Image

Instrumentation and Measurement Techniques

History of PIV

History of PIV

Extract from “Adrian, R.T, “Twenty years of Particle Image Velocimetry”, Experiments in Fluids, 2005, Vol. 39, pp 159-169, DOI 10.1007/s00348-005-0991-7

The most rudimentary form of PIV could probably be traced far back in history to the first time a person possessing the concept of velocity watched small debris moving on the surface of a flowing stream. It is almost inconceivable that a great intellect like Isaac Newton would not have observed the moving patterns and seen the potential for visualizing and even measuring the surface velocity from the displacements of the particles of algae. From this viewpoint, particle velocimetry is old and very simple.
However, in its modern form, PIV means the accurate, quantitative measurement of fluid velocity vectors at a very large number of points simultaneously, and we now understand that this is, indeed, a very challenging, complicated, and relatively recent achievement.

The first investigators to achieve such measurements actually used the method of laser speckle, originally developed in solid mechanics, and showed that it could be applied to the measurement of fluid velocity fields. In 1977, three different research groups, Barker and Fourney( 1977), Dudderar and Simpkins (1977), and Grousson and Mallick (1977), independently demonstrated the feasibility of applying the laser speckle phenomenon to fluid flow by measuring the parabolic profile in laminar tube flow. The principal elements of their experiments were the use of double-exposure photographs and planar laser light sheet illumination and interrogation by forming Young’s interference fringes from the many pairs of displaced laser speckles in small interrogation spots on the specklegrams.

By 1983, a young doctoral student working at the v. Karman Institute, Belgium, Meynart (1980,1982a,1982b, 1983a,1983b,1983c), was the leading practitioner of this method, and he had shown that practical measurements could be made in laminar flow and turbulent flow of liquid and gases, thereby simulating intense interest from the fluid mechanics community.
While Meynart referred to his work as laser speckle velocimetry (LSV), the images in his papers often contained images of individuals particles instead of speckles.

The first explicit recognition of the importance of particle images was made in two short, contemporaneous papers by Pickering and Halliwell (1984) and Adrian (1984). In the latter, it was argued that the illumination of particles in fluid flows by a light sheet would seldom, if ever, create a speckle pattern in the image plane. Instead, the image plane would contain images of individual particles. The name particle image velocimetry (PIV) was proposed to distinguish this mode of operation from the laser speckle mode. A simple criterion was defined by which one could predict the occurrence of one mode or the other using a dimensionless number called the density. The source density equals the mean number of particles in a resolution volume, and the number of overlapping images in the image plane can be expressedin terms of it. For fluids, the allowable concentration of scatterers is normally too small to produce source densities large enough to have speckle patterns formed by overlapping images. Higher particle concentrations are either not achievable or not desirable fluid dynamically (unless one intends to produce two-phase flow. Hence, one almost always sees particle images rather than speckles.

Publications

PHD Thesis of Roland Meynart: Mesure de champs de vitesse découlements fluides par analyse de suites d'images obtenues par diffusion d'un feuillet lumineux, ULB, octobre 1983, VKI PHDT 1983-02
Image

Digital Image Processing in Fluid Dynamics

Buchlin, J.M. (ed.): Digital Image Processing in Fluid Dynamics. von Karman Institute for Fluid Dynamics Lecture Series, VKI LS 1984-03. von Karman Institute, Rhode-Saint-Genèse, Bel- gium (1984).

TABLE OF CONTENTS

  • PRATT, W.K. - Vicom Systrems Inc., USA
    Digital image processing and analysis
  • HESSELINK, L. - Standford University, USA
    Optical processing
  • JIMENEZ, J. - IBM scientific center, Spain
    Planning an experiment for digital image processing
    Postprocessing: extracting and displaying useful information from digital images
  • SCHON, J.P. - Ecole Centrale de Lyon & Université de Saint Etienne, France Instantaneous concentration and velocity measurements through laser visualization associated with a digital processing system
  • MEYNART, R. - von Karman Institute for Fluid Dynamics & Université Libre de Bruxelles; FNRS & LOURENCO, L.M. -von Karman Institute for Fluid Dynamics: Laser speckle velocimetry in fluid dynamics applications