Bi-velocity hydrodynamics: Single-component fluids

Acceptance of the Navier-Stokes-Fourier (NSF) equations as the fundamental equations of single-component continuum fluid mechanics for liquids and gases is noted to be inseparably linked to Euler’s implicit, but unproved, hypothesis that but a single-velocity field is required to characterize the four physically different, context-specific, velocities appearing in the mass, momentum, and energy equations. To test Euler’s hypothesis, velocity is added to the usual list of quantities requiring constitutive formulation - namely the heat flux q and viscous stress T - in order to effect closure of the mass, momentum, and energy equations. Establishment of this enlarged set of constitutive relations is effected by using conventional linear irreversible thermodynamics (LIT) principles governing the behavior of simple fluid continua, importantly including satisfaction of Onsager reciprocity as a fundamental continuum requirement. The resulting analysis shows that, in general, two velocities rather than one are required and, concomitantly, that additional driving forces must be added to each of the standard constitutive equations for the Fourier’s-law heat flux q = −k∇T and the Newton’s-law viscous stress (wherein the “mass velocity” v_m is the context-specific velocity appearing in the continuity equation ∂ρ/∂t + ∇ · (ρv_m) = 0). For the particular case of dilute gaseous continua explicit expressions are established for the phenomenological coefficients appearing in these additional constitutive contributions. Determination of these coefficients is effected using data derived from the Chapman-Enskog-Burnett constitutive expressions for q and T, the latter obtained by solving the Boltzmann equation at small Knudsen numbers, including so-called rarefied-gas contributions. These coefficients are found to be nonzero, confirming the conclusion, inter alia, that two velocities are constitutively required to quantify hydrodynamic behavior for gases and, by inference, for liquids too. Collectively, these velocity, heat flux, and stress constitutive findings collectively negate the current belief that the NSF equations fully describe the physics of viscous fluid continua. Rather, they do so only in limiting cases where the additional constitutive terms than we have found necessary for completeness are asymptotically small.     

Applications of irreversible thermodynamics to rapid solidification of multicomponent alloys

Abstract

Solidification, as the key step in physical metallurgy, plays a decisive role in tuning the various properties of materials. From a thermodynamic perspective, the solidification processes can be considered as the evolution of non-equilibrium systems, where the metastable melts become the stable solids with lower free energy. In contrast to equilibrium thermodynamics, which focus on the static equilibrium states, irreversible thermodynamics is a powerful tool to describe the evolution of non-equilibrium systems and has been successfully applied to various fields in materials science. In the present paper, we review the basic philosophy for the phenomenological irreversible thermodynamics, the methods to obtain the governing equations for the evolution of multicomponent solidifying systems and the potential applications to other metallurgical phenomena.     

Onsager reciprocity as a consequence of Maxwell reciprocity for “equidiffuse” fluids

Linear irreversible thermodynamics (LIT) principles are used to show, in the hypothetical “equidiffuse” case where all of the various phenomenological diffusion coefficients appearing in the linear near-equilibrium constitutive laws governing the diffuse transport of energy, multicomponent species, entropy, and volume (although not necessarily including momentum) are taken to be equal, that the Onsager reciprocal relations pertinent to nonequilibrium thermodynamics follow automatically from Maxwell’s reciprocal relations governing equilibrium thermodynamics. As such, this constitutes a purely macroscopic proof of Onsager reciprocity, the first of its kind. Although the equality of diffusion coefficients required in the equidiffuse limiting case does not represent a realistic possibility in the case of most mixtures, its adoption as a foil in uniting reversible and irreversible thermodynamics neither violates nor conflicts with any known physical law. Indeed, in some idealized sense such equality represents a perfection of the well-known analogy between these distinct physical transport phenomena. Moreover, as shown for mixtures of chemically similar dilute gases of comparable molecular weights (e.g., consecutive members of a homologous series) the equidiffuse assumption is generally quite good. As a bonus, our analysis — by virtue of its accord with all known precepts of macroscopic physics — constitutes a satisfactory resolution of the long-standing criticism of Coleman and Truesdell [B.D. Coleman, C. Truesdell, On the reciprocal relations of Onsager, J. Chem. Phys. 33 (1960) 28-31] centered on the possibility that Onsager symmetry might be nothing more than a tautology (derisively referred to in the literature as “Onsagerism”).     

