Bidirectional reflectance is a fundamental property
used for the analysis of radiative heat transfer. It is a
form of reflectivity in which the spectral and directional
dependencies of both the beam incident on a surface and the
beam reflected from the surface are specified.
A new system has been designed expressly for measuring
bidirectional reflectance of engineering materials. This
apparatus features a unique goniometer design in which the
source is fixed, the sample is rotated to change the
incident beam directions, and the sensor (which moves with
the sample) is rotated about the sample to change the
measured reflected beam direction.
The system was used to measure the bidirectional
reflectance of a surface consisting of flat-white paint on
an aluminum substrate. The data for this quasi-diffuse
surface were taken over a non-uniform grid. Algorithms are
presented for interpolating and reporting values on a
uniform grid which is appropriate for use in numerical
radiative transfer codes.
Bidirectional reflectance data can be used in the form
of a look-up table although storage requirements will be
large and resolution will be limited by grid resolution.
Alternatively, the data can be modeled as continuous
functions of the incident beam angle. A simple model of
reflectance as the sum of a diffuse and a specular
component is described. A second model with a diffuse
component and a quasi-specular component is also presented
which includes spread in both the polar and azimuthal
directions. Both models are continuous and are based on
curve fits to the data. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36350 |
| Date | 05 May 1994 |
| Creators | Zaworski, Joseph Robert |
| Contributors | Welty, James R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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