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In-line PIV Using a Schlieren System

Markus Raffel (1), Alexander Heintz (1), Johannes N. Braukmann (1), C. Christian Wolf (1), James T. Heineck (2)

1. DLR, Göttingen, Germany
2. NASA, ARC, Moffett Field, Ca, United States


The article describes recent tests and developments of PIV recording and evaluation techniques that take advantage of strong forward scattering of tracer particles by in-line recording set ups. By collimating the light of a low-power light source between a pair of schlieren mirrors the observation area is increased to more than 350 mm. The same setup allows for schlieren recording of density gradients. The in-line imaging arrangements have a relatively high background intensity level on which brighter particle images can be detected. Ideally this background is constant in time such that it can be removed through subtraction. The use of forward scattering has a significant influence on the required pulse energy of the light source used. Typically, sufficient illumination is achieved with about 1% of the pulse energy that would normally be used for a conventional orthogonal PIV arrangement employing a laser light sheet.

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