Mathematical Model For Numerical Simulation Research Articles

Experimental Methods for Measuring the Viscous Friction Coefficient in Hydraulic Spool Valves

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

Modelling and numerical simulation of the transport phenomena in water thermal energy storage tanks

Mathematical model for numerical simulation of the transient heat transfer and fluid flows in water thermal energy storage tanks is developed. The model allows analysis of the thermal fields in the accumulators at different schemes and modes of charging and discharging. It was verified and validated based on experimentally obtained information about the temperature stratification at charging of a thermal accumulator at a laboratory solar system. The proposed approach for numerical study of the thermal energy storage is convenient for parametrical estimation and improvement of the efficiency of the thermal systems.

Analysis of the Characteristics and Influencing Factors of Gas Explosion in Heading Face

In order to accurately grasp the characteristics and influencing factors of gas explosion in heading face, the mathematical model of gas explosion was determined. According to the actual size of a heading face of a coal mine, a 3D geometric model with a length of 100 m was established, and the effects of ignition energy and gas explosion equivalent on the gas explosion characteristics of the heading face were analyzed. The results show the following. (1) The mathematical models for numerical simulation of gas explosion can accurately simulate the gas explosion and its propagation process. The time-space step size has a great influence on the simulation results. The grid spacing for numerical simulation of mine gas explosion is determined to be 0.1 m and the time step length is determined to be 0.001 s. (2) The ignition energy has a limited effect on gas explosion characteristics. It only has a certain influence on the gas explosion process, but has little influence on the overpressure of shock wave. The larger the ignition energy is, the faster the explosion reaction speed is, and the maximum overpressure increases slightly. When the ignition energy increases to a certain value, the time of peak shock wave and the maximum overpressure both tend to be stable. The ignition energy has little effect on gas explosion characteristics when an explosion accident occurs underground with a large amount of gas accumulation. (3) The gas explosion equivalent has a great influence on the overpressure of gas explosion shock wave. The higher the explosion equivalent is, the greater the pressure is, and the peak value of the shock wave overpressure increases with the explosion equivalent as a power function. The research results have important guiding significance for the research and development of new technology for prevention and control of gas explosion.

Path following algorithm application to automatic berthing control

This paper aims to verify a new automatic berthing system using a path following algorithm. Berthing operation is one of the most burdensome tasks for crews among several ship operations. The maneuverability of a ship at low speed during berthing operation deteriorates and becomes more vulnerable to disturbances such as wind. Therefore, it is necessary to support and automate operations that require advanced skills such as berthing operation. Previous studies on automatic berthing have investigated various methods to handle the nonlinearity of ship maneuvering motion and determine the optimal control variable. There is a trade-off between accuracy and real-time performance of berthing control from these studies. The algorithms must have sufficiently real-time performance while maintaining the accuracy of control. For these purposes, we propose the automatic berthing system applied a path following algorithm for a ship with one propeller and one rudder in this paper. We show the mathematical model for numerical simulation of berthing control and carried out system identification of the subject ship. In full-scale experiments, the proposed system performed automatic berthing control in both calm wind conditions around 2 m/s and strong wind conditions around 6 m/s.

Investigation of Dynamic Motion Processes of Modernized UAV using Mathematical Model of Numerical Simulation

Investigation of Dynamic Motion Processes of Modernized UAV using Mathematical Model of Numerical Simulation

MODELING OF PET-CONTAINERS BLOW MOLDING FROM PREFORM

The оbject and subject is the process of blowing a PET bottle from a preform. The aim of the project is to investigate the process of forming PET containers under the influence of input factors such as temperature distribution, pressure in the mold, blow-up time of the workpiece in order to achieve the most uniform and minimum wall thickness of the formed container and to find the technological regimes necessary for this. When modeling the process of blowing a PET bottle from a preform, based on an analytical review of scientific and technical literature, regulatory and design documentation, patent studies, engineering and technical calculations, the following is accomplished. As a result of the work, a number of options for the production of PET packaging made from preforms and equipment for this production were analyzed, the feasibility and directions of modernization were determined. The boundary and initial conditions of the mathematical model are determined and the adaptation of the mathematical model for numerical simulation is proposed. The simulation of the process of blow molding of PET preforms with ANSYS Polyflow system with and without stock is carried out. An improved method of blowing PET preform packaging is proposed, which allows to improve the level of productivity of finished packaging products. The numerical researches of the process of blowing the PET containers have made it possible to establish the expediency of using a tension rod. The simulation of the blow molding process with the rod made it possible to identify the relationship between the rod speed, time and pressure of the blowout. The performed numerical studies have shown the effectiveness of the method of calculating the preform heating preheating zones in order to obtain containers with a given profile of wall thicknesses

