Flow field and thermal characteristics induced by a rotationally oscillating heated flat plate
Item
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Title
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Flow field and thermal characteristics induced by a rotationally oscillating heated flat plate
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Identifier
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d_2009_2013:5178cccc8769:11735
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identifier
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12324
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Creator
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Koffi, Moise,
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Contributor
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Latif Jiji
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Date
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2013
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Language
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English
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Publisher
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City University of New York.
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Subject
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Mechanical engineering | Physics | Energy | Elephant heat dissipation | Flapping elephant pinnae | Flapping plate heat transfer | rotational oscillating surfaces | simulation of dynamic mesh | Vortex shedding
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Abstract
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The objective of this dissertation is the study the flow and heat transfer in the vicinity of a rectangular flat heated plate of subject to rotational oscillations. Of interest is the effect of the flow field on the thermal characteristics of the plate's surface. A constant heat flux is applied to both sides while the plate is rotated about a fixed edge at a frequency of 2 rad/s in an infinite domain at atmospheric pressure. A computational simulation of the flow with FLUENT reveals a hooked-shape vortex tube around the free edges of the plate, which is confirmed by the flow visualization with smoke particles. During the flapping cycle, vortices form and grow progressively on one face while they shed from the opposite, until they are completely detached from both surfaces at stroke reversal. A data acquisition system uses a numerical computing and programming software (MATLAB) to track the surface temperature recorded by J- type thermocouples at desired locations on the plate. Both experimental and computational results agree with local surface temperature profiles characterized by a transient unsteady periodic variation followed by a steady periodic phase. These characteristics are symmetrical about the median plane of the plate, which is normal to its axis of rotation. The cooling rate of the surface, proportional to the frequency of rotation, depends on the angular position of the plate and the spatial location on the plate's surface. However, the highest heat transfer coefficient is recorded at free edges, especially in the corners swept by strong tip vortices shedding in two orthogonal directions. Conclusions of the present study are used to explain the role of ear flapping in the metabolic heat regulation of large mammals such as elephants.;Flow visualization and surface temperature measurements of full size rigid and flexible elephant ear-shape models were carried out. Results indicate improved interaction between the shedding vortex and the model's boundary layer. Therefore the cooling is enhanced using flexible models by 30 percent. However, the huge size of the elephant pinna combined with its large surface to volume ratio and blood perfusion plays a key role in the enhancement of the animal's heat dissipation.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
