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The Asperities Density and Height Distribution Combined Effect on Rough Elastic Bodies Contact Characteristics 尖晶石密度和高度分布对粗糙弹性体接触特性的综合影响
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602595
I. G. Goryacheva, A. A. Yakovenko

Abstract

The combined effect of the asperities density and their height distribution in contact of the rough rigid and smooth elastic half-spaces is investigated, taking into account the mutual influence of contact spots and statistical nature of the height distribution of asperities. The normal and exponential types of the height distribution of asperities with various densities and the dispersions of their height distribution are used in calculations of the contact characteristics at macroscale (the approach of contacting bodies and the relative contact area under given normal pressure) and the microscale (real contact pressure distributions). The obtained results are compared with ones calculated from the simplified models neglecting the mutual influence of individual contact spots. It is shown that neglecting the mutual influence of asperities in contact, which is made in many models of the discrete contact, can lead to significant errors in determining the contact characteristics on both the macro- and microscales. Based on the asymptotic analysis the analytical expressions for the approach of the contacting bodies and the relative contact area were derived and used for analysis of the microgeometry parameters effects on the rigid rough half-space penetration into the elastic half-space at high nominal pressures.

摘要 研究了粗糙刚性半空间和光滑弹性半空间接触中的非主流密度及其高度分布的综合影响,同时考虑了接触点的相互影响和非主流高度分布的统计性质。在计算宏观(给定法向压力下接触体的接近和相对接触面积)和微观(实际接触压力分布)的接触特性时,使用了不同密度的尖面高度分布的正态和指数类型及其高度分布的分散性。计算结果与忽略单个接触点相互影响的简化模型计算结果进行了比较。结果表明,许多离散接触模型都忽略了接触面的相互影响,这会导致在确定宏观和微观尺度的接触特性时出现重大误差。在渐近分析的基础上,推导出了接触体接近和相对接触面积的分析表达式,并用于分析微观几何参数对高名义压力下刚性粗糙半空间穿透弹性半空间的影响。
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引用次数: 0
Wave Interaction with Fractured Porous Layer in Porous Medium 多孔介质中波与断裂多孔层的相互作用
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602145
A. A. Gubaidullin, O. Yu. Boldyreva, D. N. Dudko

Abstract

The transmission and reflection of a pulse wave in a porous medium with a layer of a fractured porous medium under normal and oblique incidence is numerically investigated. The study was carried out using a two-velocity model of a porous medium and a three-velocity model of a fractured porous medium. ‘‘Opened pores’’ condition was used on the ‘‘porous medium–fractured porous medium’’ interface. The problem is considered in a two-dimensional formulation. The features of this wave process are revealed.

摘要 对脉冲波在多孔介质中的传输和反射进行了数值研究,多孔介质层中有一层断裂的多孔介质,在正入射和斜入射下。研究使用了多孔介质的双速度模型和断裂多孔介质的三速度模型。在 "多孔介质-断裂多孔介质 "界面上使用了 "开放孔隙 "条件。问题以二维形式进行考虑。揭示了这一波过程的特征。
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引用次数: 0
Effect of a Rigid Cone Inserted in a Tube on Resonant Gas Oscillations 插入管中的刚性锥体对共振气体振荡的影响
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602340
L. R. Shaidullin, S. A. Fadeev

Abstract

Resonant oscillations of gas in a tube with an end in the form of an inverted cone have been investigated. As the height of the inverted cone inserted into the tube increases, a decrease in the resonant frequency and amplitude of gas pressure oscillations is observed. The dispersion of the resonant frequency is due to the viscosity and thermal conductivity of the gas. It is found that tubes with an inverted cone-shaped end are less efficient resonators compared to uniform tubes with a flat closed end. The decrease in the amplitude of gas pressure oscillations is attributed to the increase in the near-wall losses due to the increase in the total sidewall extent.

