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首页> 外文期刊>Theoretical and Experimental Plant Physiology >Natural convection in Bingham plastic fluids from an isothermal spheroid: Effects of fluid yield stress, viscous dissipation and temperature-dependent viscosity
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Natural convection in Bingham plastic fluids from an isothermal spheroid: Effects of fluid yield stress, viscous dissipation and temperature-dependent viscosity

机译：来自等温球体的Bingham塑料流体的自然对流：流体屈服应力，粘性耗散和温度依赖性粘度的影响

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AbstractIn this work, the buoyancy-induced convection from an isothermal spheroid is studied in a Bingham plastic fluid. Extensive results on the morphology of approximate yield surfaces, temperature profiles, and the local and average Nusselt numbers are reported to elucidate the effects of the pertinent dimensionless parameters: Rayleigh number, 102≤Ra≤ 106; Prandtl number, 20 ≤Pr≤ 100; Bingham number, 0 ≤Bn≤ 103, and aspect ratio, 0.2 ≤e≤ 5. Due to the fluid yield stress, fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levelsvis-a-visthe value of the fluid yield stress. The yielded parts progressively grow in size with the rising Rayleigh number while this tendency is countered by the increasing Bingham and Prandtl numbers. Due to these two competing effects, a limiting value of the Bingham number (Bnmax) is observed beyond which heat transfer occurs solely by conduction due to the solid-like behaviour of the fluid everywhere in the domain. Such limiting values bear a positive dependence on the Rayleigh number (Ra) and aspect ratio (e). In addition to this, oblate shapes (e< 1) foster heat transfer with respect to spheres (e= 1) while prolate shapes (eBn?Gr-1/2which predicts the onset of convection in such fluids. Similarly, another criterion is developed which delineates the conditions for the onset of settling due to buoyancy effects. The paper is concluded by presenting limited results to delineate the effects of viscous dissipation and the temperature-dependent viscosity on the Nusselt number. Both these effects are seen to be rather small in Bingham plastic fluids.]]>
机译：<！[CDATA [<标题>抽象 ara>在这项工作中，在宾厄姆塑料流体中研究了来自等温球体的浮力引起的对流。据报道了近似屈服表面，温度谱和局部和平均露天数的广泛结果旨在阐明相关无量纲参数的效果：瑞利数，10 <上标> 2 ≤<重点类型=“斜体“> Ra ≤10<上标> 6 ; Prandtl号码，20≤<重点类型=“斜体”> PR ≤100; Bingham编号，0≤<重点类型=“斜体”> Bn ≤10<上标> 3 ，纵横比，0.2≤<重点类型=“斜体”> E ≤5 。由于流体屈服应力，流体状（产生）和固体状（未粘性）区域根据主要的应力水平<重点类型=“斜体”> Vis-A-Vis 流体屈服应力的值。所产生的部件随着瑞利数的上升而逐渐增长，而这种趋势被增加的宾厄姆和普朗特数量反驳。由于这两个竞争效应，观察到宾厄姆数量的限制值（<重点类型=“斜体”> bn <下标> max ）之外，超出了由由于导致的传导而发生的传热发生域中的液体的固体行为。这种限制值对瑞利数（<重点类型=“斜体”> Ra ）和宽高比（<重点类型=“斜体”> E ）进行正依赖性。除此之外，否则形状（<强调类型=“斜体”> e <1）促进相对于球体的热传递（<强调型=“斜体”> E = 1），同时改变形状（<重点类型=“斜体”> E bn ？<重点类型=“斜体”> gr - 1/2 这预测了这种流体中的对流开始。类似地，开发了另一种标准，其描销了由于浮力效应而发出的沉降发作的条件。本文通过呈现有限的结果来描绘粘性耗散的影响和对营养数上的温度依赖性粘度的影响。在宾厄姆塑料液中看到这些效果都是相当小的。]>

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