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Tracer based Shock Visualisation (TSV)

T

3D Shock Structures

racer based shock visualisation (TSV) is a new optical non intrusive technique to visualise the position and the structure of shocks in transonic flows, for example in transonic compressor. The number per volume density of particles, which are added to the flow, and with it the density of the fluid are visualised with a laser light sheet and an intensified CCD Camera. Structures like normal and oblique shocks, l-shocks and separation regions can be identified in this way. In cascade wind tunnels or in compressors, the 3D- shape and structure of the blade passage shock can be reconstructed from the topography of the collected 2D-images at different radial positions.
This first application of this technique was the investigation of the shock structure in a transonic compressor. The following images give an idea of the quality of the results obtained. These measurements were carried out at the ERECA test facility of ONERA in the frame of a collaboration between ONERA and DLR. These pictures show the shock location as a function of the mass flow rate (design point, intermediate point of operation and near the surge).
The TBS- technique is not restricted to the measurement of compressor flows; it is just as suitable for use in transonic turbines and cascade wind tunnels.

Sample results of TSV measurements in a transonic compressor

Design Point	Intermediate Point of Operations
Near the Surge