Regensburg 2016 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 11: Poster
DF 11.28: Poster
Wednesday, March 9, 2016, 18:00–20:00, Poster E
Optical Riblet Sensor: Beam Parameter Requirements for the Probing Laser Source — •Juliane Tschentscher1, Sven Hochheim1, Hauke Brüning2, Kai Brune2, Kay-Michael Voit3, and Mirco Imlau1 — 1School of Physics, Osnabrück University, Germany — 2Fraunhofer IFAM, Bremen, Germany — 3Caesar Research Center, Bonn, Germany
Microstructured grooves on turbulent boundary layers (riblets) have a major impact on drag engineering of aircrafts in the context of kerosine consumption as they reduce skin friction considerably. Great demands are made on the geometry as deviations from theoretically designed riblets of a few percent already reduce the drag-reducing functionality drastically. A suitable optical sensor concept for deviation detection has been published previously. [Imlau et al., EU Project’s Report(2013)] We present the results of our studies on the beam parameters of the probing laser source in the riblet sensor by taking the high demands on a sensor’s precision and reliability for the determination of degradation of the riblet geometry into account. Mandatory requirements, such as minimum intensity and light polarization, are obtained by means of detailed inspection of the optical response of the riblet using ray and wave optics. Novel measures for analyzing the riblet shape without the necessity of a measurement with a reference sample are derived and values for an ideal riblet structure obtained with the riblet sensor are given. We show that a low-cost Nd:YVO4 laser pointer is sufficient to serve as a reliable laser source in an appropriate optical riblet sensor. We thank the Clean Sky Initiative (SP1-JTI-CS-2011-02).