The comparison of two approaches to numerical modelling of gas-particles turbulent flow and heat transfer in a pipe

The comparison of two theoretical approaches for the numerical investigation of turbulent gas–solid flows with heat transfer in a pipe are presented in this paper. The first approach is based on Eulerian–Eulerian modelling of investigated phenomena, the second one is formulated within the framework of the Eulerian–Lagrangian approach. The verification of numerical models under consideration. Their testing against available experimental data show good prognostic properties of the elaborated theoretical tool for research activities to study new physical fundamentals of turbulent gas-suspended particles flows in pipes and channels.     

Phase and Interfacial Tension Behavior of Certain Model Gas Condensates: Measurements and Modeling

This contribution reports on the phase and interfacial tension behavior of some model high-temperature–high-pressure gas condensates. On the one hand these types of gas condensate are becoming a subject of major interest for the oil industry, while on the other their phase and interfacial tension behavior have not been very well studied. For two different model gas condensates, both composed of the three n-alkanes, methane, butane, and decane, experimental results on their fluid phase behavior have been obtained in the temperature region 270 < T (K) < 490 and up to pressures as high as 24 MPa. Also, critical points of the two mixtures have been determined experimentally. Both mixtures show an extended retrograde region. Using the Peng–Robinson equation of state, the phase behavior of the two mixtures was modeled. In addition, the interfacial tension behavior of the model gas condensates was modeled. For that purpose, the Cahn–Hilliard theory was applied in combination with the Peng–Robinson equation of state. Satisfactory results were obtained.     

Performance prediction of animal drawn vehicle tyres in sand

Four animal drawn vehicle (ADV) tyres of 5.00–19, 6.00–19, 7.00–19 and 8.00–19 sizes were tested in sand under various but controlled conditions in an indoor soil bin. A tyre test carriage with four-bar parallel linkage was developed for accommodating a single wheel of different sizes. Performance tests were conducted at five levels of inflation pressure and load. The sand compaction level was varied in the range of 3.4–4.5 MPa/m and forward speed of the test carriage was maintained at 3.1 km/h. Performance of the tyres 7.00–19 and 8.00–19 was identical and offered less rolling resistance as compared to other tyres. However, their use in camel carts may not be recommended beyond the payload of 6 kN on single wheel with inflation pressure and sand compaction range of 172–379 kPa and 3.4 –4.5 MPa/m, respectively. Based on the experimental results, empirical models were developed to predict the performance of tyres. The accuracy of prediction of the developed empirical models was compared with that of existing semi-empirical approaches. Model with sand mobility number considered relatively simple and convenient to use in the field and yields reasonably good prediction for rolling resistance and sinkage.     

Micromechanics predictions of the effective moduli of magnetoelectroelastic composite materials

In this paper, the self-consistent, generalized Mori–Tanaka and dilute micromechanics theories are extended to study the coupled magnetoelectroelastic composite materials. The heterogeneous inclusion problem of magnetoelectroelastic behavior is formulated in terms of five interaction tensors related to the Green's functions for an infinite three-dimensional transversely isotropic magnetoelectroelastic solid. These tensors are then used to predict the effective moduli of the magnetoelectroelastic solid based on the self-consistent, Mori–Tanaka and the dilute approaches. Numerical results are obtained for various types of inclusions. These results are employed to study the effects of the inclusion properties, such as moduli, volume fractions, shapes, etc., on the effective moduli of magnetoelectroelastic composites, in particular, the related magnetic properties. The results obtained using the self-consistent model, the generalized Mori–Tanaka's model and the dilute approach are compared with the existing experimental and theoretical results.     

重大装备橡塑密封系统摩擦学进展与发展趋势

阐述了橡塑密封系统摩擦学在"工业强基"战略以及智能制造装备(中国制造2025)的主要挑战.综述了目前橡塑密封的弹性体磨损、润滑、摩擦、界面失稳研究现状,概述了橡胶摩擦学在磨损润滑、摩擦接触研究的主要难题(包括基础理论、计算方法、仪器研制等),分析了我国与世界高端橡塑密封工业先进发达国家的差距,并就未来橡塑密封理论、技术、应用领域的重点提出了若干建议,为我国基础件研究和生产制造、工业摩擦学界提出了建议.     

