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A quasi-isentropic study on the process of driving a cylinder with aluminized explosives was carried out to examine the influence of the aluminum (Al) reaction rate on cylinder expansion and the physical parameters of the detonation products. Based on the proposed quasi-isentropic hypothesis and relevant isentropic theories, the characteristic lines of aluminized explosives driving a cylinder were analyzed, and a quasi-isentropic model was established. This model includes the variation of the cylinder wall velocity and the physical parameters of the detonation products with the Al reaction degree. Using previously reported experimental results, the quasi-isentropic model was verified to be applicative and accurate. This model was used to calculate the physical parameters for cylinder experiments with aluminized cyclotrimethylenetrinitramine explosives with 15.0 % and 30.0 % Al content. The results show that this quasi-isentropic model can be used not only to calculate the cylinder expansion rule or Al reaction degree, but also to calculate the physical parameters of the detonation products in the process of cylinder expansion. For explosives with 15.0 % and 30.0 % Al, 24.3 % and 18.5 % of the Al was found to have reacted at 33.9 μs and 34.0 μs, respectively. The difference in Al content results in different reaction intensity, occurrence time, and duration of two forms of reaction (diffusion and kinetic) between the Al powder and the detonation products; the post-detonation burning reaction between the Al powder and the detonation products prolongs the positive pressure action time, resulting in a continuous rise in temperature after detonation.

Thermodynamic calculation is the theoretical basis for the study of initiation and detonation, as well as the prerequisite for forecasting the detonation performance of unknown explosives. Based on the VLWR(Virial-Wu) thermodynamic code, this paper introduced the universal solid equation of state (EOS) VINET. In order to truly reflect the compressibility of nanocarbon under the extremely high-temperature and high-pressure environment in detonation, an SVM (support vector machine) was utilized to optimize the input parameters of carbon. The detonation performance of several explosives with different densities was calculated by the optimized universal EOS, and the results show that the thermodynamic code coupled with the universal solid EOS VINET can predict the detonation performance parameters of explosives well. To investigate the application of the thermodynamic code with the improved VINET EOS in the working capacity of explosives, the interrelationship between pressure P-particle velocity u and pressure P-volume V were computed for the detonation products of TNT and HMX-based PBX (HMX: binder: insensitive agent = 95:4.3:0.7) in the CJ isentropic state. A universal curve proposed by Cooper was used to compared the computed isentropic state, where the ratio of pressure to CJ state were plotted against the ratio of velocity to CJ state. The parameters of the JWL(Jones-Wilkins-Lee) EOS for detonation products were obtained by fitting the P–V curve. The cylinder tests of TNT and HMX-based PBX were numerically simulated using the LS-DYNA, it is verified that, within a certain range, the improved algorithm has superiority in describing the working capacity of explosives.

The ultrasonic speeds, u and viscosities, η of the binary mixtures of methyl acrylate with benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene over the whole mole fraction range were measured at six different temperatures and at atmospheric pressure. From the experimental data, the excess isentropic compressibility, κ s E , excess ultrasonic speed, u E , excess molar isentropic compressibility, K s,m E , excess specific impedance, Z E and deviations in viscosity, Δ η have been calculated. The partial molar isentropic compressions, K ¯ s,m,1 and K ¯ s,m,2 , and excess partial molar isentropic compressions, K ¯ s,m,1 E and K ¯ s,m,2 E over the whole composition range, partial molar isentropic compressions, K ¯ s,m,1 ° and K ¯ s,m,2 ° , and excess partial molar isentropic compressions, K ¯ s,m,1 ° E and K ¯ s,m,2 ° E of the components at infinite dilution have also been calculated. The results specified the existence of weak interactions between unlike molecules, the interactions follow the order: benzene > toluene > p-xylene > m-xylene > o-xylene > mesitylene. The magnitude of interactions was found to be dependent on the number and position of the methyl groups in these aromatic hydrocarbons.

