide26
Pressure
    • Pressure transducers
    • Pressure Sensitive Paints
slide27

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