New versions of old flow visualization systems
Abstract
A small, modified Mach-Zehnder interferometer placed in series with a much larger schlieren optical system spanning the test section is examined. In one arm of the interferometer, light from the schlieren is focused through a pinhole and recollimating lens to produce a reference beam which interferes with the remaining object beam from the other arm. The object and reference beams are separated only over a small interval following the test section, and differential vibrations are greatly reduced. Color schlieren has technical, as well as aesthetic, advantages over black-and-white schlieren. Since each color is associated with a specific amount of refraction, quantitative evaluation of certain refractive-index fields becomes possible using very simple equations derived from ray trace theory. Rainbow schlieren of an acetylene flame, and the evaluated refractive index distribution are shown. Root-mean-square refractive index fluctuations in homogeneous, isotropic turbulence were determined using the rainbow schlieren, since these fluctuations determine the root-mean-square refraction, which is indicated by the overall color of the image.
- Publication:
-
Flow Visualization and Laser Velocimetry for Wind Tunnels
- Pub Date:
- September 1982
- Bibcode:
- 1982fvlv.rept...59H
- Keywords:
-
- Flow Visualization;
- Mach-Zehnder Interferometers;
- Schlieren Photography;
- Color Photography;
- Flow Geometry;
- Optical Filters;
- Photographic Equipment;
- Instrumentation and Photography