Search

This paper presents a study based on the probabilistic dynamic model PDM I MDP with application in TCAS. The algorithm for solving PDM is analysed and also it presents the first step focused by discretizing the state space model. The MDP is evaluated to predict the state space at the next time step for the adequate set of operations. The conformity with the least expected cost criterion allows a better action from that state space. The DP algorithm involve all potential trajectories in the state space and features the selection of the most probable trajectory from the global set. The number of potential trajectories increases exponentially in the time horizon, and hence in case of mathematical models, it is not proposed to string each potential trajectory. In the collision avoidance MDP, the number of predictable trajectories exceeds the number of particles in the universe, however DP can establish all the required data in quick numerical computations. If an aircraft equipped with TCAS receives a traffic alert from other aircraft with TCAS, it will broadcast a coordination message report to the other aircraft instructing it to neither descend nor climb, as being most acceptable. If both aircraft will choose conflicting actions simultaneously, the aircraft with the higher rank from identification number needs to turn out the direction of its advisory. In the case study when an aircraft is receiving instructions from another aircraft not to descend or climb it is powerfully advised to do level off. The results of the analysis carried on in this study are consistent with the real time operations. [ABSTRACT FROM AUTHOR]

Simulation of the aircraft assembly process is an important problem arising from the airline industry. To address this problem, a methodology was developed in previous studies, which is based on the contact problem solving. This paper is devoted to further development of numerical methods for simulation of fuselage junction riveting process. The methodology of a contact problem solving was developed to simulate the aircraft assembly process. In the developed algorithm, the initial contact problem is transformed into the problem of quadratic programming with linear constraints. As the installed fasteners restrict relative tangential displacements of assembled parts in the junction area, the relative tangential displacements are negligible in comparison with normal ones. This special feature of the problem justifies implementation of node-to-node contact model that is much simpler than general surface-to-surface model.However, this implementation imposes the restriction that all finite element nodes of parts in the contact area should coincide completely. This restriction creates difficulties during mesh building because it is much easier to build meshes of the parts independently from each other. The main contribution of this paper is introducing the method and extending the existing algorithm for airframe assembly simulation to the case of non-conformal meshes. This article introduces the method and the modernized algorithm for the riveting process with non-conformal meshes. [ABSTRACT FROM AUTHOR]

The paper presents a practical implementation of hybrid simulation using Real Time Finite Element Method (RTFEM). Hybrid simulation is a technique for investigating dynamic material and structural properties of mechanical systems by performing numerical analysis and experiment at the same time. It applies to mechanical systems with elements too difficult or impossible to model numerically. These elements are tested experimentally, while the rest of the system is simulated numerically. Data between the experiment and numerical simulation are exchanged in real time. Authors use Finite Element Method to perform the numerical simulation. The following paper presents the general algorithm for hybrid simulation using RTFEM and possible improvements of the algorithm for computation time reduction developed by the authors. The paper focuses on practical implementation of presented methods, which involves testing of a mountain bicycle frame, where the shock absorber is tested experimentally while the rest of the frame is simulated numerically. [ABSTRACT FROM AUTHOR]

The paper investigates the deformation behavior of a mechanical metamaterial. The metamaterial is made up of tetrachiral elements. An analytical solution is obtained for the deformation behavior of a unit cell of the metamaterial depending on its parameters. The results of the analytical solution were used for numerical modeling. The computer FEM model was built using beam elements. The numerical solution of the mechanical loading of the metamaterial was performed in the static case of the linear theory of elasticity. In the course of numerical simulation of the uniaxial loading of the mechanical metamaterial, it was found that the specimen inclines when elongated. The difference in inclination angles between the right and left sides of the specimen is probably related to the rotation of the ring in the tetrachiral structure. [ABSTRACT FROM AUTHOR]