The topographic dynamical effect from Eurasia (EA_Topo) and North America (NA_Topo) on the winter isentropic meridional mass circulation (IMMC) is investigated using the WACCM. The independent effect of EA_Topo and that of NA_Topo, with the former much stronger, are both to strengthen the IMMC that is composed of the lower equatorward cold air branch (CB) and the upper poleward warm air branch in the extratropical tropopshere (WB_TR) and stratosphere (WB_ST). Further investigation of the individual contributions from changes in stationary vs. transient and zonal-mean flow vs. waves reveals that, due to the topography-forced mass redistribution, changes in the low-level meridional pressure gradient force a zonal-mean counter-clockwise/ clockwise meridional cell in the southern/northern side of topography. This weakens/strengthens the IMMC south/north of 30°N from the troposphere to lower stratosphere, acting as a dominant contributor to the IMMC changes south of 50°N. Meanwhile, the EA/NA_Topo-forced amplification of stationary waves constructively interacts with those determined by land-sea contrast, making the dominant/minor contributions to the strengthening of CB and WB_TR north of 50°N. The related increase in the upward wave propagation further dominates the WB_ST strengthening in the subpolar region. Meanwhile, transient eddy activities are depressed by EA/NA_Topo along with the weakened background westerly, which partly-offset/dominate-over the contribution from stationary flow in midlatitudes and subpolar region. The coexistence of the other topography (NA/EA_Topo) yields destructive mutual interferrence, which can weaken/offset the independent-EA/NA_Topo-forced meridional mass transport mainly via changing the zonal-mean as well as the downstream wave pattern of mass and meridional wind.

Densities (ρ) and speeds of sound (u) data for the binary mixtures of benzyl alcohol (BA) with methyl ethyl ketone (MEK), diethyl ketone (DEK), methyl propyl ketone (MPK), and methyl isobutyl ketone (MIBK) have been investigated at four temperatures (T = 303.15, 308.15, 313.15 and 318.15 K) and pressure (P = 0.1 MPa) over the entire composition range. These data have been utilized to derive excess molar volume ( V m E ), excess isentropic compression ( K S E ) and excess speed of sound ( u E ) for all the systems. The experimentally determined values have been correlated by Redlich-Kister polynomial equation. Further, these results have been analysed by different theoretical treatment such as Prigogine–Flory–Patterson (PFP) theory, intermolecular free length theory and collision frequency theory. The different types of interaction between the component molecules could be addressed by the changes in positive and negative values of excess properties. The applications of present study can be used to build comprehensive theoretical models for designing various technological processes in chemical and biochemical industries.

We consider the vanishing viscosity limit for a model of a general non-Newtonian compressible fluid in R d , d = 2 , 3 . We suppose that the initial data approach a profile determined by the Riemann data generating a planar rarefaction wave for the isentropic Euler system. Under these circumstances the associated sequence of dissipative solutions approaches the corresponding rarefaction wave strongly in the energy norm in the vanishing viscosity limit. The result covers the particular case of a linearly viscous fluid governed by the Navier–Stokes system.

The initial value problems of bipolar isentropic/non-isentropic compressible Navier-Stokes-Maxwell (CNS-M) systems arising from plasmas in R 3 are studied. The main difficulty of studying the bipolar isentropic/non-isentropic CNS-M systems lies in the appearance of the electromagnetic fields satisfying the hyperbolic Maxwell equations. The large time-decay rates of global smooth solutions with small amplitude in L q ( R 3 ) for 2 ≤ q ≤ ∞ are established. For the bipolar non-isentropic CNS-M system, the difference of velocities of two charged carriers decay at the rate ( 1 + t ) − 3 4 + 1 4 q which is faster than the rate ( 1 + t ) − 3 4 + 1 4 q ( ln ⁡ ( 3 + t ) ) 1 − 2 q of the bipolar isentropic CNS-M system, meanwhile, the magnetic field decay at the rate ( 1 + t ) − 3 4 + 3 4 q ( ln ⁡ ( 3 + t ) ) 1 − 2 q which is slower than the rate ( 1 + t ) − 3 4 + 3 4 q for the bipolar isentropic CNS-M system. The approach adopted is the classical energy method but with some new developments, where the techniques of choosing symmetrizers and the spectrum analysis on the linearized homogeneous system play the crucial roles.

The density, speed of sound and viscosity data of drug pentoxifylline in aqueous solutions of glucose (monosaccharide) and lactose (disaccharide) were determined. The various properties of the solutions were characterized and their structural features determined by varying the concentrations of solute and solvent at atmospheric pressure and at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15) K. Infinite dilution limiting apparent molar volume ( $$V_{\phi }^{0}$$ ) and limiting apparent molar isentropic compression ( $$K_{\phi ,S}^{0}$$ ) parameters and their variation tendencies were considered in terms of the interactions between solute and solvent. The transfer parameters ( $$\Delta_{{{\text{tr}}}} V_{\phi }^{0}$$ and $$\Delta_{{{\text{tr}}}} K_{\phi ,S}^{0}$$ ) were positive and increased with increase in the concentrations of glucose/lactose in aqueous medium. Limiting apparent molar expansivity ( $$E_{\phi }^{0}$$ ), Hepler’s constant $$\left( {{{\partial^{2} V_{\phi }^{0} } \mathord{\left/ {\vphantom {{\partial^{2} V_{\phi }^{0} } {\partial T^{2} }}} \right. \kern-\nulldelimiterspace} {\partial T^{2} }}} \right)$$ and hydration number (nH) were also evaluated. The viscosity data have also been evaluated using the Jones–Dole equation. The results, analyzed using spectroscopic data, are discussed and rationalized in terms of various interactions.