Mathematical model and sensitivity analysis for describing emulsification in ASP flooding

Alkali-surfactant polymer flooding has become an important technique to improve oil recovery following the development of oil fields while the function of emulsification in enhanced oil recovery is rarely considered in the existing mathematical model for numerical simulation. In this paper, the mechanism of improving the recovery of the emulsification was analyzed in ASP flooding, and a relatively perfect mathematical model with deep filtration-theory was established, in which oil–water volume equation, saturation equation, viscosity equation, and permeability reduction equation are included. The new model is used to simulate the actual block of an oil field; the simulated results of the new model and an old model without considering the emulsification are compared with the actual well history. It is found that new model which is easy to be realized in numerical simulation has a high precision fitting, and the effect of adding oil and decreasing water is obvious. The sensitivity of emulsification was analyzed, and the results show that the water reducing funnel becomes wider and the rate of water cut decreases rapidly with the increase of emulsifying capacity, and then the rate of recovery slows down. The effect of increasing oil and decreasing water is better, and the degree of recovery increases. The emulsification of the ASP flooding is maintained at a moderate level, which corresponds to Φ = 0.2 in the new model, and the emulsification is applied to realize the general mathematical quantitative description, so as to better guide the oilfield development.

Mathematical Model for Numerical Simulation of Organic Compound Recovery Using Membrane Separation

AbstractA novel methodology in design and simulation of membrane‐based purification of organic solvents is proposed. A solution of water and alcohol served as model feed. Mass transfer and momentum transfer equations were derived and solved numerically to obtain the process output as function of process parameters. Water was taken as penetrant throughout the simulations. The studied process was pervaporation in which a nonporous polymeric membrane is used for purification of ethanol. Feed inlet concentration and velocity were considered as process input, water outlet concentration and removal efficiency as output. The Maxwell‐Stefan mass transfer approach was applied for estimation of diffusion, the finite element approach for numerical simulation of the process. A lower feed velocity increased the water removal efficiency.

Numerical Simulation of the Working Process in the Twin Screw Vacuum Pump

Twin screw vacuum pumps inherit the advantages of screw machinery, such as high reliability, stable medium conveying, small vibration, simple and compact structures, convenient operation, etc, which have been widely used in petrochemical and air industry. On the basis of previous studies, this study analyzed the geometric features of variable pitch of the twin screw vacuum pump such as the sealing line, the meshing line and the volume between teeth. The mathematical model of numerical simulation of the twin screw vacuum pump was established. The leakage paths of the working volume including the sealing line and the addendum arc were comprehensively considered. The corresponding simplified geometric model of leakage flow was built up for different leak paths and the flow coefficients were calculated. The flow coefficient value range of different leak paths was given. The results showed that the flow coefficient of different leak paths can be taken as constant value for the studied geometry. The analysis of recorded indicator diagrams showed that the increasing rotational speed can dramatically decrease the exhaust pressure and the lower rotational speed can lead to over-compression. The pressure of the isentropic process which was affected by leakage was higher than the theoretical process.

Numerical analysis and experimental research of the rubber boot of the joint drive vehicle

Abstract The article presents many numerical studies and experimental research of the drive rubber boot of the joint drive vehicle. Performance requirements have been discussed and the required coefficients of the mathematical model for numerical simulation have been determined. The behavior of living in MSC.MARC environment was examined. In the analysis the following have been used: hyperplastic two-parameter model of the Mooney-Rivlin material, large displacements procedure, safe contact condition, friction on the sides of the boots. 3D numerical model of the joint bootwas analyzed under influence of the forces: tensile, compressive, centrifugal and angular. Numerous results of studies have been presented. An appropriate test stand was built and comparison of the results of the numerical analysis and the results of experimental studies was made. Numerous requests and recommendations for utilitarian character have been presented.

