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Nonlinear Regimes of Electric Convection of Poorly Conducting Fluids in Weightlessness at Low Frequencies of an Electric Field 失重状态下不良导电流体在低频电场中的非线性对流状态
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462823603273
V. A. Il’in

Abstract

Electrothermal convection in a poorly conducting fluid in an alternating electric field of a horizontal capacitor is studied. The nonlinear regimes of electric convection in weightlessness are studies at low frequencies of the electric field on the basis of the pentamodal model within the framework of the electroconductive charge formation mechanism. Hysteresis transitions between two different synchronous and subharmonic regimes are found to exist. Transitions to chaos occur by means of either interemittance or a subharmonic cascade.

摘要 研究了在水平电容器的交变电场中导电不良流体的电热对流。根据电导电荷形成机制框架内的五模态模型,研究了失重状态下低频电场的电对流非线性状态。发现在两种不同的同步和亚谐波状态之间存在着滞后过渡。向混沌的过渡是通过间歇或次谐波级联发生的。
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引用次数: 0
Estimate of the Onset of Laminar-Turbulent Transition on a Plate in Flight in the Mars Atmosphere 估计火星大气中飞行板块上层流-湍流转变的起始时间
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462823603212
Yu. N. Grigor’ev, I. V. Ershov

Abstract

Comparative calculations of the location of the onset of the laminar-turbulent transition zone are performed using the eN-method for two points on the Mars “Pathfinder” entry trajectory. A three-component model of thermochemically nonequilibrium CO2–CO–O mixture is used in the calculations. The set of spatial disturbance frequencies is found using neutral curves for the first unstable modes of temporary disturbances. The transition Reynolds number ReδT is determined from the envelopes of families of N-factor curves at NT = 8. In the hypersonic regime at M = 12.6, taking into account the developed thermochemical nonequilibrium leads to a significant decrease in the static temperature of gas in the lower part of the boundary layer. As a result, the onset of the laminar-turbulent transition zone is displaced downstream by approximately 9% as compared to the case of a perfect gas.

摘要 对火星 "探路者 "进入轨迹上的两个点使用 eN 方法对层流-湍流过渡带的起始位置进行了比较计算。计算中使用了热化学非平衡 CO2-CO-O 混合物的三组分模型。利用临时扰动的第一种不稳定模式的中性曲线找到了一组空间扰动频率。过渡雷诺数 ReδT 是根据 NT = 8 时 N 因子曲线族的包络线确定的。 在 M = 12.6 时的高超声速状态下,考虑到已形成的热化学非平衡会导致边界层下部的气体静态温度显著下降。因此,与完美气体相比,层流-湍流过渡区的起始点向下游移动了约 9%。
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引用次数: 0
The Initial Stage of the Coalescence of a Compound Drop in an Impact Regime 复合水滴在撞击状态下凝聚的初始阶段
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462824600226
Yu. D. Chashechkin, A. Yu. Il’inykh, Sh. Kh. Khaiirbekov

Abstract

The evolution of the regular fine structure of the colored matter distribution produced, when a freely falling multifluid drop spreads in deep water, is for the first time traced using the techniques of engineering photo and video recording. The flow pattern is studied in the initial stage of the formation of a cavity and a crown during the coalescence of a compound drop, whose core is a drop of alizarin ink solution coated with an oil shell. The distributions of the colored fluid at the cavity bottom and the crown walls include streaky structures, whose formation can be due to the processes of the available potential surface energy (APSE) conversion occurring when the contact surfaces of the merging fluids are eliminated. In the experiments the height of the falling drop was varied. The core position in the compound drop was not checked but was determined by separation conditions. The ink core disintegration into fibers was observable in all the experiments. The areas of the cavity and crown surfaces covered by the colored fluid reached maximum at the central position of the core.

