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On the accuracy of a MJPEG-based digital image compression PIV-system |
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| Authors: | C Freek J M M Sousa W Hentschel W Merzkirch |
| Institution: | Volkswagen AG, Research and Development EZMM-1785, D-38436 Wolfsburg, Germany, DE Mechanical Engineering Department Instituto Superior Técnico, P-1096 Lisbon, Portugal, PT Universit?t GH Essen, Lehrstuhl für Str?mungslehre Postfach 10 37 64, D-45117 Essen, Germany, DE |
| Abstract: | In this communication, the Digital Image Compression (DIC) – PIV system is introduced. The present system allows the measurement of mean and RMS velocities in turbulent flow fields, using JPEG digital image compression technique for on-line recording of thousands of images. The decompression and subsequent analysis of the images, performed by means of digital cross-correlation technique, is carried out off-line. Errors incurred by the application of the compression method are assessed and discussed. The effect of the compression is firstly analysed by linearly traversing (synthetic) computer-generated PIV-images at constant velocity. Secondly, accurate LDA measurements and data from direct numerical simulation (DNS) are used as a basis for the analysis in a low Reynolds number open water channel flow. The results show that excellent agreement between LDA and DIC–PIV measurements for mean and RMS velocities can be achieved using a compression factor up to 12. Received: 27 August 1996 / Accepted: 15 December 1998 |
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