The interaction in the binary solution of polyethylene glycol 200 (PEG 200) and polyethylene glycol 400 (PEG 400) with d-panthenol at the variation of temperatures has been surveyed by merging acoustic and volumetric processes. The density and speed of sound of PEG 200 and PEG 400 mol $${\mathrm{kg}}^{-1}$$ in the aqueous solution of d-panthenol in the concentrations of (0.00, 0.03, 0.06 and 0.09) at temperature, T = (288.15, 298.15, 308.15 and 318.15) K and experimental pressure 0.1 MPa is measured. From the data of density, the apparent molar volume $${(V}_{\phi })$$ , partial molar volume $${(V}_{\phi }^{0})$$ and partial molar volume of transfer $$(\Delta {V_{\phi }^{0}} )$$ , for PEG 200 and PEG 400 in the aqueous solution of d-panthenol is calculated along with the apparent molar isentropic compression $${(K}_{\phi })$$ , partial molar isentropic compression $${(K}_{\phi }^{0})$$ and the partial molar isentropic compression of transfer, $$(\Delta {K_{\phi }^{0}} )$$ , from the of the speed of sound data. Using the partial molar volume of transfer and partial molar isentropic compression of transfer the pair and triplet coefficients as the functions of temperatures are calculated as well as the partial molar expansibilities ( $${E}_{\phi }^{0}$$ ) with its first-order derivative $$\left( {\partial {E_{\phi }^{0}} /\partial T} \right)_{P}$$ are obtained. Further, these calculated parameters are used to describe the results in terms of (solute–solute); (solute–solvent) interactions including the structure making/breaking ability of polyethylene glycols in the aqueous solution of d-panthenol.

This paper reports on the development of a magnetically driven high-velocity implosion experiment conducted on the CQ-3 facility, a compact pulsed power generator with a load current of 2.1 MA. The current generates a high Lorentz force between inner and outer liners made from 2024 aluminum. Equally positioned photonic Doppler velocimetry probes record the liner velocities. In experiment CQ3-Shot137, the inner liner imploded with a radial converging velocity of 6.57 km/s while the outer liner expanded at a much lower velocity. One-dimensional magneto-hydrodynamics simulation with proper material models provided curves of velocity versus time that agree well with the experimental measurements. Simulation then shows that the inner liner underwent a shock-less compression to approximately 19 GPa and reached an off-Hugoniot high-pressure state. According to the scaling law that the maximum loading pressure is proportional to the square of the load current amplitude, the results demonstrate that such a compact capacitor bank as CQ-3 has the potential to generate pressure as high as 100 GPa within the inner liner in such an implosion experiment. It is emphasized that the technique described in this paper can be easily replicated at low cost.

We study an asymptotic analysis of a coupled system of kinetic and fluid equations. More precisely, we deal with the nonlinear Vlasov–Fokker–Planck equation coupled with the compressible isentropic Navier–Stokes system through a drag force in a bounded domain with the specular reflection boundary condition for the kinetic equation and homogeneous Dirichlet boundary condition for the fluid system. We establish a rigorous hydrodynamic limit corresponding to strong noise and local alignment force. The limiting system is a type of two-phase fluid model consisting of the isothermal Euler system and the compressible Navier–Stokes system. Our main strategy relies on the relative entropy argument based on the weak–strong uniqueness principle. For this, we provide a global-in-time existence of weak solutions for the coupled kinetic-fluid system. We also show the existence and uniqueness of strong solutions to the limiting system in a bounded domain with the kinematic boundary condition for the Euler system and Dirichlet boundary condition for the Navier–Stokes system.

In this paper, we are concerned with the uniform regularity estimates of smooth solutions to the isentropic compressible magneto-micropolar system in T3. Under the assumption that , and by applying the classic bilinear commutator and product estimates, the uniform estimates of solutions to the isentropic compressible magneto-micropolar system are established in space, .