摘要 利用工程照片和视频记录技术,首次追踪了自由下落的多流体液滴在深水中扩散时产生的彩色物质分布的规则精细结构的演变过程。研究了复合液滴(其核心是一滴涂有油壳的茜素油墨溶液)凝聚过程中形成空腔和冠状的初始阶段的流动模式。有色液体在空腔底部和冠壁的分布包括条状结构,其形成可能是由于合并液体的接触面被消除时发生的可用势能表面能(APSE)转换过程。在实验中,下落液滴的高度是变化的。没有检查墨芯在复合墨滴中的位置,而是由分离条件决定。在所有实验中都能观察到墨芯分解成纤维的现象。在墨芯的中心位置,有色液体覆盖的空腔和墨冠表面的面积达到最大。
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引用次数: 0
Self-Similar Solution of the First Stokes Problem for Non-Newtonian Fluids with Power-Law Viscosity 具有幂律粘度的非牛顿流体的第一斯托克斯问题的自相似解
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462824602134
V. N. Kolodezhnov

Abstract

The first Stokes problem is considered for flows of non-Newtonian fluids with effective viscosity varying in accordance with the power law. Self-similar solutions are constructed for the fluids, whose mechanical behavior is described by the Ostwald–de Waele and Herschel–Bulkley rheological models with the corresponding restrictions on the nonlinearity degree exponent n. It is shown that for the Ostwald–de Waele fluid self-similar solutions exist only for 0 < n < 1, which corresponds to the pseudoplastic behavior. At the same time, self-similar solutions for the Herschel–Bulkley fluid can be obtained only at n > 1, when this fluid exhibits the properties of dilatancy.

摘要 针对有效粘度按幂律变化的非牛顿流体的流动,研究了第一斯托克斯问题。结果表明,Ostwald-de Waele 流体的自相似解仅存在于 0 < n < 1 时,即对应于假塑性行为。同时,Herschel-Bulkley 流体的自相似解只能在 n > 1 时获得,此时该流体表现出扩张特性。
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引用次数: 0
Gas Suction Effect on the Crossflow Instability in Flow Past a Swept Wing 气体吸力对掠翼流过时横流不稳定性的影响
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462824600202
A. V. Novikov, A. O. Obraz, D. A. Timokhin

Abstract

The results of the swept wing boundary layer stability investigation are presented for the case, when the wing surface has a region of gas suction through the wall normal to the surface, while the wing is in Mach number 2 flow. In the flow regime considered the predominant boundary layer instability type is the crossflow instability. The gas suction effect on the development of unstable modes in the boundary layer is investigated using the linear stability theory and direct numerical modeling. The numerical modeling of laminar (undisturbed) flow fields with regions of gas suction and disturbed flow fields is carried out by integrating Navier–Stokes equations. An analysis within the framework of the linear stability theory is performed using the ({{e}^{N}})-method. The suction region location is varied with conservation of the integral intensity. It is shown that the mode instability growth can be considerably suppressed at the expense of an optimal disposition of the suction region.

摘要 本文介绍了在翼面有一个气体吸入区域,气体通过翼面法线的壁面进入翼面,同时翼面处于马赫数为 2 的流动状态下的后掠翼边界层稳定性研究结果。在所考虑的流态中,主要的边界层不稳定性类型是横流不稳定性。利用线性稳定性理论和直接数值建模研究了气体吸力对边界层不稳定模式发展的影响。通过对纳维-斯托克斯方程进行积分,对具有气体吸力区域和扰动流场的层流(未扰动)流场进行了数值建模。使用 ({{e}^{N}} 方法在线性稳定性理论框架内进行了分析。吸力区域的位置随积分强度的变化而变化。结果表明,以吸力区的最佳位置为代价,可以大大抑制模式不稳定性的增长。
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引用次数: 0
Determination of the Shape and Dimensions of the Polymer Molecules in Solutions Using Diffusional NMR Relaxation 利用扩散 NMR 驰豫确定溶液中聚合物分子的形状和尺寸
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s001546282360325x
V. A. Ivanova, A. V. Maksimychev, P. L. Men’shikov, A. R. Pashutin, A. M. Perepukhov, A. N. Rozhkov, M. V. Tsar’kov

Abstract

A new method of determining the dimensions and shapes of polymer molecules in solutions is proposed and verified in experiments. The method is based on the measurements of the relaxation of the transverse magnetization intensity of nuclei. It is established that the decaying signal of the spin echo from elongated molecules contains two terms exponentially decaying with time, which correspond to two diffusion coefficients differing by a factor of about two. The signal from molecules with a near-spherical shape contain only one exponent.

