微重力气液两相流动与池沸腾传热

综述了近年来中国科学院微重力重点实验室(国家微重力实验室)完成的一系列微重力气液两相流动与池沸腾传热方面的地基实验、飞行实验和理论研究等方面获得的主要成果.在微重力气液两相流动方面,提出了半理论Weber数模型用于预测微重力条件下气液两相弹-环状流转换,并采用Monte Carlo方法,针对气泡初始尺寸对泡-弹状流转换的影响进行数值研究.通过俄罗斯"和平号"空间站与IL-76失重飞机实验,获得了微重力下的气液两相流型图,与此同时在地面利用小尺度毛细管模型模拟了微重力气液两相流动特征.实验测量了微重力气液两相流压降,并基于微重力流动特性建立了一个泡状流压降关联模型.在微重力池沸腾传热方面,利用我国返回式卫星完成了两次空间实验,其中,第22颗返回式卫星搭载铂丝表面R113池沸腾实验采用控制温度的稳态加热方式,而实践8号育种卫星搭载平面FC-72池沸腾实验则采用控制加热电压的准稳态加热方式.同时,还进行了地面常重力和落塔短时微重力条件下的对比实验研究.观察到丝状加热表面微重力时轻微的传热强化现象,而平板加热表面微重力核态池沸腾低热流时传热强化、高热流时传热恶化.微重力实验中观察到气泡脱落前存在横向运动现象,据此分析了气泡行为与传热之间关系,并提出了一个预测丝状加热表面气泡脱落直径的半理论模型.旨在对相关领域的进一步发展和空间两相流系统的应用提供数据及理论支持.     

第二届环太平洋微重力学术会议简介

１会议概况 第二届环太平洋微重力学术会议（２ｎｄ Ｐａｎ－Ｐａｃｉｆｉｃ　Ｂａｓｉｎ Ｗｏｒｋｓｈｏｐ ｏｎ Ｍｉｃｒｏｇｒａｖｉｔｙ　Ｓｃｉｅｎｃｅｓ）于２００１年 ５月１日～４日在美国加利福尼亚的Ｐａｓａｄｅｎａ市召开会议由美国环太平洋大学联合会（ＡＰＲＵ）,中国微重力科学与应用委员会（ＮＳＭＳＡ）和日本微重力应用协会（ＪＡＳ ＭＡ）共同主办．美国航空航天局（ＮＡＳＡ）积极参加和组织了本次会议,中国科学院,日本国家空间发展局,加拿大空间局和俄罗斯空间局也参加了本次会议的组织工作．本次会议共有２００…     

微重力条件下气/液两相流流型的研究进展

气／液两相流流型是两相流研究领域最基本的课题之一,至今已有数十年的研究历史．但是,由于气／液两相流动现象极为复杂,目前还没有得到一致的结论．近十多年来,利用微重力环境减弱甚至完全消除重力的影响,简化流动中各种不同因素间的相互作用及流型特征,大大促进了对气／液两相流动特征及流型产生与转换机理的研究．同时,微重力条件下的气／液两相流动是空间技术领域必须解决的关键技术问题之一,具有重要的学术意义和重大的应用价值．本文简要总结了微重力条件下气／液两相流流型研究的基本方法以及实验结果和理论进展,指出今后研究中应该注意的一些方向．      

微重力下成一定夹角平板间的表面张力驱动流动的研究

空间微重力环境中,由于重力基本消失,表面张力等次级力发挥主要作用,流体行为与地面迥异,因此有必要深入探究微重力环境中的流体行为规律和特征.板式贮箱利用板式组件在微重力环境中对流体进行管理,从而为推力器提供不夹气的推进剂,这对航天器精确进行姿态控制、轨道调整具有重要意义.板式组件中常包含成一定夹角的平板结构,比如蓄液叶片...     

半浮区液桥振荡对流的微重力实验

利用日本微重力中心８００ｍ落井装置，完成了半浮区液桥振荡对流的微重力实验，对振荡对流的典型物理量诸如内部温度、流场、自由面边缘变化及表面波进行了综合测量。实验结果给出了振荡对流由地球重力环境向微重力环境的过渡，以及不同几何参数半浮区液桥的振荡特征，并首次获得了微重力环境下热毛细对流的表面波位形及边缘振荡特征．     

微重力流体物理专题序

微重力流体物理主要研究微重力环境中流体的行为及运动规律以及重力变化对运动规律的影响. 微重力环境中, 浮力对流、重力沉降及分层、液体静压等极大地减小, 地面重力效应掩盖的次级效应凸显, 从而影响或改变流体运动机制与行为. 微重力流体物理研究关注微重力环境(包括低重力环境)中液体、气体或多相混合物以及分散体系等物质的流动...     

