Turbulence measurements using FARRS in a supersonic axisymmetric jet

This article details the simultaneous measurement density, pressure, temperature and the streamwise component of velocity in a supersonic free jet. The free jet is a Mach 1.2, pressure matched jet exhausted into atmospheric air. The non-intrusive measurement technique captures Rayleigh scattering from molecules created by a pulsed, frequency doubled Nd:YAG laser across a range of angles in the plane of the jet exhaust. The laser is frequency agile and is tuned to transmit on a sloping absorption region of molecular iodine. The arc of the scattered light is focused through anamorphic optics, split into two beams and captured on a single intensified CCD camera. One of the beams passes through a molecular iodine filter, while the other beam remains unaltered. The Doppler shift, as well as broadening characteristics of Rayleigh scattering, are exploited to determine flow properties and a single component of velocity from a single laser pulse. Information from multiple pulses are combined to determine mean as well as fluctuating turbulent quantities.