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Статті в журналах з теми "Method analysis grids"
1
Xu, Dan, Xiaogang Deng, Yaming Chen, Guangxue Wang, and Yidao Dong. "Effect of Nonuniform Grids on High-Order Finite Difference Method." Advances in Applied Mathematics and Mechanics 9, no. 4 (January 18, 2017): 1012–34. http://dx.doi.org/10.4208/aamm.2016.m1477.
Повний текст джерелаАнотація:
AbstractThe finite difference (FD) method is popular in the computational fluid dynamics and widely used in various flow simulations. Most of the FD schemes are developed on the uniform Cartesian grids; however, the use of nonuniform or curvilinear grids is inevitable for adapting to the complex configurations and the coordinate transformation is usually adopted. Therefore the question that whether the characteristics of the numerical schemes evaluated on the uniform grids can be preserved on the nonuniform grids arises, which is seldom discussed. Based on the one-dimensional wave equation, this paper systematically studies the characteristics of the high-order FD schemes on nonuniform grids, including the order of accuracy, resolution characteristics and the numerical stability. Especially, the Fourier analysis involving the metrics is presented for the first time and the relation between the resolution of numerical schemes and the stretching ratio of grids is discussed. Analysis shows that for smooth varying grids, these characteristics can be generally preserved after the coordinate transformation. Numerical tests also validate our conclusions.
2
Tang, Bi Qiang, Yi Jun Yu, Shu Hai Feng, and Feng Li. "A Novel Method of Static Security Analysis Based on Multithread Technology." Advanced Materials Research 732-733 (August 2013): 639–45. http://dx.doi.org/10.4028/www.scientific.net/amr.732-733.639.
Повний текст джерелаАнотація:
With the UHV (Ultra High Voltage) power grid construction and the interconnection of regional power grids, the scale of power grids in China is increasing rapidly. At the same time, significant uncertainty and variability is being introduced into power grid operation with the integration of large-scale renewable energy in power systems. All of these pose an enormous challenge to the operation control of power systems in China. For a long time, online static security analysis, as an important part of EMS (Energy Management System), has been an effective tool for power grid operation. However, it is increasingly difficult for traditional static security analysis in serial computing mode to be online applied in bulk power grids in China. A new practical parallel approach for online static security analysis is put forward in this paper. A multithread parallelism is introduced into contingency screening, detailed contingency evaluation and decision support for reducing the execution time. By employing the multithread technology, the hardware resources of multi-processor/multi-core computer can be fully used and the program can be speeded up effectively. The performance of the parallel static security analysis is demonstrated by tests on two large-scale power systems. The test results show that the proposed method can be online applied in real bulk power grids.
3
Chan, H. C., C. W. Cai, and Y. K. Cheung. "An Analytical Method for Static Analysis of Double Layer Grids." International Journal of Space Structures 4, no. 2 (June 1989): 107–16. http://dx.doi.org/10.1177/026635118900400204.
Повний текст джерелаАнотація:
An analytical method for the static analysis of double layer grids consisting of diagonals and top and bottom layers which are plane orthogonal grids is presented. It is assumed that the double layer grid is simply supported at all nodes located at the boundary of the top layer. By using the double U-transformation technique, exact solutions for the nodal displacements and axial forces of the bars in the double layer grid can be derived. The validity of the method is demonstrated with a simple example.
4
Hansbo, Anita, Peter Hansbo, and Mats G. Larson. "A finite element method on composite grids based on Nitsche's method." ESAIM: Mathematical Modelling and Numerical Analysis 37, no. 3 (May 2003): 495–514. http://dx.doi.org/10.1051/m2an:2003039.
Повний текст джерела
5
Martynenko, S. I. "Potentialities of the Robust Multigrid Technique." Computational Methods in Applied Mathematics 10, no. 1 (2010): 87–94. http://dx.doi.org/10.2478/cmam-2010-0004.
Повний текст джерелаАнотація:
AbstractThe present paper discusses the parallelization of the robust multigrid technique (RMT) and the possible way of applying this to unstructured grids. As opposed to the classical multigrid methods, the RMT is a trivial method of parallelization on coarse grids independent of the smoothing iterations. Estimates of the minimum speed-up and parallelism efficiency are given. An almost perfect load balance is demonstrated in a 3D illustrative test. To overcome the geometric nature of the technique, the RMT is used as a preconditioner in solving PDEs on unstructured grids. The procedure of auxiliary structured grids generation is considered in details.
6
Cheng, Weijie, Renli Cheng, Jun Shi, Cong Zhang, Gaoxing Sun, and Dong Hua. "Interval Power Flow Analysis Considering Interval Output of Wind Farms through Affine Arithmetic and Optimizing-Scenarios Method." Energies 11, no. 11 (November 15, 2018): 3176. http://dx.doi.org/10.3390/en11113176.
Повний текст джерелаАнотація:
Wind power belongs to sustainable and clean energy sources which play a vital role of reducing environment pollution and addressing energy crisis. However, wind power outputs are quite difficult to predict because they are derived from wind speeds, which vary irregularly and greatly all the time. The uncertainty of wind power causes variation of the variables of power grids, which threatens the power grids’ operating security. Therefore, it is significant to provide the accurate ranges of power grids’ variables, which can be used by the operators to guarantee the power grid’s operating security. To achieve this goal, the present paper puts forward the interval power flow with wind farms model, where the generation power outputs of wind farms are expressed by intervals and three types of control modes are considered for imitating the operation features of wind farms. To solve the proposed model, the affine arithmetic-based method and optimizing-scenarios method are modified and employed, where three types of constraints of wind control modes are considered in their solution process. The former expresses the interval variables as affine arithmetic forms, and constructs optimization models to contract the affine arithmetic forms to obtain the accurate intervals of power flow variables. The latter regards active power outputs of the wind farms as variables, which vary in their corresponding intervals, and accordingly builds the minimum and maximum programming models for estimating the intervals of the power flow variables. The proposed methods are applied to two case studies, where the acquired results are compared with those acquired by the Monte Carlo simulation, which is a traditional method for handling interval uncertainty. The simulation results validate the advantages, effectiveness and the applicability of the two methods.
7
Li, Chao, Tianguang Lu, and Xueshan Han. "Assessment method of large-scale distributed power consumption capacity for rural grids." Journal of Physics: Conference Series 2488, no. 1 (May 1, 2023): 012039. http://dx.doi.org/10.1088/1742-6596/2488/1/012039.
Повний текст джерелаАнотація:
Abstract As the scale of photovoltaic (PV) access continues to expand, both transmission and distribution grids are experiencing systemic consumption problems, with rural distribution grids being particularly prominent. An accurate assessment of distributed power consumption capacity is crucial to the improvement of distributed power consumption capacity. Firstly, taking into account the uncertainty of the output of the distributed power supply and comprehensive consideration of power quality, reliability of the electricity supply and operational influences, A comprehensive index evaluation system has been established to assess the ability of distributed power sources to consume; secondly, hierarchical analysis and improved gray correlation analysis are used to assign weights to the indexes; finally, a Monte Carlo model is used to identify the consumption capacity of rural power grids. This method can provide a comprehensive and accurate assessment of the consumption capacity of large-scale distributed power sources in new rural power grids, and also provide data support for solving the problem of new energy consumption in power grids.
