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61.
Benjamin Piaud Stéphane Blanco Richard Fournier Michael J. Clifton 《Journal of statistical physics》2005,121(1-2):119-131
A discrete velocity model is presented for lattice Boltzmann thermal fluid dynamics. This model is implemented and tested
in two dimensions with a finite difference scheme. Comparison with analytical solutions shows an excellent agreement even
for wide temperature differences. An alternative approximate approach is then presented for traditional lattice transport
schemes 相似文献
62.
Youssef A. Fakhreddine Paul Zoller 《Journal of Polymer Science.Polymer Physics》1994,32(15):2445-2459
This article reports on an experimental investigation of the equation of state and the transition behavior of main-chain thermotropic liquid crystalline polymers over a wide temperature range, and at pressures to 200 MPa. The materials studied were a series of azomethine ether polymers. A varying number n (= 4, 7, 8, 9, 10 and 11) of methylene spacer units in the backbone provided systematic variation of the structure. Experimental techniques used included high-pressure dilatometry (PVT measurements) to 200 MPa, high-pressure differential thermal analysis, also to 200 MPa, and conventional (atmospheric-pressure) differential scanning calorimetry (DSC). The equation of state of the materials can be well represented by the Tait equation in distinct regions, separated by a glass transition, Tg(P), a first-order transition to a nematic state, Tk-n(P), and a first-order transition to an isotropic melt state Tc(P). The atmospheric pressure values of Tk-n and Tc decreased with increasing number of spacer units and showed a clear odd-even effect. Tg and Tk-n both increased with pressure. The pressure dependence of Tc could not be observed due to the onset of degradation in the same temperature region. On isobaric cooling at 3°C/min, the crystallization from the nematic state occurred a few tens of degrees below Tk-n. This supercooling was independent of pressure for some materials, while for others it increased with increasing pressure. The values of the enthalpy and entropy associated with the first-order transition into the nematic state were lower than those of typical isotropic polymers at their melting transitions. The transition enthalpy did not have any systematic variation with increasing number of spacer units. Values of the transition enthalpy calculated from the Ciapeyron equation did not always agree with the values measured by DSC. This may be due to the two-phase nature of the low-temperature state. At the transition to the isotropic state, the transition enthalpy at P = 0 decreased with n and showed an odd-even effect. © 1994 John Wiley & Sons, Inc. 相似文献
63.
The method of molecular dynamics is applied to investigate the stability of water clusters containing up to 90 molecules. With increasing size of aggregates, (H2O)n≥10 10, their thermal stability strengthens. Mechanical stability of great clusters keeps the quickly reached level, and the coefficient of dielectric stability passes through the maximum at n = 50. 相似文献
64.
A new characteristic-based method for the solution of the 2D laminar incompressible Navier-Stokes equations is presented. For coupling the continuity and momentum equations, the artificial compressibility formulation is employed. The primitives variables (pressure and velocity components) are defined as functions of their values on the characteristics. The primitives variables on the characteristics are calculated by an upwind diffencing scheme based on the sign of the local eigenvalue of the Jacobian matrix of the convective fluxes. The upwind scheme uses interpolation formulae of third-order accuracy. The time discretization is obtained by the explicit Runge–Kutta method. Validation of the characteristic-based method is performed on two different cases: the flow in a simple cascade and the flow over a backwardfacing step. 相似文献
65.
Vimla Vyas 《Pramana》2008,70(4):731-738
Speeds of sound and densities of three ternary liquid systems namely, toluene + n-heptane + n-hexane (I), cyclohexane + n-heptane + n-hexane (II) and n-hexane + n-heptane + n-decane (III) have been measured as a function of the composition at 298.15 K at atmospheric pressure. The experimental isothermal
compressibility has been evaluated from measured values of speeds of sound and density. The isothermal compressibility of
these mixtures has also been computed theoretically using different models for hard sphere equations of state and Flory’s
statistical theory. Computed values of isothermal compressibility have been compared with experimental findings. A satisfactory
agreement has been observed. The superiority of Flory’s statistical theory has been established quite reasonably over hard
sphere models.
相似文献
66.
Given an ordered set E and a topological space X, we say that E can be realized within X if there is an injection j from E into the class of (homeomorphism classes of) subspaces of X such that, for x, y in E, x y if and only if j(x) is homeomorphically embeddable into j(y). It is known, for instance, that transfinite induction demonstrates that every partially-ordered set of cardinality c (and some larger ones) can be realized within the real line. We explore aspects of the realizability problem, indicating, in particular, how to weaken the hypothesis on E from partial- to quasi-order, and seeking to isolate the characteristics of the real line that are relevant here. 相似文献
67.
Dimple Sharma Jaibir S. Yadav Satish Kumar K.C. Singh V.K. Sharma 《Thermochimica Acta》2008,475(1-2):8-14
Molar excess volumes, VE, molar excess enthalpies, HE, and speeds of sound, u, of o-toluidine (i) + cyclohexane or n-hexane or n-heptane (j) binary mixtures have been determined over entire range of composition at 308.15 K. Speeds of sound data have been utilized to predict isentropic compressibility changes of mixing, of (i + j) mixtures. The observed VE, HE and data have been analyzed in terms of Graph theory. The analysis of VE data by Graph theory reveals that o-toluidine exists as an associated molecular entity and (i + j) mixtures contain 1:1 molecular complex. It has been observed that VE, HE and values calculated by Graph theory compare well with their corresponding experimental values. The observed data have also been analyzed in term of Flory theory. 相似文献
68.
Sathyanarayana Boodida Ranjith Kumar Bachu Murali Krishna Patwari Satyanarayana Nallani 《The Journal of chemical thermodynamics》2008,40(9):1422-1427
The values of density (ρ), viscosity (η) and speed of sound (u) have been measured for binary liquid mixtures of γ-butyrolactone (GBL), δ-valerolactone (DVL), and ε-caprolactone (ECL) with N-methylacetamide (NMA) over the whole composition range at T = (303.15 to 318.15) K and atmospheric pressure. From these data, excess molar volume (VE), deviation in viscosity (Δη), and deviation in isentropic compressibility (Δκs), are calculated. The results are fitted to a Redlich–Kister type polynomial equation to derive binary coefficients and standard deviations. 相似文献
69.
Density and sound speed measurements have been carried out for the ternary systems consisting of tetra-n-butyl ammonium bromide (TBAB) in 0.1 m aqueous magnesium sulphate heptahydrate (MgSO4.7H2O)-water over the full range of composition from T = 293.15 to 318.15 K by using volumetric method. Using this experimental data, various physical and thermodynamical parameters such as adiabatic compressibility, apparent molal compressibility, apparent molal volume, apparent and limiting partial molar volumes of the electrolytes and ions in these mixtures have been evaluated and split into respective ionic contributions. The results have been discussed in terms of ion–ion and ion–solvent interactions occurring between TBAB and aqueous MgSO4 solutions. Further, structure making/breaking behaviour of MgSO4 has been reported in terms of sign of the partial molar expansibility at infinite dilution. 相似文献
70.