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キーワード:
Turbulence; Classical Grid; Decay of turbulence; Hot-Wires; Scaling; Wind tunnel; High Reynolds number
要旨:
Turbulence is a physical state of a fluid far from equilibrium. In turbulent flows, a huge number of degrees of freedom is excited and a wide range of interacting scales determines the flow characteristics. Turbulent flows are nonlinear and non-local. They exhibit chaotic spatial and temporal dynamics and extreme events are likely to occur. Up to today, there is no unified theory of turbulence, very few exact predictions from the governing equations are available and the precise predictability of the behavior of turbulent flows is limited. Additionally, it is not known exactly, how the flow quantities depend on the turbulent flow�s vigorousness that is given by the so-called Reynolds number. In this thesis, high-Reynolds number turbulence and its dependencies on the Reynolds number are investigated by the means of hot-wire measurements in the Variable Density Turbulence Tunnel at the Max-Planck-Institute for Dynamics and Self-Organization in G?ttingen. The Reynolds number dependence of the decay exponent of freely decaying turbulence is found to be consistent with Saffmans prediction. Furthermore, with extremely long datasets, the statistical properties of turbulence in the inertial range are investigated in great detail, finding deviations from the expected scaling behavior.