8
Liu, Wen Yang, and Wen Fu Zhang. "Split Rigidity Method for Analysis of Double-Layer Space Grids Structure with Rectangular Shape." Advanced Materials Research 446-449 (January 2012): 480–83. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.480.
Повний текст джерелаАнотація:
In this paper double-layer space grids structure with rectangular shape is assumed as equivalent sandwich plate, and has been analyzed by the non-traditional theory of plate with three generalized displacements, in which shearing deformation is considered. Based upon the split rigidity method, static analysis and natural vibration analysis of double-layer space grids structure has been studied. The formulas for calculating internal forces, displacement as well as fundamental frequency are given out. The comparison with finite element method and equivalent sandwich plate method shows that split rigidity method is not only simpler than other simplified methods but also of high accuracy.
9
Liu, Wen Yang, and Wen Fu Zhang. "Split Rigidity Method for Analysis of Three-Way Double-Layer Space Grids Structure." Advanced Materials Research 594-597 (November 2012): 820–23. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.820.
Повний текст джерелаАнотація:
Abstract. In this paper three-way double-layer space grids structure is assumed as equivalent sandwich plate, and has been analyzed by the non-traditional theory of plate with three generalized displacements, in which shearing deformation is considered. Based upon the split rigidity method, static analysis and natural vibration analysis of three-way double-layer space grids structure has been studied. The formulas for calculating internal forces, displacement as well as natural vibration frequency are given out. The comparison with finite element method and equivalent sandwich plate method shows that the formulas in this paper are not only simpler than other simplified methods but also of high accuracy.
10
Feng, Jian, Changtong Li, Yixiang Xu, Qian Zhang, Fang Wang, and Jianguo Cai. "Analysis of Key Elements of Truss Structures Based on the Tangent Stiffness Method." Symmetry 12, no. 6 (June 14, 2020): 1008. http://dx.doi.org/10.3390/sym12061008.
Повний текст джерелаАнотація:
In recent years, the topic of progressive structural collapse has received more attention around the world, and the study of element importance is the key to studying progressive collapse resistance. However, there are many elements in truss structures, making it difficult to predict their importance. The global stiffness matrix contains the specific information of the structure and singularity of the matrix can reflect the safety status of the structure, so it is useful to evaluate the key elements based on the global stiffness matrix for truss structures. In this paper, according to the tangent stiffness-based method for the element importance, the square pyramid grid was chosen as an example, and the distribution rules of key elements under different support conditions, stiffness distributions, and geometric parameters were studied. Then, three common symmetric grid forms, i.e., diagonal square pyramid grids, biorthogonal lattice grids, and biorthogonal diagonal lattice grids, were selected to investigate their importance indices of elements. The principle in this work can be utilized in progressive collapse analysis and safety assessment for spatial truss structures.
Дисертації з теми "Method analysis grids"
1
Onay, Oguz Kaan. "Approximate Factorization Using Acdi Method On Hybrid Grids And Parallelization Of The Scheme." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615589/index.pdf.
Повний текст джерелаАнотація:
In this thesis study, a fast implicit iteration scheme called Alternating Cell Directions Imp licit method
is combined with Approximate Factorization scheme. This application aims to offer a mathematically
well defined version of the Alternating Cell Directions Implicit Method and increase the accuracy of
the iteration scheme that is being used for the numerical solutions of the partial differential equations.
The iteration scheme presented here is tested using unsteady diffusion equation, Laplace equation and
advection-diffusion equation. The accuracy, convergence character and the stability character of the
scheme compared with suitable iteration schemes for structured and unstructured quadrilateral grids.
Besides, it is shown that the proposed scheme is applicable to triangular and hybrid polygonal grids.
A transonic full potential solver is generated using the current scheme. The flow around a 2-D
cylinder is solved for subcritical and supercritical cases. Axi-symmetric flow around cylinder is
selected as a benchmark problem since the potential flow around bodies with a blunt leading edge is a
more challenging problem than slender bodies.
Besides, it is shown that, the method is naturally appropriate for parallelization using shared memory
approach without using domain decomposition applications. The parallelization that is performed here
is partially line, partially point parallelization. T he performance of the application is presented for a 3-D unsteady diffusion problem using Cartesian cells and 2-D unsteady diffusion problem using both
structured and unstructured quadrilateral cells.
2
Wang, Mianzhi. "Numerical Analysis of Transient Teflon Ablation with a Domain Decomposition Finite Volume Implicit Method on Unstructured Grids." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/284.
Повний текст джерелаАнотація:
This work investigates numerically the process of Teflon ablation using a finite-volume discretization, implicit time integration and a domain decomposition method in three-dimensions. The interest in Teflon stems from its use in Pulsed Plasma Thrusters and in thermal protection systems for reentry vehicles. The ablation of Teflon is a complex process that involves phase transition, a receding external boundary where the heat flux is applied, an interface between a crystalline and amorphous (gel) phase and a depolymerization reaction which happens on and beneath the ablating surface. The mathematical model used in this work is based on a two-phase model that accounts for the amorphous and crystalline phases as well as the depolymerization of Teflon in the form of an Arrhenius reaction equation. The model accounts also for temperature-dependent material properties, for unsteady heat inputs and boundary conditions in 3D. The model is implemented in 3D domains of arbitrary geometry with a finite volume discretization on unstructured grids. The numerical solution of the transient reaction-diffusion equation coupled with the Arrhenius-based ablation model advances in time using implicit Crank-Nicolson scheme. For each time step the implicit time advancing is decomposed into multiple sub-problems by a domain decomposition method. Each of the sub-problems is solved in parallel by Newton-Krylov non-linear solver. After each implicit time-advancing step, the rate of ablation and the fraction of depolymerized material are updated explicitly with the Arrhenius-based ablation model. After the computation, the surface of ablation front and the melting surface are recovered from the scalar field of fraction of depolymerized material and the fraction of melted material by post-processing. The code is verified against analytical solutions for the heat diffusion problem and the Stefan problem. The code is validated against experimental data of Teflon ablation. The verification and validation demonstrates the ability of the numerical method in simulating three dimensional ablation of Teflon.
3
Krinshnamurthy, R. "Kinetic Flux Vector Splitting Method On Moving Grids (KFMG) For Unsteady Aerodynamics And Aeroelasticity." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/288.
