INTERFEROMETRIC TOMOGRAPHY FOR FLOW VISUALIZATION OF DENSITY FIELDS IN SUPERSONIC JETS AND CONVECTIVE FLOW

Tomographic methods are used for the investigation of three-dimensiona l compressible flow fields by means of interferometric methods. A modi fied algebraic reconstruction technique algorithm is applied. The algo rithm proved to give reliable reconstructions from experimentally meas ured projection data in the case of an unrestricted angular view. The method was used for the reconstruction of density distributions of wea kly perturbed supersonic free jets exiting from a deformed Laval nozzl e. Even small perturbations of the jet resulted in significant three-d imensional effects. Reconstruction of a multiple system of jets emanat ing from a sievelike nozzle showed mutual interactions between the con stituent jets. For the investigation of unsteady flows a setup for the recording of holographic interferograms was designed. Here, because o f experimental restrictions, only a limited angular range of views was accessible. In the context of this limited-view geometry, reconstruct ions revealed considerable distortions for objects containing steep gr adients.