A New Particle Image Velocimetry Technique
Stereo and orthogonal
views of a particle-seeded flow were simultaneously recorded
using a CCD camera. A two-stage calibration algorithm was
developed to determine the optical coefficients of each view separately.
The images were digitally enhanced and algorithms
developed to match individual particles in the stereo and orthogonal views. A
three-dimensional cross-correlation algorithm was then used
to follow the particles from frame to frame and calculate the velocity vectors.
A Ph.D. student by the name of Satya Kurada obtained his degree based on this work. The
knowledge gained in this project provided an excellent background for the
optical measurement investigations currently being conducted
in our laboratory.
Preliminary Pressure Sensitive Paint Study
Pressure sensitive paints are luminescent
surface coatings that are used to determine the pressure distribution across
the surface. The coating is illuminated with light of an appropriate wavelength
and the luminescence captured within a wavelength band using a filter and CCD
camera. The intensity that is emitted as well as the luminescence decay rate
are related to the partial pressure of oxygen of the gas that is in contact
with the surface, which is proportional to the fluid pressure. Many luminescent
materials (luminophores) and binders have been reported in the literature along with a number of
techniques to extract the fluid pressure information. The advantage of this
technique is the ability to determine continuous pressure distributions on
surfaces. A disadvantage is that the technique is temperature sensitive and
clever techniques have been developed to eliminate or
reduce this effect. Non-uniformity of the paint and illumination are eliminated
by a simple ratio of the
“wind-on” and “wind-off”
conditions.
An extensive survey of
the literature in this field has been completed. In addition,
we have been successful in demonstrating the technique in our laboratory using Pt(II) meso-tetra(Pentafluorophenyl)porphine as
the luminophore,
suspended in a silicone resin binder (Genesee Polymer Corp GP-197). A white
light source and blue filter were used for
illumination while a red filter and a CCD camera were used for recording the
image. The flow field consisted of a simple air jet directed onto a painted
flat surface.
The work described here
is the background for future projects involving pressure sensitive paint.
Talbot Effect Applied to the Measurement of Turbulence
This project is a collaborative effort with Dr. O. Penyazkov of the A.V. Luikov Heat
and Mass Transfer Institute in