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The PIV ’09 conference took place in Melbourne, Australia, August 25-28. It was well attended with more than 200 delegates from all over the world.
Dantec Dynamics had an exhibition booth on which the new Volumetric Velocimetry (VV) solutions had their World Premiere.
Entering the fourth dimension
With the time-resolved VV solution, experimental fluid mechanics enters the fourth dimension: all three velocity components in space, and time. This is a major step forward for validation of CFD codes with experimental data.
Volumetric flow field information with 2, 3 or 4 cameras
Volumetric Velocimetry provides truly volumetric velocity data, using 2 to 4 cameras with telecentric lenses, and a thick light sheet or a scanning thick light sheet. Time-resolved VV solutions using time-resolved CMOS cameras, as well as “classical” solutions with CCD cameras are available. For low to medium seeding concentration, Particle Tracking Velocimetry (PTV) is used with two or three cameras, whereas for high seeding concentration (like PIV) a Least Squares Matching (LSM) algorithm provides 3 velocity components in a 3D volume.
Full shear tensor directly from the LSM data processing
The LSM is a very computationally efficient and fast processing method,
providing much more information than classic cross-correlation based PIV: the full shear tensor describing rotation, shear and translation of the flow, in addition to the three velocity components in space.
The computational speed increase is twofold: 1) LSM is faster than cross correlation, and 2) the full shear tensor is computed in the same calculation as the velocity field. With PIV processing, the shear tensor must be computed after the velocity field.
Straightforward upgrade path from Stereo PIV to Volumetric Velocimetry
Stereo PIV systems are easily upgraded to tomographic Particle Tracking Velocimetry (PTV) by adding telecentric camera objectives and a software add-on. Adding a 3rd camera, volumetric PTV in medium seeded flows is possible, and adding a 4th camera, Volumetric Velocimetry using a Least Squares Matching algorithm is possible.
True 3D data visualisation
With volumetric velocity information available, visualising and understanding the data is a challenge. DynamicStudio supports true 3D visualisation using either red-green glasses with a standard monitor, or special shutter glasses and a monitor capable of 3D viewing. This greatly helps understanding the spatial flow structures.