In the article the new method of energy storing, using cavern gas storage system is presented. The idea drew from the Compressed Air Energy Storage systems, but use natural gas stored in salt caverns as a medium, so can be called the Compressed Natural Gas Energy Storage (CNGES). The concept of the store charging is to pump the gas from lower pressure cavern to the higher pressure one by an electric powered compressor. In the discharging mode the gas expands through the expander connected with the generator, from the high pressure cavern to the lower pressure one with the electricity production. The paper covers the dynamic model of CNGES implemented in Aspen Hysys numerical environment. The main aim of the simulation was to determine the influence of selected parameters of the store (gas initial and terminal temperature and pressure). The article covers main model assumptions, implemented methodology description, results analysis and conclusions. [ABSTRACT FROM AUTHOR]

Intraguild predation (IGP) is ubiquitous in nature. The IG predator feeds on the IG prey and shares the resource with the IG prey. In this paper, a mathematical model of a tri-trophic food web based on the Beddington-DeAnglis functional response with prey switching is considered. Prey switching describes the situation where the predator consumes disproportionately more of the most abundant prey. Numerical computation of bifurcation analysis is used to study the coexistence of all species, stabilization of population dynamics, and complex dynamics of the system. Numerical simulation performed on the model with/without prey switching shows that (i) prey switching can enhance the persistence of the IG predator and IG prey and promote species coexistence for a range of parameter values, (ii) prey switching can stabilize population dynamics, (iii) chaotic attractors exist in the model with prey switching. [ABSTRACT FROM AUTHOR]

The paper presents an algorithm for constructing of synthesizing control function. This algorithm is sufficiently convenient for numerical implementation and a wide class of nonlinear nonstationary systems of ordinary differential equations, provide the passage from initial state into to origin coordinates. We obtain a constructive condition for the choice of initial state for which the passage is possible with regard of the constraints imposed on the control. We consider an problem of control of single manipulator, for which we carry numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper the numerical analysis of low cycle fatigue behavior of steel in non-isothermal conditions is presented. First the experimental tests are analyzed to recognize different aspects of material behavior. Then the appropriate constitutive model is developed and implemented into numerical procedures. The model parameters are identified on the basis of the available experimental data. Finally some benchmark simulations are performed. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical simulation of the shock loading process of steel barriers with a gradient substrate. In an elastic plastic axisymmetric statement, a shock is simulated along the normal in the range of initial velocities up to 300 m / s. A range of initial velocities was revealed, in which the presence of a substrate "saved" the obstacle from spallation. New tasks were announced to deepen scientific knowledge about the behavior of unidirectional gradient barriers at impact. The results of calculations are obtained in the form of graphs, calculated configurations of the "impact - barrier" and tables. [ABSTRACT FROM AUTHOR]

This paper is focused on a module of an automatized numerical modelling of a spread of hazardous substances developed for the Floreon+ system on demand of the Fire Brigade of Moravian-Silesian. The main purpose of the module is to provide more accurate prediction for smog situations that are frequent problems in the region. It can be operated by non-scientific user through the Floreon+ client and can be used as a short term prediction model of an evolution of concentrations of dangerous substances (SO2, PMx) from stable sources, such as heavy industry factories, local furnaces or highways or as fast prediction of spread of hazardous substances in case of crash of mobile source of contamination (transport of dangerous substances) or in case of a leakage in a local chemical factory. The process of automatic gathering of atmospheric data, connection of Floreon+ system with an HPC infrastructure necessary for computing of such an advantageous model and the model itself are described bellow. [ABSTRACT FROM AUTHOR]

The Laplace-Beltrami operator plays an important role as C² function smoother and its eigenfunction applications are studied extensively in last five decades, not only, in image processing field but we can meet with these functions ranging from molecular physics scientific field to mechanical engineering. However, in many non-trivial cases, e.g. computations on non-uniform meshes, the discrete Laplace operator could be ill-conditioned and inappropriate for numerical computations. Especially, in the spectral clustering tool, a condition number of the graph Laplacian goes to infinity, when pairwise similarities among most graph nodes go to zero. Therefore, in this paper, we reformulate the image graph Laplacian as the semi-smooth Laplace-Beltrami operator on a non-uniform mesh and study its numerical properties, then we introduce our fundamental approach for improving a numerical stability of this operator. [ABSTRACT FROM AUTHOR]

