Three-Dimensional Density Imaging by Rayleigh Scattering

A diagnostic is proposed for obtaining instantaneous three-dimensional volumetric distributions of density in a flow field at velocities ranging from subsonic to supersonic. Multiple Sheet Filtered Rayleigh Scattering (MSFRS) will be developed, which enables a series of two-dimensional images to be rapidly obtained making up a volumetric image while suppressing background scattering from wind tunnel walls and other surfaces. The approach will enable a spatial resolution of 3 mm for a measurement volume size of 100 mm x 50 mm x 12 mm and a temporal evolution of about 1 microsecond. A prototype system will be constructed and demonstrated in supersonic jets, a boundary layer, and wakes. Density measurements obtained with the system will be used in assessing the impact on a beam propagating through the flow, and the resulting wavefront will be compared to independent measurements of the same. Extension of the technique to larger measurement array sizes will also be explored.