Numerical Simulation Of Dynamic Processes Research Articles

Numerical Simulation of Dynamic Processes in the Medium of Fine-Grained Solid Particles

Numerical Simulation of Dynamic Processes in the Medium of Fine-Grained Solid Particles

Numerical Simulation of Dynamic Processes in a Medium of Fine-Grained Solid Particles

Numerical Simulation of Dynamic Processes in a Medium of Fine-Grained Solid Particles

Numerical Simulation of Dynamic Process of Variable Flow Gas Generator

In this paper, the research on the flow-adjustable gas generator of the solid rocket ramjet engine is carried out, and the internal flow field of the gas generator during the actuation of the flow control valve is analyzed. The steady and unsteady constant value simulations of the gas generator's working process are carried out respectively, and the static and dynamic flow field distributions in the control valve of the solid jet engine are obtained. The negative regulation in the gas flow adjustment process of the solid-jet engine is reproduced, and the reason for this phenomenon is analyzed based on the simulation results.

Analysis of wave processes in an underground gas pipeline (mathematical model and field experiment)

The paper studies the propagation of deformation waves in an underground gas pipeline. Deformation process occurring in the pipeline is caused by the interaction of the gas pumped through the pipe, the metal walls of the pipe and the soil surrounding the pipeline. Vibration processes in the pipeline caused by various mechanical impacts on the pipe and gas are investigated. The paper presents the results of numerical experiments and field tests carried out on the underground section of the operating main gas pipeline. The numerical simulation of dynamic processes in the “soil-pipe-gas” system allowed us to define the patterns of propagation and decay of deformation waves. In the field tests, the emphasis was placed on studying the dynamic response of the pipeline to a number of external actions, such the action of the impact force on the pipe wall and soil in the vicinity of the pipe and gas pressure surges caused by the operation of shut-off valves. Comparison between the results of numerical and field experiments demonstrates the reliability of mathematical modeling. The obtained results can be used for designing new automated gas pipeline monitoring systems. The information obtained allows us to determine the structure of the monitoring system, evaluate the sensitivity of the sensors to various factors and obtain data for verification of the mathematical model describing the vibration processes in a gas pipeline.

Numerical simulation of dynamic processes in transmission of vehicle

The article considers the issues of digital modeling of dynamic processes in the transmissions of transport vehicles. The purpose of this research was to develop an algorithm for numerical mathematical modeling of dynamic processes in the transmissions of transport vehicles using modern digital software packages. The method includes a systematic approach to the study of dynamic processes during switching, based on modeling the operation of the gearbox together with the internal combustion engine (taking into account its dynamic, speed and load characteristics). The order of application of the MATLab - Simulink, Simscape software packages for numerical simulation of dynamic processes is considered. Using the fundamental blocks of these applications, models of physical components are created: the internal combustion engine, friction clutches, gearboxes, elastic shafts, damping devices, and tractor power transmission control systems. A digital model of the tractor transmission is created, its design scheme is given, and the initial characteristics are set. It was used to simulate dynamic processes in the tractor gearbox. The main attention in this paper is paid to the application of the proposed method for calculating the dynamic processes in the gearbox during gear changes under load with forward and reverse switching, including the simultaneous use of several friction clutches.

On Numerical Simulation of Casting in New Foundries: Dynamic Process Simulations

New and more complex casting technologies are growing, and foundries are using innovative methods to reduce cost and energy consumption and improve their product qualities. Numerical techniques, as tools to design and examine the process improvements, are also evolving continuously to embrace modelling of more dynamic systems for industrial applications. This paper will present a fresh approach towards the numerical simulation of dynamic processes using an evolving and dynamic mesh technique. While the conventional numerical techniques have been employed for these dynamic processes using a fixed domain approach, the more realistic evolving approach is used herein to match the complex material processes in new foundries. The underpinning of this new dynamic approach is highlighted by an evolving simulation environment where multiple mesh entities are appended to the existing numerical domain at timesteps. Furthermore, the change of the boundary and energy sources within casting process simulations have rationally been presented and its profound effects on the computational time and resources have been examined. The discretization and solver computational features of the technique are presented and the evolution of the casting domain (including its material and energy contents) during the process is described for semi-continuous casting process applications.

Design and numerical simulation of a self-adaptive variable-diameter robot for in-pipe non-destructive inspection

This paper presents a design method and numerical simulation result of an smart in-pipe inspection robot with capability of adjusting its diameter to adapt to pipelines of non-constant inner diameter insensitive to non-smooth imperfect inner surface due to corrosion or erosion. A variable-diameter component consisting of a motor, gear wheels, a screw and nut drive system and a bar linkage is introduced to achieve this self-adaption. Moreover this paper presents a force-balance analysis by virtual displacement principle relating the normal force and internal spring force and conducts a numerical simulation of dynamic process of a 3D mechanical model across diameter-varying sections in horizontal, vertical manners and records transient inner spring force. The paper has significant reference merit for engineering application to ensure safe operation of pipelines.

