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  • 1
    Electronic Resource
    Electronic Resource
    Measurements of turbulent and periodic flows around a square cross-section cylinder (1988)
    Springer
    Experiments in fluids 6 (1988), S. 298-304 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Laser-Doppler measurements of the velocity characteristics are presented for the turbulent flow around a square cross-section cylinder mounted in a water channel for Re=14000. The study involved spectral analysis and digital filtering of the LDV data obtained behind the cylinder. The purpose of the measurements is to separate and quantify the turbulent and the periodic, non-turbulent, motions of the wake flow, in order to improve knowledge of the nature of the fluctuations in the near-wake region of two-dimensional bodies. The results show, for example, that in the zone of highest velocity oscillations the energy associated with the turbulent fluctuations is about 40% of the total energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538820
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Piston-driven, unsteady separation at a sudden expansion in a tube: Flow visualization and LDA measurements (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1249-1260 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Flow visualization studies and laser-Doppler anemometry (LDA) measurements have been performed on the flow field generated at a sudden expansion in a cylindrical pipe during the intake stroke of a piston. The range of piston Reynolds numbers investigated, based on piston diameter and velocity, was 18–125 and covered a laminar and a transition-to-turbulence regime. A detailed study of the parameters influencing the structure of the flow, i.e., the clearance volume and the piston velocity, was carried out and is presented, and the mechanism for the creation of flow instabilities at low Reynolds numbers is outlined. One of the striking features of the flow relates to the formation of vortex structures during the intake flow. It is found that under some circumstances these structures become unstable, despite the relatively low Reynolds number of the flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857348
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fluid dynamically caused cycle-to-cycle variations in piston-driven pipe expansion flows (1992)
    Springer
    Experiments in fluids 13 (1992), S. 1-10 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A piston-driven pipe flow with a sudden expansion in cross-sectional area was studied experimentally using flow visualization and laser-Doppler anemometry as basic experimental techniques. To drive the flow, a piston was moved in the larger of the two pipes. It drew in the fluid into the pipe assembly during the upward stroke and removed fluid during the downward stroke. The time-varying flow field was investigated, yielding detailed information on the flow structure, its development, and variation with time. In the present paper, particular attention is given to those flow conditions that resulted in cycle-to-cylce variations of the flow field. For some of the conditions, repetitive cycle-to-cycle variations of the flow field occurred, yielding identical flows for even-numbered flow cycles and also for odd numbered cycles. However, the latter differed from the former. The presented data show that non-repetitive cycle-to-cycle variations of the flow field also exist and that these can be driven into a state where the flow appears to be nearly chaotic. The results of the investigation clearly demonstrate that fluid dynamically caused cycle-to-cycle flow variations can exist in piston-driven internal flows with separation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208068
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Velocity characteristics of the flow around a square cross section cylinder placed near a channel wall (1991)
    Springer
    Experiments in fluids 11 (1991), S. 341-350 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Laser-Doppler measurements are reported of the flow around a square cross section cylinder placed at various heights (Y 0) above a plane channel wall for a Reynolds number Re H = 1.36 × 104.The thickness of the turbulent boundary layer on the channel wall at the obstacle position, but with it removed from the water tunnel, was equal to 0.8 H, being H the square obstacle height and the free stream turbulence intensity was 6%. The periodic character of the flow in the near wake was characterized by measurements of turbulence spectra in the range 0≤ Y 0/H ≤3.3 and the results revealed that regular vortex shedding was suppressed for a gap height less than 0.35 H. Detailed results of time averaged mean flow properties, turbulence intensities and Reynolds stresses revealed the structural differences of the near wakes with and without vortex shedding for Y O = 0.5 and Y O = 0.25 respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211788
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  • 5
    Electronic Resource
    Electronic Resource
    Finite volume computation of the turbulent flow over a hill employing 2D or 3D non-orthogonal collocated grid systems (1992)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 423-441 
    Details
    ISSN: 0271-2091
    Keywords: Finite volume method ; Non-orthogonal co-ordinates ; Turbulent recircalating flow ; 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 general numerical method for the solution of the complete Reynolds-averaged Navier-Stokes equations for 2D or 3D flows is described. The method uses non-orthogonal co-ordinates, Cartesian velocity components and a pressure-velocity-coupling algorithm adequate for non-staggered grid systems. The capability of the method and the overall performance of the κ-∊ eddy viscosity model are demonstrated by calculations of 2D and 3D flow over a hill. Solution error estimations based on fine grids, e.g. 320 × 192 control volumes, together with comparisons with standard turbulence model modifications, low-Reynoldsnumber or streamline curvature effects, have allowed the investigation of model drawbacks in predicting turbulent flows over surface-mounted hills.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650140404
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Calculation of laminar recirculating flows using a local non-staggered grid refinement system (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 535-557 
    Details
    ISSN: 0271-2091
