INVESTIGATION OF COHERENT STRUCTURES IN A TRIPLE JET BY RAMAN-SCATTERING

An optical method is developed that allows the investigation of cohere nt structures in multicomponent gas flows. The method is tested on the flow field of a triple jet with different initial conditions. Linear Raman scattering is applied for concentration measurements. The autoco rrelation function of the Raman signal is recorded. In addition, the f requency of occurrence of the amplitudes of the Raman signal is measur ed. The analysis of correlation measurements of the Raman signal toget her with the measurement of the amplitude distribution allows recovery of the regular periodic structure of the concentration variations cau sed by vortex rolls that are moving through the observation volume. Fl ow visualization by laser-induced iodine fluorescence gives an additio nal picture of the flow structure.