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  • 1
    Electronic Resource
    Electronic Resource
    Numerical study of bypass transition (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 2256-2264 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A large-eddy simulation has been performed of a flat-plate boundary layer undergoing transition to turbulence under free-stream turbulence at a level of 6%. The properties of the simulated transition match those found experimentally: not only is the position and length of transition in agreement with available data, but the mechanism of transition also appears to correspond closely, since disturbances seen in the laminar layer prior to transition are found in the simulation. Statistical data have been gathered that allow the computation of all terms in the derived equations for the Reynolds stresses at four x stations. Aspects of these balances are presented that allow new insights into the physical mechanisms at work. The importance of the wall-normal component of free-stream turbulence and the timing of the redistribution of energy into this component through the fluctuating pressure field are revealed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868473
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Affine matching pattern-recognition analysis of eddy structures in a numerically simulated boundary layer (1993)
    Springer
    Theoretical and computational fluid dynamics 5 (1993), S. 141-152 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A method is introduced of educing coherent eddy structures from turbulent flows and quantifying the variation of the structures found. The method has been applied to conditionally sampled flow fields associated with ejection events in a numerical simulation of a turbulent boundary layer at very low Reynolds number. It is found that asymmetric streamwise vortical structures, reminiscent of those seen in smoke visualizations, are consistently associated with the ejection events. The size of these organized eddies is related loosely to the position of the ejection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271655
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Subgrid-scale modelling at low mesh reynolds number (1996)
    Springer
    Theoretical and computational fluid dynamics 8 (1996), S. 131-143 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Subgrid-scale models are derived for large-eddy simulations in the limit of low mesh Reynolds number, or, equivalently, resolution approaching that required for full resolution of the simulated turbulent flow. The models are constructed from standard forms of the dissipation spectrum in a manner analogous to that used to derive the classical Smagorinsky-Lilly model from the inertial range spectrum. Practical methods for computing the subgrid-scale eddy viscosity are described, together with examples of the effects of using such models in a real simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312367
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Editorial (1995)
    Springer
    Flow, turbulence and combustion 54 (1995), S. 161-162 
    Details
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00849113
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  • 5
    Electronic Resource
    Electronic Resource
    Eddy Structures in a Simulated Low Reynolds Number Turbulent Boundary Layer (2000)
    Springer
    Flow, turbulence and combustion 64 (2000), S. 1-28 
    Details
    ISSN: 1573-1987
    Keywords: coherent structures ; turbulent boundary layer ; large-eddy simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Coherent structures in a tripped turbulent boundary layer havebeen analysed by applying a new conditional sampling algorithm tolarge-eddy simulation (LES) data. The space-time development of theevents and structural characteristics were examined. The new conditionalsampling scheme is shown to be very effective in the eduction of thecoherent eddy structures, allowing the simultaneous detection, trackingand averaging of several three-dimensional (3-D) structures. Alignmentof the triggering events in all spatial directions and flip-averaging(spatial reflection of the samples) enhance significantly the extractionof detailed features of the structures. The detection method minimisesthe smearing of the spatial details and avoids imposing artificialsymmetry, which is often intrinsic to other conditional samplingschemes. The results show the existence of cigar-shapedstreamwise vortices which are directly associated with negative pressurefluctuation peaks (positive source term of the pressure Poissonequation). They are inclined at 12° to the wall andtilted laterally at an angle of 7° to the streamwisedirection. The streamwise vortices induce ejections and sweeps throughan advection mechanism due to the tilting or inclination of thevortices. There is no evidence of hairpin vortices in either theconditional averages or instantaneous flow fields. Near-wall shearlayers are found to be related to the positive pressure fluctuationpeaks as a result of complex interactions between ejection and sweepevents. The shear layer structure has an inclination of10°, being located between two tilted, streamwisevortices of opposite direction of rotation. The presentresults are very close to other Direct Numerical Simulation studiesusing different conditional sampling schemes. Conceptual models for thestreamwise vortices and shear layer structures are proposed to accountfor the results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009998008472
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical simulation of a low-Reynolds-number turbulent wake behind a flat plate (1994)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 19 (1994), S. 377-393 
    Details
    ISSN: 0271-2091
    Keywords: Turbulence ; Numerical simulation ; Wake ; 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 numerical simulation of a plane turbulent wake at a very low Reynolds number has been performed using finite volume methods. The wake was produced by allowing two turbulent boundary layers, simulated separately in advance, to interact downstream of the trailing edge of a thin flat plate. A number of innovative numerical techniques were required in the simulation, such as the provision of fully turbulent time-dependent inflow data from a separate simulation, advective outflow boundary conditions and the approximate representation of an internal solid surface by a method which is computationally efficient. The resulting simulation successfully reproduced many of the statistical properties of the turbulent near-wake flow at low Reynolds number.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650190503
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    A DYNAMIC SUBGRID-SCALE MODEL FOR LOW-REYNOLDS-NUMBER CHANNEL FLOW (1996)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 19-27 
    Details
    ISSN: 0271-2091
    Keywords: turbulence ; channel flow ; low Reynolds number ; large-eddy simulation ; subgrid-scale model dynamic SGS model ; 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: Several issues related to applications of the dynamic subgrid-scale (SGS) model in large-eddy simulation (LES) at low Reynolds number are investigated. A modified formulation of the dynamic model is constructed and its performance in low-Reynolds-number LES of channel flow is assessed through a comparison of length scales computed respectively by this modified model, the Germano-Lilly dynamic SGS model and two empirical wall damping functions with optimum model coefficients, which have been successfully used in many simulations of channel flows. Two values of the ratio of filter widths are set for each of the dynamic models. The results have confirmed that the modified dynamic SGS model gives the correct behaviour of the subgrid eddy viscosity in the region of a plane wall to an accuracy that exceeds the best-tuned wall damping function, and almost collapses with the theoretical behaviour of the length scale near the wall without any tuning and adjustment. In addition, the impact of the choice of the ratio of filter widths on the modified dynamic SGS model is found to be much less than with the Germano-Lilly model.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Large-eddy simulations of plane impinging jets (1995)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 38 (1995), S. 489-507 
    Details
    ISSN: 0029-5981
    Keywords: large-eddy simulation ; plane jet ; impingement ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The methods used for the study of the impingement of a thermally inhomogeneous plane jet on a solid plate, using large-eddy simulation, are described. Innovative numerical methods have been introduced to produce the thermally inhomogeneous jet, to study the transmission of thermal fluctuations into the solid plate, and to prevent overshoot in the thermal computation. We have studied the impingement of water on a perspex plate in three different geometries, and also one case of the impingement of liquid sodium on a steel plate. Comparison is made with available experimental data and closure calculations.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620380309
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