深部块系岩体摆型波现象的研究进展

深部岩体具有独特的自应力块系等级构造特性, 摆型波($\mu$波)现象是深部块系岩体特有的动力特征科学现象之一,集中反映了深部块系岩体非协调、非连续的动力学特性.摆型波是一种不同于传统纵波和横波的新型非线性弹性低频低速变位波,可以直接引发深部岩体岩爆和冲击地压等地质灾害,且无法用经典连续介质力学圆满解释.本文介绍了国内外对摆型波现象的实验和理论研究进展,归纳出摆型波的主要特征参数及其变化规律,并指出该领域的重点研究方向.      

动静组合加载作用下花岗岩破碎的分形特征

在分离式霍普金森压杆实验装置上进行了花岗岩破坏的动静组合加载实验.通过对受载后岩样破碎块度进行筛分统计,得到了该加载条件下岩石破碎的粒度分布.在此基础上,通过理论计算公式,进一步得到了相应的破碎分形维数,分别探讨了静载荷和冲击载荷对分维数的影响.结果表明,动静组合加载作用下花岗岩破碎分维值在2.0～2.8之间;相同静载不同动载下,花岗岩的破碎分维值与试样的应变率有关,随应变率增大而增大;而在相同冲击动载下,静载荷变化对分形维数的影响不大.     

坝基岩体块度特征研究

岩体块度特征是岩体完整性评价的重要指标, 通常用岩石质量指标RQD来表征。但是RQD是有不足之处的, 岩体基本块度的概率分布、块度百分比、RQDt、块度指数RBI等参数是描述岩体块度特征的重要补充, 它们更全面地、更深入地表征了岩体的完整性, 丰富了岩体质量评价的定量指标。本文以金沙江下游溪洛渡水电站工程坝基岩体块度调查统计资料为基础, 对岩体基本块度的概率分布、块度百分比、RQDt、块度指数RBI等岩体块度特征进行了深入研究。     

有限厚块石砌体钢筋混凝土结构板抗贯穿性能的实验研究

用花岗岩和混凝土制备出了花岗岩板、钢丝网混凝土板、花岗岩与钢丝网混凝土组合板、花岗岩块石砌体钢筋混凝土结构板4种类型的有限厚靶板。采用口径为30 mm的火炮作为发射装置,利用形状相同、材料强度不同的2种弹体对上述靶板进行了侵彻贯穿实验,比较了各类靶板抗侵彻贯穿破坏现象。结果表明,设计良好的块石砌体钢筋混凝土结构板具有优良的抗贯穿性能,且其抗贯穿性能与块石粒径、块石强度、块石砌筑方式、粘结强度和钢筋混凝土结构形式密切相关。     

"实验","试验"二词莫混用

近来,在一些刊物,文章,报告中常见到"实验"与"试验"二词混用的现象。诸如"实验力学"在某刊物上写成"试验力学"、做"材料力学实验"说成或写成"做材料力学试验"等。实际上实验与试验二词是有区别的。     

"手机吊冰箱"揭密

近期(2010年11月中旬),我们用一部诺基亚N8手机提供的动力吊起了重达60kg的冰箱.这个视频在网上迅速蹿红,无数网友在看过之后大呼"不可思议!",但也有网友质疑"实验太假了"、"不可能做到",并由此引发了各路网友的猜想和揭秘.     

编写有微视频力学教材的过程和体会

由高等教育出版社于2015年出版的《工程力学的应用、演示和实验》是一本"新形态"教材."新形态"是指纸质教材与数字课程一体化,书中有同类教材所没有的新概念、新技术与装置、新实例,而且给不易用文字表述或因篇幅所限无法纳入书本的重要内容,配置二维码,让读者可以用智能手机"扫一扫"观看基础力学知识在重大工程、高端产品中应用的微视频,使知识在学习过程中看得见、又摸得着,让学生在体会到基础力学知识非常有用的同时也能感受到创新就在身边等.     