摘要 研究了末端为倒锥形的管中气体的共振振荡。随着插入管中的倒锥高度的增加,观察到气体压力振荡的共振频率和振幅减小。共振频率的分散是由于气体的粘度和热导率造成的。研究发现,与具有扁平封闭端头的均匀管相比,具有倒锥形端头的管子是效率较低的谐振器。气体压力振荡幅度的减小是由于侧壁总范围的增加导致近壁损失的增加。
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引用次数: 0
Numerical Investigation of the Structure of Fracture Network Impact on Interwell Conductivity 裂缝网络结构对井间导通性影响的数值研究
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602261
D. Yu. Legostaev, S. P. Rodionov

Abstract

We consider two-dimensional single-phase fluid flow of an incompressible fluid in a fractured porous medium, which is located inside a square computational domain. The fractures had a random position and orientation, and the fracture length distribution follows a power law. Fracture networks are simulated using the discrete-fracture model. Calculations were performed for fracture network realizations created by multiple random generations. Fluid flows between opposite boundaries of the computational domain (line source and sink) and between vertical wells (point source and sink) are considered. The influence of the type of source and sink on the percolation probability is determined. The dependence of the flow rate between production and injection wells on the fracture network structure was investigated. The flow between the opposite boundaries of the computational domain is considered. For this case, the numerical dependence of the equivalent permeability of the fractured porous medium on the percolation parameter was approximated by an analytical piecewise function. This approximation was used to estimate fluid flow rates between vertical wells.

摘要 我们考虑了不可压缩流体在断裂多孔介质中的二维单相流。裂缝的位置和方向随机,裂缝长度分布遵循幂律。采用离散断裂模型模拟断裂网络。计算是针对多代随机生成的断裂网络进行的。考虑了计算域相对边界(线状源和汇)之间以及垂直井(点状源和汇)之间的流体流动。确定了源和汇的类型对渗流概率的影响。研究了生产井和注水井之间的流量与裂缝网络结构的关系。考虑了计算域相对边界之间的流动。在这种情况下,裂缝多孔介质的等效渗透率对渗流参数的数值依赖性由一个解析的片断函数近似表示。该近似值用于估算垂直井之间的流体流速。
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引用次数: 0
Theory of Poisson’s Ratio for a Thermoelastic Micropolar Acentric Isotropic Solid 热弹性微极性同心各向同性固体的泊松比理论
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602480
E. V. Murashkin, Y. N. Radayev

Abstract

The present paper deals with the triple weights pseudotensor formulation of multivariant thermoelasticity for acentric isotropic micropolar solids. The fundamental concepts of pseudoinvariant volume/area/arc elements of odd integer weights in three-dimensional spaces are discussed. The developed theory of acentric isotropic micropolar thermoelasticity is formulated in terms of contravariant pseudovector of spinor displacements having positive odd algebraic weight and covariant absolute vector of translational displacements. Three energetic forms (H), (E), and (A) of thermoelasticity potential are proposed. The latter is derived from the irreducible system of algebraic invarinats/pseudoinvariants being actually their linear span with coefficients thus allowing us to introduce the conventional thermoelasticity moduli (shear modulus of elasticity, Poisson’s ratio, characteristic nano/microlength, etc.). For others energetic forms thermoelasticity anisotropic micropolar (E) moduli are determined via (A) moduli and then (H) moduli are found in terms of (A) moduli. The triple weights formulation of multivariant constitutive equations for acentric isotropic thermoelastic solid are obtained and analyzed. A comparison of proposed multivariant constitutive equations elucidates the absolute invariance of Poisson’s ratio, i.e., it insensibility to mirror reflections and prohibition of assigning any algebraic weight to this constitutive scalar.

摘要 本文论述了等向各向同性微极性固体的多变量热弹性的三权重伪张量公式。讨论了三维空间中奇数整数权的伪不变体积/面积/弧元的基本概念。用具有正奇数代数权重的旋转位移的协变伪向量和平移位移的协变绝对向量来表述所发展的同心各向同性微极热弹性理论。提出了热弹性势的三种能量形式 (H)、(E) 和 (A)。后者是从代数不变式/伪不变式的不可还原系统中推导出来的,实际上是它们与系数的线性跨度,因此允许我们引入传统的热弹性模量(剪切弹性模量、泊松比、特征纳米/微米长度等)。对于其他能量形式的热弹性各向异性微波(E)模量是通过(A)模量确定的,然后根据(A)模量找到(H)模量。得到并分析了中心各向同性热弹性固体的多变量构成方程的三重权值公式。通过对所提出的多变量构成方程进行比较,阐明了泊松比的绝对不变性,即泊松比不受镜面反射的影响,并禁止对这一构成标量赋予任何代数权重。
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引用次数: 0
Methodology for Calculating the Parameters of Non-isothermal Filtration Considering the CO $${}_{mathbf{2}}$$ –CH $${}_{mathbf{4}}$$ Replacement in Methane Hydrate 考虑甲烷水合物中 CO $${}_{mathbf{2}}$ -CH $${}_{mathbf{4}}$ 置换的非等温过滤参数计算方法
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602297
N. G. Musakaev, S. L. Borodin, D. S. Belskikh