According to baroclinic adjustment theory, the isentropic slope maintains its marginal state for baroclinic instability. However, the recent trend of Arctic warming raises the possibility that there could have been a systematic change in the extratropical isentropic slope. In this study, global reanalysis data are used to investigate this possibility. The result shows that tropospheric isentropes north of 50°N have been flattening significantly during winter for the recent 25 years. This trend pattern fluctuates at intraseasonal time scales. An examination of the temporal evolution indicates that it is the planetary-scale (zonal wavenumbers-1–3) eddy heat fluxes, not the synoptic-scale eddy heat fluxes, that flatten the isentropes; synoptic-scale eddy heat fluxes instead respond to the subsequent changes in isentropic slope. This extratropical planetary-scale wave growth is preceded by an enhanced zonal asymmetry of tropical heating and poleward wave activity vectors. A numerical model is used to test if the observed latent heating can generate the observed isentropic slope anomalies. The result shows that the tropical heating indeed contributes to the isentropic slope trend. The agreement between the model solution and the observation improves substantially if extratropical latent heating is also included in the forcing. The model temperature response shows a pattern resembling the warm-Arctic–cold-continent pattern. From these results, it is concluded that the recent flattening trend of isentropic slope north of 50°N is mostly caused by planetary-scale eddy activities generated from latent heating, and that this change is accompanied by a warm-Arctic–cold-continent pattern that permeates the entire troposphere.

The features of the fluid compression in a vapor bubble during its collapse in cold (273 K) and cool (293 K) acetone are studied. The liquid pressure $$p_{0}$$ is varied in the range 0.12–5 bar. The full hydrodynamic model is used in vapor and liquid. The non-stationary heat conductivity of both fluids and non-equilibrium mass transfer across the bubble surface are taken into account. Realistic wide-range equations of state are applied. It is shown that as the liquid pressure $$p_{0}$$ is diminished, the depth of the bubble collapse decreases in cold acetone, but grows in cool acetone. The maximum of the collapse rate decreases monotonically in cool acetone. In cold acetone it is reduced only in an interval bounded by a certain value of $$p_{0}$$ , and then it increases. As a result, with decreasing $$p_{0}$$ of cool acetone, the vapor in the bubble is compressed first by radially convergent shock waves, then by isentropic waves, and after that its nearly uniform compression takes place, whereas only the first scenario is realized in cold acetone.

Performance evaluation of low-GWP refrigerants in scroll compressor is carried out to aid the selection of suitable refrigerant for different applications. The open-source modeling platform PDSim, used for this study, is based on the mechanistic chamber model that has the accuracy comparable to the heuristic methods. A scaling model is developed to design and select the scroll geometry for 1–100 ton range of cooling capacity and seven refrigerants. This method is based on manufacturing constraints and minimization of leakage. Additionally, the ports and the bearings are scaled to make their effect fair for a range of capacities and refrigerants. The simulation model is validated using two example scroll compressors. The predicted mass flow rate and power are within 3% MAE while the isentropic efficiency is within 4% mean absolute error. A validated model and standard AHRI conditions are used for the performance evaluation of the refrigerants over a range of 1 to 100 tons of refrigeration capacity. Seven refrigerants are studied including low-pressure refrigerants, R1234ze(E) and R1234yf, medium-pressure refrigerants, R410A, R32, R454B, and R452B and high-pressure R744. The results suggest that an optimum range exists for each refrigerant to achieve good compressor performance. The leakage area is the primary contributor to the scroll compressor performance.

In this study, a thermodynamic analysis of the hybrid heat source driven organic Rankine cycle integrated flash tank vapor compression refrigeration (ORC-FTVCR) system is conducted using five different hydrocarbon fluids such as hexane, heptane, octane, nonane, and decane. The hybrid heat source consists of a solar collector and a biomass burner system. The system coefficient of performance (COPs), overall exergetic efficiency (ηoex), are taken as the indices of the thermal performance of the system. The impact of the operating parameters such as the intensity of solar radiation, inlet temperatures of expander and VCR evaporator, isentropic efficiencies of the compressor and expander, and the condenser saturated vapor temperature on system performance is also investigated. The results indicate that the system performs better using heptane as the working fluid. The values of COPs, ηoex, for ORC-FTVCR system using heptane are 0.551 and 4.21%, respectively. The solar collector and the biomass burner system contribute 88% to the total exergy destruction of the system.

