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1.
胡冉  钟翰贤  陈益峰 《力学学报》2023,55(2):543-553
岩体裂隙的有效渗透率是描述岩体非饱和或多相渗流的关键参数,而裂隙开度是影响有效渗透率的重要因素.通过自主研发的粗糙裂隙多相渗流可视化实验平台,针对天然岩体裂隙复制而成的裂隙模型开展变开度条件下的多相渗流可视化实验,研究开度变化对多相渗流流动结构以及有效渗透率的影响.研究表明:非湿润相流体运动通道,在低流量比条件下呈现出气泡流流动结构,而在高流量比条件下呈现较为稳定的通道流流动结构.随着开度的增加,非湿润相流动通道的分支变少、等效宽度增加,两相流体的有效渗透率均增大,流动结构趋于稳定.可视化结果还阐明了柱塞流流动结构下,两相流体交替占据裂隙空间的竞争机制:当非湿润相流体通道由连续转变为不连续时,裂隙进出口压差显著增加;反之,当该通道由不连续转变为连续时,压差显著减小.最后,基于分形理论以及渗透率统计建模方法,建立了考虑开度效应的岩体裂隙多相渗流有效渗透率理论模型,并通过实验测定的有效渗透率数据验证了该模型的正确性与有效性.  相似文献   

2.
张勇 《力学季刊》2006,27(2):233-239
选择低压渗流法制备泡沫铝的工艺过程为模拟对象,根据相似原理,在有机玻璃模型中用液体作为流体,对铝液在多孔介质中的低压向上渗流过程进行了模拟试验研究。试验表明,在低压渗流制备泡沫铝的过程中,原型的渗流液面是以平面沿铅垂方向向上推进的,位移和时间的关系满足四次方根规律;渗流过程中某一时间t的雷诺数、阻力系数和沿程损失可用相应的公式计算;渗流过程中,外加渗流气压的最佳值为0.04kPa,高于该值的外加渗流气压对于渗流时间的影响不大。实验还将模拟实验得到的结果与原型进行了比较,模型的充填时间与原型的充填时间一致性良好,证实了本实验结果的正确性。  相似文献   

3.
首先对夹芯泡沫材料的力学性能、动态响应和性能特性进行了简单探讨,然后通过钢筋混凝土、泡沫夹层、钢板混凝土复合结构的抗爆实验,对夹芯泡沫材料的主要特点及其在复合结构中的作用机理进行了研究.结果表明:泡沫夹层对爆炸冲击波具有很好的衰减作用,且这种衰减作用随输入压力的增大而增大.这种特性可使爆炸产生的相对集中的局部压力转化为...  相似文献   

4.
泡沫铝填充薄壁圆管的三点弯曲实验的数值模拟   总被引:2,自引:0,他引:2  
泡沫金属填充薄壁结构的应用日趋广泛,建立合理的数值计算模型对结构设计和工程应用非常重要.该文通过对泡沫铝填充薄壁铝合金圆管的三点弯曲实验的数值模拟,研究了它的力学行为.采用ABAQUS软件,建立了空管和泡沫铝全填充管的有限元模型,并对这两种结构在三点弯曲下的力学行为进行了数值模拟,所得结果与实验结果符合得较好.通过数值模拟分析了结构的承载机理和不同压头直径对结构承载能力的影响.此外,还研究了泡沫铝部分填充圆管的三点弯曲行为,分析了不同填充长度对结构承载能力的影响.  相似文献   

5.
泡沫铝夹芯板动态抗侵彻性能的实验研究   总被引:1,自引:0,他引:1  
本文研究了铝板-泡沫铝夹芯板的抗侵彻性能.设计了铝板-泡沫铝夹芯复合材料板,采用SHPB设备,测试了不同子弹冲击速度下纯铝板和泡沫铝夹芯板的动态响应,并研究了其破坏形态.结果表明应力波在纯铝板中的传播与在铝板-泡沫铝夹芯板中的传播有很大差异,由于泡沫铝的粘性效应使应力波在传播过程中有明显的波幅衰减现象.实验结果表明,铝板-泡沫铝夹芯板相对于纯铝板具有不同的破坏形态.由于铝板-泡沫铝夹芯板的特殊结构和性能,使其具有良好的抗侵彻性能.  相似文献   

