Contract for Scientific Visual Analysis and Multimedia
Digital Particle Image Velocimetry (DPIV) is the latest innovation in
experimental fluid dynamics. The great advantage of this method
is the ability to simultaneously measure two components of a fluid's velocity
at a large number of points in the space, time domain. Another advantage
is the fact that it is a non-intrusive method, which means that we do not
effect the flow field by placing any kind of instrument or probe in the area of
interest in order to obtain our measurements. Quantitative and qualitative
information is extracted simultaneously as opposed to older static, point
measurement techniques that have dominated experimental fluid mechanics until today.
There are several variations of the DPIV technique, but they all share
some common components. First of all the flow filed is seeded by small
tracer particle whose diameter varies between 10 and 100 microns. The seeding
particles have to be very small so that they do not change the properties
of the flow, and neutrally buoyant so that they accurately follow any velocity fluctuations.
Second, the interrogation area of our flow field is illuminated by
high power laser sheet. A high-speed CCD camera captures light from the laser sheet reflected by
the particles. Usually the frame rate of the CCD camera is 30 frames/sec. There are several other
components that are needed but their detailed description goes beyond the scope of this comprehensive
The extraction of the velocity components (both direction and magnitude
of the velocity vectors) is achieved by determining the particle motion
between two sequential frames using methods of image processing.
The DPIV system currently employed in the Fluid Mechanics Laboratory
of the Engineering Science and Mechanics Department uses a high frame rate
CCD camera, able to acquire up to a 1000 fps, with a resolution of 256x256 pixels, and
a color depth of 8-bits in a gray-scale format. The light source is a 45 watt pulsed
copper vapor laser with 1 kW/pulse. Also a wide variety of optics and traversing
accessories makes the sytem capable of interrogating multiple planes in the horizontal and vertical directions.
In order to reconstruct the complete flow field, the experimental investigation
using this method of DPIV requires the acquisition of frames in multiple areas of
the same plane, in planes of different elevation, and in a time period
of several seconds. Considering the specifications of our system we have as result
an enormous amount of data sets (thousands of images). Their manipulation and visualization is
the main objective of this project. Specifically the goals are as follows.
Visualization of the 2D velocity field.
Calculation and visualization of flow properties such as vorticity,
in order to extract additional information.
Animation of the 2D planes in the time domain. This way the evolution of
the phenomenon with respect to time can be observed.
Superposition of planes of different elevations, and calculation of the
3rd velocity component so that a 3 dimensional perspective of the flow
can be investigated. Again fluid properties (vorticity) will be extrapolated
to 3 dimensions
Animation of the 3 dimensional construction in time.
A Web based presentation module will be developed for the presentation
of the results.
C/C++, PV-Wave, and OpenGL for the visualization part of the project,
and HTML Java and VRLM for the WEB based project presentation.
The progress and success of each step is going to determine
any necessary changes, if needed.