Fluid Mechanics and Acoustics Laboratory - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique
Lyon
France


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Home > Research Support > Scientific instrumentation > Techniques > PIV - Particle Image Velocimetry

PIV - Particle Image Velocimetry

The Particle Image Velocimetry or PIV is a non-intrusive measurements technique based on light diffusion allowing to measure the two planar velocity components of a flow section (2D-2C). It relies on the flow seeding by tracing particles, the recording at two distinct instants of their positions and the measure of their travel. The velocity is easily calculated by the equation Velocity=Distance/Time. Most frequently the light source is a two cavities pulsed Nd:Yag laser and the laser sheet is generated by a cylindrical lens. The cameras used then are double frames CCD sensor cameras.

Each frame is then divided in small inquiry areas in order to do an intercorrelation by FFT. The obtained correlation peak matches the particles most probable travel.

Scanning all the inquiry areas, we get an instantaneous velocity field. From the acquisition of a high pictures number, we can calculate the velocity statistical quantities such as the average, the standart deviation, etc.

BMP - 745.6 kb
Instantaneous field
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Average field

Measurements tools:
- Seven double cavity Nd:Yag lasers: 2*50 mJ, 2*65 mJ, 2*120 mJ, 2*140 mJ, 2*150 mJ, 2*1.5 J ; pulse duration from 3 to 8 ns ; repetition frequency from 0.01 to 20 Hz
- A double cavity Nd:YLF laser: 18 mJ at 1 kHz, pulse duration: 120 ns, repetition frequency from 0.1 to 10 kHz
- Several continuous wave solid lasers
- Eight double frames CCD cameras: three cameras 1280*1024 pixels 12 bits, one camera 4032*2688 pixels 14 bits, one intensified camera 1280*1024 pixels 12 bits, one camera 1600*1186 pixels 10 bits, one camera 1008*1018 pixels 8 bits
- Nine CMOS cameras: two cameras 1280*800 pixels 12 bits at maximum 6 kHz, one camera 1024*1024 pixels 12 bits at maximum 3.6 kHz, onen camera 800*600 pixels 8 bits at maximum 1 kHz, two cameras 2560*2160 pixels 16 bits at maximum 50 Hz, one camera 2048*2048 pixels 12 bits at maximum 75 Hz, one camera 1280*1024 pixels 10 bits at maximum 50 Hz
- Six synchronization and acquisition systems