6.
岩体中饱和渗流应力耦合模型研究进展   总被引:8,自引:1,他引:7  
刘仲秋  章青 《力学进展》2008,38(5):585-600
在大坝渗流与控制、各种水工隧洞和交通隧道以及地下各种洞室开挖、采矿工程与油藏开采中的水力劈裂、 岩坡和坝基的稳定性研究等领域中经常会遇到岩体的饱和渗流应力耦合问题.本文对这些领域中的渗流应力耦合问题分为6种力学模型: 等效连续介质模型、 裂隙网络模型、 双重介质模型、 断裂力学模型、 连续损伤力学模型和统计模型.前3种主要从经典的黏弹塑性本构着手考虑, 着重对渗流场的处理, 后3种则是从考虑岩体在耦合作用下发生损伤破裂行为方面切入, 着重于岩体结构内部发生质的改变带来的更加复杂的耦合效应.对这些模型进行了详细的介绍, 指出了这些模型的优缺点与适用范围, 给出了一些有代表性的研究成果, 并对该研究领域中未来的研究方向进行了展望.  相似文献   

7.
湿润性对孔隙介质两相渗流驱替效率的影响   总被引:1,自引:0,他引:1  
魏鹳举  胡冉  廖震  陈益峰 《力学学报》2021,53(4):1008-1017
孔隙介质中多相渗流的驱替效率对二氧化碳封存效率和石油采收率具有决定性影响, 是实际工程调控中的一个关键指标. 湿润性是影响多相渗流驱替模式及其效率的一个重要因素. 本文通过微流体模型-显微镜-高速相机可视化实验平台, 对基于真实砂岩孔隙结构的微流体模型进行湿润性修饰, 开展了5种流量和2种湿润性的两相驱替可视化实验, 研究了湿润性对砂岩孔隙结构中两相渗流驱替模式及其效率的重要影响. 实验结果表明: 随着流速的增大, 两相渗流驱替模式由毛细指流向稳定流发生转变; 在低流速条件下, 由于毛细力的主导效应, 亲水性介质中指进的宽度和被驱替流体团簇的数目均小于疏水性介质, 而被驱替流体团簇的最大半径、平均半径和方差均大于疏水性介质. 实验结果还证实了亲水性介质中由于单支优势通道和"绕流"现象的发生, 驱替效率显著小于疏水性介质. 最后, 通过考虑接触角效应对毛细管数进行修正, 建立了考虑湿润性影响的驱替效率和毛细管数之间的统一关系式, 为不同湿润性条件下驱替效率的预测提供了一种潜在方法.   相似文献   

8.
张勇 《力学与实践》2005,27(6):64-67
根据相似原理对黏度不同的液态铝在多孔介质中的低压向上渗流过程进行了模拟试验研究。试验表明,渗流液面以平面沿铅垂方向推进,并满足次方根规律;某一时刻t的雷诺数、阻力系数和沿程损失可用相应的公式计算;液态铝的黏度在一定范围(5%)的变化对渗流速度的影响不大,模拟与原型的充填时间有良好的一致性。  相似文献   

9.
金波  胡明  方棋洪 《力学学报》2022,54(5):1322-1330
深埋海底隧道经常处于高水压工况,地下水渗流对隧道围岩及衬砌结构安全性有较大影响.本文提出了一种含衬砌深埋海底隧道力学模型,研究了海底隧道服役阶段地下水渗流对围岩及衬砌结构稳定性的影响机理.应用保角映射方法将包含海水与围岩弹性区的半无限域映射成圆环域,根据渗流边界条件建立了各界面间极坐标下的渗流方程,得到了海底隧道渗流场解析解.将渗流场以体积力形式作用到应力场中,根据应力边界条件建立了应力平衡方程,基于考虑中间主应力影响的Drucker-Prager (D-P)准则,得到了渗流效应影响下围岩与衬砌结构的弹塑性解析解.以深圳妈湾跨海通道工程为例,将解析解与有限元数值解进行了对比,验证了本文理论解的准确性,研究了渗流效应对隧道围岩与衬砌结构应力场的影响规律.最后,分析了海水深度与内水水头对塑性区半径的影响.研究结果表明:渗流效应对围岩与衬砌结构中的环向应力影响显著,径向应力随ρ增大呈非线性增长;随着海水加深,隧道承受水压不断加大,围岩塑性区范围显著增大;增加内水水头可以有效限制围岩塑性区发展,初始阶段限制效果明显,后续增加内水水头限制效果逐渐减弱.  相似文献   

10.
利用实验研究与理论分析相结合的方法研究了泡沫铝填充金属薄壁圆管在准静态侧向压缩下的力学响应.基于能量法,建立了泡沫铝填充圆管和金属薄壁圆管在侧向均匀压缩时的瞬时侧向力、平均侧向力和总吸能的理论公式.对泡沫铝填充管与金属薄壁圆管进行了准静态侧向压缩实验,并且将实验结果与理论公式进行了对比,结果表明理论预测值与实验结果吻合较好.基于建立的理论分析模型,研究了管的几何尺寸以及泡沫铝材料的密度对结构的瞬时侧向力、平均侧向力、总吸能和比吸能的影响.结果表明,在准静态侧向压缩下,泡沫铝填充管的总吸能大于对应的金属薄壁圆管;泡沫铝填充管的侧向压缩力和总吸能随管长度、壁厚和直径的增加而增大;当填充材料泡沫铝密度增大时,填充管的总吸能与侧向压缩力均增加.  相似文献   

