5,360 research outputs found

    Rayleigh number dependence of the Archimedes number dependent large-scale flow structure formation in mixed convection

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    We report on experimental investigations of large-scale flow structure formation in mixed convection. We characterize the flow field by measuring the velocity fields within a rectangular model room using 2D2C PIV. The control parameters are the Reynolds number Re, the Rayleigh number Ra and the Prandtl number Pr. All parameters are linked through the Archimedes number Ar. In 6.4x10-2 ≤ Ar ≤ 1.39x101, 4.2x103 ≤ Re ≤ 6.35x104 and Ra = 3.1x107, Ra = 1.8x108 and Pr = 0.713 we found flow 3 different flow structures. While keeping Ra and Pr constant and varying Ar through Re variations, we found an Ar dependence of the largescale flow structure formation within 6.4x10-2 ≤ Ar ≤ 1.39x101. Furthermore, we found a Ra dependence of the structure formation, which shifts the transition points between the structures to higher Archimedes numbers and reduces the mean velocities within the investigated domain

    Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection

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    We report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV

    Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection

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    We report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either

    Lagrangian Raylaigh-Bénard convection

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    Using passive tracers as sensors, we obtain Lagrangian measurements of tracers position, velocity and temperature in Rayleigh-Bénard convection at Ra=10^7-10^9. We report on statistics of temperature, velocity, and heat transport (Nusselt number). We observe that the Nusselt number is characterized by a largely intermittent behavior, likely due to the interaction of temperature with turbulent velocity fluctuations

    The iconicity of celebrity and the spiritual impulse

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    Celebrity has a powerful material presence in contemporary consumer culture but its surface aesthetic resonates with the promise of deeper meanings. This Marketplace Icon contribution speculates on the iconicity of celebrity from a spiritual perspective. The social value or authenticity of contemporary celebrity, and the social processes through which it emerges, are matters of debate amongst researchers and competing approaches include field theory, functionalism, and anthropologically inflected accounts of the latent need for ritual, myth and spiritual fulfilment evinced by celebrity “worship.” We focus on the latter area as a partial explanation of the phenomenon whereby so many consumers seem so enchanted by images of, and stories about, individuals with whom they, or we, often have little in common. We speculate that the powerful presence of celebrity in Western consumer culture to some extent reflects and exploits a latent need for myths of redemption through the iconic character of many, though by no means all, manifestations of celebrityconsumption

    Photochemical behavior of some p-styryistilbenes and related compounds: Spectral properties and photoisomerization in solution and in solid state

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    Author Posting. © The Authors (2006) This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in PHOTOCHEMISTRY AND PHOTOBIOLOGY, 82(6): 1645-1650. https://doi.org/10.1562/2006-01-17-RA-780ArticlePhotochemistry and Photobiology. 82(6): 1645-1650 (2006)journal articl
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