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The process of wave formation at the contact boundary of colliding metal plates is a fundamental basis of explosive welding technology. In this case, the metals are in a pseudo-liquid state at the initial stages of the process, and from a mathematical point of view, a wave formation process can be described by compressible multiphase models. The work is devoted to the development of a three-fluid mathematical model based on the Baer–Nunziato system of equations and a corresponding numerical algorithm based on the HLL and HLLC methods, stiff pressure, and velocity relaxation procedures for simulation of the high-speed impact of metal plates in a one-dimensional statement. The problem of collision of a lead plate at a speed of 500 m/s with a resting steel plate was simulated using the developed model and algorithm. The problem statement corresponded to full-scale experiments, with lead, steel, and ambient air as three phases. The arrival times of shock waves at the free boundaries of the plates and rarefaction waves at the contact boundary of the plates, as well as the acceleration of the contact boundary after the passage of rarefaction waves through it, were estimated. For the case of a 3-mm-thick steel plate and a 2-mm-thick lead plate, the simulated time of the rarefaction wave arrival at the contact boundary constituted 1.05 μs, and it was in good agreement with the experimental value 1.1 μs. The developed numerical approach can be extended to the multidimensional case for modeling the instability of the contact boundary and wave formation in the oblique collision of plates in the Eulerian formalism.

A multifluid mathematical model for the computation of a high speed collision of metallic plates is constructed. Each material—steel, of which the first plate is made; lead, of which the second plate is made; and the surrounding air—is assumed to be a compressible fluid. The Baer–Nunziato equations are solved. The determining system of equations is hyperbolic, and it is numerically solved using the HLL method. The problem statement corresponds to the full-scale experiment. A lead plate is thrown in the direction of a steel plate at a velocity of 500 m/s. Both plates have free boundaries. The main characteristics of the process—formation of shock waves, their propagation to the free boundaries of the plates, reflection in the form of rarefaction waves, and interaction of the rarefaction waves with the interface between the metals—are obtained in the computations. The relative error of the parameters of the shock waves compared with the known computational and experimental data does not exceed 7%. An estimate of the acceleration of the interface between the plates due to the passage of the rarefaction wave propagating from the free boundary of the steel plate is obtained.

The magnetorotational instability (MRI) in axisymmetric rotating dusty plasmas with viscous effects is investigated by means of a three-component model MRI with a vertical weak magnetic field. Starting from the three-fluid equations and Maxwell’s equations, I derive the general linear dispersion relation governing local MRI. The dust rotational flow is assumed to have the same angular velocity as ions and electrons. The dispersion relation of two special cases, without viscosity and dust effects respectively, is discussed in detail by taking into account the high-frequency approximation in order to make the perturbation frequency larger than the ion cyclotron frequency. The numerical results demonstrate that both the viscosity and dust effects can prevent the MRI growth, and the dust-induced effects are shown to be especially significant.

Three-fluid model is used to calculate the pressure drops in a vertical pipe with the annular flow pattern for condensing steam. The three-fluid models are based on the mass, momentum, and energy balance equations for each of the fluid streams in the annular flow. There are discrepancies between predictions of three-fluid model for pressure drops and the experimental data for pressure drops when using the avail?able correlations for steam-film interfacial friction. The correlation by Stevanovic et at provides good match with experimental data, but it does not take into account some important factors affecting the pressure drops in its three-fluid model. One of these significant factors which is considered in the three fluid model used in the present paper is virtual mass (added mass) force term. Inclusion of the virtual mass force improves the pressure drop predictions such that they agree much better with the experiments. nema

We have investigated heating of solar polar coronal holes and acceleration of fast solar wind by means of lower hybrid (LH) waves. A three-fluid Maxwell model comprising electrons, protons, and α -particles is employed at around two solar radii heliocentric distance, where wave dissipation starts to be dominated by collisionless processes. We suggest specific wavenumber ranges corresponding to LH as well as stochastic instabilities and find that these instabilities may bring about a significant energy gain in positive ions.

