Experimental Investigation of Turbulent Thermal Convection with Slip-free Boundary Conditions PDF Download
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Author: Xiaozheng Zhao
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 114
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Author: Xiaozheng Zhao
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 114
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Author: Claudia Zimmermann
Publisher: Cuvillier Verlag
ISBN: 3736980612
Category : Technology & Engineering
Languages : en
Pages : 358
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Book Description
Die vorliegende Arbeit beschäftigt sich mit der numerischen und experimentellen Modellierung turbulenter thermisch angetriebener Luftströmungen in unterschiedlichen Test-Konfigurationen. Diese so genannten Konvektionsströmungen stellen eines der fundamentalen Probleme der Strömungsmechanik dar. Sie ziehen ein großes wissenschaftliches Interesse auf sich, da sie in vielen Bereichen, wie z. B. in der Meteorologie oder auch in industriellen Anwendungen, eine wesentliche Rolle spielen. Vor allem vor dem Hintergrund atmosphärischer Konvektionsströmungen, die durch eine durch die Erdbewegung hervorgerufene Corioliskraft beeinflusst werden und sich zu Wirbelstürmen ausbilden können, ist ein Verständnis dieser Strömungen sehr wichtig. Die Konvektionsströmung wird in jeder einzelnen Test-Konfiguration immer zwischen zwei sich gegenüberliegenden, isotherm beheizten Wänden erzeugt. Neben der Validierung des gewählten numerischen Modells einer Large-Eddy-Simulation (LES), geben die erzielten Ergebnisse der Arbeit Aufschluss über die Strömungsdynamik, die entstehenden Turbulenzstrukturen sowie die Wärmeübertragung in der jeweiligen Test-Konfiguration. Hierbei steht vor allem die Auflösung der thermalen Wandgrenzschicht im Mittelpunkt. Hervorzuheben ist die numerische sowie auch experimentelle Untersuchung eines sogenannten Rayleigh-Bénard Problems, das unter Einfluss einer zusätzlich wirkenden Corioliskraft steht. Das hierfür realisierte Experiment in einer Großzentrifuge und die zugehörige numerische Studie geben Aufschluss über die Auswirkung der zusätzlich wirkenden Relativbeschleunigungen auf die Turbulenzproduktion und die Wärmeübertragung im Fluid.
Author: Gary Michael Kinsella
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 182
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Author: Ding Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 714
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 495
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The turbulence structure of convective beat transfer was studied experimentally in complex three-dimensional and separating turbulent boundary layers. Three test cases whose fluid dynamics have been well documented were examined. In case 1, time- and spatially-resolved surface heat transfer was measured in the nose region of a wing-body junction formed by a wing and a flat plate. Both the wing and the endwall were heated and held at a constant uniform temperature 20 C above ambient temperature. Heat flux rates were increased up to a factor of 3 over the heat flux rates in the approach boundary layer. The rms of the heat flux fluctuations were as high as 25% of the mean heat flux in the vortex-dominated nose region. Away from the wing, upstream of the time-averaged vortex center, augmentation in the heat flux is due to increased turbulent mixing caused by large-scale unsteadiness of the vortex. Adjacent to the wing the augmentation in heat flux is due to a change in the mean velocity field. In case 2, simultaneous surface heat flux and temperature profiles were measured at 8 locations in the spatially-developing pressure-driven three-dimensional turbulent boundary layer upstream of a wing-body junction. Mean heat transfer was decreased 10% by three-dimensionality. The turbulent Prandtl number in the near-wall region of logarithmic temperature variation was approximately 0.9 at all measurement locations in the three-dimensional boundary layer. Profiles of the skewness factor of temperature fluctuations and conditionally-averaged temperature signals during a sweep/ejection event suggest that the strength of ejections of hot fluid from the near-wall region are decreased by three-dimensionality.
Author: Pengfei Qi
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 69
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Author: Irving H. Brooks
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
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The study deals with an experimental investigation into the natural convection inside a horizontal cylinder. The fluid, geometry, and thermal boundary condition were chosen so as to have a high Prandtl number and unit order Grashof number. The thermal boundary condition was established by imposing temperatures at two points, 180 degrees apart, on the circumference of the cylinder. The resulting boundary condition for the full 360 degrees was found experimentally and is presented. The apparatus was constructed so that the entire cylinder could be rotated. This was done so that the diameter containing the two imposed temperatures could vary from being horizontal to being vertical. In this way an arbitrary heating angle was incorporated into the boundary condition. Temperature profiles and streamline patterns were observed at steady state for various values of this heating angle and for various initial conditions. For some cases, velocity profiles were also plotted. It was found that the interior 'core' of fluid was thermally stratified when the diameter containing the two imposed temperatures was horizontal. The flow occurred primarily in the region close to the cylinder wall. The cylinder was rotated so that the diameter containing the two imposed temperatures made an angle with the horizontal. (Author).
Author: Hussain Shaukatullah
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 218
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Author: John Julius Oras
Publisher:
ISBN:
Category :
Languages : en
Pages : 474
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Author: Fenglei Niu
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 270
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