Exposing students to hands-on experiments has been a common approach to illustrating complex physical phenomena that have been otherwise modelled solely mathematically. Compressible, isentropic flow in a duct is an example of such a phenomenon, and it is often demonstrated via a de Laval nozzle experiment. We have improved an existing converging/diverging nozzle experiment so that students can modify the location of the normal shock that develops in the diverging portion to better understand the relationship between the shock and the pressure. We have also improved the data acquisition system for this experiment and explained how visualisation of the standing shock is now possible. The results of the updated system demonstrate that the accuracy of the isentropic flow characteristics has not been lost. Through pre- and post-laboratory quizzes, we show the impact on student learning as well.

Finite volume methods were used to study the process of gas expansion in the stage of a turboexpander unit (TEU) in a three-dimensional, nonstationary setting. The main objectives of the work are to verify the calculation methodology based on a real experiment, to obtain a qualitative and quantitative agreement of data for further studies of the processes occurring in the flow path of the stage of a turboexpander unit, namely, phase transitions during condensation of impurities in the bulk. Due to the fact that the experiment is only preliminary tests, there is no reliable data on the intermediate values of the macroparameters; therefore, the verification of the proposed method was carried out only in terms of the temperature at the outlet from the diffuser and the isentropic efficiency. The calculation technique used in this work, thanks to the use of sliding interfaces, made it possible to study the turboexpander unit not in parts but with the help of a unified calculation model, taking into account the leaks and overflows of the working fluid (helium). In the course of calculations, the fields of velocity, pressure, and temperature were obtained in the longitudinal and cross sections of the turboexpander unit as well as on its walls. A simplified h, s-process diagram, and the values of isentropic efficiency are determined for several points. The proposed calculation method, applied for a specific model of a turboexpander unit, can be extrapolated to other variants of the flow paths of microturbine expander units for boundary conditions and operating modes close to the original variant. To prepare an extended calculation method, it is necessary to carry out additional studies as well as to establish the limits of applicability of the finite volume method on a larger data set.

Shock loss is the primary source of total pressure loss of transonic axial compressors. Reducing the shock by redesigning the geometry of rotor is of great interest for turbomachinery designers. However, the complex flow field involving shock waves, shock-boundary interaction, intense secondary flows, etc., in the compressor makes the design of rotor difficult. The conventional method of design and optimization is computationally intensive and time-costly. This study introduces an inverse design method to design rotor blades corresponding to prescribed isentropic Mach number distributions with no modification of flow-governing equations. An artificial neural network is trained to predict the isentropic Mach number distributions of any deformed blades. Then, with the pattern search optimization, the blade corresponding to the prescribed isentropic Mach number distributions can be achieved. When the aerodynamic parameter database is calculated and the neural network is obtained, this method can design large numbers of blades of changed isentropic Mach number distributions immediately, without modifying the computational fluid dynamics (CFD) flow solver. The design process is fully automatic and efficient. In this study, NASA Rotor 37 is redesigned and optimized as test cases. Some analysis on the influence of blade shape on aerodynamic characteristics of the rotor is represented in this study.

We study compressible isentropic Navier-Stokes-Poisson equations in ℝ3. With some appropriate assumptions on the density, velocity and potential, we show that the classical solution of the Cauchy problem for compressible unipolar isentropic Navier-Stokes-Poisson equations with attractive forcing will blow up in finite time. The proof is based on a contradiction argument, which relies on proving the conservation of total mass and total momentum.

The indirect method of obtaining in situ particle velocity of sample, under dynamic high-pressure loading experiments, generates an error due to the influence of rarefaction wave from the sample-wi...

In this study, a novel organic Rankine cycle (ORC) based on a pump driven by internal multi-potential, i.e., gravity-assisted thermally driven pump (GTP), is presented. The newly proposed cycle consists of a GTP, a condenser, an expander, and an evaporator. The GTP component is composed of three top-down organized units, and it drives the transport of liquid from the low-pressure condenser to the high-pressure evaporator by thermal energy and gravity. Such a component substitutes the conventional electricity-driven pump. Moreover, the modified scroll expander of the ORC-GTP system is experimentally studied, and the results show that the best conversion efficiency from shaft work to electricity and the best isentropic efficiency are 82.0% and 84.2%, respectively. The experimental setup of the ORC-GTP power system is built for low-grade thermal energy recovery. It is tested under the average evaporator outlet temperature of 96.4°C, 106.1°C, and 108.8°C at the ambient temperature of around 25°C. The highest shaft work is achieved at 96.4°C evaporator outlet temperature, and the largest ratio of time lasting for power generation is 100%. Since the ORC-GTP system has much less sensible heat loss of the evaporator, the highest average thermal efficiency of the ORC-GTP reaches 3.57%, which is increased by 71.74% compared with the pumpless ORC system in the literature.

