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  • Turbulence
  • Springer  (7)
  • Wiley-Blackwell  (4)
  • American Meteorological Society
  • 1980-1984  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Structure and dynamics of the stratosphere and mesosphere revealed by VHF radar investigations (1980)
    Springer
    Pure and applied geophysics 118 (1980), S. 494-527 
    Details
    ISSN: 1420-9136
    Keywords: MST radar ; Gravity waves ; Turbulence ; Stratospheric structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Powerful VHF radars are capable of almost continuously monitoring the threedimensional velocity vector and the distribution of turbulence in the middle atmosphere, i.e. the stratosphere and mesosphere. Methods of radar investigations of the middle atmosphere are outlined and the basic parameters, mean and fluctuating velocities as well as reflectivity and persistency of atmospheric structures, are defined. Results of radar investigations are described which show that the tropopause level as well as a criterion on the stability of the lower stratosphere can be deduced. Besides mean wind velocities, VHF radars can measure instantaneous velocities due to acoustic gravity waves. The interaction of gravity waves with the background wind is discussed, and it is shown that cumulus convection is an effective source of gravity waves in the lower stratosphere. The vertical microstructure of the stratosphere, manifesting itself in thin stratified sheets in which temperature steps occur, is investigated by applying knowledge from investigations of the oceanic thermocline. Possible origins, like shear generation and lateral convection of the microstructure of the stratosphere, are discussed. Observations of gravity waves in the mesosphere are reviewed and their connection with turbulence structures is pointed out. Finally, some open questions which could be answered by further VHF radar investigations are summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586465
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  • 2
    Electronic Resource
    Electronic Resource
    Variabilité de la densité spectrale de la température et du vent moyen dans la couche limite planétaire (1982)
    Springer
    Pure and applied geophysics 120 (1982), S. 95-107 
    Details
    ISSN: 1420-9136
    Keywords: Boundary layer ; Spectral density ; Turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have carried out a series of recordings reproducing the small scale structures of temperature and windspeed within the boundary layer. The results obtained have been processed by computer and a direct comparison made between the slope of the spectral density functions and the theoretical slopen=5/3 defining the turbulence in the region of the inertial subrange. The measurements made at various altitudes on thin atmospheric samples demonstrate the variability of the spectral density slope with altitude. The hypotheses put forward by A. M. Obukhov, R. Bolgiano, G. H. Shur, P. Misme, A. Monin or S. Panchev, for example, enable the spectral variations and certain discontinuities in the turbulence observed during the experiments, within and beyond the boundary layer, to be explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879429
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  • 3
    Electronic Resource
    Electronic Resource
    A theoretical value for von Karman's constant (1982)
    Springer
    Pure and applied geophysics 120 (1982), S. 648-661 
    Details
    ISSN: 1420-9136
    Keywords: Atmospheric turbulence ; Entrainment ; Turbulence ; Karman constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This paper extends the theory of the entity and entrainment model of turbulence to obtain a numerical value of von Karman's constant,k=0.37. The formula is, $$k = (2a^3 /A)^{{1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}} \ln \beta $$ where,a=1/12 is the entrainment constant,A=1 is the turbulent decay constant, and β is the ratio in height of the successive self-similar layers of the theory, where β is evaluated as β=e 2. These new values fork and β improve the surface roughness length estimates derived from this theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876650
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  • 4
    Electronic Resource
    Electronic Resource
    Small scale turbulent diffusion determined with underwater flow visualization (1982)
    Springer
    Pure and applied geophysics 120 (1982), S. 758-771 
    Details
    ISSN: 1420-9136
    Keywords: Diffusion ; Turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Dye plumes were generated at three depths in the seasonal thermocline between 7 and 11 m, 22 km south of Key West on 21 August 1980 and photographed at about 10 second intervals with an underwater camera system. Eleven pairs of consecutive pictures are analyzed to determine the mean current vertical shear and the width of the plumes by positioning reference points relative to the rod attached to the camera system. The relative distances of reference points are calibrated with the stereophotogrammetric method for one pair. The eddy diffusivity is calculated by use of a model of turbulent diffusion developed byTaylor (1921). Its values range from 5 to 25 cm2s−1 for the plume widths ranging from 33 to 132 cm. The Richardson number is calculated for each pair of pictures with the vertical density gradient estimated from temperature profiles. Its values are higher than the critical value of 0.25 except for one case. The diffusivity was higher by orders of magnitude than the molecular one and indicates the presence of turbulence together with billow like features of the plumes in spite of high Richardson numbers. This suggests that the billow turbulence might be caused by effects of surface gravity waves and not by the Kelvin-Helmholtz instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876658
