A Seminar
On
“Particle Image velocimeter”
Submitted for
The requirements for the award of the Degree of
BACHELOR OF TECHNOLOGY
at
DEPARTMENT OF MECHANICAL ENGINEERING
GANDHI INSTITUTE OF ENGINEERING AND TECHNOLOGY
GUNUPUR – 765022
ACKNOWLEDGEMENT
My sincere thanks to Prof.A.Biswas, Head of the Department of Mechanical Engineering, Gandhi Institute of Engineering and Technology, Gunupur for his encouragement and valuable suggestions on this seminar topic.
I would like to thank Jadabpur university, kolkata for allowing me to study a real time model of Particle Image velocimeter.
I express my heartfelt gratitude to Principal Dr. S.P. Chaudhuri, GIET, Gunupur for permitting me to carry out this seminar.
SAMEER DUBEY - (0601210153)
Study on Particle Image Velocimeter (PIV).
Figure- 1: Particle Image Velocimeter.
1. Introduction:
Particle Image Velocimetry (PIV) is a non-intrusive measurement technique for studying the velocity of particles in some type of flow. This is most commonly either a gas flow in a wind tunnel, or a liquid flow of some viscous fluid. The medium is then seeded with some sort of tracer particles and then illuminated periodically by some high power light source, which is often a laser. The idea is to obtain successive digital images from charged coupled device (CCD) cameras. These images can then be analyzed by a computer, which determines the velocities of the tracer particles, which can be used to understand the velocity of the given medium.
Particle Image Velocimetry (PIV) measures whole velocity fields by taking two images shortly after each other and calculating the distance individual particles travelled within this time. From the known time difference and the measured displacement the velocity is calculated. Since the flow can be quite fast one has to avoid blurred images and that‘s one reason to use laser pulses. They are only 6-10 ns. long and freeze any motion. The other reason is that only laser light can be focused into a thin enough light sheet so that only particles in that plane are imaged. Otherwise the scattered light from particles in other planes would make this measurement impossible. A special camera is utilized so that it can store the first image (frame) fast enough to be ready for the second exposure. The "dead" time between the frames when the camera is "blind" is very short down to 100 ns.
Advantages:
• The method is to a large degree non-intrusive. The added tracers (if they are properly chosen) generally cause negligible distortion of the fluid flow.
• Optical measurement avoids the need for Pitot tubes, hotwires or other intrusive Flow measurement probes.
• Additionally the method is capable of measuring an entire two-dimensional cross section (geometry) of the flow field simultaneously.
• High speed data processing allows the generation of large numbers of image pairs which, on a modern personal computer may be analyzed in real time or at a later time.