Purpose Usage of gas turbine engines has increased by day due to rising demand for military and civil applications. This case results in investigating diverse topics related to energy efficiency and irreversibility of these systems. The purpose of this paper is to perform a detailed entropy assessment of turbojet engines for different flight conditions. Design/methodology/approach In this study, for small turbojet engines used in unmanned aerial vehicles, parametric cycle analysis is carried out at (sea level-zero Mach (hereinafter phase-I)) and (altitude of 9,000 m- Mach of 0.7 (hereinafter phase-II)). Based on this analysis, variation of performance and thermodynamic parameters with respect to change in isentropic efficiency of the compressor (CIE) and turbine (TIE) is examined at both phases. In this context, the examined ranges for CIE is between 0.78 and 0.88 whereas TIE is between 0.85 and 0.95. Findings Increasing isentropic efficiency decreases entropy production of the small turbojet engine. Moreover, the highest entropy production occurs in the combustor in the comparison of other components. Namely, it decreases from 2.81 to 2.69 kW/K at phase-I and decreases from 1.44 to 1.39 kW/K at phase-II owing to rising CIE. Practical implications It is thought that this study helps in understanding the relationship between entropy production and the efficiency of components. Namely, the approach used in the current analysis could help decision-makers or designers to determine the optimum value of design variables. Originality/value Due to rising isentropic efficiencies of both components, it is observed that specific fuel consumption (SFC) decreases whereas specific thrust (ST) increases. Also, the isentropic efficiency of a compressor affects relatively SFC and ST higher than that of the turbine.

We analyse exact solutions to the Riemann problem for a one-dimensional isentropic and perfectly conducting non-ideal dusty gas flow in the presence of a transverse magnetic field. We give the expression of wave curves as well as the behaviors of these wave curves. A new technique is provided to get a complete list of analytical solutions with the corresponding criteria. Moreover, the numerical solutions to the Riemann problem are also given. It is shown that the analytical solutions match well with the corresponding numerical solutions.

We present data on the quasi-isentropic compressibility of a strongly coupled (nonideal) plasma of a deuterium–helium mixture in the range of pressures 150–250 GPa in devices with a cylindrical geometry and a new result obtained in an experiment with “pure” deuterium at a pressure ~200 GPa. The trajectory of the plasma-compressing metallic shells was recorded using powerful pulsed X-ray sources with a boundary electron energy up to 60 MeV. The densities of the plasma of deuterium and its mixture with helium were determined from the measured radii of the shells at the instant of their “stopping.” We derived the pressure of the compressed plasma based on gasdynamic computations including the real characteristics of the experimental devices. The data obtained confirm the conclusion previously reached at VNIIEF about a phase transition in the plasma of compressed deuterium in the range of pressures 150–160 GPa and suggest that this phase transition is retained in the mixture of deuterium with helium.

We present first principles predictions of the absolute entropy of a silicate liquid (CaSiO3) over a wide pressure-temperature range encompassing the Earth’s mantle (2000–6000 K, 0–270 GPa). The results are derived from molecular dynamics simulations based on density functional theory and the two-phase thermodynamic (2PT) method, which divides the vibrational density of states into solid-like and gas-like parts, and which we describe in detail. The heat capacity derived from the absolute entropy agrees well with experimental measurements at low pressure. We find that the vibrational contribution accounts for more than 75% of the total entropy over the range of our study. We find that the two-body approximation to the excess entropy (relative to the ideal gas), which is computed with knowledge only of the radial distribution function, is excellent over most of the range considered, except at the lowest pressures and temperatures. We also compute the entropy of CaSiO3 perovskite and use the entropy of liquid and solid phases to determine their absolute free energies and the melting curve. The melting curve agrees well with experiment and independent theoretical determinations based on Clausius-Clapeyron integration and the ZW method, showing a melting temperature of 5600 K at the Earth’s core-mantle boundary. We find a nearly universal scaling of the self-diffusion coefficients with the excess entropy D ∗ = 0.9 exp 1.2 S ex , where D* is the self-diffusion coefficient suitably non-dimensionalized using macroscopic thermodynamic properties, and Sex is the excess entropy in units of the Boltzmann constant per atom. We use our results to estimate the temperature distribution in an isentropic, molten silicate Earth, finding 4.4 kJ/kg/K to be the lowest entropy that is completely molten, and producing a temperature at the core-mantle boundary of 6000 K.