Повний текст джерелаАнотація:
Analysis of unsteady flows is a very challenging topic of research. A decade ago, potential flow equations were used to predict unsteady pressures on oscillating bodies. Recognising the fact that nonlinear aerodynamics is essential to analyse unsteady flows accurately, particularly in transonic and supersonic flows, different Euler formulations operating on moving grids have emerged recently as important CFD tools for unsteady aerodynamics. Numerical solution of Euler equations on moving grids based on upwind schemes such as the ones due to van Leer and Roe have been developed for the purpose of numerical simulation of unsteady transonic and supersonic flows. In the present work, Euler computations based on yet another recent robust upwind scheme (for steady flows) namely Kinetic Flux Vector Splitting (KFVS) scheme due to Deshpande and Mandal is chosen for further development of a time accurate Euler solver to operate on problems involving moving boundaries. The development of an Euler code based on this scheme is likely to be highly useful to analyse problems of unsteady aerodynamics and computational aeroelasiticity especially when it is noted that KFVS has been found to be an extremely robust scheme for computation of subsonic, transonic, supersonic and hypersonic flows. The KFVS scheme, basically exploits the connection between the linear scalar Boltzmann equation of kinetic theory of gases and the nonlinear vector conservation law, that is, Euler equations of fluid dynamics through moment method strategy. The KFVS scheme has inherent simplicity in splitting the flux even on moving grids due to underlying particle model.
The inherent simplicity of KFVS for moving grid problems is due to its relationship with the Boltzmann equation. If a surface is moving with velocity w and a particle has velocity v, then it is quite reasonable to do the splitting based on (v-w)<0 or >0. Only particles having velocity v greater than w will cross the moving surface from left to right and similar arguments hold good for particles moving in opposite direction. It is therefore quite natural to extend KFVS by splitting the Maxwellian velocity distribution at Boltzmann level based on the sign of the normal component of the relative velocity. The relative velocity is the difference between the molecular velocity (v) and the velocity of the moving surface(w). This inherent simplicity of the Kinetic Flux Vector Splitting scheme on Moving Grids (KFMG) method has prompted us to extend the same ideas to 2-D and 3-D problems leading to the present KFMG method. If w is set to zero then KFMG formulation reduces to the one corresponding to KFVS. Thus KFMG formulations axe generalisation of the KFVS formulation. In 2-D and 3-D cases, in addition to the KFMG formulation, the method to move the grids, the appropriate boundary conditions for treating moving surfaces and techniques to improve accuracy in space and time are required to be developed. The 2-D and 3-D formulations based on Kinetic Flux Vector Splitting scheme on Moving Grids method have been developed for computing unsteady flows.
Between two successive time steps, the body changes its orientation in case of an oscillation or it deforms when subjected to, aerodynamic loads. In either of these cases the grid corresponding to the first time step has to be moved or regenerated around the displaced or deformed body. There are several approaches available to generate grids around moving bodies. In the present work, the 'spring analogy method' is followed to obtain grid around deflected geometries within the frame work of structured grid. Using this method, the grids are moved from previous time to the current time. This method is capable of tackling any kind of aeroelastic deformation of the body.
For oscillating bodies, a suitable boundary condition enforcing the flow tangency on the body needs to be developed. As a first attempt, the body surface has been treated as an 1-D piston undergoing compression and expansion. Then, a more general Kinetic Moving Boundary Condition(KMBC) has been developed. The KMBC uses specular reflection model of kinetic theory of gases. In order to treat fixed outer boundary, Kinetic Outer Boundary Condition(KOBC) has been applied. The KOBC is more general in the sense that, it can treat different type of boundaries (subsonic, supersonic, inflow or out flow boundary).
A 2-D cell-centered finite volume KFMG Euler code to operate on structured grid has been developed. The time accuracy is achieved by incorporating a fourth order Runge-Kutta time marching method. The space accuracy has been enhanced by using high resolution scheme as well as second order scheme using the method of reconstruction of fluxes.
First, the KFMG Euler code has been applied to standard test cases for computing steady flows around NACA 0012 and NACA 64AQ06 airfoils in transonic flow. For these two airfoils both computational and experimental results are available in literature. It is thus possible to verify (that is, prove the claim that code is indeed solving the partial differential equations + boundary conditions posed to the code) and validate(that is, comparison with experimental results) the 2-D KFMG Euler code. Having verified and validated the 2-D KFMG Euler code for the standard test cases, the code is then applied to predict unsteady flows around sinusoidally oscillating NACA 0012 and NACA 64A006 airfoils in transonic flow. The computational and experimental unsteady results are available in literature for these airfoils for verification and validation of the present results. The unsteady lift and normal force coefficients have been predicted fairly accurately by all the CFD codes. However there is some difficulty about accurate prediction of unsteady pitching moment coefficient. Even Navier-Stokes code could not predict pitching moment accurately. This issue needs further in depth study and probably intensive computation which have not been undertaken in the present study.
Next, a two degrees of £reedom(2-DOF) structural dynamics model of an airfoil undergoing pitch and plunge motions has been coupled with the 2-D KFMG Euler code for numerical simulation of aeroelastic problems. This aeroelastic analysis code is applied to NACA 64A006 airfoil undergoing pitch and plunge motions in transonic flow to obtain aeroelastic response characteristics for a set of structural parameters. For this test case also computed results are available in literature for verification. The response characteristics obtained have showed three modes namely stable, neutrally stable and unstable modes of oscillations. It is interesting to compare the value of airfoil-to-air mass ratio (Formula) obtained by us for neutrally stable condition with similar values obtained by others and some differences between them are worth mentioning here. The values of \i for neutral stability are different for different authors. The differences in values of (Formula) predicted by various authors are primarily due to differences which can be due to grid as well as mathematical model used. For example, the Euler calculations, TSP calculations and full potential calculations always show differences in shock location for the same flow problem. Changes in shock location will cause change in pressure distribution on airfoil which in turn will cause changes in values of \L for conditions of neutral stability. The flutter speed parameter(U*) has also been plotted with free stream Mach number for two different values of airfoil - to - air mass ratio. These curves shown a dip when the free stream Mach number is close to 0.855. This is referred as "Transonic Dip Phenomenon". The shock waves play a dominant role in the mechanism of transonic dip phenomenon.
Lastly, cell-centered finite volume KFMG 3-D Euler code has been developed to operate on structured grids. The time accuracy is achieved by incorporating a fourth order Runge-Kutta method. The space accuracy has been enhanced by using high resolution scheme. This code has 3-D grid movement module which is based on spring analogy method. The KMBC to treat oscillating 3-D configuration and KOBC for treating 3-D outer boundary have also been formulated and implemented in the code.
The 3-D KFMG Euler code has been first verified and validated for 3-D steady flows around standard shapes such as, transonic flow past a hemisphere cylinder and ONERA M6 wing. This code has also been used for predicting hypersonic flow past blunt cone-eylinder-flare configuration for which experimental data are available. Also, for this case, the results are compared with a similar Euler code. Then the KFMG Euler code has been used for predicting steady flow around ogive-cylinder-ogive configuration with elliptical cross section. The aerodynamic coefficients obtained have been compared with those of another Euler code. Thus, the 3-D KFMG Euler code has been verified and validated extensively for steady flow problems.