This paper deals with the simulation of UNS A92024 aluminium alloy cutting processes. In particular, 2D and 3D Finite Element Method (FEM) simulations were carried out in order to estimate cutting forces and chip morphology during turning operations. The material is modelled with two different set of parameters for the Johnson-Cook's (J-C) constitutive equation and a failure Cockroft and Latham's model exploited considers damage. The comparison between the predicted chip morphology and principal cutting forces at varying of J-C parameters and cutting regimes with those experimentally found are presented and discussed. The paper shows the importance of damage criterion in the cutting forces, during the simulation, especially in 3D. [ABSTRACT FROM AUTHOR]

This paper presents numerical study of the seismic behavior of reinforced concrete beam to concrete filled steel tube column connections with ring-beam. The material stress-strain relations, element type and boundary condition are selected, which are consistent with actual situation. Then the seismic behavior of this type of joint are researched by ABAQUS, and finite element analyses are conducted under cyclic loading. Its parameters are discussed including thickness of steel tubular column wall, sectional dimension of the ring-beam and strength of the core concrete . The results show that the ultimate capacity of the connections is improved with sectional dimension of the ring-beam increased. In the meanwhile, the influence on skeleton curve of the joints is slight of which included thickness of steel tubular column wall and strength of the core concrete. [ABSTRACT FROM AUTHOR]

The paper presents utility functions for computing of a distance matrix, which plays a crucial role in data mining. The goal in the design was to enable operating on relatively large datasets by overcoming basic shortcoming - computing time - with an interface easy to use. The presented solution is a set of functions, which were created with emphasis on practical applicability in real life. The proposed solution is presented along the theoretical background for the performance scaling. Furthermore, different approaches of the parallel computing are analyzed, including shared memory, which is uncommon in Matlab environment. [ABSTRACT FROM AUTHOR]

In this paper generalized linear model (GLM) and credibility theory which are frequently used in nonlife insurance pricing are combined for reliability analysis. Using full credibility standard, GLM is associated with limited fluctuation credibility approach. Comparison criteria such as asymptotic variance and credibility probability are used to analyze the credibility of risk classes. An application is performed by using one-year claim frequency data of a Turkish insurance company and results of credible risk classes are interpreted. [ABSTRACT FROM AUTHOR]

Over the recent years, the reported incidents on failed aircraft ramp-ups or the delayed production in small-lots have increased substantially. In this paper, we present a production management platform that combines agent-based techniques with the Service Oriented Architecture paradigm. This platform takes advantage of the functionality offered by the semantic web language OWL, which allows the users and services of the platform to speak a common language and, at the same time, facilitates risk management and decision making. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present the estimation of the components of variance in structured stair nesting models. The relationship between the canonical variance components and the original ones, will be very important in obtaining that estimators. [ABSTRACT FROM AUTHOR]

This paper presents the recent results of the integration of computational and conceptual solutions for the complex case of environmental information management. The solution for the major goal of creating and developing long-term multi-disciplinary knowledge resources and conceptual and computational support was achieved by implementing and integrating key components. The key components are long-term knowledge resources providing required structures for universal knowledge creation, documentation, and preservation, universal multi-disciplinary and multi-lingual conceptual knowledge and classification, especially, references to Universal Decimal Classification (UDC), sustainable workflows for environmental information management, and computational support for dynamical use, processing, and advanced scientific computing with Integrated Information and Computing System (IICS) components and High End Computing (HEC) resources. [ABSTRACT FROM AUTHOR]

The variable demand on the energy market enforces that hydraulic turbine to operate at different regimes, far from the best efficiency point. An experimental test rig was developed in our laboratory in order to reproduce these regimes. As a result, the investigated flow regimes allow us to quantify the flow behavior from part load operation to full load operation. The paper focuses on experimental and numerical investigations of mean velocity profiles and of stagnant region developed in the centre of draft tube cone. First the numerical results are validated against experimental results. At the end a qualitative analysis of the streamline pattern is complemented, giving us an evaluation of the stagnant region from the draft tube cone at different runner speeds. [ABSTRACT FROM AUTHOR]

