Multi Point Velocity, Density and Temperature Measurements using LITA

Laser induced thermal acoustics (LITA) is a nonintrusive, transient-grating optical technique that provides simultaneous high-accuracy measurements of velocity, sound-speed, and thermal diffusivity among other parameters. In a fluid of known composition, sound speed and thermal diffusivity are readily correlated to temperature and density. Thus LITA provides a measurement of thermodynamic state. We are developing a computer-controlled semi-portable LITA system for robust, long-baseline measurements. This novel system automatically adjusts its own alignment to optimize accuracy. In prior work, LITA velocimetry was incorporated into this system and demonstrated. System level requirements for multi point LITA measurements were identified and system components, which as a whole, meet these requirements were designed or identified. In the proposed effort, elements of the design will be separately validated and will then be incorporated into a complete system for delivery to NASA in Phase II. By providing velocimetry and multi point capability the proposed system will beideal for high-value ground-test experiments.