Finally, the 3-D KFMG based Euler code has been applied to an oscillating ogive-cylinder-ogive configuration in transonic flow. This test case has been chosen as it resembles the core body of a flight vehicle configuration of interest to DRDO,India. For this test case, the unsteady lift coefficients are available in literature for verifying the present results. Two grid sizes are used to perform the unsteady calculations using the present KFMG 3-D Euler code. The hysteresis loops of lift and moment coefficients confirmed the unsteady behaviour during the oscillation of the configuration. This has proved that, the 3-D formulations are capable of predicting the unsteady flows satisfactorily.
The unsteady results obtained for a grid with size of 45x41x51 which is very close to the grid size chosen in the reference(Nixon et al.) are considered for comparison. It has been mentioned in the reference that, a phase lag of (Formula) was observed in lift coefficients with respect to motion of the configuration for a free stream Mach number of 0.3 with other conditions remaining the same. The unsteady lift coefficients obtained using KFMG code as well as those available in literature are plotted for the same flow conditions. Approximately the same phase lag of (Formula) is present (for (Formula)) between the lift coefficient curves of KFMG and due to Nixon et al. The phase lag corrected plot of lift coefficient obtained by Nixon et al. is compared with the lift coefficient versus time obtained by 3-D KFMG Euler code. The two results compare well except that the peaks are over predicted by KFMG code. It is nut clear at this stage whether our results should at all match with those due to Nixon et al. Further in depth study is obviously required to settle the issue.
Thus the Kinetic Flux Vector Splitting on Moving Grids has been found to be a very good and a sound method for splitting fluxes and is a generalisation of earlier KFVS on fixed grids. It has been found to be very successful in numerical simulation of unsteady aerodynamics and computational aeroelasticity.
4
Krinshnamurthy, R. "Kinetic Flux Vector Splitting Method On Moving Grids (KFMG) For Unsteady Aerodynamics And Aeroelasticity." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/288.
Повний текст джерелаАнотація:
Analysis of unsteady flows is a very challenging topic of research. A decade ago, potential flow equations were used to predict unsteady pressures on oscillating bodies. Recognising the fact that nonlinear aerodynamics is essential to analyse unsteady flows accurately, particularly in transonic and supersonic flows, different Euler formulations operating on moving grids have emerged recently as important CFD tools for unsteady aerodynamics. Numerical solution of Euler equations on moving grids based on upwind schemes such as the ones due to van Leer and Roe have been developed for the purpose of numerical simulation of unsteady transonic and supersonic flows. In the present work, Euler computations based on yet another recent robust upwind scheme (for steady flows) namely Kinetic Flux Vector Splitting (KFVS) scheme due to Deshpande and Mandal is chosen for further development of a time accurate Euler solver to operate on problems involving moving boundaries. The development of an Euler code based on this scheme is likely to be highly useful to analyse problems of unsteady aerodynamics and computational aeroelasiticity especially when it is noted that KFVS has been found to be an extremely robust scheme for computation of subsonic, transonic, supersonic and hypersonic flows. The KFVS scheme, basically exploits the connection between the linear scalar Boltzmann equation of kinetic theory of gases and the nonlinear vector conservation law, that is, Euler equations of fluid dynamics through moment method strategy. The KFVS scheme has inherent simplicity in splitting the flux even on moving grids due to underlying particle model.
The inherent simplicity of KFVS for moving grid problems is due to its relationship with the Boltzmann equation. If a surface is moving with velocity w and a particle has velocity v, then it is quite reasonable to do the splitting based on (v-w)<0 or >0. Only particles having velocity v greater than w will cross the moving surface from left to right and similar arguments hold good for particles moving in opposite direction. It is therefore quite natural to extend KFVS by splitting the Maxwellian velocity distribution at Boltzmann level based on the sign of the normal component of the relative velocity. The relative velocity is the difference between the molecular velocity (v) and the velocity of the moving surface(w). This inherent simplicity of the Kinetic Flux Vector Splitting scheme on Moving Grids (KFMG) method has prompted us to extend the same ideas to 2-D and 3-D problems leading to the present KFMG method. If w is set to zero then KFMG formulation reduces to the one corresponding to KFVS. Thus KFMG formulations axe generalisation of the KFVS formulation. In 2-D and 3-D cases, in addition to the KFMG formulation, the method to move the grids, the appropriate boundary conditions for treating moving surfaces and techniques to improve accuracy in space and time are required to be developed. The 2-D and 3-D formulations based on Kinetic Flux Vector Splitting scheme on Moving Grids method have been developed for computing unsteady flows.
Between two successive time steps, the body changes its orientation in case of an oscillation or it deforms when subjected to, aerodynamic loads. In either of these cases the grid corresponding to the first time step has to be moved or regenerated around the displaced or deformed body. There are several approaches available to generate grids around moving bodies. In the present work, the 'spring analogy method' is followed to obtain grid around deflected geometries within the frame work of structured grid. Using this method, the grids are moved from previous time to the current time. This method is capable of tackling any kind of aeroelastic deformation of the body.
For oscillating bodies, a suitable boundary condition enforcing the flow tangency on the body needs to be developed. As a first attempt, the body surface has been treated as an 1-D piston undergoing compression and expansion. Then, a more general Kinetic Moving Boundary Condition(KMBC) has been developed. The KMBC uses specular reflection model of kinetic theory of gases. In order to treat fixed outer boundary, Kinetic Outer Boundary Condition(KOBC) has been applied. The KOBC is more general in the sense that, it can treat different type of boundaries (subsonic, supersonic, inflow or out flow boundary).
A 2-D cell-centered finite volume KFMG Euler code to operate on structured grid has been developed. The time accuracy is achieved by incorporating a fourth order Runge-Kutta time marching method. The space accuracy has been enhanced by using high resolution scheme as well as second order scheme using the method of reconstruction of fluxes.
First, the KFMG Euler code has been applied to standard test cases for computing steady flows around NACA 0012 and NACA 64AQ06 airfoils in transonic flow. For these two airfoils both computational and experimental results are available in literature. It is thus possible to verify (that is, prove the claim that code is indeed solving the partial differential equations + boundary conditions posed to the code) and validate(that is, comparison with experimental results) the 2-D KFMG Euler code. Having verified and validated the 2-D KFMG Euler code for the standard test cases, the code is then applied to predict unsteady flows around sinusoidally oscillating NACA 0012 and NACA 64A006 airfoils in transonic flow. The computational and experimental unsteady results are available in literature for these airfoils for verification and validation of the present results. The unsteady lift and normal force coefficients have been predicted fairly accurately by all the CFD codes. However there is some difficulty about accurate prediction of unsteady pitching moment coefficient. Even Navier-Stokes code could not predict pitching moment accurately. This issue needs further in depth study and probably intensive computation which have not been undertaken in the present study.