In this paper, we consider a contaminant transport model with Langmuir sorption under nonequilibrium conditions which is described by two coupled equations. Three numerical methods are used namely; Euler scheme forward in space, Euler scheme backward in space and nonstandard finite difference (NSFD) schemes. We compare the performance of the three methods by computing some errors: L1 error, dispersion and dissipation errors for both coarse and fine grids and short and long propagation times. We also perform a spectral analysis of the dispersive and dissipative properties of the three methods for the transport model. [ABSTRACT FROM AUTHOR]

Hybrid RANS-LES models are proven to be capable of predicting massively separated flows with reasonable computation cost. In this paper, Spalart-Allmaras (S-A) based detached eddy simulation (DES) model and three SST based hybrid models with different RANS to LES switching criteriaare investigated. The flow over periodic hill at Re = 10,595 is chosen as the benchmark for comparing the performance of the different models due to the complex flow physics and reasonablecomputational cost. The model performances are evaluated based on their prediction capabilities of velocity and stress profiles, and separation and reattachment point. The simulated results are validatedagainst experimental and numerical results available in literature. The S-A DES model predicted separation bubble accurately at the top of the hill, as reported earlier in experiments and other numerical results. This model also correctly predicted velocity and stress profiles in recirculation region. However, the performance of this model was poor in the post reattachment region. On the other hand, the k-ω SST based hybrid models performed poorly in recirculation region, but it fairly predicted stress profiles in post reattachment region. [ABSTRACT FROM AUTHOR]

Parallel computational fluid dynamics simulations produce vast amount of numerical result data. This paper introduces a method for reducing the size of the data by replaying the interprocessor traffic. The results are recovered only in certain regions of interest configured by the user. A known test case is used for several mesh partitioning scenarios using the OpenFOAM toolkit®[1]. The space savings obtained with classic algorithms remain constant for more than 60 Gb of floating point data. Our method is most efficient on large simulation meshes and is much better suited for compressing large scale simulation results than the regular algorithms. [ABSTRACT FROM AUTHOR]

The paper focuses on numerical analysis of temperature field into a magneto-rheological break. The magnetorheological fluid is used for a brake operated at different speeds. The magneto-rheological brake application was developed due to the magnetic control and fast response. The two dimensional axi-symmetric computational domain corresponds to the experimental magneto-rheological break. The numerical simulations have been performed for seven speed values with zero magnetic field. Firstly, the temperature map for magneto-rheological break is computed. Secondly, the temperature value obtained on the outside casing wall is validated against experimental data. Next, the maximum temperature value was identified based on numerical simulation in a point located into the magnetorheological fluid. The numerical results will be used to improve the magneto-rheological break operation/design. [ABSTRACT FROM AUTHOR]

Parallel computational fluid dynamics simulations produce vast amount of numerical result data. This paper introduces a method for reducing the size of the data by replaying the interprocessor traffic. The results are recovered only in certain regions of interest configured by the user. A known test case is used for several mesh partitioning scenarios using the OpenFOAM toolkit®[1]. The space savings obtained with classic algorithms remain constant for more than 60 Gb of floating point data. Our method is most efficient on large simulation meshes and is much better suited for compressing large scale simulation results than the regular algorithms. [ABSTRACT FROM AUTHOR]

The paper focuses on numerical analysis of temperature field into a magneto-rheological break. The magnetorheological fluid is used for a brake operated at different speeds. The magneto-rheological brake application was developed due to the magnetic control and fast response. The two dimensional axi-symmetric computational domain corresponds to the experimental magneto-rheological break. The numerical simulations have been performed for seven speed values with zero magnetic field. Firstly, the temperature map for magneto-rheological break is computed. Secondly, the temperature value obtained on the outside casing wall is validated against experimental data. Next, the maximum temperature value was identified based on numerical simulation in a point located into the magnetorheological fluid. The numerical results will be used to improve the magneto-rheological break operation/design. [ABSTRACT FROM AUTHOR]

