Local density information obtained by means of the Background Oriented Schlieren(BOS) method

The fairly new measurement system BOS is providing promising results by allowing the visualisation of qualitative density gradients as presented by Richard et al (2000). This paper shows that it is possible to measure local density information by means of BOS for the specific application of a 2D jet. An experiment is described to present the feasibility of BOS to measure local density information. A slit nozzle blowing an air / helium mixture was investigated by BOS and Catharometry. Comparing the obtained results and taking the Catharometry measurement as the reference, the accuracy of the density information provided by BOS can be evaluated: The small difference between the results of the two measurement techniques confirms the applicability and accuracy of BOS for local density measurements in 2D density gradient investigations.