A Caltech Library Service

Soap film thickness imaging by infrared methods

Mackey, Ryan M. E. (1997) Soap film thickness imaging by infrared methods. Engineer's thesis, California Institute of Technology.


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)
Degree Grantor:California Institute of Technology
Major Option:Aeronautics
Thesis Committee:
  • Gharib, Morteza (chair)
  • Leonard, Anthony
  • Hornung, Hans G.
Defense Date:1 December 1996
Record Number: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:25 Dec 2012 14:58

Thesis Files

[img] PDF (Mackey_rme_1997.pdf)
Restricted to Caltech community only
See Usage Policy.


Repository Staff Only: item control page