Particle Image Velocimetry (PIV) Introduction Imaging Techniques for Flow and Motion Measurement Lecture 3 Particle Image Velocimetry (PIV) Introduction Lichuan Gui University of Mississippi 2011

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

Flow visualization with small particles Stroboscopic illumination techniques

Flow visualization with small particles Multiple exposed particle images Oil drop in laminar pipe flow (Air) Solid particles in water flow

2D & 2-component PIV Systems CW laser with high-speed photo or video camera

2D & 2-component PIV Systems Consecutive singly exposed PIV recordings Fluorescent particles in a microdevice 0.540.41 mm2, 30 fps Smoke flow in air 0.50.5 mm2, 500 fps

2D & 2-component PIV Systems Standard 2D PIV Light sheet t=t0 Lens Measurement volume Laser t=t0 Image #1 Single exposed recording Fluid flow seeded with small tracer particles Double exposed recording Exposure #1 Lens system & Camera

2D & 2-component PIV Systems Standard 2D PIV Light sheet t=t0+t Lens Measurement volume Laser Image #1 t=t0 Fluid flow seeded with small tracer particles t=t0+t Image #2 Exposure #2 Exposure #1 Lens system & Camera Single exposed recording Double exposed recording

2D & 2-component PIV Systems Velocity determination with standard 2D PIV Image plane Objective Lens Laser light sheet Scale factor: M=L/L’ Time interval: t Velocity: V=S/t=M·S’/ t Laser light sheet Image plane Objective Lens S S’ L L’

Micro-scale PIV (MPIV) System Nd:YAG Laser Micro Device Flow in Flow out Glass cover CCD Camera (1280x1024 pixels) Beam Expander Epi-fluorescent Prism / Filter Cube Microscope Nd:YAG LASER MICROSCOPE BEAM EXPANDER CCD CAMERA MCROFLUIDIC DEVICE Flood Illumination l=532 nm Focal Plane l = 610 nm Micro-Fluidics Lab Purdue University Micro-PIV image pair

3D or 3-component PIV Systems 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 (Brücker, 1997) Scanning a 3D volume with a laser beam Single high speed camera

3D or 3-component PIV Systems Stereo PIV configurations a. Translation systems (lateral displacement) b. Rotational systems (angular displacement) Scheimpflug condition

3D or 3-component PIV Systems Stereo PIV data reduction Translation systems (Mn=di/do)

3D or 3-component PIV Systems Stereo PIV data reduction Rotational system (Mnconstant)

Holographic PIV (HPIV) System Holographic diagnostics of a 3D particle filed Hologram recording Hologram reconstruction

Holographic PIV (HPIV) System Holographic recording of particles Interference pattern in a HPIV recording

Holographic PIV (HPIV) System Reconstructed HPIV particle images

Holographic PIV (HPIV) System Example of HPIV system (recording)

Holographic PIV (HPIV) System Example of HPIV system (reconstruction)

Homework Practice with EDPIV software Read EDPIV help manual page to know details in “Raw Image Format” window 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/