11.
采用一修正的十四面体结构模型(Kelvin结构模型)对开孔泡沫金属的弹性性能进行研究,对低密度开孔泡沫材料表现出不可压的特性进行了分析。该模型考虑作用在泡沫筋条上的弯矩、剪力和轴向力,以及轴向力的平衡。修正模型的数值计算结果与实验结果及其他模型的结果进行了对比,结果表明修正模型计算的杨氏模量比原有模型的略有提高,筋条截面为星形的修正模型计算的结果与实验比较符合。在密度等同的条件下,筋条截面惯性矩越大的开孔泡沫材料,其弹性模量也越大,而泊松比则越小。Kelvin结构的开孔泡沫材料的泊松比随相对密度的减小而趋于0.5。  相似文献   

12.
There are still many open questions and problems in both fundamental research and practical applications of foams. Despite the fact that foams have been extensively studied, many aspects of foam physics and chemistry still remain unclear. Experiments on foams performed under microgravity allow studying wet foams, such as those obtained early during the foaming process. On Earth, wet foams evolve too quickly due to gravity drainage and only dry foams can be studied. This paper reviews the foam and foam film studies that we have performed in gravity-free conditions. It highlights the importance of surface rheology as well as of confinement effects in foams and foam films behaviour.  相似文献   

13.
Liquid foam is a dense random packing of gas or liquid bubbles in a small amount of immiscible liquid containing surfactants. The liquid within the Plateau borders, although small in volume, causes considerable difficulties to the investigation of the spatial structure and physical properties of foams, and the situation becomes even more complicated as the fluid flows. To solve these problems, a discrete model of two-dimensional liquid foams on the bubble scale is proposed in this work. The bubble surface is represented with finite number of nodes, and the liquid within Plateau borders is discretized into lattice particles. The gas in bubbles is treated as ideal gas at constant temperatures. This model is tested by choosing an arbitrary shape bubble as the initial condition. This then automatically evolves into a circular shape, which indicates that the surface energy minimum routine is obeyed without calling external controlling conditions. Without inserting liquid particle among the bubble channels, periodic ordered and disordered dry foams are both simulated, and the fine foam structures are developed. Wet foams are also simulated by inserting fluid among bubble channels. The calculated coordination number, as a function of liquid fractions, agrees well with the standard values.  相似文献   

14.
The velocity field in a single Plateau border(PB) of the aluminum foam in the drainage process is studied using a mathematical model for the flow inside a microchannel.We show that the liquid/gas interface mobility characterized by the Newtonian surface viscosity has a substantial effect on the velocity inside the single PB.With the same liquid/gas interfacial mobility and the same radius of the curvature,the maximum velocity inside an exterior PB is about 6~8 times as large as that inside an interior PB.We also find a critical value of the interfacial mobility in the interior PB.For the values greater and less than this critical value,the effects of the film thickness on the velocity in the PB show opposite tendencies.Based on the multiscale methodology,with the coupling between the microscale and the macroscale and the results obtained from the microscopical model,a simplified macroscopical drainage model is presented for the aluminum foams.The comparisons among the computational results obtained from the present model,the experimental data quoted in the literature,and the results of the classical drainage equation show a reasonable agreement.The computational results reveal that the liquid holdup of the foams is strongly dependent on the value of the mobility and the bubble radius.  相似文献   

15.
参照层状密度梯度泡沫模型实现方法,利用3D-Voronoi技术设计了新型径向密度梯度泡沫模型,并用有限元软件,对它在不同冲击载荷下的力学行为进行数值模拟。研究冲击速度、密度梯度和平均相对密度对金属泡沫冲击端、支撑端应力和能量吸收能力的影响,发现:径向正梯度泡沫与层状正、负梯度泡沫相比,其两端的应力值均较小,可同时保护冲击端、支撑端物体;径向负梯度泡沫两端应力变化幅度较小,能够保证物体受力稳定;几种泡沫金属的能量吸收能力在不同冲击速度下发生交替变化。对于径向梯度泡沫,能量吸收能力对密度梯度大小不敏感,对梯度方向敏感,径向负梯度泡沫的能量吸收能力始终大于径向正梯度泡沫;平均相对密度越大,径向正、负梯度泡沫两端应力越大、吸能效果越好。  相似文献   

