密集斜槽流颗粒靶的流动性（英文）

研究了中子辐照装置密集斜槽流颗粒靶设计的流动性,该靶设计能够提供适用于聚变反应堆材料研究的高能中子。本文通过数值模拟和理论分析的方法描述了流动的稳定性和稳固性,这在其他文献中很少被提及。结果发现,25°对于稳定的流动是可以接受的,这种颗粒流有潜力成为热介质的选择。     

惯性约束聚变靶丸内杂质气体抽空流洗过程的数值模拟

低温冷冻靶是实现惯性约束聚变(inertial confinement fusion,ICF)的关键部件之一.低温靶靶丸内杂质气体的去除程度和效率对低温靶燃料冰层的在线制备具有重要意义.依据低温靶物理对冰层杂质含量的设计要求,在计算靶丸内杂质气体最大允许分压的基础上,建立了靶丸内气体在微米级充气管内流动的抽空流洗模型.模拟研究了不同微管尺度及结构、温度对靶丸内杂质气体抽空流洗效率的影响规律,获得了靶丸充气微管的最佳管型设计方案.基于最佳管型设计,优化得到了具有最高抽空流洗效率的抽空时间与流洗次数组合策略.     

螺旋管内气液固三相流颗粒相分布规律

为了深入认识螺旋管多相流相分离现象,并为新型螺旋管除砂器设计提供指导,本文应用马尔文粒度仪,测量了螺旋管气水砂三相流底部水平段液膜中的颗粒浓度和粒度分布。研究表明:在泡状流和分层流条件下,螺旋管底部水平段可形成稳定的连续液膜流动;在宽广的气速范围内,液膜中的颗粒浓度分布规律均为内弯侧较低、外弯侧较高,说明螺旋管除砂器对于实际生产中流动工况的变化具有良好的适应性;泡状流中提高气速有利于分离;分层流中在中等气速条件下外弯侧颗粒浓度最大,中等气速是相分离的最佳操作工况。     

固液双相电流变系统流动过程的相转变特性

考虑电流变液多粒子近程相互作用，利用等效平板电导模型，研究了电流变液流动过程相转变点的特性，并设计实验观察了电流变液中的这种相转变现象.研究结果表明，电流变液在一定压力梯度作用下发生流动，此时为双相流；当外加电场达到某一值时，电流变液中颗粒不流动，由固液双相流转变为液体单相流动，发生场控相转变，理论模拟结果与实验观察结果基本相符.阈值电场随外加压力梯度的增加而加大，随颗粒浓度的增加而减小. 关键词： 电流变液 颗粒流 相转变     

气粒并流上行流动中颗粒团特性的实验研究

用流动显示法和图像分析法研究了气粒并流上行流动中颗粒团的瞬态行为,通过灰度梯度识别颗粒团,由颗粒团成像的象素确定其尺寸,采用相关分析法计算颗粒团的速度。随着颗粒流量的提高和表现气速的降低,气粒并流上行流动中开始出现颗粒团,由于颗粒团与气相的相互作用,流态具有不稳定和不规则的现象.在一定操作条件下,在壁面附近出现了一些长时间停留的大尺寸颗粒团.     

开口角度对二维颗粒流稀疏流-密集流转变的影响

用计算机模拟的方法研究了开口角度对二维颗粒流稀疏流—密集流转变的影响.在固定入口流量和固定颗粒数两种条件下,均发现当开口角度大于零时,开口角度的增大可以提高颗粒流由稀疏流向密集流转变的最大出口流量.在稀疏流状态下,出口流量与开口角度无关;而在密集流状态下,出口流量随开口角度的增大而增大.进一步的计算还发现增加开口角度可以提高颗粒流出开口的流动速度,且最大出口流量与颗粒的流动速度呈线性关系. 关键词： 颗粒物质 颗粒流 分子动力学模拟     

颗粒流电磁垂直输运装置物理设计

为满足中国加速器驱动的次临界系统(C-ADS) 对于可靠性的要求, 计划采用基于螺线管的电磁垂直输运方案, 将经过质子束辐照后下落的散裂靶颗粒球再次输运至初始高度。基于解析方法对颗粒流垂直输运装置进行了分析和设计, 通过基于螺线管散热、径轴向颗粒流聚散焦效应和互感损耗等方面的考虑, 得到了适合于垂直输运颗粒流的螺线管驱动方式和螺线管构型及排布。利用基于本文解析方法的模拟程序, 对不同输运管道内径、不同螺线管驱动电流和不同螺线管构型和排布下的颗粒流垂直输运装置进行了模拟, 并从中筛选出了该装置的优化设计。模拟表明, 采用该优化设计的输运装置可将质量流量为19.6kg/s的颗粒流垂直输运至40m高度, 并满足颗粒球出口速度足够大的要求。     

