Particle Image Velocimetry (PIV) - Real Word Applications
What does PIV do?
Particle Image Velocimetry (PIV) is a technique used in industrial and research sectors to create a visualization of how materials such as liquids, gases, and sand flow. It is frequently used in aeronautics, mechanical engineering, environmental engineering, and other technical disciplines to obtain instantaneous velocity measurements and related properties in fluids. Generally, seeding (or tracing) particles are introduced in a fluid and then the fluid is illuminated so that the particles become visible. The motion of these particles is then measured to calculate speed and direction of the fluid flow.
PIV is a non-intrusive approach - a succession of images is used to create a measureable visualization of the movement of the particles in the fluid. This leads to an accurate depiction of flow since it does not tamper with the fluid in its natural state. Also, rather than characterizing a single point of the flow, this technique provides a full-view, either in 2D or 3D representation.
Where does PIV play a part in our lives?
As a practical tool, PIV leads to improvements across a wide gamut of industries. For example, in aeronautics, mechanical engineering, chemical engineering, and environmental engineering PIV has made better experiences possible in driving, flying, printing with ink jet printers, listening with hearing aids, and avoiding flood damage with human built structures.
PIV reveals the aerodynamics of vehicles like cars, airplanes, and helicopters. Measurements of the motion of air and its interaction with these moving objects provides the necessary information to then optimize vehicle design so there is less noise pollution (particularly during take-off and landing) and travel is smoother (minimal wind resistance).
Velocity measurements in water flow enable mechanical engineers to build ship hulls designed for more efficient travel, pipes that support fluid flow for extended durations, and prosthetic heart valves that last longer. PIV exposes where the greatest wear and resistance are in structures. Engineers use this information to redesign structures so that resistance is minimized or prevented. PIV also leads to design improvements by enabling inspiration from biology. For example, the study of movement of marine animals allows researchers to better create objects that move more efficiently in liquids.
Chemical engineers use PIV to improve chemical mixtures/compositions so that they are more efficient and/or less destructive. PIV is used in studies to understand initial chemical reactions, the dynamics as the reaction takes place, and the effects once the reaction completes. This information leads to developments such as greener cars where there is more efficient fuel consumption because researchers can identify how to achieve lower fuel consumption and less pollutants.
Flow measurements provide crucial information to environmental engineers whose goal is to restore or preserve a natural environment. For example, it is used in studies of physical and biological processes before and during floods so systems can be designed to prevent flood damage or to even restore an area to its pre-flood state.
Why scientists can benefit?
PIV is a well-known method used in laboratory environments. There are many flavors of this technique including 2D PIV, stereoscopic PIV, micro PIV, and high speed PIV. It leads to analyses and predictions of the behavior of flows and the reaction of moving and non-moving materials to those flows.
PIV is a useful technique used to formulate new ideas and theories, interpret observed phenomena, and develop new experimental tools. In short, it enables both theoreticians and application-centric scientists to come up with novel ideas/methods.
Boulder Imaging’s PIV solution
The PIV technique is used to measure flow by taking two images shortly after each other (i.e. – nanoseconds apart in time) and calculating the distance individual particles travel within this time. From the known time difference and the measured displacement, the velocity is calculated. These two images are captured repeatedly providing continuous feedback over time about the flow.
A specialized camera must be used so that the first image is transferred fast enough from the sensor so the camera can capture a second image. To enhance flow visualization, tracer particles close in behavior to the properties of the observed medium are seeded in the medium. Then, to sufficiently light the particles while minimizing blur in the fast moving flow, image capture is synchronized with a pulsing laser. The components for a typical PIV system include:
- PIV camera and optics
- Pulsing laser
- Cabling for camera and laser
- Mechanism to synchronize camera and laser
- Light Sheet
- Laboratory environment (i.e. - wind tunnel, aquarium/large pool)
- Medium (i.e. – Gas, Liquid) whose flow is to be characterized
- Tracer particles
- Image processing software
Variations in PIV systems reside at many parts of the system and depend on the experiment. For example, cameras used to detect small particles would be different than those to detect macro particles. Additionally, different camera speeds are required depending on the speed of the flow. Also, some PIV applications require one camera whereas others require multiple cameras (i.e. - 2D PIV versus stereo PIV). Furthermore, each PIV system utilizes different image processing software.
Boulder Imaging provides flexibility for your PIV application. Our HPDVRs support a wide range of PIV cameras simultaneously (up to eight in one system), synchronize laser firing with image capture, and enable the end user to integrate any image processing software for real-time or post-processing. The end result is a single system scalable to support your PIV demands for today and tomorrow. And we sell a variety of cameras to meet your application demands for today.