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To find out if Particle Image Velocimetry can be used for your test, contact:

James E. Bridges

Special Instrumentation
Particle Image Velocimetry

Particle Image Velocimetry uses light reflected from seed particles in the flow to measure velocities of the air exhausting through nozzles in the Small Hot Jet Acoustic Test Rig.

Shedding light on the mysteries of high-speed hot jets
This we know—aircraft jet noise is caused by the intense turbulent mixing of hot high-speed exhaust gases and cool ambient air. By controlling the way a jet mixes with the surrounding air, we can potentially control the amount of noise it produces.

Easier said than done!

NASA Glenn is broadening our understanding of high energy flows through the development of advanced instrumentation systems like Particle Image Velocimetry (PIV). Systems like these allow us to gather new data that can be used to validate critical turbulence modeling quantities which are at the heart of many noise prediction schemes.

Particle Image Velocimetry is a technique used to measure unsteady velocities in hot jets. Particles are introduced to the stream(s) of interest which are illuminated by a sheet of laser light. Images captured by a pair of cross correlation cameras are processed, yielding turbulence data faster and in far more detail than previous techniques. More detailed measurements coupled with more accurate theories enable engineers to design quieter nozzles.

PIV is able to measure mean velocity, RMS velocity, and two-point correlation statistics which are all used to validate the latest aeroacoustic theories. And while there are a number of PIV systems are commercially available, researchers at NASA Glenn have recently deployed a new High Resolution Stereo Particle Imaging Velocimetry system that expanded the field of view to over four times that of the previous PIV system while dramatically reducing facility testing time and data acquisition system complexity.

+ Aero-Acoustic Propulsion Lab
+ Small Hot Jet Acoustic
   Test Rig

+ Nozzle Acoustic Test Rig
+ Advanced Noise Control
   Fan Rig

+ 9’x15’ Low Speed Wind Tunnel
+ Acoustical Testing Laboratory
– Particle Image Velocimetry
+ Rotating Microphone Rake
+ Linear Microphone Array
+ Phased Array Microphones
+ Rayleigh Scattering
+ Hotwire, Hotfilm, and Laser    Doppler Velocimetry

Read more about other particle image velocimetry experiments

+ High-speed hot jet measurements
+ Open rotor PIV
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NASA Official: Paula J. Dempsey, Ph.D.
Last Updated: March 22, 2019

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