综放顶煤爆破能量的分形研究

基于综放开采预爆破弱化坚硬顶工艺,利用分形理论建立岩石断耗能量与块度分维值之间的理论关系,推导出岩石爆破块度分数维与炸药单耗之间关系,进行了室内相似材料模型爆破实验,验证了上述理论关系,利用爆破岩石表面裂隙分布的分形维数值作了衡量指标,优化爆破孔网参数。     

块谱特征与疲劳裂纹随机扩展

目前的疲劳裂纹随机扩展模型大多建立在损伤逐步累积的基础上，其数学描述繁琐复杂，计算用时较多。本文较为深入地研究了载荷分散性对裂纹随机扩展的影响，定义了块谱强度Ｓｅｑ和形状因子α，并用这些特征去描述载荷分散性对裂纹随机扩展的影响，结果表明裂纹随机扩展的均值可以用块谱强度Ｓｅｑ恰当地描述，而块谱的形状因子α可以很好地反映裂纹随机扩展的方差，因此通过块谱的特征迅速获取裂纹随机扩展的参数是可行的。     

锯切花岗石过程中金刚石节块磨损特征及影响因素分析

在已有的节块磨损规律的基础上，对锯切花岗石过程中的金刚石及其固位载体－粘合剂的磨损规律进行了研究。通过实验，跟踪观察了不同金刚石节块在各种加工条件下的磨损状态。结果表明；金刚石的工作状态与节块的使用性能有良好的对应关系，金刚石的微破碎和完善晶型比例越高节块耐磨性越好；宏观破碎和脱落比例越高节块耐磨性越差。金刚石的粒度，含量，品级，粘合剂和金刚石的匹配以及锯切用量组合等均明显影响锯切效果。     

三维Euler方程的分区和并行计算

三维全机绕流区域分解成多块子区域,多块区域之间采用迎风型通量守恒内边界耦合条件,分区计算总体区域,形成总体耦合流场的分区数值解。利用PVM并行环境,采用纯结点并行计算编程方式和“先进先出”的同步控制等待机制,对三维复杂流动跨音速流场相应分区实现了多区域并行计算。分析了影响并行效率的主要因素,将并行计算结果与串行计算结果和实验结果作了比较,讨论了多种区域分解数目的并行计算效率。在负载平衡程度较好时,可得到较高的并行效率。     

Propagation of spherical and cylindrical blast waves in a nonhomogeneous atmosphere with counterpressure taken into account

We present an approximate method for calculating the propagation of a weak spherical or cylindrical shock wave (with counterpressure taken into account) into a nonhomogeneous exponential atmosphere. In the case of a cylindrical wave with an arbitrary orientation of the cylinder axis the three-dimensional problem is reduced to a two-dimensional one upon introducing the principle of planar sections, i.e., motions of the gas along the cylinder axis are neglected. By means of a parametrization with respect to the positional angle the two-dimensional problem is reduced to a one-dimensional one. To solve the one-dimensional problem, we use the method of parallel layers: the atmosphere is partitioned into a number of parallel layers of small thickness in each of which the atmosphere may be considered to be homogeneous, and the passage of the wave through a boundary of the layers may be regarded as a passage across the boundary separating two media.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 84–90, May–June, 1972.The author thanks L. V. Ovsyannikov, V. P. Korobeinikov, L. A. Chudov, and Kh. S. Kestenboim for a valuable discussion of the problem.     

拉氏反变换的数值并行算法及其在弹性动力学边界元法中的应用

本文讨论了快速拉氏反变换的数值并行算法，并将其应用于瞬态弹性动力学的边界元法。为了本文提出的并行算法的优越性，还给出了串行算法，最后将串行和并行计算结果与解析解进行了比较，说明本文方法的正确性和有效性。对拉氏反变换的数值并行算法及其应用于瞬态弹性动力学边界元法的优越性进行了研究。从计算时间可以看出，并行计算的时间比串行计算时间可大幅度减少，说明了本文方法的优越性。     

DNS and scaling laws from new symmetry groups of ZPG turbulent boundary layer flow

