Division of Engineering and Applied SciencesDivision of Engineering and Applied Sciences

California Institute of TechnologyCalifornia Institute of Technology

MoryMory GharibGharib

Particle Image VelocimetryThe Revolution of Quantitative Visualization

From Qualitative to Quantitative Flow Visualization

Dye Visualization

Digital Particle Image Velocimetry

Particle Tracing

Other Field Quantities,Multiple Quantity Diagnostics

DPITVSimultaneous Velocity and Temperature measurement

using Liquid Crystal Particles

Park & Gharib, 2001

Re=550

Ultrasound Speckle Velocimetry

Application of High framing rate (300fpm) to obtain the velocity field in an opaque elastic tube

Gharib, Hickerson, Lin (2002)

Biological ApplicationsInside The Embryonic Zebrafish Heart

Forouhar et al, Science 2004

Experimental Evaluation of Fluid-Dynamic Forcesfrom Velocity Field Data obtained with DPIV

• A cylinder performs a combined translation and in-line oscillation (peak Re = 100, oscillation frequency St = 0.164).

Sequence of velocity fields for one complete oscillation cycle

Dra

g co

effic

ient

Non-dimensional time Dotted line: DPIV (Noca et. al 1999)Solid line: Computations (Shiels 1998)

termsmotionbody ˆ +⋅+−= ∫∫SV

fluid dSndVadtdF Bρρ

• Stereo imaging / photogrammetry

• Holography

• Defocusing technique

• Time-resolved techniques (TR-PIV)

Striving to Higher Dimensions

Stereoscopic DPIV of Wing tip VortexPlanar, Three component

Wing Tip Vortex Zuhal&Gharib(2001)

HPIV

Three-dimensional velocity vector field obtained by a phase-conjugated holographic PIV technique (Barnhart 1994)

“Defocused” Particle Imaging 1990• triangle size is function of

Z-distance from lens• particles in focal plane turn

into single spots

25 mm C-mount lens with triple aperture

3-D Visualization of Vortex RingVideo originally shown at 1990 APS-DFD Meeting (Cornell)

close

far

DDPIV Today

Pereira and Gharib (2002)

DDPIV Camera for 3-D flow mapping of surface deformation measurement under impact loading

DDPIV Camera for Naval Applications

Unsteady flow field around flapping plate

Investigation of compliance and shape on vortex formation in flapping motion

Daegyoum Kim & M. Gharib, California Institute of Technology

Clapping motionConventional planar PIV

Clapping motionVolume-resolved velocity data

The capability of whole field measurement techniques such as (PIV) in providing velocity vector or scalar field information in a format compatible with CFD simulations offers many new avenues for interaction between these techniques.

A Straight Case of Validation: DNS v.s. DPIV

Gharib & Henderson (1994)

DPIV

DNS

Longo& Stern (Univ. of Iowa)

Comparative studies of RANS and PID

PIV inside a Transonic CompressorPeak efficiency, 87.5% channel height

CFD (TRACE)Experiment (PIV)

M. Voges, R. Schnell et al., ASME-GT 2008

HOLOGRAPHIC PIV (HPIV) HAS HELPED TO TEST SOME OF THE FUNDAMENTAL HYOPOTHESIS OF LES TECHNIQUE REGARDING ALIGNMENT of SGS STRESS TENSOR

- Observed alignment due to the resolved scale contribution

ijijijdij RC ++= Lτ

Leonard stress cross stress SGS Reynolds stress

(Leonard, 1974; Germano, 1986)

ijS~k

j

k

iij x

uxuL∂∂

∂∂Δ

=~~

12~

2

ijdij S~−τ

ijL versus

- Compute components from data, e.g:dijτ

jijiij uuuu ~~~~~~ −=L '''' ~~jijiij uuuu −=R , where iii uuu ~' −=

nlijτ~

- Residue stress versus : eddy-viscosity behavior ijS~ijdij

d L−=Ψ τ

)( ijijdijij LRC +−=τ

Bo Tao1, Joseph Katz2 and Charles Meneveau2

Purdue University & Johns Hopkins University,

Alignment between eigenvectors of and ijS~dijτ−

Bo Tao1, Joseph Katz2 and Charles Meneveau2

Purdue University & Johns Hopkins University,

contradicts eddy -viscosity models !

αβγ−βαγconfiguration

αβγ−αβγconfiguration

“Bi-modal Behavior”

In the new computational paradigm, simulation and experiment will become a symbiotic feedback system for diverse flow-based applications, e.g. controlled flow-structure interactions, smart combustion systems, active micro- fluidic networks, etc.

Schematics of the initial vortex pair and its interaction with the wall.

DPIV results

DNS simulation with Gaussian vorticitydistribution for the initial vortex

DNS with vorticitydistribution from DPIV for the initial vortex

A comparative study of DNS simulation based on initial conditions from a model or DPIV vorticitydistribution (Liepmann & Dommermuth 1991; Fabris et al. 1995)

The Advantage of Experimentally Initiated CFD

Proper Orthogonal Decomposition

… the small eddies are almost numberless, and large things are rotated only by large eddies and not by small ones, and small things are turned by both small eddies and large.- Leonardo The Deluge

This is a reality check on the real limitation of CFD!!

Where do we go from here in order to solve some of the main issues of today’s CFD?

PIV (2-D or 3-D) offers key assistants either as a problem solving tool or by helping

CFD to design affordable problem solving strategies

ExperimentExperiment--based versus DNSbased versus DNS--based POD modesbased POD modes

Conclusion

The rise of PIV as a method of choice in fluid research has offered a new paradigm in global quantitative flow visualization

PIV is bound to remain as an important tool for search and discovery as well as validation for the modern fluid mechanician