Measurements in fluid flows using molecular filter-based techniques

Filtered Rayleigh scattering is an unseeded, non-intrusive diagnostics technique that allows the measurement of thermodynamic properties and velocity of the fluid by resolving the scattering spectrum from the gas molecules with the aid of a molecular filter as the flow is irradiated with a spectrally narrow laser. This work describes the technique and application to measure fluid properties and one velocity component in the compressible flow produced by a laser-induced energy deposition in quiescent air. The flow is investigated applying three different capabilities of the technique, namely flow visualization, multiple-property and velocity measurements, and temperature measurements. In all cases two-dimensional fields are captured. As the application of FRS is described, modifications to the technique are discussed to simplify data acquisition and background calibration. The uncertainty of the measurement technique is also discussed and evaluated.