16.
This study is concerned with the understanding and modeling of the compressive response of open cell foams. The response starts with a nearly linear elastic regime which terminates into a limit load followed by an extensive load plateau. The plateau, which is responsible for the excellent energy absorption capacity of foams, is followed by a second stiff branch. Results from polyester urethane open cell foams with relative densities of about 0.025 are used to illustrate this behavior using experiments coupled with several levels of modeling. The experiments include characterization of the microstructure and the properties of the base material and measurement of the compressive response of the foams of various cell sizes.A sequence of models for predicting the complete response of such foam is developed. The foam is idealized to be periodic using the space-filling Kelvin cell assigned the major geometric characteristics found in the foams tested. The cells are elongated in the rise direction, the ligaments are assumed to be straight, to have Plateau border cross-sections and nonuniform cross-sectional area distribution. The ligaments are modeled as shear-deformable extensional beams and the base material is assumed to be linearly elastic. Prediction of the initial elastic moduli are addressed in Part I. Closed form expressions for the material constants are presented as well as results using a FE model of the characteristic cell. Comparison between measurements and predictions is very favorable. The paper finishes with results from a limited parametric study of the elastic moduli. The results demonstrate that inclusion of the geometric complexities mentioned above is essential for successful prediction of the moduli of such foams. The nonlinear parts of the response including the foam crushing behavior are addressed in Part II.  相似文献   

17.
Foam Drainage in Porous Media   总被引:1,自引:0,他引:1  
In this paper we present a simple analysis of liquid drainage in foams confined in porous media. First we derive the equation for the evolution of the liquid saturation using general mass and momentum conservation arguments and phenomenological relations between the transport parameters and liquid saturation. We find an unusual foam drainage equation in which the determinant terms express the competition between the external force field, represented here by the gravity field, and capillary pressure gradient. We present analytical solutions of the drainage equation in three cases: (a) gravity forces are dominant over capillary forces, (b) capillary forces are dominant over gravity forces, and (c) capillary and gravity forces are comparable in order of magnitude.  相似文献   

18.
Propagation of sound and weak shock waves in gas-liquid foams is investigated theoretically and experimentally. An original physical model is developed to describe the evolution of small perturbations in a foam of polyhedral structure. The model developed takes into account both peculiarities of interface heat transfer in foam and liquid motion through the system of Plateau-Gibbs borders which results in the appearance of an additional hydrodynamic dissipative force. The Rayleigh equation analog, which takes into account the latter phenomenon, is obtained. Structure and dynamics of weak shock waves are investigated. A vertical shock tube was constructed and used to measure the parameters of weak shock wave propagation in gas-liquid foams of polyhedral structure. Spectral analysis of the data obtained shows that there are weak dispersion and strong dissipation of the initial signal. Comparison of the evolution of experimental and theoretical profiles permits to conclude that the suggested model allows to describe the peculiarities of acoustical perturbations in gas-liquid foam more precisely than it follows from the standard models. Received 15 September 1993 / Accepted 27 December 1993  相似文献   

19.
A robust understanding and modeling of the yield behavior in solid foams under complex stress states is essential to design and analysis of optimal structures using these lightweight materials. In pursuit of this objective a new custom-built Multi-Axial Testing Apparatus (MATA) is developed to probe the yield surface of transversely isotropic Divinycell H-100 PVC foam under a multitude of uniaxial, biaxial and triaxial strain paths. Experimental yield data produced constitutes the most comprehensive data set ever produced for any foam as it covers the entire spectrum of stress paths from hydrostatic compression to hydrostatic tension. Experimental results reveal that yielding in foams exhibits not only a quadratic pressure dependence, which is widely recognized in literature, but also a significant linear pressure dependence, which has been largely overlooked in previous studies. A new energy-based yield criterion developed for transversely isotropic foams is also validated using the experimental yield data.  相似文献   

20.
Lattice gas simulations of two-dimensional liquid foams   总被引:2,自引:0,他引:2  
Liquid foam is a dense random packing of gas bubbles in a small amount of immiscible liquid containing surfactants. The liquid within the Plateau borders, although small in volume, causes considerable difficulties to investigations of the physical properties of foams, and the situation becomes even more complicated if the flow of the liquid through the foam is considered too. Here we propose a fresh approach to tackling these issues by introducing a discrete two-dimensional hybrid lattice gas model of liquid foams. While lattice gas models have been used to model two-phase liquids in the past, their application to the study of liquid foams is novel and proves promising. We represent bubble surfaces by a finite number of nodes, and model the surrounding liquid as a lattice gas (with a finite number of liquid particles). The gas in the bubbles is treated as an ideal gas at constant temperature. The model is tested by choosing an arbitrarily shaped bubble that evolves into a circular shape in agreement with Laplaces law. The model is then employed to simulate periodic ordered and disordered dry and wet foams. Since our model is specifically designed to handle wet foams up to a critical liquid fraction of 0.16 (void fraction of random packing of disks), we are able to compute the variation in coordination number (average number of neighbours of a bubble) over the whole range of liquid fractions, and we find it to be a linear function of the shear modulus.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal, 11–13 September 2003.  相似文献   

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