Numerical simulation and experimental validation of gas–solid flow in the riser of a dense fluidized bed reactor

Gas–solid flow in the riser of a dense fluidized bed using Geldart B particles (sand), at high gas velocity (7.6–15.5 m/s) and with comparatively high solid flux (140–333.8 kg/m² s), was investigated experimentally and simulated by computational fluid dynamics (CFD), both two- and three-dimensional and using the Gidaspow, O’Brien-Syamlal, Koch-Hill-Ladd and EMMS drag models. The results predicted by EMMS drag model showed the best agreement with experimental results. Calculated axial solids hold-up profiles, in particular, are well consistent with experimental data. The flow structure in the riser was well represented by the CFD results, which also indicated the cause of cluster formation. Complex hydrodynamical behaviors of particle cluster were observed. The relative motion between gas and solid phases and axial heterogeneity in the three subzones of the riser were also investigated, and were found to be consistent with predicted flow structure. The model could well depict the difference between the two exit configurations used, viz., semi-bend smooth exit and T-shaped abrupt exit. The numerical results indicate that the proposed EMMS method gives better agreement with the experimental results as compared with the Gidaspow, O’Brien-Syamlal, Koch-Hill-Ladd models. As a result, the proposed drag force model can be used as an efficient approach for the dense gas–solid two-phase flow.     

The effect of water vapor on the distribution of the parameters of a turbulent wake

In the experimental study of phenomena occurring in the flow of air round models flying along a aeroballistic range with hypersonic velocities, the question arises of the effect of water vapor along the range on the measurements of the gas parameters, for example, on the electron concentration or on the intensity of the radiation. Water vapor is usually present in atmospheric air and, in the absence of special measures to remove it, it may have an influence on the results of measurements. In [1] a theoretical study has been made of the effect of chemical reactions involving the participation of water vapor in the air on the chemiluminescent radiation in the wake alone. In particular, there was no consideration of the effect of water vapor on the electron concentration. In the present study, the results are given of calculations of the distributions of the nonequilibrium parameters in the wake, with allowance for the occurrence of chemical reactions in the air and water vapor under conditions characteristic of aeroballistic experiments [1–3].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 138–142, January–February, 1985.     

Sound generation by a laser beam in a liquid with absorbing particles

Sound generation by a laser beam within a liquid, related to liquid boiling at absorption centers, has been studied relatively little. Acoustic effects upon liquid boiling in a laser beam were first reported in [1]. A change in the index of refraction of a liquid has been observed under the action of acoustical radiation of microbubbles formed on absorbing particles in the zone irradiated by a laser beam [2–4]. However direct measurements of acoustical radiation from a set of microbubbles uniformly distributed over the volume of laser beam-liquid interaction has yet to be performed, to the authors' knowledge. The present study is a preliminary report of results of an experimental study of this class of opticoacoustical phenomena.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 9–12, January–February, 1984.In conclusion, the authors consider it their pleasant duty to thank G. A. Askar'yan for evaluating the study and S. V. Luk'yanov for assistance in measuring the particle size distribution.     

Derivation of the equations of slow nonisothermal gas flows

In recent years, some new phenomena have been predicted theoretically on the basis of the Burnett approximation. These include thermal-stress and concentration-stress convection [1–3], and also effects due to the influence of a magnetic field in a multiatomic gas (viscomagnetic heat flux, etc., [4]). It has been shown theoretically (see [5]) that under certain conditions various terms of the Burnett approximation must be taken into account in the expression for barodiffusion. The conclusions relating to a viscomagnetic heat flux have recently been confirmed experimentally [4]. The predicted phenomena follow rigorously from the Burnett equations. However, many hydrodynamicists adopt a sceptical attitude to these equations, which is due partly perhaps to attachment to the classical Navier-Stokes equations, which have served theoreticians without fail for a century and a half. In this connection, we discuss the evolution of ideas relating to the validity of the Burnett approximation. We discuss the minimal assumptions which must be made in order to derive the equations of slow [Reynolds number R = 0(1)], essentially nonisothermal [ ln T = 0(1)] flows of a gas as a continuous medium (Knudsen number K O) in the case when the derivatives of the thermal Burnett stresses in the momentum equation have the same order of magnitude as the Euler and Navier-Stokes terms of this equation [1–3].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 77–84, November–December, 1979.We thank G. I. Petrov and L. I. Sedov for discussions that stimulated the above analysis.     

