piv lecture

8/11/2019 PIV Lecture

1/20

1

Imaging Techniques for Flow and Motion Measurement

Lecture 3

Lichuan Gui

University of Mississippi

2011

Particle Image Velocimetry (PIV)

Introduction


2/20

2

Particle Image Velocimetry (PIV)

Optical, non- or minimally-intrusive, fluid flow measurement

technique;

Instantaneous flow measurements in two-dimensional (2D) area

or three-dimensional (3D) volume field of views;

Basic procedure of PIV Flow visualization

Flow field seeded with small tracer particles

Particles usually illuminated by a laser light sheet

Image recording

Particle images captured by an imaging system

Image evaluation

Usually using auto- or cross-correlation algorithm


3/20

3

Stroboscopic illumination techniques

Flow visualization with small particles


4/20

4

Oil drop in laminar pipe flow (Air) Solid particles in water flow

Multiple exposed particle images

Flow visualization with small particles


5/20

5

2D & 2-component PIV Systems

CW laser with high-speed photo or video camera


6/20

6

Fluorescent particles in a microdevice

0.540.41 mm2, 30 fps

Smoke flow in air

0.50.5 mm2, 500 fps

Consecutive singly exposed PIV recordings



7/20


8/20

8

Measurement

volume

Lens

t=t

0

t=t0+t

Lens system

& Camera

Light

sheet

Single exposed recording Double exposed recording

Fluid flow seeded with

small tracer particles

Image #1

t=t0+t

Image #2

Exposure #1

Exposure #2

Laser

Standard 2D PIV



9/20

9

Image plane

Objective

Lens

Laser light sheet

Laser light sheet

Image plane

Objective Lens

S

S

L

L

Scale factor: M=L/L

Time interval: t

Velocity: V=S/t=MS/ t

Velocity determination with standard 2D PIV



10/20

10

Flood Illumination

l=532 nm

l= 610 nm

Nd:YAG LASER

MICROSCOPE

BEAM EXPANDER

CCD CAMERA

MCROFLUIDIC DEVICE

Nd:YAG Laser

Micro Device

Flow in Flow out

Glass

cover

CCD Camera

(1280x1024 pixels)

Beam

Expander

Epi-fluorescent

Prism / Filter Cube

Microscope

Focal Plane

Micro-PIV image pair

Micro-Fluidics Lab

Purdue University

Micro-scale PIV (MPIV) System


11/20

11

Stereo PIV 3 velocity components in a plane

Two cameras

Holographic PIV

3 velocity components in a 3 dimensional volume

Complex and precise illumination

Defocusing PIV (Pereira et al. 2000)

Allow images to become defocused

Single camera/ color CCD, particle image tracking

Multiple-sheet PIV (Raffel et al.,1995 )

Multiple laser light sheet, single camera

3D scanning PIV (Brcker, 1997)

Scanning a 3D volume with a laser beam

Single high speed camera

3D or 3-component PIV Systems


12/20

12

Stereo PIV configurationsa. Translation systems

(lateral displacement)

b. Rotational systems

(angular displacement)

Scheimpflug condition



13/20

13

Stereo PIV data reduction

- Translation systems (Mn=di/do)



14/20

14

Stereo PIV data reduction

- Rotational system (Mnconstant)



15/20

15

Holographic PIV (HPIV) System

Holographic diagnostics of a 3D particle filed

a. Hologram recording

b. Hologram reconstruction


16/20

16


Holographic recording of particles

Interference pattern in a HPIV recording


17/20

17


Reconstructed HPIV particle images


18/20

18


Example of HPIV system (recording)


19/20

19


Example of HPIV system (reconstruction)


20/20

20

Practice with EDPIV software

1. Read EDPIV help manual page to know details in Raw Image Format window

2. Open images in application example #0 with EDPIV and look at image details.

EDPIV software and sample images are available at http://www.edpiv.com/

Homework

piv lecture

Documents