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical applications of topology and group theory (1983)
    Springer
    Theoretical chemistry accounts 63 (1983), S. 323-338 
    Details
    ISSN: 1432-2234
    Keywords: Dynamic systems ; Chaotic chemical reactions ; Kinetic logic ; Turbulence ; Belousov-Zhabotinskii reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Earlier approaches to the analysis of chemical dynamic systems using kinetic logic are refined to deal more effectively with systems having the two or more feedback circuits required for chaos. The essential kinetic features of such a system can be represented by a directed graph (called aninfluence diagram) in which the vertices represent the internal species and the directed edges represent kinetic relationships between the internal species. Influence diagrams characteristic of chaotic chemical systems have the following additional features: (1) They are connected; (2) Each vertex has at least one edge directed towards it and one edge directed away from it; (3) There is at least one vertex, called a turbulent vertex, with at least two edges directed towards it. From such an influence diagram a state transition diagram representing the qualitative dynamics of the system can be obtained using the following 4-step procedure: (1) A logical relationship is assigned at each turbulent vertex; (2) A local truth table is generated for each circuit in the influence diagram; (3) The local truth tables are combined to give a global truth table using the logical relationships at the turbulent vertices; (4) The global truth table is used to determine the corresponding state transition diagram using previously described methods. This refined procedure leads to a more restricted set of influence diagrams having the interlocking cycle flow topology required for chaos than the procedure described earlier. Systems with 3 internal species are examined in detail using the refined procedure. All systems with 3 dynamic variables shown in the simulation studies of Rössler to give chaotic dynamics correspond to influence diagrams which give inter-locking cycle (chaotic) flow topologies by the refined procedure. In addition, two models for the Belousov-Zhabotinskii reaction are examined using the refined procedure. The results are potentially informative concerning possible mechanisms for the limitation of the accumulation of autocatalytically produced HBrO2 (one of the internal species) during the course of this reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01151610
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of external noise in the Lorenz model of the Bénard problem (1981)
    Springer
    Journal of statistical physics 24 (1981), S. 345-358 
    Details
    ISSN: 1572-9613
    Keywords: Turbulence ; Lorenz model ; random behavior of nonlinear differential equations ; response to external random forces ; dynamic correlation and response functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effect of external random forces on the static and dynamic behavior of the Lorenz model is investigated. Results of a numerical calculation in the conductive, convective, and turbulent regimes are reported. The properties of static and time-dependent correlation functions of the three degrees of freedom of the model are analyzed for varying strength of the external noise level and compared with the behavior of the unforced system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01013305
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  • 7
    Electronic Resource
    Electronic Resource
    Turbulence in pulsatile flows (1984)
    Springer
    Annals of biomedical engineering 12 (1984), S. 357-369 
    Details
    ISSN: 1573-9686
    Keywords: Oscillatory flow ; High frequency ventilation ; Unsteady pipe flow ; Turbulence ; Pulsatile flow ; Transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Turbulence during pulsatile flow has been suggested as a possible mechanism to enchance the transport of gases during high-frequency ventilation. Experimental studies on oscillatory flow in straight, circular tubes have identified three types of flow: (a) laminar; (b) conditionally turbulent, in which high-frequency disturbances occur during the decelerating phase of the flow cycle but relaminarize by the beginning of the subsequent accelerating phase; and (c) fully turbulent flow, in which disturbances occur throughout the flow cycle. Fully turbulent flow has been observed only when a mean flow is present, and only laminar or conditionally turbulent flow has been observed for purely oscillatory flow. A critical Reynolds number based on the Stokes layer can be defined, and transition Reynolds numbers between 400 and 550 have been experimentally determined for purely oscillatory flow in a circular tube, although lower values are expected for physiological flows. There are some indications that the structure of oscillating turbulent flow is similar to steady turbulent flow, and preliminary work in our laboratory shows that the spectral content of flows during high-frequency ventilation is similar to that in steady turbulent flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407780