Кінцево-різницевий метод розрахунку течії газу у дозвуковому газовому ежекторі

Проведено аналіз сучасних математичних моделей турбулентної в’язкості для численного моделювання течії в’язкого газу в дозвукових газових ежекторах з поворотом потоку. Розглянуті переваги та недоліки кожного з них. Запропоновано до використання кінцево-різницевий метод для проведення розрахунку течії в’язкого газу в дозвукових газових ежекторах.

Simulation of Fuel Ignition Delay in Diesel Engines with Various Fuel Feeding Systems

A mathematical model for numerical simulation of the fuel combustion delay in a diesel engine as a problem of dynamic thermal explosion during the adiabatic compression has been established. Ignition of fuel and air mixture in the local volume is considered at simultaneous evaporation of drops and gas chemical reaction within overall kinetics. Satisfactory correlation of computation and experimental fuel combustion delays on speed ability and load ability of the diesel is obtained. Numerical modeling of ipact of general kinetics constants on the fuel combustion delay is carried out. The features of self-ignition in the diesel are considered at low values of chemical reaction activation energy.

Mathematical model for numerical simulation of current density in microvaristor filled insulation materials

This contribution deals with mathematical models for numerical simulation of the volume current density in microvaristor filled insulation materials. Due to the nonlinear material properties it is difficult to estimate the current and, even more important, the power losses depending on the applied voltage and electrical field, respectively. This is, however, essential to know for macroscopic simulation of the overall performance of such materials in insulation systems. This kind of insulating material should usually be operated in the pre-breakdown region of its nonlinear voltage-current characteristic. At voltages above the continuous operating voltage the material changes its resistance and becomes more conductive. In the first part of this contribution the pre-breakdown region of microvaristor filled materials is analyzed. Investigations on the field dependent conductivity and permittivity are performed. In the second part a mathematical model to describe the conductivity of microvaristor filled materials in all three regions of their nonlinear voltage-current characteristic is presented. Furthermore, a method is shown how to estimate the parameters from the mathematical model.

Numerical study of dynamic fracture aperture during production of pressure-sensitive reservoirs

In fractured reservoirs, some dynamic behavior, such as fracture opening or closure and fracture shear dilation, is induced by the variation of pressure and in-situ stress, which is associated with the fracture aperture and conductivity. In this paper, we focus on the dynamic behavior of fractures and various kinds of affecting factors, including in-situ stress, lithology and fluid pressure. A mathematical model for numerical simulation of the fracture dynamic behavior is developed, which consists of a matrix-fracture stress–strain model and a matrix-fracture flow model. The stress–strain model of fractures is derived, which contains two sections of shear dilation: before-peak dilation and after-peak shear dilation. Then a discrete fracture network (DFN) technology is used to depict the shape of fractures in reality and the model is solved by the finite element method to investigate what the range-ability the fracture aperture presents under the influence of the affecting factors. Based on this model, the effects of pressure distribution, lithology, anisotropic in-situ stress and well production proration are investigated and the specific effects by different affecting factors are analyzed. The numerical outcome indicates that the fracture aperture increases as the field pressure rises. The anisotropic in-situ stress and water injection can trigger large shear dilation, which serves as a positive function in fracture opening.

A case study on thermal performance assessment of a heat exchanger tube equipped with regularly-spaced twisted tapes as swirl generators

Effects of the regularly-spaced twisted tape (RS-TT) on the heat transfer, friction factor and thermal performance factor behaviors in a heat exchanger are reported along with those of a full length twisted tape. The full length (or typical) twisted tapes with two different twist ratios (y=P/W=6.0 and 8.0), and the regularly-spaced twisted tape (RS-TT) with two different twist ratios (y=6.0 and 8.0) and three free space ratios (s=S/P=1.0, 2.0, and 3.0) were employed for comparative study. The article also presents the application of a mathematical model for numerical simulation of the swirling flow in a tube induced by regularly-spaced twisted tape (RS-TT) insertion. The numerical simulation was performed in order to gain an understanding of physical behavior of the fluid flow (decaying swirling flow field), fluid temperature and local Nusselt number characteristics of a tube fitted with RS-TT in the turbulent flow regime. The Navier–Stokes equation in common with the energy equation was solved using the SIMPLE technique with the RNG k–ε turbulence model. The experimental results show that heat transfer rate and friction increased with decreasing twist ratio and space ratio. At similar conditions, full length twisted tapes (s=0) offered higher heat transfer rate, friction factor and thermal performance factor than RS-TT ones (s=1.0, 2.0 and 3.0) as they induced more consistent swirling flows and thus turbulence. This reveals that it is possible to gain promising tradeoff between enhanced heat transfer and increased friction by selecting the twisted tape with proper geometries.