We investigate the asymptotic behavior of solutions to the initial boundary value problem for the micropolar fluid model in a half line ℝ+ ≔ (0, ∞). Inspired by the relationship between a micropolar fluid model and Navier-Stokes equations, we prove that the composite wave consisting of the transonic boundary layer solution, the 1-rarefaction wave, the viscous 2-contact wave and the 3-rarefaction wave for the inflow problem on the micropolar fluid model is time-asymptotically stable under some smallness conditions. Meanwhile, we obtain the global existence of solutions based on the basic energy method.

It is well known that people can derive the radiation MHD model from an MHD-P1 approximate model. As pointed out by F. Xie and C. Klingenberg (2018), the uniform regularity estimates play an important role in the convergence from an MHD-P1 approximate model to the radiation MHD model. The aim of this paper is to prove the uniform regularity of strong solutions to an isentropic compressible MHD-P1 approximate model arising in radiation hydrodynamics. Here we use the bilinear commutator and product estimates to obtain our result.

This study is concerned with the large time behaviour of the three-dimensional isentropic compressible Navier–Stokes–Korteweg equations, which are used to model viscous and compressible fluids with internal capillarity. Based on the fact that the rarefaction wave is nonlinearly stable to the one-dimensional isentropic compressible Navier–Stokes–Korteweg equations, the planar rarefaction wave to the three-dimensional isentropic compressible Navier–Stokes–Korteweg equations is first constructed. Then it is shown that the planar rarefaction wave is asymptotically stable in the case that the initial data are a suitably small perturbation of the planar rarefaction wave and the strength of the rarefaction wave is small. The proof is based on the delicate energy method. The result indicate that the planar rarefaction wave of the inviscid Euler system is stable for the three-dimensional isentropic compressible fluids with physical viscosities and internal capillarity.

Starting and buzz characteristics of high-speed intakes were investigated with nanoparticle injection. Isentropic and Kantrowitz contraction limits were estimated at particle mass loading ratios of...

Wave rotor refrigeration is a new method of expansion refrigeration. Non-equilibrium phase transition is one of the key factors that influence the refrigeration performance of wave rotor. Since the process of phase transition is transient and high-frequency, there are challenges in related researches. At first, this paper traces the movement trajectory of small particles in wave rotor and confirms the existence of evaporation in wave rotor. Based on this, the numerical analysis model of wave rotor that takes into account the phase transition regarding evaporation as reverse process of condensation is built up. On this basis, the change of droplet radius, droplet number and liquefaction fraction in wave rotor is obtained. Besides, the influence of inlet pressure and humidity on refrigeration performance of wave rotor is found out. The results show that with the increase of pressure of HP inlet, the isentropic expansion efficiency increases and the increase becomes gentle. With the increase of relative humidity of HP inlet, the efficiency decreases and the decrease reaches 2.8% at maximum. The results can help optimize wave rotor performance and be used for reference to wet gas transient temperature change.

The present study reports densities, ρ, speeds of sound, u, molar heat capacities, CP of binary piperidine or 1-methylpiperidine (1) + 2- or 3- or 4-picolines (2) mixtures over entire composition range by varying temperature range from 293.15 to 308.15 K with step of 5 K interval. Experimental data have been used to access excess molar volumes, VE, excess isentropic compressibilities, $$\kappa_{{\rm S}}^{\text{E}}$$ and excess heat capacities, $$C_{{\rm P}}^{\text{E}}$$ . The VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ data have been fitted to Redlich–Kister polynomial equation to evaluate the adjustable parameters and standard deviations. The $$C_{{\rm P}}^{\text{E}}$$ data of piperidine (1) + 2- or 3- or 4-picolines (2); 1-methylpiperidine (1) + 3- or 4-picolines (2) are positive and those for 1-methylpiperidine (1) + 2-picoline (2) mixture, sign and magnitude of $$C_{{\rm P}}^{\text{E}}$$ values change with increase in mole fraction of 1-methylpiperidine. Further, VE and $$\kappa_{{\rm S}}^{\text{E}}$$ of 1-methylpiperidine (1) + 2- or 3- or 4-picolines (2); piperidine (1) + 2- or 3-picolines (2) are negative; and those for piperidine (1) + 4-picoline (2) are positive across full range of composition. The VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ data have been utilized to test the applicability of Graph theory. It has been observed that VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ values calculated from the Graph theory compare reasonably well with their corresponding experimental values. The Quantum mechanical calculations and IR spectral studies on the aforesaid mixtures support the presence of various molecular entities (estimated by analyses of VE data) in pure and mixed state.