摘要 提出了一种确定溶液中聚合物分子尺寸和形状的新方法,并在实验中得到了验证。该方法基于对原子核横向磁化强度弛豫的测量。实验证明,拉长分子的自旋回波衰减信号包含两个随时间呈指数衰减的项,这两个项对应于两个相差约 2 倍的扩散系数。近球形分子的信号只包含一个指数。
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引用次数: 0
Linear Waves on Shallow Water Slowing Down near the Shore over Uneven Bottom 浅水区的线性波浪在不平整的海底近岸处减速
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462823603066
I. E. Melnikov, E. N. Pelinovsky

Abstract

The exact solutions to the system of equations of the linear theory of shallow water that represent travelling waves with some specific properties on the time propagation interval are discussed. These solutions are infinite when approaching the shore and finite when leaving for deep water. The solutions are obtained by reducing one-dimensional equations of shallow water to the Euler-Poisson-Darboux equation with negative integer coefficient ahead of the lower derivative. An analysis of the wave field dynamics is carried out. It is shown that the shape of a wave approaching the shore will be differentiated a certain number of times. This is illustrated by a number of examples. When the wave moves away from the shore, its profile is integrated. The solutions obtained within the framework of linear theory are valid only on a finite interval of variation in the depth.

摘要 讨论了浅水线性理论方程组的精确解,这些解表示在时间传播间隔上具有某些特定性质的行波。这些解在接近岸边时是无限的,而在驶向深水区时是有限的。这些解是通过将浅水一元方程简化为下导数前带负整数系数的欧拉-泊松-达尔布方程得到的。对波场动力学进行了分析。结果表明,接近岸边的波浪形状会被微分一定次数。这可以通过一些例子来说明。当波浪远离海岸时,其轮廓将被整合。在线性理论框架内获得的解仅在深度变化的有限区间内有效。
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引用次数: 0
Anomalous Heat Transfer Enhancement in Separated Flow over a Zigzag-Shaped Dense Package of Inclined Grooves in a Channel Wall at Different Temperature Boundary Conditions 不同温度边界条件下通道壁上人字形斜槽密集包分离流的异常传热增强
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462823602875
S. A. Isaev, O. O. Mil’man, A. A. Klyus, D. V. Nikushchenko, D. S. Khmara, L. P. Yunakov

Abstract

Rapid development of the anomalous enhancement of separated turbulent Re = 6000 air flow and heat transfer in an in-line single-row package of 31 inclined grooves, 0.2 in dimensionless depth, in a singled-out longitudinal region of the wall of a narrow channel is studied. It is due to the interference of vortex wakes behind the grooves and the acceleration in the channel flow core with the formation of a zone of ultrahigh longitudinal velocity. The wave-shaped parameter characteristics are stabilized in the region of approximately 15th groove, whereupon the oscillation amplitudes are moderately reduced. The return flows in the grooves are enhanced with distance from the entry section, the minimum negative friction diminishing from −2 to −4. The total relative heat removal from the structured region increases at q = const by a factor of approximately 2.75 and by the factor of two at T = const with increase in the relative hydraulic losses by the factor of 1.7, as compared with the case of a plane–parallel channel. The relative heat removal from the surface bounded by the contour of the 20th inclined groove amounts to 3.7 (q = const) with increase in the hydraulic losses by the factor of 2.2. An increase in the local maximum of the longitudinal velocity up to a factor of 1.5, as compared with the mean-mass velocity, can be observable.

