Abstract
In the transitional cylinder wake as well as the primary vortex street, the separated shear layer becomes unstable and sequences of small-scale vortex structures are produced intermittently. This paper describes how LDA data can be collected exclusively for these intermittent events. A real-time digital signal processing algorithm is developed in order to detect the instability of the shear layer from the characteristic hot-wire signal. Simultaneously, LDA data is selected so that the turbulence production in the unstable separated shear-layer can be derived. This trigger technique can be used for any kind of intermittent signal and measurement process.
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Acknowledgements
The author gratefully acknowledges the support of this research project by the Deutsche Forschungsgemeinschaft (DFG) with the grant No. LE713/11–1.
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Brede, M. Measurement of turbulence production in the cylinder separated shear-layer using event-triggered Laser-Doppler anemometry. Exp Fluids 36, 860–866 (2004). https://doi.org/10.1007/s00348-003-0768-9
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DOI: https://doi.org/10.1007/s00348-003-0768-9