Planar measurement technique for compressible flows using laser-induced iodine fluorescence

A laser-induced fluorescence technique for conducting planar measurements of temperature, pressure, and velocity in nonreacting, compressible flows has been developed, validated, and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled charge-coupled device camera. The temperature measurement, which has been described earlier, is used in conjunction with a sophisticated model of the fluorescence excitation spectrum to produce accurate pressure measurements. The demonstration velocity measurements represent the first planar velocity mapping using molecular seed in a highly three-dimensional supersonic flow of practical importance. In the measurement technique, temperature is determined from the fluorescence induced with the laser-operated broadband. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum, which is measured with the laser operated narrow band. A parametric relationship has been developed to relate the complex fluorescence excitation spectrum to pressure for specified temperatures. The important of this novel approach is that it significantly reduces the computational requirements for relating the line shape to pressure, thereby making accurate measurements of pressure at a large number of points in a plane practical. The uncertainty of the measurement is estimated to be 6% for temperature, 5% for pressure, and 25 m/s for velocity.