The Lie group, or symmetry approach, developed by Oberlack (see e.g. Oberlack [26] and references therein) is used to derive new scaling laws for various quantities of a zero pressure gradient turbulent boundary layer flow. The approach unifies and extends the work done by Oberlack for the mean velocity of stationary parallel turbulent shear flows. From the two-point correlation (TPC) equations the knowledge of the symmetries allows us to derive a variety of invariant solutions (scaling laws) for turbulent flows, one of which is the new exponential mean velocity profile that is found in the mid-wake region of flat-plate boundary layers. Further, a third scaling group was found in the TPC equations for the one-dimensional turbulent boundary layer. This is in contrast to the Navier–Stokes and Euler equations, which have one and two scaling groups, respectively. The present focus is on the exponential law in the outer region of turbulent boundary layer corresponding new scaling laws for one- and two-point correlation functions. A direct numerical simulation (DNS) of a flat plate turbulent boundary layer with zero pressure gradient was performed at two different Reynolds numbers Re=750,2240. The Navier–Stokes equations were numerically solved using a spectral method with up to 140 million grid points. The results of the numerical simulations are compared with the new scaling laws. TPC functions are presented. The numerical simulation shows good agreement with the theoretical results, however only for a limited range of applicability. PACS 02.20.-a, 47.11.+j, 47.27.Nz, 47.27.Eq     

Asymptotic theory of the turbulent boundary layer as a problem of singular perturbations

We consider an asymptotic theory of the turbulent boundary layer [1,2]. In this paper we make an attempt to further develop the mathematical aspects of this theory. We demonstrate the features of this theory by applying it to a problem which is close to the so-called equilibrium turbulent boundary layer with a pressure gradient and blowing.Notation x, y coordinates, parallel and perpendicular to the wall - u velocity component in the x direction - p, ',v pressure, density, and kinematic viscosity coefficient - l' scale of turbulence - tangential stress - u speed at the outer edge of the boundary layer - thickness of the boundary layer - * displacement thickness - ** momentum loss thickness - Cf coefficient of friction - R Reynolds number Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 86–95, September–October, 1971.The author thanks S. S. Kutateladze, A. I. Leont'ev, and G. V. Aronovich for their interest in this effort.     

An analysis on the flow resistance in the entrance region of diffuse laminar flow between two parallel spherical surfaces

In this paper, V.V. Golubef method is first extended to the diffuse laminar flow between two parallel spherical surfaces. With the boundary layer motion equation in spherical coordinates, we derive the momentum integral equation together with the energy integral equation for the laminar boundary layer of the entrance region between two parallel spherical surfaces. And then by applying Picards gradually approaching method for the momentum integral equation, we get the approximate expression which the entrance region length varies with the thickness of boundary layer. In the end every coefficient of entrace region effect is analyzed and calculated. Projects Suported by the Science Fund of the Chinese Academy of Sciences.     

RMS spanwise vorticity measurements in a turbulent boundary layer

Turbulent boundary layer measurements of the rms spanwise vorticity t_z with a four hot-wire probe are in reasonable agreement with direct numerical simulations and other published measurements at comparable Reynolds numbers. It is shown that a reasonable accurate approximation for _z can be obtained with only two parallel hot wires.     

Semi-similar solutions to the three-dimensional laminar boundary layer

The theory of semi-similar solutions is developed for and applied to the problem of three-dimensional laminar boundary layer flow. A number of specific examples are calculated. Particular attention is given to certain flows in which separation is approached and the nature of three-dimensional laminar boundary layer separation is inferred from the behavior of these solutions close to separation. Two types of separation are observed: singular separation characterized by the vanishing of the total shear along the line of separation and ordinary separation characterized by limiting streamlines which become parallel to the line of separation.     

On the pulsating flow superposed on the steady laminar motion of a second order viscous liquid between two parallel plates

Summary In this note, we study the pulsating flow superposed on the steady laminar motion of a second order viscous liquid between two parallel plates. The principal flow characters such as the mean velocity, skin friction, mean rate of work done by the internal friction, the coefficient of excess of work have been examined. The results have been obtained in terms of a non-dimensional non-Newtonian parameter . The flow for large frequencies has a boundary layer character. The results for the flow with a single Fourier component are illustrated and discussed in detail.     

The new solution for the axially symmetrical laminar boundary layer equations between two parallel sherical surfaces

The transformations, which are similar to Mangler’s transformations, are given in this paper. They change the entrance region flow of axially symmetrical laminar boundary layer between two parallel spherical surfaces into the flow of two-dimensional boundary layer, and simplify the problems. The simplified equations can be solved by the two-dimensional boundary layer theory and numerical methods. Therefore, a new way is opened up to solve the diffusive laminar flow in the entrance region between two parallel spherical surfaces.