弯管内气液固三相流中液膜区流场的PIV测量

为了深入认识螺旋管内多相流相分离现象,应用粒子图象测速仪(PIV),对组合弯管内气水砂三相流底部水平段和上升段中液膜区的流场进行了测量。研究表明:底部水平段流动主流速度分布比较均匀,颗粒跟随流体运动;二次流十分微弱,颗粒在离心力作用下由内弯侧向外弯侧运动;速度脉动强烈,不利于相分离。上升段中流动受到重力的阻碍,同底部平段相比主流速度降低,离心力作用减弱,颗粒径向时均速度较低;流动的间歇性更强,两相速度脉动更剧烈。     

颗粒沉降运动的虚拟区域法直接数值模拟

文采用基于四边形网格的分布式拉格朗日乘子／虚拟区域方法(DLM／FD method)对二维方槽内775个圆形颗粒在流体中的沉降过程进行了直接数值模拟。得到了颗粒流沉降过程中流体和颗粒速度和涡量分布、流场压力分布等流动细节,展示了颗粒在沉降过程中由于相间的相互作用以及颗粒间的作用,使得颗粒流在流场内形成大小不一的旋流区,颗粒回旋着沉降,同时颗粒的尾涡影响附近颗粒的运动．本文的结果说明分布式拉格朗日乘子／虚拟区域方法对模拟存在很多颗粒的悬浮体流动是可行的。     

气固两相90°弯管流中静电影响颗粒运动的大涡模拟研究

本文采用欧拉–拉格朗日方法对静电平衡情况下的圆形截面90°弯管中的气固两相湍流流动进行了大涡模拟研究,重点研究了弯管中的饱和静电作用和Prandtl第二类二次流对于颗粒输送的影响。结果表明,模拟得到Reb=58k工况下的90°弯管中的载流相流场计算结果与实验结果吻合良好,弯管中平均二次流速度最大可以达到体积速度的55%,并且二次流对于离散颗粒相的输送影响显著。静电作用对于管道中心区域的颗粒影响较小,但对于近壁面区域的颗粒作用影响较大,加强了近壁面区域颗粒运动的湍泳现象。动力学分析结果表明,在远离壁面的大部分管道中心区域内流动对颗粒的拖曳力主导颗粒的运动。而对近壁面区域内的颗粒,静电力与拖曳力大小相当甚至超过拖曳力,静电力主导了近壁面区域内颗粒的运动。     

A method for MR quantification of flow velocities in blood and CSF using interleaved gradient-echo pulse sequences

The aim of this study was to establish a rapid method for in vivo quantification of a large range of flow velocities using phase information. A basic gradient-echo sequence was constructed, in which flow was encoded along the slice selection direction by variation of the amplitude of a bipolar gradient without changes in sequence timings. The influence of field inhomogeneities and eddy currents was studied in a 1.5 T scanner. From the basic sequence, interleaved sequences for calibration and in vivo flow determination were constructed, and flow information was obtained by pairwise subtraction of velocity-encoded from velocity non-encoded phase images. Calibration was performed in a nongated mode using flow phantoms, and the results were compared with theoretically calculated encoding efficiencies. In vivo flow was studied in healthy volunteers in three different areas using cardiac gating; central blood flow in the great thoracic vessels, peripheral blood flow in the popliteal vessels, and flow of cerebrospinal fluid (CSF) in the cerebral aqueduct. The results show good agreement with results obtained with other techniques. The proposed method for flow determination was shown to be rapid and flexible, and we thus conclude that it seems well suited for routine clinical MR examinations.     

油气水多相流压力和压差信号特征分析与流型在线识别

在宽广的实验参数范围内测量了水平管内油气水多相流动时压力和压差信号，对信号的时域、频域、小波尺度域、分形等特征进行了提取与分析；建立了流型的规则识别和模式识别的融合方法。经过实验测试，该方法可以识别出泡状流、分层流、间歇流和环状流，流型识别率高于９０％．     

Measurement of Mach probe on plasma flow velocity in highly collisional plasma jet

A normalized plasma flow velocity in highly collisional plasma formed by a microwave plasma jet, which is dimensionless unit for plasma flow velocity/ion acoustic velocity, was measured by the parallel Mach probe. To deduce the normalized plasma flow velocity under highly collisional plasma conditions, the collisional model of a Mach probe was proposed. In addition, neutral gas flow velocity which assumed to be plasma flow velocity was calculated by the turbulent model. The results for the two different models were compared with those for the collsionless models of the Mach probe. The turbulent model produced 2–4 times reduced values than by measurements with collsionless models. The measured results with the collisional model were shown as approximately 100–250% lower than those for collsionless models. They were obtained to be in good agreement with difference rate of 10–30% when compared to those for the turbulent model.     