Next, a two degrees of £reedom(2-DOF) structural dynamics model of an airfoil undergoing pitch and plunge motions has been coupled with the 2-D KFMG Euler code for numerical simulation of aeroelastic problems. This aeroelastic analysis code is applied to NACA 64A006 airfoil undergoing pitch and plunge motions in transonic flow to obtain aeroelastic response characteristics for a set of structural parameters. For this test case also computed results are available in literature for verification. The response characteristics obtained have showed three modes namely stable, neutrally stable and unstable modes of oscillations. It is interesting to compare the value of airfoil-to-air mass ratio (Formula) obtained by us for neutrally stable condition with similar values obtained by others and some differences between them are worth mentioning here. The values of \i for neutral stability are different for different authors. The differences in values of (Formula) predicted by various authors are primarily due to differences which can be due to grid as well as mathematical model used. For example, the Euler calculations, TSP calculations and full potential calculations always show differences in shock location for the same flow problem. Changes in shock location will cause change in pressure distribution on airfoil which in turn will cause changes in values of \L for conditions of neutral stability. The flutter speed parameter(U*) has also been plotted with free stream Mach number for two different values of airfoil - to - air mass ratio. These curves shown a dip when the free stream Mach number is close to 0.855. This is referred as "Transonic Dip Phenomenon". The shock waves play a dominant role in the mechanism of transonic dip phenomenon.
Lastly, cell-centered finite volume KFMG 3-D Euler code has been developed to operate on structured grids. The time accuracy is achieved by incorporating a fourth order Runge-Kutta method. The space accuracy has been enhanced by using high resolution scheme. This code has 3-D grid movement module which is based on spring analogy method. The KMBC to treat oscillating 3-D configuration and KOBC for treating 3-D outer boundary have also been formulated and implemented in the code.
The 3-D KFMG Euler code has been first verified and validated for 3-D steady flows around standard shapes such as, transonic flow past a hemisphere cylinder and ONERA M6 wing. This code has also been used for predicting hypersonic flow past blunt cone-eylinder-flare configuration for which experimental data are available. Also, for this case, the results are compared with a similar Euler code. Then the KFMG Euler code has been used for predicting steady flow around ogive-cylinder-ogive configuration with elliptical cross section. The aerodynamic coefficients obtained have been compared with those of another Euler code. Thus, the 3-D KFMG Euler code has been verified and validated extensively for steady flow problems.
Finally, the 3-D KFMG based Euler code has been applied to an oscillating ogive-cylinder-ogive configuration in transonic flow. This test case has been chosen as it resembles the core body of a flight vehicle configuration of interest to DRDO,India. For this test case, the unsteady lift coefficients are available in literature for verifying the present results. Two grid sizes are used to perform the unsteady calculations using the present KFMG 3-D Euler code. The hysteresis loops of lift and moment coefficients confirmed the unsteady behaviour during the oscillation of the configuration. This has proved that, the 3-D formulations are capable of predicting the unsteady flows satisfactorily.
The unsteady results obtained for a grid with size of 45x41x51 which is very close to the grid size chosen in the reference(Nixon et al.) are considered for comparison. It has been mentioned in the reference that, a phase lag of (Formula) was observed in lift coefficients with respect to motion of the configuration for a free stream Mach number of 0.3 with other conditions remaining the same. The unsteady lift coefficients obtained using KFMG code as well as those available in literature are plotted for the same flow conditions. Approximately the same phase lag of (Formula) is present (for (Formula)) between the lift coefficient curves of KFMG and due to Nixon et al. The phase lag corrected plot of lift coefficient obtained by Nixon et al. is compared with the lift coefficient versus time obtained by 3-D KFMG Euler code. The two results compare well except that the peaks are over predicted by KFMG code. It is nut clear at this stage whether our results should at all match with those due to Nixon et al. Further in depth study is obviously required to settle the issue.
Thus the Kinetic Flux Vector Splitting on Moving Grids has been found to be a very good and a sound method for splitting fluxes and is a generalisation of earlier KFVS on fixed grids. It has been found to be very successful in numerical simulation of unsteady aerodynamics and computational aeroelasticity.
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Stern, Louis G. "An explicitly conservative method for time-accurate solution of hyperbolic partial differential equations on embedded Chimera grids /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6758.
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Bas, Onur. "Development Of An Incompressible Navier-stokes Solver With Alternating Cell Direction Implicit Method On Structured And Unstructured Quadrilateral Grids." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608775/index.pdf.
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In this research, the Alternating Cell Direction Implicit method is used in temporal discretisation of the incompressible Navier-Stokes equations and compared with the well known and widely used Point Gauss Seidel scheme on structured and quadrilateral unstructured meshes. A two dimensional, laminar and incompressible Navier-Stokes solver is developed for this purpose using the artificial compressibility formulation. The developed solver is used to obtain steady-state solutions with implicit time stepping methods and a third order data reconstruction scheme (U-MUSCL) is added to obtain high order spatial accuracy. The Alternating Cell Directions Implicit method and Point Gauss Seidel scheme is compared in terms of convergence iteration number and total computation time using test cases with growing complexity, including laminar flat plate, single and multi-element airfoil calculations. Both structured and quadrilateral unstructured grids are used in single element airfoil calculations. In these test cases, it is seen that a reduction between 13% and 20% is obtained in total computation time by usage of Alternating Cell Directions Implicit method when compared with the Point Gauss Seidel method.
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Acikgoz, Nazmiye. "Adaptive and Dynamic Meshing Methods for Numerical Simulations." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14521.
Повний текст джерелаАнотація:
For the numerical simulation of many problems of engineering interest, it is desirable to have an automated mesh adaption tool. This is important especially for problems characterized by anisotropic features and require mesh clustering in the direction of high gradients. Another significant issue in meshing emerges in unsteady simulations with moving boundaries, where the boundary motion has to be accommodated by deforming the computational grid. Similarly, there exist problems where current mesh needs to be adapted to get more accurate solutions. To solve these problems, we propose three novel procedures.
In the first part of this work, we present an optimization procedure for three-dimensional anisotropic tetrahedral grids based on metric-driven h-adaptation. Through the use of topological and geometrical operators, the mesh is iteratively adapted until the final mesh minimizes a given objective function. We propose an optimization process based on an ad-hoc application of the simulated annealing technique, which improves the likelihood of removing poor elements from the grid. Moreover, a local implementation of the simulated annealing is proposed to reduce the computational cost.
Many challenging unsteady multi-physics problems are characterized by moving boundaries and/or interfaces. When the boundary displacements are large, degenerate elements are easily formed in the grid such that frequent remeshing is required. We propose a new r-adaptation technique that is valid for all types of elements (e.g., triangle, tet, quad, hex, hybrid) and deforms grids that undergo large imposed displacements at their boundaries. A grid is deformed using a network of linear springs composed of edge springs and a set of virtual springs. The virtual springs are constructed in such a way as to oppose element collapsing.