Abstract

A mathematical model of non-isothermal filtration of methane, carbon dioxide and water is constructed based on the methods and equations of multiphase media mechanics considering the replacement of methane in the gas hydrate with carbon dioxide. The equations of the mathematical model and the methodology for their numerical solution are presented. The numerical solutions for one-dimensional plane-parallel approximation are constructed for the problem of injecting carbon dioxide into a reservoir initially saturated with methane and its hydrate. Those solutions describe the distributions in the reservoir of pressure, temperature, mass concentrations of gas phase components and saturations of methane and carbon dioxide hydrates.

摘要 根据多相介质力学的方法和方程,考虑到用二氧化碳替代天然气水合物中的甲烷,构建了甲烷、二氧化碳和水的非等温过滤数学模型。介绍了数学模型方程及其数值求解方法。针对向初始饱和甲烷及其水合物的储层注入二氧化碳的问题,构建了一维平面平行近似的数值解。这些解描述了储层中的压力、温度、气相成分的质量浓度以及甲烷和二氧化碳水合物的饱和度分布。
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引用次数: 0
Oscillations of Nanofilms in a Fluid 流体中纳米薄膜的振荡
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602212
M. A. Ilgamov

Abstract

Oscillations and waves in a nanofilm in contact with a gaseous medium are considered. It is assumed that the excitation frequencies are in the ultrasonic range. The simplest model is constructed, based on Timoshenko theory of plate bending and on the first approximation of the reaction from the gaseous medium. This takes into account the surface effect caused by the difference in elastic characteristics in the near-surface layer and in the main volume of the material. The derived relations within the Timoshenko model are simplified, which makes it possible to obtain visible results. The contribution of surface effects and reactions from the gaseous medium is assessed. Linear dynamics of a semi-infinite film is studied.

摘要 研究考虑了与气体介质接触的纳米薄膜中的振荡和波。假设激励频率在超声波范围内。根据季莫申科板弯曲理论和气体介质反应的第一近似值,建立了最简单的模型。该模型考虑到了近表面层和材料主体积弹性特性不同所造成的表面效应。简化了季莫申科模型中的推导关系,从而可以获得可见的结果。对表面效应和气体介质反应的贡献进行了评估。研究了半无限薄膜的线性动力学。
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引用次数: 0
The Influence of the Annular Gap Thickness on the Critical Reynolds Number During the Flow of Thermoviscous Liquids 热粘性液体流动过程中环形间隙厚度对临界雷诺数的影响
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602315
A. D. Nizamova, V. N. Kireev, S. F. Urmancheev

Abstract

Issues related to transient regimes of fluid flow in channels with different cross sections are a priority when solving problems of hydrodynamics. Currently, research related to the influence of heat exchange on the stability of fluid flow in processes in which the change in viscosity with temperature cannot be neglected has become particularly relevant. This article examines some features of the loss of stability of a laminar fluid flow with an exponential dependence of viscosity on temperature in an annular channel with a given temperature regime on its walls. For this purpose, the generalized Orr–Sommerfeld equation was derived, which was eventually written in relation to the stream function. A numerical study of the corresponding boundary value problem was carried out using the spectral method based on Chebyshev polynomials. It was shown that taking into account the effect of temperature on the viscosity of the liquid, which implies its non-uniform distribution over the cross section of the channel, leads to a decrease in the critical Reynolds number, which is consistent with the results of previous studies. In particular, as previously noted, for a narrow channel and a small thermoviscosity parameter, the spectrum of eigenvalues is identical to the spectrum for an isothermal flow in a flat channel. A change in the relative channel width and an increase in the thermoviscosity parameter leads to a significant restructuring of the structure of the eigenvalue spectra of the generalized Orr–Sommerfeld equation. As a result of the studies carried out in the presented work, the dependencies of the critical Reynolds number on the exponential factor or, in other words, the thermoviscosity parameter, which characterizes the intensity of the change in viscosity with increasing temperature, and on the parameter determining the ratio of the width of the annular channel to the radius of the inner cylindrical surface were constructed. It has been established that with increasing parameter of the relative channel width, the value of the critical Reynolds number changes non-monotonically, and its minimum value depends on the specific liquid. The latter circumstance can serve as a theoretical justification for carrying out optimization calculations when modeling technological processes. The dependence of the critical Reynolds number on the thermoviscosity parameter has a form close to a decreasing exponential function for all sizes of annular channels.