Oscillating method for monitoring the technical condition of the hydraulic cylinders of manipulator machines

The substantiation of the oscillatory method for monitoring the technical condition of the hydraulic cylinders of manipulator-type machines is presented on the example of the boom hydraulic cylinder of a John Deere 1470 forest machine. The results of numerical simulation of dynamic processes in pressure cavities of hydraulic cylinders of manipulator-type machines are described on the basis of a developed mathematical model based on the method of theoretical description of the hydraulic drive structural components using hydromechanical circuits. The hydraulic system of the hydraulic drive boom was adopted as the calculated one. For the formation of dynamic processes in the pressure cavity of the hydraulic cylinder of the boom drive of the described machine, a shut-off valve installed in the drain line is used. This valve made it possible to provide an almost instantaneous stop of the piston, resulting in a hydraulic shock. The calculations also used the method of forming a hydraulic shock with an almost instantaneous stop of the piston at the end of its stroke. The research allowed us to justify the most informative parameter for monitoring the current technical condition of hydraulic cylinders in the functional mode-the logarithmic decrement of damped oscillations, as well as to develop a new hydro-shock method for monitoring the technical condition of hydraulic cylinders.

State change modal method for numerical simulation of dynamic processes in a nuclear reactor

Modeling of dynamic processes in nuclear reactors is carried out, mainly, on the basis of the multigroup diffusion approximation for the neutron flux. The basic model includes a multidimensional set of coupled parabolic equations and ordinary differential equations. Dynamic processes are modelled by a successive change of the reactor states, which are characterized by given coefficients of the equations. In the modal method, the approximate solution is represented as an expansion on the first eigenfunctions of some spectral problem. The numerical-analytical method is based on the use of the dominant time-eigenvalues of a multigroup diffusion model taking into account delayed neutrons. In this work, the application of the modal methodology based on calculation of the dominant eigenvalues and eigenfunctions of α-eigenvalue problem has been tested for the VVER-1000 reactor test model. The last is characterized by the fact that some eigenvalues are complex. Reactor dynamics behavior is simulated for symmetrical and non-symmetrical control rods insertion/withdrawal. The power calculation results obtained with the modal method were compared with the numerical solution of the dynamics problem. A rather good agreement was shown for the problem with single delayed neutron precursor group.

Digital simulation of physical processes in vehicles engine power units

This article studies the issues of digital simulation of physical operating processes in vehicles transmission. Simulation of dynamic processes is carried out in power transmissions at the design stage. The procedure for using the digital packages such as MATLab – Simulink and Simscape was considered for the numerical simulation of dynamic processes in mechanical systems based on the example of the theoretical calculation of K-744 tractor transmission dynamics. A digital model of K-744 tractor transmission is constructed, its calculation scheme is given, the initial characteristics are determined. A digital model of the tractor engine was created by means of the Simulink package. A nature of change in tractor engine torqueis determined by it. The calculated analysis of normal transmission frequencies is performed. Forced torsional vibrations are calculated in the tractor change gearbox generated by the vehicle engine operation. The conditions of resonance in the transmission are analyzed. The unfavorable modes of joint operation of the engine and the gearbox are determined for K-744 tractor.

Designing a Mechanotherapy Device for Rehabilitation of Lower Extremities of Humans

An approach to designing a mechanotherapeutic device for rehabilitation of lower extremities in humans using numerical simulation of dynamic processes taking place in the device is described. The device is based on a multilink biomechatronic device with linear actuators.

Discontinuous galerkin method for numerical simulation of dynamic processes in solids

This paper examines the application of the discontinuous Galerkin method for deformation and destruction problems of elastic and elastoplastic bodies and combined problems of elasticity and acoustics. It proposes a 2-sided crack model in the problems of destruction, an account of the elastoplastic rheology in the Prandtl-Reuss model, implementation of the dynamic contact of bodies, an algorithm for the joint solution of linear systems of acoustics and elasticity, and in particular, the issues of shelf seismic prospecting, a comparison of the responses for the model of saturated fluid and infinitely thin cracks, and a modeling of perturbations from underwater objects. The method has been implemented to find the wave picture in heterogeneous media and also the solution of deformation problems by the use of high performance computation systems.

Numerical simulation of dynamic processes in biomechanics using the grid-characteristic method

Results of the numerical simulation of mechanical processes occurring in biological tissues under dynamic actions are presented. The grid-characteristic method on unstructured grids is used to solve the system of equations of mechanics of deformable solids; this method takes into account the characteristic properties of the constitutive system of partial differential equations and produces adequate algorithms on interfaces between media and on the boundaries of integration domains.

