Weiterentwicklung der C-Programmbibliothek zur tomographischen Auswertung von Dichtefeldern mit der Hintergrundschlieren-Methode

Abstract

By means of the Background Oriented Schlieren (BOS) procedure one can measure a 3-D density field. This optical measurement procedure takes advantage of the relationship between density and optical refraction. In order to process the data obtained by the BOS procedure, an algorithm was implemented in Matlab by GOLDHAHN 2003. This includes instant processing of the data measured, so one can detect and fix any systematic error promptly. This project improves the algorithm mentioned in order to increase its applicability. Anticipating the rising amount of data in future applications, the new architecture of the program was adjusted to meet these needs. Visualizing a 3-D density field proves to be quite challenging. To facilitate this for the user, a new program feature is the possibility to display any 2-D section of the 3-D density field. Since running the procedure requires the input of numerous parameters, the user needs a proper interface, which is implemented by a text-based input. To accelerate the time consuming operation of this algorithm, the program offers multiple file processing initiated by a single command. These concepts are implemented in C++. The underlying mathematical principles are discussed in detail in order to assess the potential and possible systematic errors of the tomographic algorithm. The final chapter of this paper contains a test run of the program processing data obtained in an experiment at the DLR. Special attention is given to operation time and applicability.