Boundary-Layer Stress Instabilities in Neutral,Rotating Turbulent Flows |
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Authors: | Enrico Ferrero Luca Mortarini Massimigliano Manfrin Arnaldo Longhetto Rita Genovese Renato Forza |
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Affiliation: | (1) Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale, Via Bellini 25/G, 15100 Alessandria, Italy;(2) Dipartimento di Fisica Generale, Università di Torino, via Pietro Giuria 1, 10125 Torino, Italy |
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Abstract: | Boundary-layer instabilities are studied by analyzing the results of laboratory simulations of wall turbulence in a shear-driven rotating flow. The experiments were carried out in the Turin University Laboratory rotating water tank, where a circular flow was generated by either increasing (spin-up) or decreasing (spin-down) the rotation speed of the platform. The flow was measured using a Particle Image Velocimetry technique and the developed turbulence analyzed. Two cases were accounted for, in the former the measurements were performed over a smooth surface (bottom of the tank), while in the latter a rough-to-smooth transition was considered. The turbulent boundary layer developed inside the tank is analyzed by means of vertical profiles of mean and turbulent quantities and on the basis of drag coefficients. Then turbulent structures developed in the different cases are shown and discussed in terms of the vorticity fields. Finally, an analysis based on the concept of swirling strength was carried out to select among the vortex extremes those associated with a coherent structure. |
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Keywords: | Laboratory simulation Neutral boundary layer Roughness transition Wall turbulence |
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