微重力燃烧基础研究概述

本文介绍了国外微重力燃烧基础研究的概况。在微重力条件下不存在浮力和由其引起的自然对流,从而影响了燃烧基本过程。理论和实验研究表明,在微重力条件下火焰结构,火焰传播,火焰稳定等一系列燃烧基本过程都明显不同于通常在地球表面上所观察到的现象。      

机器人卫星自主控制系统地面微重力实验平台

机器人卫星自主控制系统地面微重力实验平台１）刘宏洪炳熔彭成宝蔡鹤皋（哈尔滨工业大学，哈尔滨１５０００１）本文介绍了我国自行研制的第一个机器人卫星自主控制系统地面微重力实验平台的关键技术及“九五”期间将开发的新一代机器人卫星自主控制系统地面微重力实验平...     

中国科学院国家微重力实验室简介

微重力科学是随着当今载人航天技术的发展而发展起来的前沿学科．微重力环境为诸多科学问题的研究提供了机遇,蕴育着自然科学的重大突破,并正在培育新一代高技术产业,是空间科学研究的热点．为适应我国空间科学发展的需要,1995年9月4日由总装备部和中国科学院共同投资建设中国科学院国家微重力实验室,2003年4月通过全面验收,成为我国微重力科学研究基地．实验室主任为中科院院士、国际宇航科学院院士胡文瑞研究员．依托单位是中科院力学所．     

线性稳定性理论在圆管充分发展两相流型研究中的应用

圆截面光滑直管内充分发展的两流体同心环状流的线性稳定性研究不仅具有重要的学术意义,而且在预测两相流型转换方面也有着重要应用.本文评述了该流动构型的线性稳定性研究进展,着重分析了该流动构型的失稳机制及其与两相流型转换间的关系,并针对微重力气-液两相流地面模拟实验问题,探讨了今后需要着重研究的若干方面.      

Gas-particle two-phase turbulent flow in a vertical duct

Two-phase gas-phase turbulent flows at various loadings between the two vertical parallel plates are analyzed. A thermodynamically consistent turbulent two-phase flow model that accounts for the phase fluctuation energy transport and interaction is used. The governing equation of the gas-phase is upgraded to a two-equation low Reynolds number turbulence closure model that can be integrated directly to the wall. A no-slip boundary condition for the gas-phase and slip-boundary condition for the particulate phase are used. The computational model is first applied to dilute gas-particle turbulent flow between two parallel vertical walls. The predicted mean velocity and turbulence intensity profiles are compared with the experimental data of Tsuji et al. (1984) for vertical pipe flows, and good agreement is observed. Examples of additional flow properties such as the phasic fluctuation energy, phasic fluctuation energy production and dissipation, as well as interaction momentum and energy supply terms are also presented and discussed.

Applications to the relatively dense gas-particle turbulent flows in a vertical channel are also studied. The model predictions are compared with the experimental data of Miller & Gidaspow and reasonable agreement is observed. It is shown that flow behavior is strongly affected by the phasic fluctuation energy, and the momentum and energy transfer between the particulate and the fluid constituents.     

关于二相流、多相流、多流体模型和非牛顿流等概念的探讨

本文分析了单相流、二相流和多相流等概念上的差异,也分析了单流体模型、双流体模型和多流体模型等概念上的差异,指出前面三种概念是按流动介质的客观物理构成划分的,而后者是按主观采用的研究方法划分的．目前这些概念在使用中存在一些混乱,如二相流与多相流,多相流与多流体模型等．本文还研究了扩散模型、非牛顿流模型和颗粒流模型等,指出前两种模型在分类上属于单流体模型,分析了非牛顿流模型、扩散模型和双（多）流体模型的特点和应用范围,最后,以泥石流为例讨论了以上概念的应用．      

A three-layer model for solid-liquid flow in horizontal pipes

A three-layer model for solid-liquid flow in horizontal pipes is proposed. This model overcomes the limitations of the two-layer model. The model predictions exhibit satisfactory agreement with the experimental data and existing correlations.     

Integrated numerical model for vegetated surface and saturated subsurface flow interaction

The construction of an integrated numerical model is presented in this paper to deal with the interactions between vegetated surface and saturated subsurface flows. A numerical model is built by integrating the previously developed quasi-three-dimensional (Q3D) vegetated surface flow model with a two-dimensional (2D) saturated groundwater flow model. The vegetated surface flow model is constructed by coupling the explicit finite volume solution of 2D shallow water equations (SWEs) with the implicit finite difference solution of Navier-Stokes equations (NSEs) for vertical velocity distribution. The subsurface model is based on the explicit finite volume solution of 2D saturated groundwater flow equations (SGFEs). The ground and vegetated surface water interaction is achieved by introducing source-sink terms into the continuity equations. Two solutions are tightly coupled in a single code. The integrated model is applied to four test cases, and the results are satisfactory.     

A THREE-FLUID MODEL OF THE SAND-DRIVEN FLOW

ＡＴＨＲＥＥ－ＦＬＵＩＤＭＯＤＥＬＯＦＴＨＥＳＡＮＤ－ＤＲＩＶＥＮＦＬＯＷ￥(刘大有，董飞)ＬｉｕＤａｙｏｕ；ＤｏｎｇＦｅｉ（ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａｎｉｃｓ，ＡｃａｄｅｍｉａＳｉｎｉｃａ，Ｂｅｉｊｉｎｇ１０００８０，Ｐ．Ｒ．Ｃｈｉｎａ）Ａｂｓ...     

