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Air-Flow Visualization Using Interferometric Detection of Thermal Markings

IP.com Disclosure Number: IPCOM000119829D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Crawforth, L: AUTHOR [+3]

Abstract

Disclosed is a nonintrusive technique to quantitatively measure two dimensional air flows by creating a temperature change in an air flow and tracing the temperature change through the flow using holographic interferometry. This reusable technique, which is nonintrusive, allows two-dimensional fluid-flow characteristics, such as velocity, turbulence intensity, and vorticity, to be determined.

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Air-Flow Visualization Using Interferometric Detection of Thermal
Markings

      Disclosed is a nonintrusive technique to quantitatively
measure two dimensional air flows by creating a temperature change in
an air flow and tracing the temperature change through the flow using
holographic interferometry.  This reusable technique, which is
nonintrusive, allows two-dimensional fluid-flow characteristics, such
as velocity, turbulence intensity, and vorticity, to be determined.

      The two-dimensional visualization of airflow is achieved by
first placing a diffusively reflective target so that the area of
flow to be measured lies between the target and the viewing
direction.  A single exposure reference hologram is taken of the
target and played back, interfering with the live image of the
target.  Subsequent changes of the refractive index of the air
between the target and the holographic plane will be displayed as
interference fringes.  The required index changes are brought about
by changing the temperature of the flow in a well-defined
two-dimensional pattern.  The air flow is seeded with a molecular
species that absorbs pulsed radiation from a pump laser.  The
absorption of the radiation results in a temperature increase, and
hence refractive index change of the flow medium.  The change in
refractive index, when viewed interferometrically, results in an
intensity change wherever the flow has been heated.  The magnitude of
the intensity change can be found by first con...