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  • 1985-1989  (60)
  • 1975-1979  (35)
  • 1
    Electronic Resource
    Electronic Resource
    The fine-scale intermittency of turbulence (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1431-1438 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The technique of Rao et al. [J. Fluid Mech. 48, 339 (1971)], which consists of identifying pulses or regions of strong activity in a narrow bandpass filtered signal, is reexamined in the context of Sreenivasan's theory [J. Fluid Mech. 151, 81 (1985)], by applying it to white noise and turbulent signals. For white noise, the dependence of pulse characteristics on the threshold and filter center frequency are in close agreement with the theory. There are, however, important differences between white noise and turbulence results, even when the white noise spectrum is shaped to simulate the turbulent spectrum. For the turbulent signal, the theory is valid only for a range of filter parameters for which the departure of the filtered signal from a Gaussian distribution is small. Using wall shear stress and velocity fluctuations in a fully developed turbulent duct flow, the pulse frequency is found to be closely related to the zero-crossing frequency. It is concluded that the pulse frequency, which is proportional to the Kolmogorov frequency, cannot scale on outer variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866734
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  • 2
    Electronic Resource
    Electronic Resource
    Coherent structures in the far field of a turbulent wake (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3612-3617 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The topology of a typical group of large-scale coherent structures in the far-field of a slightly heated cylinder wake is clearly delineated by using averages of the velocity vector components conditioned on the occurrence of spatially coherent temperature fronts. Velocities are determined relative to a frame of reference traveling with the approximate convection velocity of the structures. When the results for a number of positions across the wake are assembled a clear topology picture of a typical group of structures in the plane of the main shear is obtained. The contributions of the coherent and random motions of all structures to the momentum and heat transports have been determined. In all cases the contribution that results from the random motion is larger than that of the coherent motion. This difference is more pronounced for the momentum transport than for the lateral heat transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865789
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  • 3
    Electronic Resource
    Electronic Resource
    Scaling of the "bursting'' period in turbulent boundary layer and duct flows (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 318-325 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements have been made in fully developed turbulent duct and boundary layer flows of the average bursting period over a one decade variation in Reynolds number. The bursting period was determined by two methods: the variable interval time averaging scheme in the form used by Blackwelder and Haritonidis [J. Fluid Mech. 132, 87 (1983)] and the modified u-level scheme of Luchik and Tiederman [J. Fluid Mech. 174, 529 (1987)] in which ejections from the same burst are grouped. All these authors concluded that the bursting period scaled on inner variables. The present results indicate that this conclusion is valid only over a relatively small Reynolds number range, in which low Reynolds number effects are known to be important. At higher Reynolds numbers, scaling on mixed variables provides the best agreement with the data although scaling on outer variables cannot be ruled out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857450
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  • 4
    Electronic Resource
    Electronic Resource
    Dissipation and vorticity spectra in a turbulent wake (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1805-1807 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reasonable spectral analogy is found between the temperature dissipation and either the energy dissipation or the vorticity in the turbulent far wake of a circular cylinder. The high-wavenumber behavior of the spectra of vorticity, energy dissipation, and temperature dissipation is consistent with isotropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866671
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  • 5
    Electronic Resource
    Electronic Resource
    The organized motion outside a turbulent wake (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2040-2045 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Velocity fluctuations are measured in both the intermittent and irrotational regions outside the turbulent/nonturbulent interface of a self-preserving wake. In the outer part of the intermittent region, there is a tendency for all the predictions of the theory of Phillips [Proc. Cambridge Philos. Soc. 51, 220 (1955)] to be satisfied by the nonturbulent data. At larger distances from the interface, the level of the velocity fluctuations becomes comparable with the background turbulence but the organized motion induced by coherent structures within the wake can still be identified. The contribution of this motion to the normal stresses satisfies irrotationality and homogeneity and the amplitude of this motion decays in a manner consistent with Phillips' theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866138
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  • 6
    Electronic Resource
    Electronic Resource
    Spectra of velocity derivatives in a turbulent wake (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3455-3462 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One-dimensional spectra have been measured in the self-preserving wake of a circular cylinder for each of the nine major velocity derivatives that feature in the average dissipation of turbulent kinetic energy. The comparison between measured spectra and isotropic calculations indicates that isotropy is approached only at high wavenumbers, especially for spectra of derivatives with respect to lateral directions of lateral velocity fluctuations. This result is discussed in the context of the organized large scale motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866478
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  • 7
    Electronic Resource
    Electronic Resource
    Relations between spectra of spatial derivatives of temperature in a turbulent jet (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 420-423 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectrum of the lateral derivative of temperature has been measured on the center line of a turbulent plane jet and compared with calculations, based on local isotropy, derived from the spectra of either the streamwise derivative or the temporal derivative of temperature. To within the experimental uncertainty, quantitative agreement between measurement and calculation is satisfactory for sufficiently large wavenumbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865167
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  • 8
    Electronic Resource
    Electronic Resource
    Instantaneous dissipations of turbulent energy and temperature in a wake (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1374-1382 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Approximations to the instantaneous dissipation of temperature variance and to an instantaneous pseudodissipation of kinetic energy in the turbulent far wake of a cylinder have been measured, using either four hot wires or four cold wires arranged in the form of a square. Results, including probability density functions and spectra as well as joint probability density functions and cospectra between individual components of the dissipations, suggest a close similarity between the two dissipations. The influence of the organized motion on the flow structure is briefly discussed in the context of cospectra and correlation coefficients for the components of the two dissipations. One implication of the similarity between the spectra of the two dissipations is the constancy of the time scale ratio, defined on a spectral basis, of the velocity and temperature fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857313
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  • 9
    Electronic Resource
    Electronic Resource
    Reynolds shear stress and heat flux measurements in a cylinder wake (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 709-713 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of Reynolds shear stress profiles and lateral heat flux profiles in the nearly self-preserving region of the turbulent wake of a heated circular cylinder are compared with calculations obtained from the mean momentum and mean enthalpy equations. Two types of self-preserving scales are used. The first uses the free-stream velocity U1 and the length scale [(x−x0)d]1/2, where x is the distance from the cylinder, x0 is the virtual origin, and d the cylinder diameter. The second uses the centerline velocity defect U0 and the velocity defect half-width L. Consistent results are obtained with both types of scales. In particular, the comparisons do not support the need for determining a new virtual origin, as suggested by Hariri et al. [Phys. Fluids 25, 1964 (1982)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865923
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  • 10
    Electronic Resource
    Electronic Resource
    Isotropic forms of vorticity and velocity structure function equations in several turbulent shear flows (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 4016-4024 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Isotropic forms of the vorticity and velocity structure function equations are valid in the logarithmic regions of a fully developed turbulent duct flow and a boundary layer over a wide range of Reynolds numbers. These equations are also valid in a low Reynolds number turbulent wake and a high Reynolds number atmospheric surface layer. However, these equations are not satisfied in the near-wall region of duct and boundary layer flows where the production of vorticity is significantly larger than the dissipation. The appropriateness of the equations as indicators of local isotropy is discussed in the context of the present and other published measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865742
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