We are concerned with the vanishing flux-approximation limits of solutions to the isentropic relativistic Euler equations governing isothermal perfect fluid flows. The Riemann problem with a two-parameter flux approximation including pressure term is first solved. Then, we study the limits of solutions when the pressure and two-parameter flux approximation vanish, respectively. It is shown that, any two-shock-wave Riemann solution converges to a delta-shock solution of the pressureless relativistic Euler equations, and the intermediate density between these two shocks tends to a weighted δ-measure that forms a delta shock wave. By contract, any two-rarefaction-wave solution tends to a two-contact-discontinuity solution of the pressureless relativistic Euler equations, and the intermediate state in between tends to a vacuum state.

By introducing an isentropic Euler system with a new version of extended Chaplygin gas equation of state, we study two kinds of occurrence mechanism on the phenomenon of concentration and the formation of delta shock waves in the zero-exponent limit of solutions to the extended Chaplygin gas equations as the two exponents tend to zero wholly or partly. The Riemann problem is first solved. Then, we show that, as both the two exponents tend to zero, that is, the extended Chaplygin gas pressure tends to a constant, any two-shock-wave Riemann solution of the extended Chaplygin gas equations converges to a delta-shock solution to the zero-pressure flow system, and the intermediate density between the two shocks tends to a weighted δ-measure which forms a delta shock wave; any two-rarefaction-wave Riemann solution tends to a two-contact-discontinuity solution to the zero-pressure flow system, and the nonvacuum intermediate state in between tends to a vacuum. It is also shown that, as one of the exponents goes to zero, namely, the extended Chaplygin gas pressure approaches to some special generalized Chaplygin gas pressure, any two-shock-wave Riemann solution tends to a delta-shock solution to the generalized Chaplygin gas equations.

An experimental study has been made of the density and the velocity of sound for liquid decalin and cyclohexane in the range of temperatures 298.15–433.15 K and pressures 0.1–100.1 MPa. Parameters of equations have been obtained that describe the dependences of the specific volume of liquid decalin and cyclohexane on their temperature and pressure and of the isobaric heat of these substances on their temperature at atmospheric pressure. The density, the velocity of sound, the isobaric and isochoric heats, the isobaric expansion coefficient, and the coefficients of isentropic and isothermal compressibilities of liquid decalin and cyclohexane have been determined in the range of temperatures 298.15–433.15 K at pressures to 100 MPa.

The densities, ρ, speeds of sound, u, of binary piperidine or 1-methylpiperidine (1) + 2-pyrrolidinone or pyridine (2), and densities, ρ123, speeds of sound, u123, of ternary piperidine or 1-methylpiperidine (1) + 2-pyrrolidinone (2) + pyridine (3) mixtures and molar heat capacities, CP, for the aforesaid binary mixtures have been measured over the entire composition range at temperatures ranging from (293.15–308.15) K with an increment of 5 K. The excess molar volumes $$V^{\text{E}}$$ , $$V_{123}^{\text{E}}$$ , excess isentropic compressibilities, $$\kappa_{S}^{\text{E}}$$ , $$(\kappa_{S}^{\text{E}} )_{123}$$ for the binary and ternary mixtures and excess heat capacities, $$C_{P}^{\text{E}}$$ , for investigated binary mixtures (determined by using experimental data) were fitted with the Redlich–Kister equations, and adjustable binary as well as ternary parameters along with the standard deviations have been estimated. The analyses of $$V^{\text{E}}$$ , $$\kappa_{S}^{\text{E}}$$ , $$C_{P}^{\text{E}}$$ data, quantum mechanical calculations and IR spectra of binary mixtures have revealed that piperidine (1) + 2-pyrrolidinone (2) mixtures are characterized by interactions between nitrogen and hydrogen atoms of piperidine with the hydrogen and oxygen atoms of 2-pyrrolidinone; 1-methylpiperidine (1) + 2-pyrrolidinone (2) mixtures are characterized by interactions between nitrogen and electron deficient carbon atom of 1-methylpiperidine with hydrogen and oxygen atoms of 2-pyrrolidinone; piperidine (1) + pyridine (2) mixtures are characterized by interactions between the hydrogen atom of piperidine with the nitrogen atom of pyridine; 1-methylpiperdine (1) + pyridine (2) mixtures are characterized by the interaction of the nitrogen atom of 1-methylpiperidine with the Π-electron cloud of pyridine’s aromatic ring.