Interferometric tomography for flow visualization of density fields in supersonic jets and convective flow.

Tomographic methods are used for the investigation of three-dimensional compressible flow fields by means of interferometric methods. A modified algebraic reconstruction technique algorithm is applied. The algorithm proved to give reliable reconstructions from experimentally measured projection data in the case of an unrestricted angular view. The method was used for the reconstruction of density distributions of weakly perturbed supersonic free jets exiting from a deformed Laval nozzle. Even small perturbations of the jet resulted in significant three-dimensional effects. Reconstruction of a multiple system of jets emanating from a sievelike nozzle showed mutual interactions between the constituent jets. For the investigation of unsteady flows a setup for the recording of holographic interferograms was designed. Here, because of experimental restrictions, only a limited angular range of views was accessible. In the context of this limited-view geometry, reconstructions revealed considerable distortions for objects containing steep gradients.