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Turbulent Fluctuations (turbulent + fluctuation)
Selected AbstractsDoppler spectral line shapes in low frequency turbulent plasmasCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2004Y. Marandet Abstract In this paper we investigate the influence of low frequency, i.e. drift wave like turbulence on the spectral line shapes in magnetized plasmas. The measured spectrum, which is obtained through both spatial and time averaging processes, is shown to contain information on turbulence. Using a statistical description of the turbulent fluctuations, we investigate the effects of density, fluid velocity and temperature fluctuations on the Doppler profile of a spectral line. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Axial liquid mixing in high-pressure bubble columnsAICHE JOURNAL, Issue 8 2003G. Q. Yang Axial dispersion coefficients of the liquid phase in bubble columns at high pressure are investigated using the thermal dispersion technique. Water and hydrocarbon liquids are used as the liquid phase. The system pressure varies up to 10.3 MPa and the superficial gas velocity varies up to 0.4 cm/s, which covers both the homogeneous bubbling and churn-turbulent flow regimes. Experimental results show that flow regime, system pressure, liquid properties, liquid-phase motion, and column size are the main factors affecting liquid mixing. The axial dispersion coefficient of the liquid phase increases with an increase in gas velocity and decreases with increasing pressure. The effects of gas velocity and pressure on liquid mixing can be explained based on the combined mechanism of global liquid internal circulation and local turbulent fluctuations. The axial liquid dispersion coefficient also increases with increasing liquid velocity due to enhanced liquid-phase turbulence. The scale-up effect on liquid mixing reduces as the pressure increases. [source] A novel type of intermittency in a non-linear dynamo in a compressible flowMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2009Erico L. Rempel ABSTRACT The transition to an intermittent mean-field dynamo is studied using numerical simulations of magnetohydrodynamic turbulence driven by a helical forcing. The low-Prandtl number regime is investigated by keeping the kinematic viscosity fixed while the magnetic diffusivity is varied. Just below the critical parameter for the onset of dynamo action, a transient mean field with low magnetic energy is observed. After the transition to a sustained dynamo, the system is shown to evolve through different types of intermittency until a large-scale coherent field with small-scale turbulent fluctuations is formed. Prior to this coherent field stage, a new type of intermittency is detected, where the magnetic field randomly alternates between phases of coherent and incoherent large-scale spatial structures. The relevance of these findings to the understanding of the physics of mean-field dynamo and the physical mechanisms behind intermittent behaviour observed in stellar magnetic field variability are discussed. [source] A physical basis for a maximum of thermodynamic dissipation of the climate systemTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 572 2001Garth W. Paltridge Abstract A mechanism is proposed by which the energy flow through a turbulent medium might be constrained to maximize its dissipation or (equivalently) its thermodynamic efficiency. The mechanism may provide a physical basis for the various findings over the years that the earth-atmosphere system has adopted a format which maximizes its overall rate of entropy production. The qualitative picture is of a system which, because of the asymmetry of its turbulent fluctuations about the locus of possible steady states determined by energy balance, moves to a preferred steady state and therefore to a preferred turbulent transfer coefficient. [source] | ||||||||||