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抗浮安全；隧道施工期；隧道运营期；覆土厚度 1

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How did Archimedes discover the law of buoyancy by experiment?

Hidetaka KUROKI

《机械工程前沿（英文）》 2016年第11卷第1期页码 26-32 doi: 10.1007/s11465-016-0368-z

摘要：

After Archimedes and Vitruvius era, for more than 2000 years, it has been believed that the displaced water measurement of golden crown is impossible, and at his Eureka moment, Archimedes discovered the law of buoyancy (Proposition 7 of his principles) and proved the theft of a goldsmith by weighing the golden crown in water.

A previous study showed that a small amount of displaced water was able to be measured with enough accuracy by the introduced method. Archimedes measured the weight of displaced water. He did not find the law of buoyancy but rather specific gravity of things at the moment.

After which, Archimedes continued to measure the specific gravity of various solids and fluids. Through these measurements, he reached the discovery of the law of buoyancy directly by experiment. In this paper, the process to the discovery of Archimedes’ principle (Proposition 5) is presented.

关键词： Archimedes’ principle buoyancy specific gravity Eureka Vitruvius displaced water balance floating body

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基于抗浮稳定的盾构隧道合理覆土厚度研究

刘学彦,袁大军,姜曦

《中国工程科学》 2015年第17卷第1期页码 88-95

摘要：

运用理论分析和数值计算相结合的方法，分别从施工期和运营期角度提出了隧道抗浮稳定合理覆土厚度设定原则和理论计算方法；对于隧道施工期，考虑土体侧向摩阻力和管片环间摩阻力的影响等较为有利因素，同时考虑未凝浆液的影响等不利因素，建立了合理覆土厚度的理论计算公式；对于隧道运营期，建议只考虑隧道上覆土体自重进行抗浮，对于存在洪水冲刷的隧道设计，其上覆土体厚度还要加上设计冲刷深度；为南京某在建隧道的纵断面设计提供了一定的参考，同时也为其他过江海盾构隧道满足抗浮稳定的覆土厚度设定提供理论支持。

关键词：抗浮安全；隧道施工期；隧道运营期；覆土厚度

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Heat transfer with water flowing upward in a tube for pressures up to supercritical region

Yuzhou CHEN, Chunsheng YANG, Shuming ZHANG, Minfu ZHAO, Kaiwen DU,

《能源前沿（英文）》 2010年第4卷第3期页码 358-365 doi: 10.1007/s11708-009-0071-4

摘要： A heat transfer experiment was conducted in a tube of 6.07mm in diameter with water flowing upward, covering the ranges of pressure of 10―23MPa, mass flux of 288―1298kg/(m·s), local water temperature of 78°C―270°C, heat flux of 0.23―1.18MW/m and Reynolds number of 5.5×10―3.9×10. The experimental results were compared with the predictions of the Dittus-Boelter correlation, Jackson correlation, Bishop correlation, Swenson correlation and Yamagata correlation. Significant deterioration in heat transfer was observed in both subcritical and supercritical region due to the effect of buoyancy force, but it was not predicted reasonably by the existing correlations.

关键词： heat transfer deterioration buoyancy supercritical water

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How far have we been? ―Summary of investigations on rotating cavity at IDG, RWTH Aachen University

Dieter BOHN, Jing REN,

《能源前沿（英文）》 2009年第3卷第4期页码 489-497 doi: 10.1007/s11708-009-0040-y

摘要： Annular cavities are found inside rotor shafts of turbomachines with an axial or radial throughflow of cooling air, which influences the thermal efficiency and system reliability of the gas turbines. The flow and heat transfer phenomena in those cavities should be investigated in order to minimize the thermal load and guarantee the system reliability. An experimental rig is set up in the Institute of Steam and Gas Turbines, RWTH Aachen University, to analyze the flow structure inside the rotating cavity with an axial throughflow of cooling air. The corresponding 3D numerical investigation is conducted with the in-house flow solver CHTflow, in which the Coriolis force and the buoyancy force are implemented in the time-dependent Navier-Stokes equations. Both the experimental and numerical results show that the whole flow structure rotating slower than the cavity rotating speed. The flow passing the observation windows in the experimental and numerical results indicates the quite similar trajectories. The computed sequences and periods of the vortex flow structure correspond closely with those observed in the experiment. Furthermore, the numerical analysis reveals a flow pattern changing between single pair, double pair, and triple pair vortices. It is suggested that the vortices inside the cavity are created by the gravitational buoyancy force in the investigated case, while the number and strength of the vortices are controlled mainly by the Coriolis force.

关键词： rotating cavity buoyancy unsteady flow