Both frequent remeshing, and exact-pinpointing of clustering locations are great challenges of numerical simulations, which can be overcome by adaptive meshing algorithms. Therefore, we conclude this work by defining a novel mesh adaptation technique where the entire mesh is adapted upon application of a force field in order to comply with the target mesh or to get more accurate solutions. The method has been tested for two-dimensional problems of a-priori metric definitions as well as for oblique shock clusterings.
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Demir, H. Ozgur. "Computational Fluid Dynamics Analysis Of Store Separation." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605294/index.pdf.
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In this thesis, store separation from two different configurations are solved using computational methods. Two different commercially available CFD codesCFD-FASTRAN, an implicit Euler solver, and an unsteady panel method solver USAERO, coupled with integral boundary layer solution procedure are used for the present computations. The computational trajectory results are validated against the available experimental data of a generic wing-pylon-store configuration at Mach 0.95. Major trends of the separation are captured. Same configuration is used for the comparison of unsteady panel method with Euler solution at Mach 0.3 and 0.6. Major trends are similar to each other while some differences in lateral and longitudinal displacements are observed. Trajectories of a fueltank separated from an F-16 fighter aircraft wing and full aircraft configurations are found at Mach 0.3 using only the unsteady panel code. The results indicate that the effect of fuselage is to decrease the drag and to increase the side forces acting on the separating fueltank from the aircraft. It is also observed that the yawing and rolling directions of the separating fueltank are reversed when it is separated from the full aircraft configuration when compared to the separation from the wing alone configuration.
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Häggblom, Johan, and Jonathan Jerner. "Photovoltaic Power Production and Energy Storage Systems in Low-Voltage Power Grids." Thesis, Linköpings universitet, Fordonssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156875.
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In recent years, photovoltaic (PV) power production have seen an increase and the PV power systems are often located in the distribution grids close to the consumers. Since the distributions grids rarely are designed for power production, investigation of its effects is needed. It is seen in this thesis that PV power production will cause voltages to rise, potentially to levels exceeding the limits that grid owners have to abide by. A model of a distribution grid is developed in MathWorks MATLAB. The model contains a transformer, cables, households, energy storage systems (ESS:s) and photovoltaic power systems. The system is simulated by implementing a numerical Forward Backward Sweep Method, solving for powers, currents and voltages in the grid. PV power systems are added in different configurations along with different configurations of ESS:s. The results are analysed, primarily concerning voltages and voltage limits. It is concluded that addition of PV power production in the distribution grid affects voltages, more or less depending on where in the grid the systems are placed and what peak power they have. It is also concluded that having energy storage systems in the grid, changing the power factor of the inverter for the PV systems or lowering the transformer secondary-side voltage can bring the voltages down.På senare tid har det skett en ökning i antalet solcellsanläggningar som installeras i elnätet och dessa är ofta placerade i distributionsnäten nära hushållen. Eftersom distributionsnäten sällan är dimensionerade för produktion så behöver man utreda effekten av det. I det här arbetet visas det att solcellsproduktion kommer att öka spänningen i elnätet, potentiellt så mycket att de gränser elnätsägarna måste hålla nätet inom överstigs. En modell över lågspänningsnätet skapas i MathWorks MATLAB. Modellen innehåller transformator, kablar, hushåll, energilager och solcellsanläggningar. Systemet simuleras med hjälp av en numerisk Forward Backward Sweep-lösare som beräknar effekter, strömmar och spänningar i elnätet. Solcellanläggningarna placeras ut i elnätet i olika konfigurationer tillsammans med olika konfigurationer av energilager. Resultaten från simuleringarna analyseras främst med avseende på spänningen i elnätet utifrån dess gränser. De slutsatser som dras i arbetet är att solcellsproduktion kommer att påverka spänningen, mycket beroende på var i elnätet anläggningarna placeras och storleken hos dem. Det visas också att energilager, justering av effektfaktor hos solcellsanläggningarna eller en spänningssänkning på transformatorns lågspänningssida kan få ner spänningen i elnätet.
LiTH-ISY-EX--19/5194--SE
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Dai, Ruxin. "Richardson Extrapolation-Based High Accuracy High Efficiency Computation for Partial Differential Equations." UKnowledge, 2014. http://uknowledge.uky.edu/cs_etds/20.
Повний текст джерелаАнотація:
In this dissertation, Richardson extrapolation and other computational techniques are used to develop a series of high accuracy high efficiency solution techniques for solving partial differential equations (PDEs).
A Richardson extrapolation-based sixth-order method with multiple coarse grid (MCG) updating strategy is developed for 2D and 3D steady-state equations on uniform grids. Richardson extrapolation is applied to explicitly obtain a sixth-order solution on the coarse grid from two fourth-order solutions with different related scale grids. The MCG updating strategy directly computes a sixth-order solution on the fine grid by using various combinations of multiple coarse grids. A multiscale multigrid (MSMG) method is used to solve the linear systems resulting from fourth-order compact (FOC) discretizations. Numerical investigations show that the proposed methods compute high accuracy solutions and have better computational efficiency and scalability than the existing Richardson extrapolation-based sixth order method with iterative operator based interpolation.
Completed Richardson extrapolation is explored to compute sixth-order solutions on the entire fine grid. The correction between the fourth-order solution and the extrapolated sixth-order solution rather than the extrapolated sixth-order solution is involved in the interpolation process to compute sixth-order solutions for all fine grid points. The completed Richardson extrapolation does not involve significant computational cost, thus it can reach high accuracy and high efficiency goals at the same time.
There are three different techniques worked with Richardson extrapolation for computing fine grid sixth-order solutions, which are the iterative operator based interpolation, the MCG updating strategy and the completed Richardson extrapolation. In order to compare the accuracy of these Richardson extrapolation-based sixth-order methods, truncation error analysis is conducted on solving a 2D Poisson equation. Numerical comparisons are also carried out to verify the theoretical analysis.
Richardson extrapolation-based high accuracy high efficiency computation is extended to solve unsteady-state equations. A higher-order alternating direction implicit (ADI) method with completed Richardson extrapolation is developed for solving unsteady 2D convection-diffusion equations. The completed Richardson extrapolation is used to improve the accuracy of the solution obtained from a high-order ADI method in spatial and temporal domains simultaneously. Stability analysis is given to show the effects of Richardson extrapolation on stable numerical solutions from the underlying ADI method.
Книги з теми "Method analysis grids"
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Anderson, W. Kyle. Grid generation and flow solution method for Euler equations on unstructured grids. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, 1992.
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Carney, Dan. The adjoint method for optimal aerodynamic design on unstructured grids. [Downsview, Ont.]: University of Toronto, Institute for Aerospace Studies, 2003.
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3
Hu, Fang Q. Eigensolution analysis of the discontinuous Galerkin method with non-uniform grids. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 2001.
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4
T, Tzong, and United States. National Aeronautics and Space Administration., eds. A general interface method for aeroelastic analysis of aircraft. [Washington, DC: National Aeronautics and Space Administration, 1996.