    Keywords: Embedding non-staggered grids ; Incompressible recirculating flows ; Finite volume method ; 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 grid-embedding technique for the solution of two-dimensional incompressible flows governed by the Navier-Stokes equations is presented. A finite volume method with collocated primitive variables is employed to ensure conservation at the interfaces of embedding grids as well as global conservation. The discretized equations are solved simultaneously for the whole domain, providing a strong coupling between regions of different refinement. The formulation presented herein is applicable to uniform or non-uniform Cartesian meshes. The method was applied to the solution of two scalar transport equations, to cavity flows driven by body and shear forces and to a sudden plane contraction flow. The numerical predictions are compared with the exact solutions when available and with experimental data. The results show that neither the convergence rate nor the stability of the method is affected by the presence of embedded grids. Embedded grids provide a better distribution of grid nodes over the computational domain and consequently the solution accuracy was improved. The grid-embedding technique proved also that significant savings in computing time could be achieved.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650120603
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  • 7
    Electronic Resource
    Electronic Resource
    Computation of particle dispersion in turbulent liquid flows using an efficient Lagrangian trajectory model (1998)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 345-364 
    Details
    ISSN: 0271-2091
    Keywords: liquid-particle flow ; computational efficiency ; Eulerian-Lagrangian model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The dispersion of solid particles in a turbulent liquid flow impinging on a centrebody through an axisymmetric sudden expansion was investigated numerically using a Eulerian-Lagrangian model. Detailed experimental measurements at the inlet were used to specify the inlet conditions for two-phase flow computations. The anisotropy of liquid turbulence was accounted for using a second-moment Reynold stress transport model. A recently developed stochastic-probabilistic model was used to enhance the computational efficiency of Lagrangian trajectory computations. Numerical results of the stochastic-probabilistic model using 650 particle trajectories were compared with those of the conventional stochastic discrete-delta-function model using 18 000 particle trajectories. In addition, results of the two models were compared with experimental measurements. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Comparison of four combustion models for simulating the premixed combustion in inert porous media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 22 (1998), S. 187-197 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This work reports one-dimensional predictions of methane/air fuel combustion in inert porous media using four combustion models: full mechanism (FM, 49 species and 227 elemental reactions), skeletal mechanism (SM, 26 species and 77 elemental reactions), 4-step reduced mechanism (4RM, 9 species) and 1-step global mechanism (1GM). The effects of these models on temperature, species, burning speeds and pollutant emissions are examined. The calculations are compared with available experimental data. It is concluded that the already known limitation of the 1-step global mechanism can be partially eliminated by the present 4-step reduced mechanism. This 4RM model compares very satisfactorily with the full mechanism in the simulation of combustion in porous media. This conclusion is encouraging for the simulation of practical porous media burners because the 4RM model improves the stability of the calculation process and can be used with reduced computational resources and cost. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 9
    Electronic Resource
    Electronic Resource
    Comparison of several open boundary numerical treatments for laminar recirculating flows (1993)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 16 (1993), S. 403-419 
    Details
    ISSN: 0271-2091
    Keywords: Outflow boundary conditions ; Laminar recirculating flows ; Non-staggered grid systems ; 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 open boundary conditions (OBCs) are compared and evaluated in the framework of the SIMPLE algorithm using staggered and non-staggered grid systems. The benchmark laminar flow test cases used for the OBC evaluation are Poiseuille-Benard flow in a channel and stratified backward-facing step flow. The investigated OBCs are linear explicit step space extrapolation, Orlanski's monochromatic wave, and pressure extrapolation. Orlanski's and pressure extrapolation open boundary treatment for unsteady and steady flows, respectively, yield little reflection and has proved to be adequate for engineering calculations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650160505
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  • 10
    Electronic Resource
    Electronic Resource
    A comparison of second order convection discretization schemes for incompressible fluid flow (1996)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 395-411 
    Details
    ISSN: 1069-8299
    Keywords: finite volume ; high-order discretization ; non-oscillatory schemes ; pressure interpolation ; non-staggered grid ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper addresses the problem of convection discretization by extension and application of numerical schemes used in compressible flows: SONIC-A, SONIC-B, UNO2, MUSCL and MINMOD to predict steady incompressible recirculating convection dominated flows. A new scheme, SONIC-Q, is proposed together with a third-order non-oscillatory practice for pressure interpolation in non-staggered grids. Finite-volume calculations of the Navier-Stokes equations of a standard 2D driven square cavity standard test case and the laminar flow over a fence using primitive variables and non-staggered grid systems have shown that the schemes are alternatives to the conventional ones used in general algorithms for incompressible recirculating flows. In general these composite high-order schemes have proved to be good candidates to overcome the problems of false-diffusion and unboundedness encountered in non-composite high-order upwind schemes used in incompressible flows.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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