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Soap Film Thickness Imaging by Infrared Methods


Mackey, Ryan Murrill Ezekiel (1997) Soap Film Thickness Imaging by Infrared Methods. Engineer's thesis, California Institute of Technology. doi:10.7907/7bv0-m741.


A new method of studying soap film flows is introduced and discussed from several viewpoints. Using a commercial infrared camera and a cold background as an infrared light source, one can recover nonintrusively a measurement of the film thickness distribution. Once the thickness is known it is easy to compute the two-dimensional pressure in the film, allowing one to compute other film properties as well.

Blackbody and infrared detector theory are covered in brief and a simple theory of operation is introduced to explain the connection between emissivity and thickness. This theory is demonstrated to behave similarly to the physical system, predicting detected temperature values as a function of thickness of the same approximate magnitude as observed, but is too simple to provide a perfect match. An empirical calibration routine is demonstrated allowing one to calculate the film thickness to a high degree of precision.

The infrared method is applied to a number of familiar test problems as a demonstration. A gravity driven soap film tunnel has been constructed, and infrared images of the film surface are provided for unobstructed flow, separated flow past a cylinder held at one wall, and turbulent flow through a grid. These images are presented in raw and processed formats and the phenomena observed are discussed.

Item Type:Thesis (Engineer's thesis)
Subject Keywords:(Aeronautics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gharib, Morteza
Thesis Committee:
  • Gharib, Morteza (chair)
  • Leonard, Anthony
  • Hornung, Hans G.
Defense Date:1 December 1996
Record Number:CaltechETD:etd-01182008-085524
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:220
Deposited By: Imported from ETD-db
Deposited On:14 Feb 2008
Last Modified:09 Aug 2022 17:56

Thesis Files

PDF (Mackey_rme_1997.pdf) - Final Version
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