Cumulative streams during the impact collapse of cavities in thin liquid layers

High-speed motion-picture photography has been used to study the dynamics of the impactr induced collapse of air-filled bubbles in thin layers of various liquids. The circular surface of the bubble is disruptive in an arbitrary manner during the collapse, and high-velocity cumulative streams arise. The stream parameters have been measured as functions of the initial experimental conditions.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhicheskoi Fiziki, Vol. 11, No. 2, pp. 148 – 151, March–April, 1970.     

In the footsteps of Ernst Mach — A historical review of shock wave research at the Ernst-Mach-Institut

The aim of this paper is to recall some of the historical work on shock waves and to give a brief survey of research activities at the Ernst-Mach-Institut (EMI). Some fundamental results of Ernst Mach (1838 – 1916) are demonstrated and historical remarks are given to the shock tube as an important tool in shock wave research. The activity at EMI in this field was initiated by Prof. H. Schardin (1902 – 1965) in 1955 and has since been continued. Propagation processes of shock and blast waves, blast loading phenomena, shock attenuation, shock reflection at various surfaces, development of new types of blast simulators, electromagnetically driven T-tubes, precursor and decursor phenomena are only a few examples of research topics at EMI that will be discussed.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

The effects of ionization on the compression of a gas by a converging shell

One of the effective methods of obtaining a dense high-temperature plasma is compression of the gas by converging shells, which can be accelerated to high velocities by the products of an explosion either as a result of ablation caused by laser radiation, or by an electron beam [1–3]. In order to interpret the results of such experiments, it is very important to construct satisfactory physical models which enable us to obtain plausible estimates for the parameters of the plasma which are realized as a result of the compression. In a number of cases the process of compression may be described with sufficient accuracy by a system of simple hydro-dynamic equations which have particular analytical solutions (see, for example, [4–7]); however, as a rule, for more realistic estimates it is necessary to take into account the complex of physical phenomena accompanying the process, and in such cases the most effective method is numerical simulation of the process, which enables a fuller study to be made of the effect of various factors [7–9]. Compression regimes corresponding to velocities of projection of the shells of some tens of kilometers a second (attainable in experiments with laser compression of shells of a width of some microns) have at present been considered in detail in studies devoted to a pulse thermonuclear synthesis (for example, [8–10]), from which it follows that the process corresponds with sufficient accuracy to the compression of a gas which is completely ionized at the initial moment. In experiments with more massive shells (of the order of 100 m and more), the velocities attained in practice do not exceed 5–20 km/sec [1]. At such velocities, the energy densities contained in the shock wave detaching from the shell may turn out to be insufficient for complete ionization of the gas which has been compressed, and this must have an effect on its further compression and heating. The present study considers precisely these regimes of compression of gas-filled targets. The studies were carried out by the numerical method. For comparison, the studies were made in a number of cases both with allowance for ionization of the gas which was being compressed, and also on the assumption that the gas was already completely ionized at the initial moment.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 155–160, January–February, 1935.In conclusion the author expresses his appreciation to S. I. Anisimov for his constant attention to this study, and to M. F. Ivanov for his help in carrying out the calculations.     