Asymptotic modelling of flows in microchannel by using Navier-Stokes or Burnett equations and comparison with DSMC simulations

The modelling of isothermal gas flows driven by pressure drops, in coplanar microchannels is investigated. The goal is to construct an asymptotic model deduced from Navier-Stokes or Burnett equations for this type of flow, assuming slip boundary conditions along the walls. The dimensionless balance equations are written, taking into account a geometrical parameter introduced in this study. The application of the Principle of Least Degeneracy produces models with small Mach numbers and small or moderate Knudsen numbers and allows the development of asymptotic models. The first and second approximations associated with the Navier-Stokes or Burnett equations are presented and discussed. Navier-Stokes and Burnett second approximations reduce the mass flow rates.Additionally, first asymptotic solutions as against Direct Simulation Monte Carlo (DSMC) simulations show overall satisfactory agreements.     

Rarefied gas mixtures flows driven by surface absorption

Steady one-dimensional flows of a binary mixture of hard sphere gases in the presence of an absorbing planar wall are studied by numerical solutions of two coupled Boltzmann equations. The relationship among the problem parameters in steady flow conditions is obtained, paying particular attention to cases where component species have different mole fractions and absorption probabilities. The analogies with a classical condensation problem with unit condensation coefficient are discussed.     

双氧水工作液的多组分分析

本文根据双氧水工作液中各组分的紫外吸收光谱,用多组分分析技术建立并优化了二乙基蒽醌和四氢二乙基蒽醌的标准校正曲线,标准预计误差(SEP)为0.005。实现了对双氧水工作液的快速适时监测。该方法与极谱法的相对测定误差小于8%。     

常压等离子多元共渗及其在气缸套上的应用

利用常压等离子体扫描金属表面，实现快速扫描多元共渗，用此技术对硼铸铁气缸套进行了Ｂ－Ｓｉ－Ｒｅ等多元共渗，通过电子探针，金相显微镜对多元共渗层的成分，组织进行了观察，利用显微硬度计测定了共渗层的硬度分布，９５型硼铸铁气缸套分别进行等离子多元共渗气缸套的耐磨性及配副性能优于激光处理，对比磨损试验结果表明，等离子体多元共渗气缸套的耐磨性及配副性能优于激光处理气缸套；缸套耐磨性提高７．７％，活塞环耐磨性     

Multicomponent complexes of piroxicam with cyclodextrins and hydroxypropyl methylcellulose

The purpose of the study was to investigate the effect of hydroxypropyl methylcellulose (HPMC) on the complexation of piroxicam (PX) with β-cyclodextrin (β-CD) and dimethyl-β-cyclodextrin (DM-β-CD) in solution and in the solid state. Phase solubility study revealed a positive effect of the polymer on the drug complexation. Improvement in stability constants values, K_s, of ternary complexes clearly proves the benefit of the HPMC addition for promoting higher complexation efficiency. Solid binary and ternary complexes were prepared by spray drying. Drug-CD and drug-CD-polymer interactions were studied in the solid state by differential scanning calorimetry (DSC), zeta-potential measurements, and particle size distribution. A marked increase in the PX dissolution rate was observed even in binary and ternary complexes. The presence of HPMC in ternary complexes slightly retarded the release of PX. Cyclodextrin complexation increased the PX concentration gradient over the semipermeable membrane, resulting in an increased PX flux. The retarded diffusion of PX to the membrane interface decreased the PX flux values of the ternary complexes.     

Multicomponent Complexes of Piroxicam with Cyclodextrins and Hydroxypropyl Methylcellulose

The purpose of the study was to investigate the effect of hydroxypropyl methylcellulose (HPMC) on the complexation of piroxicam (PX) with β‐cyclodextrin (β‐CD) and dimethyl‐β‐cyclodextrin (DM‐β‐CD) in solution and in the solid state. Phase solubility study revealed a positive effect of the polymer on the drug complexation. Improvement in stability constants values, K_s, of ternary complexes clearly proves the benefit of the HPMC addition for promoting higher complexation efficiency. Solid binary and ternary complexes were prepared by spray drying. Drug‐CD and drug‐CD‐polymer interactions were studied in the solid state by differential scanning calorimetry (DSC), zeta‐potential measurements, and particle size distribution. A marked increase in the PX dissolution rate was observed even in binary and ternary complexes. The presence of HPMC in ternary complexes slightly retarded the release of PX. Cyclodextrin complexation increased the PX concentration gradient over the semipermeable membrane, resulting in an increased PX flux. The retarded diffusion of PX to the membrane interface decreased the PX flux values of the ternary complexes.     