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  • 8
    Electronic Resource
    Electronic Resource
    Applicability of algebraic models based on unidirectional flow to duct flow with lateral motion (1981)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 1 (1981), S. 225-235 
    Details
    ISSN: 0271-2091
    Keywords: Turbulence ; Fluid Flow ; Mathematical Models ; Reynolds Stresses ; Channels Lateral Motion ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The solution for the stress transport turbulence model equations for the situation where the flow is unidirectional is now commonly applied to flows with weak secondary currents in closed ducts, open channels, and rod bundles in nuclear reactor channels. Here, perturbations to the unidirectional flow solutions are studied by solving the exact equations using an iterative procedure. Now the equations also contain the small lateral velocity gradients formerly neglected. The applicability as well as the limitation of the use of the unidirectional flow turbulence model for the description of channel flow with lateral motion are discussed. Modifications for weak lateral motion are suggested.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650010304
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  • 9
    Electronic Resource
    Electronic Resource
    Aspects of large eddy simulation of homogeneous isotropic turbulence (1981)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 1 (1981), S. 273-290 
    Details
    ISSN: 0271-2091
    Keywords: Large Eddy ; Simulation ; Isotropic ; Turbulence ; Filtering ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: HOMTY, a code for Large Eddy Simulation of homogeneous isotropic turbulence is proven by successful simulation of two experiments. The role of each term in the equations of motion and the concept of filtering is examined. It is shown that ‘prefiltering’ is unnecessary, and the resulting additional term in the equations, instead of transferring energy to the subgrid scales, backscatters energy from the resolved large wavenumerbers to the small ones. The kinetic energy decay exponent is shown to depend on the low wavenumber part of the velocity spectrum. Pressure statistics are computed and found to be in agreement with previous computations.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650010306
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  • 10
    Electronic Resource
    Electronic Resource
    Modelling flow over a backward-facing step using the F.E.M. and the two-equation model of turbulence (1981)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 1 (1981), S. 295-304 
    Details
    ISSN: 0271-2091
    Keywords: Numerical Methods ; Turbulence ; Separation ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Flow over a downstream-facing step is predicted using the F.E.M. A two-equation model of turbulence is employed where the transport of turbulence kinetic energy and dissipation rate are depicted using transport-type equations, i.e. the two-equation model of turbulence. The results obtained are compared with other models and experimental results. Generally, the model was found to be under-predictive with regard to the reattachment length when previous empirical data was used in the transport equations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650010403
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  • 11
    Electronic Resource
    Electronic Resource
    Buoyancy effects on turbulent swirling flows (1984)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 4 (1984), S. 1165-1184 
    Details
    ISSN: 0271-2091
    Keywords: Turbulence ; Buoyancy ; Swirl ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A three-parameter model of turbulence applicable to free boundary layers has been developed and applied for the prediction of axisymmetric turbulent swirling flows in uniform and stagnant surroundings under the action of buoyancy forces. The turbulent momentum and heat fluxes appearing in the time-averaged equations for the mean motion have been determined from algebraic expressions, derived by neglecting the convection and diffusion terms in the differential transport equations for these quantities, which relate the turbulent fluxes to the kinetic energy of turbulence, k, the dissipation length scale of turbulence, L, and the temperature covariance, T′2. Differential transport equations have been used to determine these latter quantities. The governing equations have been solved using fully implicit finite difference schemes. The turbulence model is capable of reproducing the gross features of pure jet flows, buoyant flows and swirling flows for weak and moderate swirl.The behaviour of a turbulent buoyant swirling jet has been found to depend solely on exit swirl and Froude numbers. The predicted results indicate that the incorporation of buoyancy can cause significant changes in the behaviour of a swirling jet, particularly when the buoyancy strength is high. The jet exhibits similarity behaviour in the initial region for weak swirl and weak buoyancy strengths only, and the asymptotic case of a swirling jet under the action of buoyancy forces is a pure plume in the far field. The predicted results have been found to be in satisfactory agreement with the available experimental data and in good qualitative agreement with other predicted results.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650041206
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