Numerical Simulation of Dynamic Process under Low Pressure Casting Based on Two Phase Flow

It has been proved that the mold filling under low pressure casting can be described by the second order nonlinear differential equations characterized by damping oscillations. To obtain higher accuracy of the velocity field, the mold filling process with damping oscillations should be considered. A computational model taking the liquid level droping in the crucible into account based on two phase flow for filling process of damping oscillations is presented in this paper. Hydraulic simulation with the particle image velocimetry was adopted to verify the numerical simulation result. It is proved that the nemuerical simulation results used the presented model perfecly match with the particle image velocimetry results. Liquid level droping in crucible is the main reason for damping oscillations in mold filling. Velocity oscilations can be eliminated when the melt flow across a sudden expansion section. The detailed flow field based on the presented model can provide guidance to optimize the process parameters.

Numerical simulation of dynamic process for liquid film spreading by lattice Boltzmann method and its experimental verification

Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmann method (LBM). By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient λ is introduced to measure the liquid film retraction capacity.

Dynamics of an Unstabilized Spacecraft During the Deployment of an Elastic Pantograph Structure

An unstabilized spacecraft with a pantograph structure deployed in orbit to carry solar batteries is the subject of study. The objective of the study is to construct a mathematical model of this system taking into account the elastic properties of elements of the pantograph in longitudinal and transverse directions. This model is based on the Lagrangian formalism as applied to a mechanical system with rheonomic constraints. The expressions for the coefficients of the equations of motions are obtained using Mathematica 5 © . A Fortran application software package is used for numerical simulation of dynamic processes. This package can be adapted, if necessary, to study other structures. The behavior of the spacecraft during the deployment of the pantograph is numerically analyzed using different values of spacecraft parameters and the parameters of the deployment process in the gravity field.

Numerical Simulation of Dynamic Processes of Elastoplastic Interaction Between Three-Dimensional Heterogeneous Bodies on the Basis of Semi-Analytical Finite Element Method. Part 2. A Study of the Dynamic Deformation of Complex-Shaped Three-Dimensional Structures

Possibilities of the semi-analytical finite element method in the investigation of transient processes of the three-dimensional deformation of heterogeneous bodies of revolution and complex-shaped prismatic bodies by the action of pulsed stressing with allowance for contact interaction zones and nonlinear work of material are shown by calculations of real structures.

Numerical simulation of dynamic processes of the methane migration and oxidation in landfill cover

The coupling model of the multicomponent gas flow and transport was developed to describe methane oxidation in landfill cover. A two‐part simulation was carried out to investigate the dynamic processes of methane oxidation. The reliability of the coupling model was validated by comparing the simulated data on gas concentrations with the measured data. To evaluate the influence of the pumping well on the oxidation reaction, methane emission throughout the landfill cover was simulated. Methane oxidation in the landfill cover demonstrated dynamic characteristics. The results suggest that the oxidation effect is closely related to methane emission. Sensitivity parameters were also introduced to determine the maximum oxidation rate and permeability. The critical targets of the reduction rate and reduction volume of methane were analyzed based on 20 years' worth of pumping operation data. The result further illustrates the dynamic behavior of methane oxidation, which is influenced by the degree of methanotrophic reaction and the balance between methane and air influx in the landfill cover. The results highlight the significance of the study in quantitatively assessing the capacity of landfill covers to reduce methane emissions in landfills. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1419–1424, 2014

Numerical Simulation of Dynamic Processes of Elastoplastic Interaction between Three-Dimensional Heterogeneous Bodies on the basis of Semi-Analytical Finite Element Method. Part 1. Computational Relationships of the Semi-Analytical Finite Element Method and Algorithms for the Study of Transient Processes of Dynamic Deformation of Heterogeneous Prismatic Bodies and Bodies of Revolution

On the basis of a semi-analytical finite element method, an effective approach has been developed for studying transient processes of dynamic deformation of three-dimensional heterogeneous bodies of revolution and prismatic bodies of complex shape and structure by the action of time-and space-varying pulsed stressing with allowance for the plastic properties of the material and time-varying contact interaction conditions. New types of finite elements have been created, on the basis of which computational relationships of the semi-analytical finite element method (SAFEM) for problems of dynamics have been constructed. Modified relationships of the Newmark method have been obtained, which have been formulated for the amplitude subsystems of SAFEM. Effective block iteration algorithms for the solution of large systems of nonlinear equations of SAFEM have been developed and realized.

Numerical simulation of seismic responses in multilayer geologic media by the grid-characteristic method

The aim of the present work is to simulate and study the propagation of seismic signal through multilayer rocks. Test computations were made in order to check that the problem of contact discontinuity is correctly formulated, and numerical simulation of dynamic processes in multilayer rocks was carried out. The work adopts the grid-characteristic method that permits devising computation algorithms that would perform properly both at the boundaries of a domain of integration and at contact interfaces between layers in a multilayer medium. The suggested approach makes it possible to determine the number of layers and their thicknesses from the response. The possibility to apply such an approach in the calculation of responses from curved interfaces between rock strata is demonstrated.