The critical energy constant is of significant interest for the theoretical and numerical analysis of Boussinesq type equations. In the one-dimensional case this constant is evaluated exactly. In this paper we propose a method for numerical evaluation of this constant in the multi-dimensional cases by computing the ground state. Aspects of the numerical implementation are discussed and many numerical results are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper we discuss the effect of sharp property variations on the turbulent heat transfer in fluids close the critical point. The governing equations for this flow regime are discussed, a short description of the numerical tools that have been developed to study these flows is given. Finally, some results for supercritical heat transfer in developing turbulent pipe flow are presented. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical analyses carried out for 2D models of aluminum plates undergoing crack propagation. Different types of numerical analyses were performed to show the area of applicability of a non-local discrete formulation of mechanical continua for NDE and QNDE. The authors' interests dealt with: Lamb wave propagation, higher harmonics generation, the phenomenon of clapping, and wave generation and its propagation for growing crack. In the first case a 2D model allowed to find the displacements for the vertical cross-section along the direction of wave propagation and therefore assess its disturbance when introducing a notch. In-plane components of the displacements were considered for the latter 3 cases, in turn. The above cases and elaborated non-local numerical models were discussed in terms of detection of propagating crack. Apart from theoretical aspects of the presented work, the obtained results seem to be of great importance for improvement of experiments in terms of sensor distribution and required accuracy. [ABSTRACT FROM AUTHOR]

The paper deals with a mathematical and numerical study of the Atmospheric Boundary Layer (ABL) flow over a complex topography represented either by part of the Giant mountains or by a surface brown coal mine and a coal depot, both located in the North Bohemia. Various types of protective obstacles have been tested and compared, mainly with respect to the reduction of dustiness in the latter case. The mathematical model is based on system of Reynolds Averaged Navier-Stokes (RANS) equations for viscous and incompressible flow. The artificial compressibility method was used. The numerical method is based either on the finite-volume explicit scheme or on a semi-implicit finite-difference scheme. A simple algebraic turbulence model is applied to close the governing system of equations. Moreover, an additional transport equation for a passive pollutant has been considered. [ABSTRACT FROM AUTHOR]

Modified and conventional Adomian decomposition methods are two power full methods in solving nonlinear equation. In this paper the ability of modified and conventional Adomian decomposition methods for modeling the nonlinear instability of cantilever nano beam is comparatively investigated. advantage and disadvantage of each method are presented result shows that MAD is more power full than AD and converge to numerical values but AD converge to a values in the neighborhood of numerical value. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present the results of a numerical study of the aerodynamic parameters of a wingless and a winged-hull airship. The total forces and moment coefficients of the airships have been computed over a range of angles. The results obtained show that addition of a wing to a conventional airship increases the lift has three times the lifting force at positive angle of attack as compared to a wingless airship whereas the drag increases in the range of 19% to 58%. The longitudinal and directional stabilities were found to be statically stable, however, both the conventional airship and the hybrid or winged airships were found to have poor rolling stability. Wingless airship has slightly higher longitudinal stability than a winged airship. The winged airship has better directional stability than the wingless airship. The wingless airship only possesses static rolling stability in the range of yaw angles of -5° to 5°. On the contrary, the winged airship initially tested does not possess rolling stability at all. Computational fluid dynamics (CFD) simulations show that modifications to the wing placement and its dihedral have strong positive effect on the rolling stability. Raising the wings to the center of gravity and introducing a dihedral angle of 5° stabilizes the rolling motion of the winged airship. [ABSTRACT FROM AUTHOR]

This paper presents a programming code to provide numerical solution of elastohydrodynamic lubrication problem in line contacts which is modeled through an infinite cylinder on a plane to represent the application of roller bearing. In this simulation, vegetable oils will be used as bio-based lubricants. Temperature is assumed to be constant at 40°C. The results show that the EHL pressure for all vegetable oils was increasing from inlet flow until the center, then decrease a bit and rise to the peak pressure. The shapes of EHL film thickness for all tested vegetable oils are almost flat at contact region. [ABSTRACT FROM AUTHOR]

The water entry problem is considered as a classic problem which has a long research history; however, projectile water entry is still a difficult problem that has not been completely solved. In this paper, the effects of the projectile nose shape on laws of velocity attenuations for all projectiles were studied by a series of numerical simulations using the AUTODYN-2D. The result showed that the drag coefficient increases monotonically with the initial velocities for an identical projectile and decreases with the CRH values for projectiles at the same velocity. A simple and effective model was proposed to determine the relations between the drag coefficients, nose shape coefficient and initial velocities of projectiles. [ABSTRACT FROM AUTHOR]

