Module 3: Velocity Measurement
  Lecture 11: Light sources and LDV
 

Table 3.2: Overview of optical methods suitable for measurement of temperature and species concentration. LDV is laser Doppler velocimetry; PIV is particle image velocimetry; LCT is liquid crystal thermography; CARS is coherent anti-Stokes Raman spectroscopy; and LIF is laser-induced fluorescence. Temperature and concentration are represented as and respectively.

Method

physical mechanism

incident light

attribute measured

quantities detected

real-time

spatial extent

   

interferometry

refractive index

laser beam

intensity

and

yes

2D (integrated)

 

 

 

(via fringes)

 

 

 

schlieren and

refractive index

laser beam

intensity field

and

yes

2D (integrated)

shadowgraph

 

 

 

 

 

 

rainbow schlieren

refractive index

white light

hue

and

yes

2D (integrated)

LDV

elastic scattering

2 laser beams

Doppler shift

u

yes

point

 

 

per dimension

 

 

 

 

PIV

Mie scattering

laser sheet

intensity

u

Yes

2D and 3D

LCT

Mie scattering

white light

hue

and wall shear

yes

2D

LIF

fluorescence

laser sheet

intensity

and

yes

2D

CARS

inelastic scattering

2 laser beams

intensity spectrum

and

no

point