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  Products Glossary of Technical Terms  


Holographic Particle Image Velocimetry


Holographic Particle Image velocimetry” is a technique that measures the instantaneous three-dimensional (3D) velocity field of fluid flows in a volume using holography. The 3D information of flow particles -seeded or inherent in the flow- is recorded on a hologram instantaneously using two or more short laser pulses. The reconstructed 3D-image field contains information about the 3D positions, size and shape of the particles. By finding the 3D displacements of particles in the image volume between two exposures separated by a short time lapse, an instantaneous, volumetric 3D velocity field can be retrieved. HPIV can measure velocities with accuracy within a few percent and spatial resolution ~1mm.

The HPIV process consists of three steps: recording the hologram, reconstructing the object field from the recording, and interrogating the reconstructed field. During recording, an ‘object’ wave (light scattered from the particles) is combined on a holographic plate with a reference wave (unscattered) to produce an optical interference pattern. During reconstruction, the re-introduction of the reference wave on the hologram reconstructs the object wave in the 3D space. The reconstructed 3D image can then be interrogated, typically scanning it with a video camera, in order to retrieve particle information. When applied in conjunction with cinematography, both time- and space-resolved measurements can be obtained.

HPIV is now a diagnostic tool accepted for interrogating and extracting 3D information from particle fields and multiphase flows. Yet, holography systems are not produced in a commercially available form due to the complexity and variety of systems needed for different applications. Customized designs are usually tailored to specific applications.

Meng H; Hussain F (1991) Holographic particle velocimetry: a 3D measurement technique for vortex interactions, coherent structures and turbulence. Fluid Dynamics Research 8: 33-52.

Barnhart DH; Adrian RJ; Meinhart CD; Papen GC (1994) Phase-conjugate holographic system for high-resolution particle image velocimetry. Applied Optics 33: 7159-7169.

Zhang J; Tao B; Katz J (1997) Turbulent flow measurement in a square duct with hybrid holographic PIV. Experiments in Fluids 23: 373-381.