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  • 1
    Electronic Resource
    Electronic Resource
    Anisotropy of the dissipation tensor in a turbulent boundary layer (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 2475-2479 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The second and third invariants of the Reynolds stress anisotropy tensor and the Reynolds stress dissipation rate anisotropy tensor have been evaluated from direct numerical simulation data for a boundary layer. The departure from isotropy increases in both inner and outer regions of the layer as the momentum thickness Reynolds number Rθ decreases. The relationship between the two anisotropy tensors has been examined in some detail. A linear relation, with a constant of proportionality depending on the local turbulence Reynolds number, is well supported by the outer region data for three values of Rθ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868195
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  • 2
    Electronic Resource
    Electronic Resource
    Laminar boundary layer over riblets (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 2993-2999 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser doppler anemometry (LDA) measurements and numerical calculations have been made for a laminar boundary layer on triangular riblets. Calculated mean velocity distributions along the riblet contour are in good agreement with the measured ones. The results show that no transversal motion exists above and within the riblet valleys (e.g., no secondary motion). It is found that despite the large wetted area increase, the frictional drag is not increased on riblets relative to a smooth wall. This result suggests that the viscous effects are at play in the drag reduction for a turbulent boundary layer, in the sense that they compensate for the increase in wetted area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868429
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Advantages of using a power law in a low Rθ turbulent boundary layer (1997)
    Springer
    Experiments in fluids 22 (1997), S. 348-350 
    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  At low values of the momentum thickness Reynolds number, R θ, a relatively accurate estimate of the friction velocity U r can be obtained by assuming a power law velocity distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050058
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristics of fluorescein dye and temperature fluctuations in a turbulent near-wake (2000)
    Springer
    Experiments in fluids 28 (2000), S. 462-470 
    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  The Laser Induced Fluorescence (LIF) technique was used to determine a few characteristics of a high Schmidt number (Sc) passive scalar (fluorescein) in the near-wake of a circular cylinder. The mean and rms concentration indicate that increasing the Reynolds number (Re) improves the large-scale mixing and accelerates the homogenisation of the scalar. As Re increases, the intensity of segregation decreases because of turbulent diffusion but the scale of segregation increases due to dispersion. Comparison between concentration and temperature rms profiles indicates that molecular diffusion has a much smaller effect on the decay of the scalar variance than the Reynolds number. The ratio of mean-squared values of lateral and streamwise spatial derivatives of the scalar fluctuation deviates from isotropy, the departure increasing with Re. This reflects more the effect of dispersion by the turbulent velocity field rather than any molecular diffusion effect. At a given Re, the ratio decreases as the distance from the cylinder increases. This trend is more accentuated near the edge of the wake than at the centreline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050406
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    LDA measurements in a turbulent boundary layer over a d-type rough wall (1994)
    Springer
    Experiments in fluids 16 (1994), S. 323-329 
    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 Two-component LDA measurements in smooth wall and d-type rough wall boundary layers indicate that there are important differences in the turbulence intensities over a significant distance above the two surfaces. All the Reynolds stresses—especially the shear stress—are larger over the d-type rough wall, reflecting the relatively strong momentum exchange which occurs over the roughness cavities. Flow visualisations indicate that this exchange is associated with strong ejections of cavity fluid into the outer flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195431
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    LDA measurements in low Reynolds number turbulent boundary layer (1993)
    Springer
    Experiments in fluids 14 (1993), S. 280-288 
    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 LDA measurements of the mean velocity Ū in a low Reynolds number turbulent boundary layer allow a direct estimate of the friction velocity U τ from the value of ∂Ū/∂y at the wall. The trend of the Reynolds number dependence of Ū ≡ Ū/Ū τ is similar to the direct numerical simulations of Spalart (1988).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194020
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Low-Reynolds-number effects in a turbulent boundary layer (1995)
    Springer
    Experiments in fluids 19 (1995), S. 61-68 
    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 Low-Reynolds-number effects in a zero pressure gradient turbulent boundary layer have been investigated using a two-component LDV system. The momentum thickness Reynolds number R θ is in the range 400 to 1320. The wall shear stress is determined from the mean velocity gradient close to the wall, allowing scaling on wall variables of the inner region of the layer to be examined unambiguously. The results indicate that, for the present R θ range, this scaling is not appropriate. The effect of R θ on the Reynolds normal and shear stresses is felt within the sublayer. Outside the buffer layer, the mean velocity is more satisfactorily described by a power-law than by a logarithmic distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192235
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Riblet modelling using a second-moment closure (1995)
    Springer
    Flow, turbulence and combustion 54 (1995), S. 249-266 
    Details
    ISSN: 1573-1987
    Keywords: turbulence ; riblets ; modelling ; second-moment closure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A low Reynolds number second-moment closure has been used to calculate a turbulent boundary layer which develops over a riblet surface with zero pressure gradient. The calculated mean velocity distributions compare favourably with measurements. Calculated Reynolds stresses away from the riblet surface region are also in agreement with measurements. In the vicinity of the riblets, the model reflects the increased anisotropy of the Reynolds stress tensor inadequately. Possible reasons for this shortcoming are discussed and suggestions for improving the model are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863512
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Riblet flow calculation with a low Reynolds number κ - ε model (1993)
    Springer
    Flow, turbulence and combustion 50 (1993), S. 267-282 
    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
    Notes: Abstract A low Reynolds number κ - ε model has been used to calculate the turbulent boundary layer over riblets. Calculated mean velocity, Reynolds shear stress and kinetic energy distributions are generally in good agreement with available experimental data. The comparison between these distributions and those in a corner flow points to a significant difference between the two flows and the unlikelihood of counter-rotating vortices within the riblet grooves. One shortcoming of the present κ - ε model is the relatively slow return to a two-dimensional turbulence state as the distance from the riblet surface increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00850561
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Numerical and experimental investigation of the laminar boundary layer over riblets (1989)
    Springer
    Flow, turbulence and combustion 46 (1989), S. 263-270 
    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
    Notes: Abstract One of the main aims of this work is to show to what extent drag reduction in a turbulent boundary layer can be ascribed to a purely viscous effect. A numerical and experimental study is performed in a laminar boundary layer over triangular riblets. The 2-D parabolic equations of motion are integrated using an x marching method and the discretised system is solved with the MSI algorithm. The influence of the riblet geometrical parameters and of the number of grid points is studied. Measurements are carried out in a water tunnel with forward scatter and backscatter laser-Doppler velocimetry extending within the riblets. The longitudinal velocity component measurements and computations are practically identical. Numerical results presented herein show that a slight drag reduction is obtained for s/h=1.2. It appears that, as far as friction is concerned, the wetted area is not the surface to be considered. Thus, the boundary layer over riblets would behave like a boundary layer on an equivalent smooth plate located beneath the crest plane. The numerical study in terms of the riblet height h shows best results are for h tending to zero, with the ratio s/h being equal to 1.2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404823
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    Paper (German National Licenses)
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