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Institute for Computer Applications in Science and Engineering., ed. Multigrid method for the equilibrium equations of elasticity using a compact scheme. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 1986.
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1942-, Eiseman Peter R., United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., and Langley Research Center, eds. A time-accurate adaptive grid method and the numerical simulation of shock-vortex interaction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1990.
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1942-, Eiseman Peter R., United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., and Langley Research Center, eds. A time-accurate adaptive grid method and the numerical simulation of shock-vortex interaction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1990.
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United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., ed. An algebraic homotopy method for generating quasi-three-dimensional grids for high-speed configurations. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.
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C, Taylor Arthur, Barnwell Richard W, and United States. National Aeronautics and Space Administration., eds. Aerodynamic shape sensitivity analysis and design optimization of complex configurations using unstructured grids. [Washington, DC: National Aeronautics and Space Administration, 1997.
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Hu, Chang-Qing. Weighted essentially non-oscillatory schemes on triangular meshes. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 1998.
Знайти повний текст джерелаЧастини книг з теми "Method analysis grids"
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Murari, André L. L. F., J. S. Solís-Chaves, Ademir Pelizari, Alfeu J. Sguarezi Filho, Bruno H. P. da Silva, and Renato M. Monaro. "Electromagnetic Analysis of a DFIG‘s Controlled Operation Using Finite Elements Method." In Smart Grids—Renewable Energy, Power Electronics, Signal Processing and Communication Systems Applications, 277–96. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-37909-3_10.
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Litzenberger, Niklas. "Comparison between Advanced State Space Grids and a Standard Research Method." In Introduction of Advanced State Space Grids and Their Application to the Analysis of Physics Teaching, 175–95. Wiesbaden: Springer Fachmedien Wiesbaden, 2023. http://dx.doi.org/10.1007/978-3-658-42732-0_9.
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Pilsl, Michael, Florian B. Heiss, Gisela Pöll, Mona Höcherl, Philipp Milkereit, and Christoph Engel. "Preparation of RNA Polymerase Complexes for Their Analysis by Single-Particle Cryo-Electron Microscopy." In Ribosome Biogenesis, 81–96. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2501-9_6.
Повний текст джерелаАнотація:
AbstractRecent technological progress revealed new prospects of high-resolution structure determination of macromolecular complexes using cryo-electron microscopy (cryo-EM). In the field of RNA polymerase (Pol) I research, a number of cryo-EM studies contributed to understanding the highly specialized mechanisms underlying the transcription of ribosomal RNA genes. Despite a broad applicability of the cryo-EM method itself, preparation of samples for high-resolution data collection can be challenging. Here, we describe strategies for the purification and stabilization of Pol I complexes, exemplarily considering advantages and disadvantages of the methodology. We further provide an easy-to-implement protocol for the coating of EM-grids with self-made carbon support films. In sum, we present an efficient workflow for cryo-grid preparation and optimization, including early stage cryo-EM screening that can be adapted to a wide range of soluble samples for high-resolution structure determination.
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Yaermaimaiti, Ailixier, Yongheng Yang, and Yiqun Kang. "SISO Impedance-Based Stability Analysis Method for PLL-Based Power Converters in Weak AC Grids." In Lecture Notes in Electrical Engineering, 560–72. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1439-5_52.
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Hackbusch, Wolfgang. "Fourier Analysis." In Multi-Grid Methods and Applications, 169–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-662-02427-0_8.
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Nome, Morten A., and Tor Sørevik. "Discrete Fourier Analysis on Lattice Grids." In Numerical Methods and Applications, 251–60. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10692-8_28.
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Lindberg, Anne-Sofie Wessel, Thomas Martini Jørgensen, and Vedrana Andersen Dahl. "Interpolation from Grid Lines: Linear, Transfinite and Weighted Method." In Image Analysis, 338–49. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-59129-2_29.
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Grice*, James, and Brenda L. McDaniel. "Evaluating Self-Reflexion Analysis Using Repertory Grids." In Computational Methods for Counterterrorism, 211–25. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01141-2_11.
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Grogan, Myles. "Chapter 15. Repertory grids." In Research Methods in Applied Linguistics, 246–63. Amsterdam: John Benjamins Publishing Company, 2024. http://dx.doi.org/10.1075/rmal.6.15gro.
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Recent literature suggests that classroom-based assessment should perhaps work from a different set of assumptions than large-scale testing. This idea is explored through RGT by asking how seven teachers, each with a unique approach to teaching and assessment, create their grades in a multi-faculty undergraduate EFL course in Japan. In an interview, the researcher asked each teacher to compare a sample of their own students achieving different grades, demonstrating the teachers’ constructs for teaching and assessment. These were then analyzed, and subject to a form of content analysis used in RGT. The process revealed that, although the assessment approach used by each teacher differed, the grade reflected similar underlying teaching values that seemed to be legitimate expressions of the framework provided by the institution.
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Korch, Matthias, Thomas Rauber, and Gudula Rünger. "Performance Optimization of RK Methods Using Block-Based Pipelining." In Performance Analysis and Grid Computing, 41–56. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4615-0361-3_3.
Повний текст джерелаТези доповідей конференцій з теми "Method analysis grids"
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Kumar, Ashok V., and Ravi K. Burla. "Local Hierarchical Grid Refinement for Analysis Using Structured Grids." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87564.
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Structured grids with regular shaped uniform elements are easy to generate automatically and have been used in extended finite element approaches to avoid mesh generation difficulties. But the grid or mesh should ideally have higher resolution in areas where the solution has large gradients. In this paper a technique for refinement of structured grids is presented that allows refinement of the grid without violating compatibility requirements by using solution structures constructed using approximate step functions. Essential boundary conditions are applied using implicit boundary method, which allows boundary conditions to be imposed even when there are no nodes on the boundary. This grid refinement technique is evaluated using two dimensional elasticity problems that involve stress concentration.
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Nazeer, S. Mohamed, Francisco Chinesta, and Adrien Leygue. "A Novel Proper Generalized Decomposition (PGD) Based Approach for Non-Matching Grids." In ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82506.
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Proper Generalized Decomposition (PGD) is a recent model reduction technique, successfully employed to solve many multidimensional problems. This method is able to circumvent, or at least alleviate, the curse of dimensionality. This method is based on the use of separated representations. By avoiding the exponential complexity of standard grid based discretization techniques, the PGD circumvents the curse of dimensionality in a variety of problems. With the PGD, the problem’s usual coordinates (e.g. space, time), but also model parameters, boundary conditions, and other sources of variability can be viewed globally as coordinates of a high-dimensional space wherein an approximate solution can efficiently be computed at once. Non-matching grids are very common in advanced scientific computing (e.g. contact problems, sub-domains coupling,).In this framework, approximate solutions from one grid to a non-matching second grid needs to be projected. This approach poses substantial numerical complexity which increases when going from one to higher dimensional interfaces. In this paper, we try to simulate a domain, which has a coarse mesh on one side and a fine mesh on other side by PGD. We show that PGD can handle these non -matching grids by using a smooth transition of the separated representation description.