The generation and evolution of artificial plasma clouds is a complicated process that is strongly dependent on the background environment and release conditions. In this paper, based on a three-dimensional two-species fluid model, the evolution characteristics of artificial plasma clouds under various release conditions were analyzed numerically. In particular, the effect of ionospheric density gradient and ambient horizontal wind field was taken into account in our simulation. The results show that an asymmetric plasma cloud structure occurs in the vertical direction when a nonuniform ionosphere is assumed. The density, volume, and expansion velocity of the artificial plasma cloud vary with the release altitude, mass, and initial ionization rate. The initial release velocity can change the cloud's movement and overall distribution. With an initial velocity perpendicular to the magnetic field, an O+ density cavity and two bumps exist. When there is an initial velocity parallel to the magnetic field, the generated plasma cloud is bulb-shaped, and only one O+ density cavity and one density bump are created. Compared to the cesium case, barium clouds expand more rapidly. Moreover, Cs+ clouds have a higher density than Ba+ clouds, and the snowplow effect of Cs+ is also stronger.

Purpose – The purpose of this paper is to analyse the dynamic behaviour of a three-fluid heat exchanger subjected to a step change in the temperature and velocity of the fluids at the inlet. Design/methodology/approach – The analysis is carried out using the finite element methodology, adopting the Galerkin’s approach, using implicit method for transient behaviour. Findings – The effect of step changes in the inlet temperature of hot and cold fluids show that an increase in the fluid inlet temperatures leads to increased outlet temperatures of all fluids and decreased hot fluid effectiveness. The exit temperatures of the fluids do not show any response initially for a certain period of time with the step changes. The time to reach steady state is independent of the step change in inlet temperature of the hot and the cold fluids. Research limitations/implications – The findings of this paper is limited to constant property situations. Practical implications – The findings will be useful in designing control and regulation systems of heat exchangers used in different industrial processes and operations, such as in nuclear reactors, cryogenic and petrochemical process plants. Social implications – The analysis provides a time frame in which the controls and regulation systems work, so that the necessary safety precautions for the people working in the surrounding area can be taken care of. Originality/value – As per the best knowledge of the authors, none of the papers so far have discussed the effect of the change in the inlet temperature and velocity of both the fluids. Performance parameters such as effectiveness, time to reach steady state, etc. have not been studied so far.

In internal combustion engines, only a part of the fuel energy flow is transformed into power available at the crankshaft, while the most part of the fuel energy flow is lost as coolant, exhaust gases and other waste heat flows.The focus of this study is to evaluate the performance of three-fluid re-circulating type heat exchanger to recover energy from exhaust gas The cold fluid is re-circulated to enhance the recovery of heat from the exhaust gases. Finite element model of the heat exchanger is developed based on the detailed geometry and the specific working conditions and the effectiveness of the heat exchanger is computed. Non-Dimensional parameters are introduced which makes the analysis more versatile. The effectiveness is computed for different values of NTU, Heat capacity ratios, Overall heat transfer coefficient ratio between fluid channels and the inlet temperature.

Today the climate conditions are generally averse for practicing a competitive agriculture because in areas with little precipitations during the summer some solutions are needed to be adopted in order to supplement the distributed water volume amount on cultivated areas through intensive irrigation process. For this practice specialized installations are needed that able to take water from natural or artificial sources, such as irrigation channels, realizing convey and transport to the irrigation specialized installations. The main component within these installations is represented by a pump, which is usually a centrifugal pump having an profiled impeller inside by which it can take water and send it forward due to the rotary motion of the rotor. A theoretical model for calculating the flow of the working fluid through the interior of a centrifugal pump model is presented in this paper as well as the numerical analysis on the virtual model performed with the ANSYS CFX software in order to highlight the flow parameters and flow path-lines that are formed during centrifugal pump operation.

Land subsidence has become a widespread engineering geological problem, which can quickly induce many derived disasters. Over-exploitation of groundwater is one of the main factors of urban land subsidence. There is severe land subsidence in Jining, mainly induced by groundwater over-extraction. Therefore, the numerical simulation method is used in this paper to analyze and predict the law of land subsidence in Jining. Combined with the engineering geological and hydrogeological conditions of Jining City, a three-dimensional fluid–solid coupling model of land subsidence was established by using COMSOL software. The numerical results were verified using site monitoring data. The article predicts the land subsidence in the study area in 2030. In 2030, the maximum land subsidence is 224 mm. And this paper analyzes the land subsidence pattern under different groundwater extraction amounts. The results show that the land subsidence in the study area is effectively alleviated under the condition of reducing water extraction by 30%. It provides a basis for preventing and controlling land subsidence in Jining city. It is proved that land subsidence caused by groundwater extraction positively correlates with the pumping time and amount of water pumped.