硐室岩壁过渡型破坏模式及最大线应变理论分析研究

地下硐室所在的岩体应力条件复杂,破坏模式随着与开挖面距离的不同发生转变,开挖所引起的原位脆性岩体应力集中会导致平行于自由面的局部损伤演化,称为表面不稳定性。而在深层条件下,低强度硐室岩壁的表面不稳定性及过渡型破坏模式很常见。针对目前实验室中圆柱形试样在单轴压缩试验中试样受力不符合岩壁单元实际应力状态的局限性,研发一款可模拟硐室岩壁过渡式破坏的试验测试仪。对长方体砂岩、花岗岩试样进行单临空面双向应力加载试验,分析岩石试样的裂纹发展、应力应变规律和破坏模式过渡转化。基于最大线应变理论及胡克定律提出最大线应变强度分析公式,建立基于最大线应变理论的岩壁表面不稳定性破坏的试验测试和分析方法,并且同Mohr-Coulomb准则及Hoek-Brown强度理论进行比较,通过试验数据验证最大线应变理论解释硐室岩壁过渡型破坏模式的适用性。

新型磁性液体性能研究装置设计

针对磁性液体在太空微重力环境下的表面不稳定性问题,基于磁性液体表面不稳定性与其磁响应特性的关系,运用OPC(OLE for Process Control)通信技术设计出一种新型磁性液体性能研究装置。研究装置由硬件和软件两部分组成,硬件包括计算机、控制面板、可编程逻辑控制器、电压调节模块和电磁铁等,软件部分主要采用OPC实现MATLAB与S7-200PLC的通信,可通过三种模式调节磁场来研究磁性液体的表面不稳定性,装置运行稳定,实现对磁性液体表面不稳定现象的控制及动态展示。

环下润滑结构中非圆柱液流在横向气流中脱落现象分析

为分析靠圆柱孔一侧射出的弓形截面非圆柱液流在横向气流中的脱落现象,使用CLSVOF(Couple Level Set VOF)多相流模型与大涡模拟(LES)模型相结合的方法,对非圆柱液流的脱落过程进行数值模拟。结果表明:非圆柱液流在横向气流中的脱落现象是由迎风面上气液密度差产生的Rayleigh-Taylor(R-T)不稳定性和液流边缘气液速度差产生的Kelvin-Helmholtz(K-H)不稳定性共同形成的表面波引起的,同时液流边缘外侧产生的连续漩涡也促进了液流的脱落;横向气流速度增加时,由于表面波增强液流的脱落量增大,横向气流方向改变时由于迎风面上的表面波现象减弱脱落量降低,说明了迎风面上形成的不稳定性表面波是引起液流脱落的主要因素。

Surface Tension Effect on Harmonics of Rayleigh-Taylor Instability

Using the method of the parameter expansion up to the third order, explicitly investigates surface tension effect on harmonics at weakly nonlinear stage in Rayleigh-Taylor instability （RTI） for arbitrary Atwood numbers and compares the results with those of classical RTI within the framework of the third-order weakly nonlinear theory. It is found that surface tension strongly reduces the linear growth rate of time, resulting in mild growth of the amplitude of the fundamental mode, and changes amplitudes of the second and third har- monics, as is expressed as a tension factor coupling in amplitudes of the harmonics. On the one hand, surface tension can either decrease or increase the space amplitude; on the other hand, surface tension can also change their phases for some conditions which are explicitly determined.

State of Pepsin and Acidic Protease in Solid Phase System and the Factors Increasing Their Destabilization

The adsorption state and catalytic properties of pepsin and acidic protease from microorganisms Asp. awamori and Asp. oryzae were studied in solid phase system （in presence of sorsilen, DEAE- and CM-cellulose）. According to the results, adsorption capacity and catalytic activity of enzymes depend on the physical nature of surface groups of the solid phase. Changing the stability of enzymes in the system with solid phase is observed even the adsorption bond is less stable （in the case of DEAE- and CM-cellulose in acidic media）. Injection to the medium ethanol, surfactants, sodium chloride and changing the temperature of the incubation medium could prevent the negative effects of the solid phases. When sorsilen is used as solid phase, pepsin and acidic protease from Asp. awamori suffer from high surface inactivation. Various surfactants influence adsorption state of enzymes differently. Non-ionic surfactants （Triton X-100） prevent adsorption and restore catalytic properties of enzymes.

脉冲激光冲击液滴变形和破裂的数值仿真

通过建立激光与液滴相互作用的物理模型,采用数值仿真研究了激光冲击液滴形成的速度场对液滴变形和流动的影响规律。使用流体体积法,结合层流模型,确定了变形的主要特征和流动的精确细节。结果表明,液滴变形过程和破裂时间与已报道的实验结果有很好的一致性。同时,利用Rayleigh--Taylor不稳定性分析,确定了液滴形变、破裂时间与韦伯数的依赖关系。当韦伯数低于110.7时,液滴向前推进,不会发生整体破碎;韦伯数越高,液滴形变越剧烈,且液滴破裂的碎片越小。另外,液滴破碎后,由于涡量的作用,细小液滴出现自旋、融合、破裂等有趣的现象。

双油路离心喷嘴雾化特性的半经验预测方法

为了掌握主、副油路相互干涉的机制,进而获得双油路离心喷嘴雾化特性的预测工具,开展了双油路离心喷嘴的理论和试验验证研究,研究中所涉及的供油压差范围为0.05~3MPa。理论推导了双油路离心喷嘴液膜破碎长度和索太尔平均直径(SMD)的半经验预测公式,并使用了3个不同结构的双油路离心喷嘴进行了试验验证。结果表明:双油路离心喷嘴破碎长度和SMD的预测精度达到±20%。这些半经验关系式可以作为双油路离心喷嘴设计阶段的预测工具和仿真边界条件。

Transformation optics applied to van der Waals interactions

The van der Waals force originates from the electromagnetic interaction between quantum fluctuationinduced charges. It is a ubiquitous but subtle force which plays an important role and has a wide range of applications in surface related phenomena like adhesion, friction,and colloidal stability. Calculating the van der Waals force between closely spaced metallic nanoparticles is very challenging due to the strong concentration of electromagnetic fields at the nanometric gap. Especially, at such a small length scale, the macroscopic description of the dielectric properties no longer suffices. The diffuse nonlocal nature of the induced surface electrons which are smeared out near the boundary has to be considered. Here,we review the recent progress on using three-dimensional transformation optics to study the van der Waals forces between closely spaced nanostructures. Through mapping a seemingly asymmetric system to a more symmetric counterpart, transformation optics enables us to look into the behavior of van der Waals forces at extreme length scales,where the effect of nonlocality is found to dramatically weaken the van der Waals interactions.