Time Resolved Filtered Rayleigh Scattering Measurement of a Buoyant Jet In a Co-flow

Abstract

The filtered Rayleigh scattering technique is implemented using a continuous wave laser in conjunction with a high speed camera and a molecular filter to obtain near field concentration measurements of a carbon dioxide jet in a co-flow of air with a sampling rate of 400 Hz. The beam from a 12-Watt Coherent Verdi laser was directed through the jet, of diameter ranging from 8.9 mm to 17.1 mm, at two streamwise stations, spaced about one diameter apart, and image sequences were collected with a Phantom high-speed camera for up to 20 seconds. In addition to the mean of the concentration and standard deviation of the scattered light intensity, space-time correlations of multiple points in the flow field are illustrated. The jet trajectory and mixing properties are investigated with and without the co-flow. The results demonstrate the significance the addition of the co-flow has on flattening the jet trajectory and increasing the mixing rate. The effects of various flow parameters such as the jet velocity, the jet-to-co-flow velocity ratio, the relative velocity between the jet and the co-flow, the Froude number, and the Reynolds number on the jet trajectory are studied. The results indicate that, within the range of test conditions, the velocity of the jet has the most significant effect on the jet trajectory. Furthermore, the investigation of the jet trajectory with respect to the Froude number highlighted the need to use a more robust Froude number definition that takes into account the effects of the addition of a co-flow in the flow field.

Quantitative gas property measurements by filtered Rayleigh scattering: a review

“…These can be seen in figure 12. Benhassen et al [119,120] also studied buoyant CO 2 jets and characterized the resulting flowfields with a similar CW laser setup at a sampling rate of 400 Hz.…”