Multicomponent oxide thin-film transistors fabricated by a double-layer inkjet printing process

In this work we report on the fabrication and characterization of multicomponent metal oxide thin-film transistors with a double-layer inkjet printing process. Both the active area and source-drain electrodes of the devices are printed with inks based on metal salt precursors to form Ga₂O₃-In₂O₃-ZnO and In₂O₃-SnO respectively. Electrical characterization has shown that the devices' performance, apart from the active area composition, can also be affected by the printing drop spacing. In general, devices printed with Ga:In:Zn 2:4:1 composition present the highest field effect mobility (~ 1.75-3 cm² V⁻¹ s⁻¹). More stable devices with improved switching, but with a compromise over field effect mobility (~ 0.5-0.9 cm² V⁻¹ s⁻¹) were obtained for the 2:4:2 composition.     

Decomposition of Multicomponent Exponential Decays by Spectral Analytic Techniques

It is shown that multicomponent exponential decays can be analysed using a technique which produces a spectrum whose peaks correspond in amplitude and position to the various exponential components present in the data. This technique is analogous to the Fourier Transform which provides a spectrum of the frequency components (complex exponentials) of a signal. Three techniques—the Orthonormal Exponential Transform, the Inverse Laplace Transform and the Gardner Transform are examined and their relative effectiveness in producing the desired spectra from theoretically generated and experimental data is discussed. It is shown that the updated Gardner Transform can be Ilsed to analyse experimental multicomponent exponential decays.     

减小应变式多维力传感器测量误差的一种方法

针对目前多维力传感器各维间耦合造成的测量误差过大的问题,提出了适用于应变式多维力传感器的互耦补偿电阻解耦方法。理论分析与实际应用结果表明,该方法能有效地消除传感器各维间的耦合作用,大大减小因此而产生的测量误差。     

Japanese research on thermophysical properties of fluids

Japanese research activities on thermophysical properties of gases and liquids, as well as some historical background, are outlined. The current situation is explained for industrially important substances, such as water and steam, high pressure gases and liquids, refrigerants, molten salts, and other fluids. Related activities are also briefly introduced. Although some of the Japanese studies can be traced back to more than 50 years ago, a systematic effort has been visible only in the last 20 years. However, quite recently, thermophysical properties research has begun to attract attention of more people in science and industry in Japan, probably as the natural sequence to the progress of technology.Presented at the Japan-United States Joint Seminar on Thermophysical Properties, October 24–26, 1983, Tokyo, Japan.     

两相流中相积存造成多元混合制冷剂浓度变化分析

因多相流动中汽液速度差而造成相积存（Holdup）是深冷混合工质节流制冷系统中混合物浓度偏析的一个重要因素。建立了因相积存造成浓度变化的计算模型,采用Palmer对Beggs-Brill—Moody关联式的修正式,详细考察了管道倾角及流体温度对深冷多元混合物因汽液相积存异造成的浓度偏析影响。计算结果表明,管道倾角对积存具有显著影响,其中倾斜向上会显著增加积存,造成混合物浓度显著变化。浓度变化发生在两相区,并随温度变化导致不同组分的浓度变化趋势不同。     

A thermodynamic framework for fatigue crack growth in concrete

The phenomenon of fatigue is commonly observed in majority of concrete structures and it is important to mathematically model it in order to predict their remaining life. An energy approach is adopted in this research by using the framework of thermodynamics wherein the dissipative phenomenon is described by a dissipation potential. An analytical expression is derived for the dissipation potential using the concepts of dimensional analysis and self-similarity to describe a fatigue crack propagation model for concrete. This is validated using available experimental results. Through a sensitivity analysis, the hierarchy of importance of different parameters is highlighted.     

Irreversible thermodynamics of polydisperse fluids

The entropy production, conservation laws, and linear constituative equations that describe the irreversible behavior of polydisperse fluids near equilibrium are presented. The problems of computing transport coefficients and solving the hydrodynamic equations are discussed.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Marryland, U.S.A.     

Evaluation of the inelastic heat fraction in the context of microstructure-supported dynamic plasticity modelling

Under dynamic adiabatic conditions, the plastic work is known to dissipate into heat and induce thermal softening. From both theoretical and numerical viewpoints, the proportion of effectively dissipated plastic work is commonly evaluated using the so-called Taylor–Quinney coefficient usually assumed to be a constant empirical value. On the other hand, experimental investigations have shown its dependence on strain, strain rate and temperature.