Crack movement in layered composites under electric field affect

The variation principle is applied for defining a crack in the solid body. The methods proposed in [G. Sih, C. Chen, Non-self-similar crack growth in elastic–plastic finite thickness plate, Theoretical and Applied Fracture Mechanics 3 (1985) 125–139] extend to presence of electromagnetic fields in material. Crack propagation in non-homogeneous media has been considered. It is shown that electromagnetic fields in the material are essentially affecting the trajectory. The crack trajectory stability has been studied as function of fracture energy, phase portraits of the trajectory in different media have been built, and various attractor types have been revealed. Different crack morphologies from single straight and oscillating crack propagation to straight double crack propagation were theoretically founded. In compliance with the experimental data of [R. Niefanger, V.-B. Pham, G. Schneider, H.-A. Bahr, H. Balke, U. Bahr, Quasi-static straight and oscillatory crack propagation in ferroelectric ceramics due to moving electric field: experiments and theory, Acta Materialia 52 (1) (2004) 117–127], it has been demonstrated that periodic electromagnetic field results in trajectory stochastization. This can be used for switching the crack over from the mode of mainline propagation into the mode of development of the field of diffused microcracks.     

Determination of interfacial tension by the retraction method of highly deformed drop

The traditional retraction of the deformed drop method (DDRM) to determine the interfacial tension is reformulated to relax the limit the small deformation assumption. The kernel of the new formalism is the calculation of the velocity gradient on the vertex of the ellipsoidal drop. Two models were used for such calculations: the Jackson and Tucker model [J Rheol 47:659–682] and the Yu and Bousmina model [J Rheol 47:1011–1039]. The method can be used either in the retraction of shear deformed drop, or in the retraction of elongated drops produced by the breakup of a long thread. Comparison with experimental results of the literature showed that conversely to the classical DDRM, good accuracy is obtained when the new modeling for the determination of interfacial tension is used both under small and large deformations.     

Fluctuations of bed load solid discharge and grain size distribution on steep slopes with image analysis

A new device using image analysis has been designed to measure the grain size distribution and the solid discharge of natural particles downstream of an experimental mobile bed flume. Experiments were performed in a 10 cm wide, 15% steep flume, with both uniform (4–5 mm) and non-uniform materials (3–15 mm). For the uniform material, outgoing solid discharge fluctuations were not significant, whereas they were large for the non-uniform material. The lower solid discharges were coarser than the higher solid discharges; this behavior is associated with the smallest particles playing a major role through building and destroying transient antidune-like bedforms.     

Unsteady flows of an erosion plasma in irradiation of solid targets by annular beams

In recent times high-pressure physics has made ever wider application of constructions which use convergent shock waves [1–8]. The study of gas dynamic flows with convergent shock waves imposes the need for more careful calculation of the motions of a gas in regions whose dimensions are much less than the characteristic dimensions of the flow. In the present study the numerical method is used to study the gas dynamic phenomena accompanying the irradiation of solid obstacles by annular beams of monochromatic radiation.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 179–182, November–December, 1988.In conclusion we note that at very short durations t t_k the solution to the problem is similar to the flow during separation of a gaseous toroid [19].     

Transient simulation of 2–3D stratified and intermittent two-phase flows. Part II: Applications

In this paper a new type of transient multidimensional two-fluid model has been applied to simulate intermittent or slug flow problems. Three different approaches to modelling interfacial friction, including an interfacial tracking scheme, have been investigated. The numerial method is based on an implicit finite difference scheme, solved directly in two steps applying a separate equation for the pressure. 2D predictions of Taylor bubble propagation in horizontal and inclined channels have been compared with experimental data and analytical solutions. The 2D model has also been applied to investigate a number of special phenomena in slug flow, including slug initiation, bubble turning in downflow and the bubble centring process at large liquid flow rates.     

A two dimensional, experimental study on the evolution of the detachment and its time-behavior in filled rubber

Summary The detachment of a rubber matrix from a rigid inclusion under monotonic loading and at subsequent relaxation is investigated within two dimensional analysis. Examined are stress–strain experimental data acquired with the help of a test bed equipped with a digital image-acquisition device. The influence of the interfacial bonding strength and the particle size on the detachment process is analyzed. The influence of the interfacial bonding strength is visible in the stress–strain diagram of loading and in the recorded images. The relaxation test reveals no influence of the bonding strength on the stress-relaxation. However, the image analysis indicates a secondary transient creep of the contour of detachment, which depends on the interfacial bonding.