Socrates: The First Professor

A classical or holographic interferometer can be used to measure the average fluid temperature integrated in the direction of the test/object beam. However, such beamaveraged measurements are not exact for a three-dimensional temperature field, when a standard two-dimensional analysis technique is applied. In the current study, an analysis is performed to determine the error in the average fluid temperature measurement caused by temperature variations in the light beam direction. The error has been calculated for both an ideal gas and water as the test fluid. The results show that for typical experimental conditions, the measurement error introduced by this temperature variation is less than 2%, even for the most adverse temperature distribution in the light beam direction. For reasons discussed in this article, this result may promote the wider application of interferometry to three-dimensional heat transfer problems.