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  • 1
    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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    Paper (German National Licenses)
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  • 2
    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)
  • 3
    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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    Paper (German National Licenses)
    Fulltext
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