Reynolds数22 000的孤立方柱绕流的大涡模拟

方柱绕流是典型的钝体绕流问题,蕴含了丰富的流体力学现象,对这类流动的准确预测面临着诸多挑战.采用自主发展的大涡模拟程序,对来流Mach数M=0.3,Reynolds数Re_D=22 000的绕孤立方柱流动进行了细致模拟,亚格子模型使用动力涡黏模型.对计算结果的分析表明,大涡模拟所得的平均流场及Reynolds应力分布与已有实验数据和直接数值模拟结果均吻合较好,验证了预测结果的可靠性;在此基础上对瞬态流场进行了研究,展示了计算条件下方柱绕流分离转捩及尾迹区旋涡交替脱落形成Karman涡街的全过程,为更细致的流动机理探索奠定了基础.      

在COIL中碘量变化与激光功率波形的关系

 针对碘量在一定范围内变化对激光功率影响不敏感,采用碘量变化的方法,通过对大量的250mmol/s列管式射流氧发生器的出光实验的分析,得到了激光功率波形随碘量变化的实验规律。这一实验结果可用于根据功率波形变化来调节最佳碘量。并对其机理进行了理论分析。     

DMFC两相流及其对传质影响的研究

采用自制的实验系统对液态进料直接甲醇燃料电池(DMFC)阳极交叉指状流道内的两相况功特性进行了可视化实验研究.自制的DMFC单电池带有透明窗口,采用镀金的不锈钢阴极极板和透明的聚碳酸脂阳极流场板,电解质为Nafion117膜.实验过程中燃料电池的进口总管和出口总管是水平的,进口流道和出口流道是竖直的.实验发现,出口流道中典型的两相流流型是泡状流、而出口总管中的典型流型是弹状流.进口流道中的气弹和气柱导致了阳极传质恶化.     

Numerical simulation of pulsation processes in hydraulic turbine based on 3D model of cavitating flow

A new approach was proposed for simulation of unsteady cavitating flow in the flow passage of a hydraulic power plant. 1D hydro-acoustics equations are solved in the penstock domain. 3D equations of turbulent flow of isothermal compressible liquid-vapor mixture are solved in the turbine domain. Cavitation is described by a transfer equation for liquid phase with a source term which is responsible for evaporation and condensation. The developed method was applied for simulation of pulsations in pressure, discharge, and total energy propagating along the flow conduit of the hydraulic power plant. Simulation results are in qualitative and quantitative agreement with experiment. The influence of key physical and numerical parameters like discharge, cavitation number, penstock length, time step, and vapor density on simulation results was studied.     

并联换热系统中冷媒分配的优化分析

为减小并联换热系统的质量,本文在一定的简化和假设之上,建立了其流动与传热的物理和数学模型;并以系统总换热面积最小为优化目标,通过对分配系数的变量转换,提出了一种可准确求解最佳分配系数的方法,并对计算结果进行了讨论,发现分配系数的结果与势容耗散最大基本一致.根据计算结果.本文给出了支路较少时分配系数与换热支路效能之间的近似关联式.     

Setting up an experimental apparatus for the study of multimodal acoustic propagation with turbulent mean flow

An experiment has been set up to study multimodal acoustic propagation inside a cylindrical duct in presence of a turbulent mean flow. This paper describes the preliminary work which has been found necessary for assembling the experiment together with first measurement results. In order to set up this experimental facility, a high level acoustic source was developed to generate higher propagating modes in the presence of mean flow. A microphonic antenna was designed for detecting the propagating modes. LDV measurements were performed and synchronous detection was used to extract both the mean flow and the acoustic components of the particle velocity. Results of aeraulic measurements are presented. Then, results of acoustic velocity measurements are compared to results obtained from the microphonic antenna.     

库特（Couette）剪切流准确解的一般形式

 从N-S方程出发,得到了轴对称异型断面管纯剪切流动速度分布的一般解,进而推出了纯剪切流动有限宽度矩形断面管的速度分布和流量计算公式,证明了库特剪切流是有限宽度矩形断面管当宽度趋向无穷大时的一种特例。并对库特剪切流流量的计算误差进行了分析,给出了该公式的适用范围,同时对有限宽度矩形断面管剪切流公式进行了曲线拟合,得到了便于工程使用的流量计算公式。