| 講演要旨： |
Transonic flow phenomena and the generation of sound occurring during
the impingement of a supersonic free jet on a plate have been studied
both, experimentally and numerically. This happened under conditions
typical of the cold spray deposition process. Therefore, also
particle-laden jets were considered. Under certain conditions a
recirculation bubble is formed in the shock layer ahead of the plate.
Numerical computations of this flow that have been performed with the
DLR TAU-code, are compared with shadowgraphs. Experimental results
obtained with a newly developed multi-exposure method combined with
synchronized pressure measurements, show that the formation of
recirculation bubbles is typically connected with self-excited flow
oscillations. Based on a spectral analysis, different mechanisms of
self-excited oscillations are discussed and compared with related
phenomena reported in the literature. The importance of flow
oscillations on the behaviour of a particle cloud that is formed
ahead of the plate in the case of two-phase flows, will also be
explained.
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