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  • 1
    Electronic Resource
    Electronic Resource
    Alignment of vorticity and scalar gradient with strain rate in simulated Navier–Stokes turbulence (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2343-2353 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The alignment between vorticity and eigenvectors of the strain-rate tensor in numerical solutions of Navier–Stokes turbulence is studied. Solutions for isotropic flow and homogeneous shear flow from pseudospectral calculations using 1283 grid points have been examined. The Taylor Reynolds number is 83 or greater. In both flows there is an increased probability for the vorticity to point in the intermediate strain direction and at three-fourths of the sample points this strain is positive (extensive). This propensity for vorticity alignment with a positive intermediate strain is a consequence of angular momentum conservation, as shown by a restricted Euler model of the coupling between strain and vorticity. Probability distributions for intermediate strain, conditioned on total strain, change from a symmetric triangular form at small strain to an asymmetric one for large strain. The most probable value of the asymmetric distribution gives strains in the ratios of 3:1: −4. The evolution of the distribution from a symmetric to an asymmetric form as the strain magnitude increases is essentially the same in both flows, indicating a generic structure of intense turbulence. The alignment between the gradient of a passive scalar and eigenvectors of the strain-rate tensor for Prandtl numbers of 0.1, 0.2, 0.5, and 1.0 has also been studied. There is an increased probability for the scalar gradient to align in the most compressive strain direction, and the average gradient is larger when it is pointing in that direction. Estimates for the scalar dissipation from the turbulent kinetic energy, its dissipation, and the root-mean-square scalar value are in reasonable agreement with calculated scalar dissipation if no explicit Prandtl number dependence is used in the estimate. Statistical analysis of scalar dissipation conditioned on energy dissipation yields a power-law relation between conditioned mean values. Both simulated flows are found to obey the qualitative predictions of the Gurvich–Yaglom (lognormal) intermittency model. Energy and scalar intermittency exponents are estimated and compared to measured values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866513
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Calculation of Minimum Reflux in Distillation Columns (1950)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 42 (1950), S. 871-876 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50485a034
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Reply (1979)
    Springer
    Boundary layer meteorology 17 (1979), S. 273-274 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117986
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Sea surface stress measurements (1978)
    Springer
    Boundary layer meteorology 15 (1978), S. 215-228 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Sea-surface stress measurements were made from a rigid tower in shallow water near San Diego, California, by both the direct covariance and inertial dissipation techniques. Stress estimates from the dissipation technique were generally higher than the directly measured values, with average drag coefficients of 0.99 x 10-3 and 0.77 x 10-3, respectively, for 8-m wind speeds of 5 to 7 m s-1. In the inertial subrange, ratios of vertical to streamwise velocity spectra averaged 1.06 ± 0.16, significantly less than the isotropic value of 4/3 observed over land, suggesting that turbulence over water may be altered by the presence of waves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121923
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    Paper (German National Licenses)
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