摘要 研究了在狭窄通道壁的单一纵向区域,由 31 个无量纲深度为 0.2 的倾斜凹槽组成的直列单排包中,分离湍流 Re = 6000 气流和传热的快速发展异常增强现象。这是由于沟槽后方的涡流漩涡的干扰和通道流心的加速,形成了一个超高纵向速度区。波形参数特征在大约第 15 个沟槽区域趋于稳定,振荡幅度适度减小。凹槽中的回流随着与入口部分距离的增加而增强,最小负摩擦力从-2 减小到-4。与平面平行通道相比,结构区的总相对散热量在 q = const 时增加了约 2.75 倍,在 T = const 时增加了 2 倍,相对水力损失增加了 1.7 倍。在水力损失增加 2.2 倍的情况下,第 20 个斜槽轮廓边界表面的相对散热量为 3.7(q = 常值)。与平均质量速度相比,纵向速度的局部最大值增加了 1.5 倍。
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引用次数: 0
Natural Vibrations of Fluid in a Well Connected with the Reservoir by a System of Radial Fractures 通过径向裂缝系统与储层相连的油井中流体的自然振动
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s001546282460024x
R. A. Bashmakov, D. A. Nasyrova, Z. R. Khakimova

Abstract

The problem of natural vibrations of a fluid in a horizontal well with multiple fractures obtained by hydraulic fracturing is considered. A mathematical model of the natural vibrations of fluid in a horizontal oil well connected to the reservoir by a system of radial hydraulic fractures is constructed and the frequency characteristics of the natural vibrations of fluid as functions of the hydraulic fracture and reservoir parameters are determined. Using a numerical analysis of the frequency characteristics of vibrations, the effect of changes in the fracture width, the number of fractures, and the reservoir permeability on the natural frequencies is demonstrated.

摘要 考虑了通过水力压裂获得的多裂缝水平井中流体的自然振动问题。建立了通过径向水力压裂系统与储层相连的水平油井中流体自然振动的数学模型,并确定了流体自然振动的频率特性作为水力压裂和储层参数的函数。通过对振动频率特性的数值分析,证明了裂缝宽度、裂缝数量和储层渗透率的变化对固有频率的影响。
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引用次数: 0
Failure of a Detonation Wave in a Plane Channel with Multiple Obstacles 有多个障碍物的平面通道中引爆波的失效
IF 0.9 4区 工程技术 Q3 Chemical Engineering Pub Date : 2024-05-08 DOI: 10.1134/s0015462823603224
T. A. Zhuravskaya, V. A. Levin

Abstract

The results of numerical study of the interaction of a formed cellular detonation wave propagating in a plane channel occupied by a quiescent stoichiometric hydrogen-air mixture with multiple obstacles (barriers) located on the inner surface of the channel are given. The study is carried out to determine the conditions that ensure suppression of detonation. The influence of geometric parameters of the area with obstacles on wave propagation is studied. It is found that localization of the obstacles in a recess in the channel wall leads to a decrease in their destructive effect on detonation. Quenching of detonation combustion by the layer of a non-reacting gas located along the channel wall, limited by single barriers, is considered. The effect of gas composition on the interaction of the detonation wave with the layer is studied. Non-reacting gas mixtures, which, being filled into the area with obstacles, enhance the destructive effect of barriers on the detonation wave are proposed.

摘要 数值研究了在静止的静态氢气-空气混合物占据的平面通道中传播的已形成的蜂窝爆轰波与位于通道内表面的多个障碍物(屏障)之间的相互作用。研究旨在确定确保抑制爆轰的条件。研究了有障碍物区域的几何参数对波传播的影响。研究发现,将障碍物设置在通道壁的凹槽内会降低其对爆燃的破坏作用。在单个障碍物的限制下,考虑了沿通道壁的非反应气体层对爆燃的淬火作用。研究了气体成分对爆轰波与该层相互作用的影响。提出了非反应气体混合物,这种混合物充入有障碍物的区域,会增强障碍物对爆轰波的破坏作用。
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引用次数: 0
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Fluid Dynamics
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