Flow equation and similarity criterion during centrifugal casting in micro-channel

Liquid metal filling flow process in the microscale during the centrifugal casting process was studied by means of similar physical simulation. The research was focused on derived similarity criterion. Based on the traditional flow equations, the flow equation and the Bernoulli's equation for liquid metal flows in micro-scale space were derived, which provides a mathematical model for numerical simulation of micro-scale flow. In the meanwhile, according to the micro-flow equation and the similarity theory, the similarity criterion for the physical simulation of the mold filling behaviors was presented under centrifugal force field, so as to achieve the visual observation and quantitative analysis of micro-flow process.

Influence of the Biomass Gasification Processes on the Final Composition of Syngas

Interest in the technology of gasification has shown a number of ups and downs since its first appearance. It appears that interest in gasification research correlates closely with the relative cost and availability of liquid and gaseous fossil fuels. Gasification is a versatile thermo-chemical conversion process which produces a gas mixture of H2, CO and CH4 the proportions being determined by the use of air, oxygen or steam as oxidizer, with a concomitant range of heat values, low (4–6MJ/Nm3), medium (12–18MJ/Nm3) and high (40MJ/Nm3). A variety of biomass gasifiers have been developed. Differentiation is based on the means of supporting the biomass in the reactor vessel, the direction of flow of both the biomass and oxidant, and the way heat is supplied to the reactor. Gases formed by gasification are contaminated by some constituents such as particles, alkali metals, nitrogen components, tars, sulfurs and chlorides. The level of contamination varies, depending on the gasification process and the feedstock. Gas cleaning must be applied to prevent erosion, corrosion and environmental problems in downstream equipment. In this work, a global perspective about the producer gas final composition dependence, the so-called syngas, from the biomass, oxidizer, reactor type, temperature and pressure is given based on a literature benchmarking. This study shows that there are some discrepancies in the values given by various authors. This highlights the strong dependence of the syngas final composition from the biomass conditions, type of gasifier and pressure and temperature of the process. Thus, in order to make precise studies on the use of syngas it will be necessary to consider that its composition will be rather constant. The development of mathematical models for numerical simulation fully validated experimentally are strongly desirable and may be a very useful tool to determine the final composition of syngas by changes in initial conditions without laborious and expensive experimental tests.

Simulation and Test of the Blade Models’ Output Characteristics of Wind Turbine

This electronic document is a “live” template. Based on the momentum-element theory, mathematical model of numerical simulation of the output characteristics is set up for resemble models of MW-scale wind turbine blades, which is under a test system with three different setting angles of 10.5°, 30.5°and 50.5°. The initial values of axial and tangential induction factors are determined by Newton-Raphson method, the powers P, power coefficients CP and torque coefficients CM of the three model test systems are simulated by programming in Matlab and Visual Basic. At the same time, characteristic output tests are carried out by in-truck test method of the three model test systems. The results show that each relative error of simulation and testing results of the model test systems is less than 10%; it proves that the simulation method is reliable and the testing results are reasonable.

Implicit Bidiagonal Numerical Scheme for Simulation of 2D Flood Waves

This paper is concerned with a mathematical model for numerical simulation of 2D flood waves due to partial dam-break. The governing water equations are solved by an implicit bidiagonal numerical scheme, based on the MacCormack’s predictor-corrector technique. The mathematical model is used to compute 2D flood waves due to partial instantaneous symmetrical dam-break in a rectangular open channel with a rectangular cylinder barrier downstream. Results, in terms of water velocity vectors and contours of water depth, water surface, following dam-break phenomena, are investigated in the two-dimensional problems.

Numerical Simulation of Hydraulic Jump

This paper is concerned with a mathematical model for numerical simulation of 2D flow accompanied with a hydraulic jump. The governing water equations are solved by the MacCormack’s predictor-corrector technique. The mathematical model is used to numerically predict 2D hydraulic jump in a rectangular open channel. The comparison and the analysis show that the proposed method is accurate, reliable and effective in simulation of hydraulic jump flows.