Prediction of the slug-to-churn flow transition in vertical two-phase flow

An assessment is made of the various viewpoints on the slug-to-churn flow transition in vertical upward flow in the light of recent experimental results obtained at Harwell Laboratory. It is found that the flooding model of McQuillan & Whalley and the bubble entrainment model of Barnea & Brauner give satisfactory results at low and high liquid flow rates, respectively. An improved model for flooding, which takes account of the effect of the falling film, has been proposed. It is shown that this new model is in good agreement with experimental results at both low and high liquid flow rates.     

Numerical solution of the turbulent flow of an incompressible fluid in curved planar and axially symmetrical channels

The governing equations for axially symmetric flow, where the Reynolds stresses are expressed by scalar turbulent viscosity, are the Reynolds equations. The turbulence model k, ? is used in the well-known form for fully developed turbulent flow.The numerical method, a continuation of the MAC system¹, is adapted so that even for high Reynolds cell numbers precision (δx²) can be achieved for the steady flow. Irregular cells join the rectangular network on the curved surface. Von Neumann's stability condition of the linearised numerical system is investigated. Special problems concerning the numerical solution of the turbulence model equations are stated and a special procedure is worked out to ensure that the fields k, ? do not converge to physically meaningless values. The program for the computer is universal in that the boundary problems can be assigned by input data.As an example, an axially symmetrical diffuser with an area ratio of widening 1.40 is computed. Fields of velocity and pressure at the wall as well as fields v_T and k are assessed. The results are compared with an experiment. The conclusion is that this method is suitable for the problems mentioned in this study as well as for unsteady flow.     

低渗透多孔介质中的非线性渗流理论简

文中论述了低渗透性多孔介质中非线性渗流理论的几个问题,阐明了渗流流体的性质,指出了多孔介质对流体通过的选择性,提出了新的非线性渗流方程,用实验资料对其进行了验证,分析了该方程演变功能,表明它可以描述各种渗流规律.该方程的各项参数都可从实验中直接得到,应用方便,并且参数的物理意义明确.     

Modeling fluid-particle interaction in dilute-phase turbulent liquid-particle flow simulation

The present work examines the predictive capability of a two-fluid CFD model that is based on the kinetic theory of granular flow in simulating dilute-phase turbulent liquid-particle pipe flows in which the inter-stitial fluid effect on the particle fluctuating motion is significant.The impacts of employing different drag correlations and turbulence closure models to describe the fluid-particle interactions(i.e.drag force and long-range interaction)are examined at both the mean and fluctuating velocity levels.The model pre-dictions are validated using experimental data of turbulent liquid-particle flows in a vertical pipe at different particle Reynolds numbers(ReP > 400 and ReP < 400),which characterize the importance of the vortex shedding phenomenon in the fluid-phase turbulence modulation.The results indicate that(1)the fluctuating velocity level predictions at different ReP are highly sensitive to the drag correlation selec-tion and(2)different turbulence closure models must be employed to accurately describe the long-range fluid-particle interaction in each phase.In general,good agreement is found between the model predic-tions and the experimental data at both the mean and fluctuating velocity levels provided that appropriate combinations of the drag correlation and the turbulence closure model are selected depending on Rep.     

Vertical integration of three-phase flow equations for analysis of light hydrocarbon plume movement

A mathematical model is derived for areal flow of water and light hydrocarbon in the presence of gas at atmospheric pressure. Vertical integration of the governing three-dimensional, three-phase flow equations is performed under the assumption of local vertical equilibrium to reduce the dimensionality of the problem to two orthogonal horizontal directions. Independent variables in the coupled water and hydrocarbon areal flow equations are specified as the elevation of zero gauge hydrocarbon pressure (air-oil table) and the elevation of zero gauge water pressure (air-water table). Constitutive relations required in the areal flow model are vertically integrated fluid saturations and vertically integrated fluid conductivities as functions of air-oil and air-water table elevations. Closed-form expressions for the vertically integrated constitutive relations are derived based on a three-phase extension of the Brooks-Corey saturation-capillary pressure function. Closed-form Brooks-Corey relations are compared with numerically computed analogs based on the Van Genuchten retention function. Close agreement between the two constitutive models is observed except at low oil volumes when the Brooks-Corey model predicts lower oil volumes and transmissivities owing to the assumption of a distinct fluid entry pressure. Nonlinearity in the vertically integrated constitutive relations is much less severe than in the unintegrated relations. Reduction in dimensionality combined with diminished nonlinearity, makes the vertically integrated water and hydrocarbon model an efficient formulation for analyzing field-scale problems involving hydrocarbon spreading or recovery under conditions for which the vertical equilibrium assumption is expected to be a satisfactory approximation.