Conference on Turbulence and Interactions TI2006 May June Porquerolles France

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Guy Courbebaisse

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Conference on Turbulence and Interactions TI2006, May 29- June 2, 2006, Porquerolles, France Contribution to the Measurement of Turbulent Structures Guy Courbebaisse CREATIS UMR 5515 CNRS – U630INSERM – UCBL - INSA de Lyon Bat. Blaise Pascal, Avenue Jean Capelle, Villeurbanne 69621, France ABSTRACT This study provides a non classical way to quantify turbulent scales inside an internal combustion engine, by measuring the size of turbulent structures with a Schlieren optical method, and essentially with theoretical tools from the domain of signal processing. Within the last thirty years, a great deal of works has been oriented toward measurements of integral length scales with either the hot-wire anemometry method or with the Laser Doppler Velocimetry (L.D.V.) method. The drawback of the L.D.V. method comes from the choice of an associated empirical cut-off frequency to filter signals of turbulence from those of all fluctuations. The step suggested here is based on an analysis by means of a time-frequency distribution; original approach making it possible to estimate the size of turbulent structures. INTRODUCTION Measurements of integral length scales (I.L.S.) have been performed by many researchers with either the hot-wire anemometry method or with the Laser Doppler Velocimetry (L.D.