This project combines a novel interferometric measurement technique, Coherent Gradient-Sensing Interferometry (CGI), with multi-view tomography to develop a powerful new tool for transient, three-dimensional (3D) measurement of temperature, concentration, or density in fluid systems. The unique advantages of CGI over traditional interferometric techniques include: (1) complete insensitivity to vibration, (2) no reference-beam requirement, (3) continuously variable sensitivity, and (4) lower cost, and (5) more reliable operation. These features make a CGI-based instrument particularly well suited for portable and commercial applications. This novel instrument consists of a CGI interferometer capable of rotating around a transparent test cell to capture interferometric images at different angles, which are then used to compute transient, 3-D profiles of thermophysical properties such as temperature, concentration, or density for the fluid-thermal system in the test cell.
Measurement of three-dimensional, time-varying profiles of temperature, concentration, and density is critical for the understanding and optimization of many engineering, biological, and geophysical thermal-fluid systems. Examples include advanced materials processing; natural and forced convection, and surface-tension-driven heat transfer; mass transfer, and species pro-duction; and biological and bio-engineering phenomena. Such measurements are needed to vali-date computer simulations of such situations. The successful development of the CGI Tomo-graphic Interferometer provides, for the first time, direct, transient, 3-D measurement capabilities for transport phenomena in fluid-thermal systems. Some immediate applications of the instru-ment will include measuring temperature and concentration during simulated crystal growth, measuring temperatures during laser-induced surface-tension-driven flows, monitoring tracer concentrations in flow through mechanical heart valves, measuring temperature and concentra-tion during melting and solidification, and assessing 3D crack structures in transparent solids. A prototype instrument is also being developed that will be portable and available for other labo-ratories and local companies for evaluation and application. Furthermore, the instrument devel-opment itself is an excellent vehicle for training students in optical systems and image process-ing.