摘要 在解决流体力学问题时,与不同截面通道中流体流动的瞬态有关的问题是一个重点。目前,在不能忽略粘度随温度变化的过程中,与热交换对流体流动稳定性的影响有关的研究变得尤为重要。本文研究了层流流体在环形通道中失去稳定性的一些特征,该层流流体的粘度与温度呈指数关系,通道壁上有给定的温度机制。为此,推导了广义的奥尔-索默费尔德方程,并最终将其写入流函数。利用基于切比雪夫多项式的频谱法对相应的边界值问题进行了数值研究。结果表明,考虑到温度对液体粘度的影响(这意味着液体粘度在通道横截面上的分布不均匀),临界雷诺数会降低,这与之前的研究结果是一致的。特别是,如前所述,对于狭窄的通道和较小的热粘滞参数,特征值谱与平坦通道中等温流动的谱相同。相对通道宽度的变化和热粘度参数的增加会导致广义 Orr-Sommerfeld 方程特征值谱结构的显著调整。本文研究的结果是,临界雷诺数与指数因子或热粘度参数(表征粘度随温度升高而变化的强度)的关系,以及与决定环形通道宽度与内圆柱面半径之比的参数的关系。结果表明,随着相对通道宽度参数的增加,临界雷诺数的值会发生非单调变化,其最小值取决于特定的液体。后一种情况可以作为技术过程建模时进行优化计算的理论依据。临界雷诺数与热粘滞度参数的关系在所有尺寸的环形水道中都接近于指数递减函数。
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引用次数: 0
Jet Impact During Bubble Collapse Near a Local Bump on a Solid Wall 固体壁上局部凹凸附近气泡坍塌过程中的喷流冲击
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602194
T. S. Guseva

Abstract

The jet impact process during the nonspherical bubble collapse near a local bump on a solid wall has been studied in detail using the CIP-CUP method to solve the Euler equations. Three scenarios were considered, the first of which corresponds to a nearly plane wall compared to the bubble size, and the other two correspond to the bubble-sized local bump. In all cases, the distance from the impact location to the wall and the jet tip diameter are close, the jet velocity is about 100 m/s. The main difference between the considered scenarios is the initial zone of contact of the jet with the opposite bubble side. Namely, it is a single point in the first case, and in the other two cases it is a bowl-shaped area and an annular area with the formation of a tip bubble. The latter two scenarios have been found to result in significantly higher wall pressure, as well as larger loaded area and load duration.

摘要 采用 CIP-CUP 方法求解欧拉方程,详细研究了固体壁上局部凸起附近非球形气泡坍塌时的射流冲击过程。研究考虑了三种情况,第一种情况是与气泡大小相比几乎是平面的墙壁,另外两种情况是气泡大小的局部凸起。在所有情况下,撞击位置到墙壁的距离和射流尖端直径都很接近,射流速度约为 100 米/秒。所考虑情况的主要区别在于射流与对面气泡侧的初始接触区。也就是说,在第一种情况下,它是一个单点,而在另外两种情况下,它是一个碗形区域和一个形成尖端气泡的环形区域。研究发现,后两种情况会导致更高的壁压,以及更大的负载面积和负载持续时间。
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引用次数: 0
On One Optimization Problem in Nanoelectronics 论纳米电子学中的一个优化问题
IF 0.7 Q2 MATHEMATICS Pub Date : 2024-08-28 DOI: 10.1134/s1995080224602546
V. I. Zubov

Abstract

The work analyzes one optimal control problem that arises in nanoelectronics. It is shown that the use of an approximate expression for the variation of electron density leads to an incorrect value for the gradient of the cost functional. It is demonstrated that the formulated optimal control problem is incorrect. For the correct formulation of the optimal control problem, other cost functions should be used.

摘要 该研究分析了纳米电子学中出现的一个最优控制问题。结果表明,使用电子密度变化的近似表达式会导致成本函数梯度值不正确。结果表明,所提出的最优控制问题是不正确的。为了正确地提出最优控制问题,应使用其他成本函数。
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引用次数: 0
期刊
Lobachevskii Journal of Mathematics
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