Numerical simulation became an important tool in optimization of energy consumption in buildings. The dimensioning of heating/cooling systems must supply the necessary energy in order to reach the standard indoor environmental conditions, but, on the other hand, energy-savings measures should not sacrifice people's comfort and health. In this paper, the temperature distribution in a test geometry corresponding to a building at real dimensions is numerically calculated for different environmental conditions, specific to summer and winter seasons. The influence of different types of boundary conditions is investigated. The possibility to control the indoor temperature field using heat sources is also discussed. The computations were performed using CrysVUn software, special designed for modeling of heat transfer in complex geometries by conduction, convection and radiation. [ABSTRACT FROM AUTHOR]

Numerical simulation of binary alloy solidification process is a challenging task due to coexistence of phenomena related to various temporal/spatial scales and coexistence of zones, i.e. columnar and equiaxed dendrites, where various fluid flow models should be applied. Presented paper is devoted to exploration of the recently developed numerical model of solidification based on the front tracking approach. The influence of the columnar dendrites region porosity on the macrosegregation formation is investigated. Presented results stay in qualitative agreement with the reference data but expose some additional details absent in the results of simulation performed with the simpler model. [ABSTRACT FROM AUTHOR]

Conical parts have a lot of usage in aerospace and special industries. These parts usually formed by spinning, explosive forming, multistage deep drawing. Due to their bad forming condition in conventional methods, some new forming methods have been explored to increase the drawing ratio, hydroforming is one of the more effective methods. In this study hydrodynamic deep drawing assisted by radial pressure is used to form the conical-cylindrical parts. Commercially pure copper is used in this research. The process is initially simulated using the FEM solver ABAQUS. Experiments have been conducted with different punch geometries. The punch geometries consist of conical and cylindrical wall segments. This paper examines the effect of cone angle on drawing ratio and thickness distribution of conical cups. Using the measurements of thickness variations on the cup wall, the quality of the cups drawn has been evaluated. The results of the study demonstrated that increasing the cone angle has a important effect on drawing ratio and cause uniform thickness distribution. Also it was concluded that the conical-cylindrical parts had two critical regions at contact area of punch tip with the blank and the transition zone between the conical and cylindrical portions that variation at cone angle affected these regions and resulted to variation of these areas. It was proved that the results from the experiment and the simulation were in a reasonable agreement. [ABSTRACT FROM AUTHOR]

Cage roll forming is one of the advanced methods of cold roll forming process which is used widely for producing ERW pipes. In addition to decreasing the production cost and time, using cage roll forming provides smooth deformation on the strip. Few studies can be found about cage roll forming because of its complexity, and the available knowledge is experience-based more than science-based. In this paper, deformation of pipes with low ratio of thickness/diameter is investigated by 3D finite element simulation in Marc-Mentat software. Edge buckling defect in cage roll forming of low ratio of thickness/diameter pipes is very important. Due to direct influence of longitudinal strain on the edge buckling phenomenon, longitudinal strains at the edge and center line of the strip are investigated and high risk stands are introduced. The deformed strip is predicted using the simulation results and effects of each cage forming stage on the deformed strip profile are specified. In order to verify the simulation results, strip width and opening distance of the two edges in different forming stages are obtained from the simulations and compared with the experimental data which were measured from the production line. A good agreement between the experimental and simulated results is observed. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the class of high order compact schemes in the context of numerical simulation of stratified flow. The numerical schemes presented here are based on the approach outlined in Lele [1]. The numerical model presented in this contribution is based on the solution of the Boussinesq approximation by a finite-difference scheme. The numerical scheme itself follows the principle of semi-discretization, with high order compact discretization in space, while the time integration is carried out by suitable Runge-Kutta time-stepping scheme. In the case presented here the steady flow was considered and thus the artificial compressibility method was used to resolve the pressure from the modified continuity equation. The test case used to demonstrate the capabilities of the selected model consists of the flow of stably stratified fluid over low, smooth hill. [ABSTRACT FROM AUTHOR]