Flow Visualization

Particle Imaging Velocimetry technique has gained

significant popularity in engineering and scientific

fluid mechanics from aerospace wind tunnels

to prosthetic heart valve vortex formation.

PIV is used to measure instantaneous velocities

and other properties in fluids and gases.

Fluid, seeded with small tracer particles

that follow flow dynamics, is

illuminated by a laser to make the

particles visible. A camera takes a

series of images from which speed

and direction of the particles

are calculated.

particle imaging velocimetry example  

The ability to visualize the flow and ascertain instantaneous velocity measurements in fluids is the hallmark of particle imaging velocimetry (PIV).  In a typical setup, so-called “tracer” particles are implanted in a fluid and, assuming the particles are sufficiently small, will then undergo and experience conventional flow dynamics.  The ability to track the particles comes at the behest of laser illumination, enabling the tracking of the particles in order to determine the velocity field (i.e., speed and direction) of the flow under study.  PIV is unique in that it is applicable across an immense scale: from the highly macro to the microscopic.  As such, PIV has applications throughout many industries, including aerospace for studying the hydrodynamics of airflow over aircraft wings; agriculture for researching seed dispersal patterns from flowering plants; and medicine for modeling blood vortices in heart valves to enable the design of prosthetics and medical devices.

Both pulsed and CW lasers can be used in the acquisition of PIV data. IPG's nanosecond pulsed lasers, synchronized with the camera, are employed due to their ability to produce high powers in visible range with concomitant short pulse durations. In some cases laser output is shaped in the form of a light sheet with the use of cylindrical lenses. Most commonly employed are lasers emitting at a fundamental wavelength of 1 micron or its second harmonic green light.  The green pulsed laser such as IPG's GLPN laser is often used as it is visible to the human eye and is cost effective. 

Typical temporal resolutions can range from the hundreds of picoseconds to the millisecond range, dependent upon the system being studied and type of information to be gleaned.

Tailoring emission wavelengths, pulse durations, or laser powers to the particular system of interest enables a truly customizable, unique solution to PIV research. IPG Photonics offers a number of lasers applicable to PIV researcher, such as CW fiber lasers, including CW green GLR lasers.

  particle visualization with lasers
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