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Theodoro, Edson A. R., Raphael A. S. Benedito, and Luis F. C. Alberto. "A fast method for islanding analysis in power system grids." In 2011 IEEE International Symposium on Circuits and Systems (ISCAS). IEEE, 2011. http://dx.doi.org/10.1109/iscas.2011.5937948.
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Rault, P., F. Colas, X. Guillaud, and S. Nguefeu. "Method for small signal stability analysis of VSC-MTDC grids." In 2012 IEEE Power & Energy Society General Meeting. New Energy Horizons - Opportunities and Challenges. IEEE, 2012. http://dx.doi.org/10.1109/pesgm.2012.6345318.
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Liu, Huaqin, Yi Luo, Hua Liu, and Changjin Hao. "Grid gallop analysis using the Euler angle estimation method." In 2023 2nd International Conference on Smart Grids and Energy Systems (SGES). IEEE, 2023. http://dx.doi.org/10.1109/sges59720.2023.10366909.
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Hu, Fang, and Harold Atkins. "Eigensolution analysis of the discontinuous Galerkin method with non-uniform grids." In 7th AIAA/CEAS Aeroacoustics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-2195.
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Ortleb, S., A. Meister, Th Sonar, Theodore E. Simos, George Psihoyios, Ch Tsitouras, and Zacharias Anastassi. "Adaptive Spectral and DTV Filtering on Triangular Grids for the DG Method Applied to Compressible Fluid Flow." In NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2011: International Conference on Numerical Analysis and Applied Mathematics. AIP, 2011. http://dx.doi.org/10.1063/1.3636883.
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Lin, Wenzhou, Zhong Lin, and Quan Liu. "Numerical test of the open void method of slide line with unstructured polygon grids." In INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS (ICNAAM 2016). Author(s), 2017. http://dx.doi.org/10.1063/1.4992164.
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Zhang, Haiping, Zhenzhi Yu, Ming Xu, and Yueling Shi. "An Improved Method to Building a Score Lexicon for Chinese Sentiment Analysis." In 2012 Eighth International Conference on Semantics, Knowledge and Grids (SKG). IEEE, 2012. http://dx.doi.org/10.1109/skg.2012.18.
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Milagre, Alexandre, and Silvio Barbin. "Analysis of Influence of Non-Uniform Grids Method on the Self-Teleportation of Fields Method." In XXII Simpósio Brasileiro de Telecomunicações. Sociedade Brasileira de Telecomunicações, 2005. http://dx.doi.org/10.14209/sbrt.2005.451.
Повний текст джерелаЗвіти організацій з теми "Method analysis grids"
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Huang, Zhenyu, Ning Zhou, Francis K. Tuffner, Yousu Chen, Daniel J. Trudnowski, Ruisheng Diao, Jason C. Fuller, William A. Mittelstadt, John F. Hauer, and Jeffery E. Dagle. MANGO ? Modal Analysis for Grid Operation: A Method for Damping Improvement through Operating Point Adjustment. Office of Scientific and Technical Information (OSTI), October 2010. http://dx.doi.org/10.2172/1008256.
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Webster, Clayton, Raul Tempone, and Fabio Nobile. The analysis of a sparse grid stochastic collocation method for partial differential equations with high-dimensional random input data. Office of Scientific and Technical Information (OSTI), December 2007. http://dx.doi.org/10.2172/934852.
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Stjernberg, Mats, Anna Vasilevskaya, and Oskar Penje. Towards a grid-based Nordic territorial typology - A new tool for analysis across the urban-rural continuum. Nordregio, March 2024. http://dx.doi.org/10.6027/r2024:91403-2503.
Повний текст джерелаАнотація:
This report presents the grid-based Nordic urban–rural typology, which was developed as a new analytical tool for studying different types of spatial phenomena across Nordic territories. In this study this meant developing a typology that classifies all Nordic territories into seven different typology classes based on different degrees of urbanity and rurality. A key starting point for this work was the need for a territorial typology that would help enrich and provide new understanding of different types of urban and rural areas across the Nordic countries and shed light on how they are developing. This report first presents how the typology was created, including the rationale behind the typology, key considerations at different stages of the work, and the main operational steps taken. The main purpose was to create a new territorial typology, to which different types of data could be combined, thus helping to provide a more nuanced and fine-grained understanding of territorial differences across the Nordic countries. Several key principles were specified early in the work. These include that the typology should be created at grid-level (1 x 1 km) as this allows identifying the characteristics of different types of areas at a very detailed territorial level. Another key decision was to create the typology mainly using open-source data and following a replicable method, to make any possible future updates to the typology easier and less costly. For the development of the Nordic typology, the Finnish grid-based urban–rural classification (Kaupunki-maaseutuluokitus) was the main source of inspiration. This Nordic typology and population data at grid level (linked to the typology) is then used as an analytical lens for studying territorial differences, settlement pattens and demographic change dynamics in the five Nordic countries. According to the typology, the Nordic countries are predominantly rural when considering how their land areas are classified. However, an examination of settlement patterns according to the Nordic typology shows that the settlements are rather unevenly distributed in all the Nordic countries, and the majority of the population live relatively concentrated in areas that are classified as urban. In general, the population is largely concentrated in coastal areas and along waterways, where the major urban regions are found, reflecting historical patterns and features of physical geography. The Nordic typology is also used to examine what types of population change dynamics occurred in the Nordic countries during the period 2008–2022. The analysis shows that urbanisation has been a general trend during the past couple of decades, with the largest population growth occurring in the typology classes inner urban and outer urban. A relatively noticeable increase in population is also evident in peri-urban areas, suggesting suburbanisation and that intermediate areas located on the urban fringes have increasingly attracted new residents. In rural areas, the general trend shows that depopulation has occurred in many rural localities, but different types of rural areas have developed quite differently. Based on the analysis, rural areas that are in the vicinity of cities and towns appear to have become more attractive places for people to settle, while sparsely populated rural areas seem to be less favourably placed and have generally witnessed population decrease. This report shows how this typology and more fine-grained data can help reveal territorial differences that cannot be observed with more general statistics and data. The grid-based Nordic typology shows that many municipalities are at the same time both urban, intermediate, and rural, and in many cases these different categories seem to be undergoing quite different types of development. While the Nordic urban–rural typology is used in this study to examine settlement patterns and population change dynamics, it should be stressed that the typology is also well-suited to be used in combination with other types of data and as an analytical framework for studying also other types of spatial phenomena across the urban–rural continuum.
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Knight, R. D., and B. A. Kjarsgaard. Comparative pXRF and Lab ICP-ES/MS methods for mineral resource assessment, Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331239.
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The Geological Survey of Canada undertook a mineral resource assessment for a proposed national park in northern Canada (~ 33,500 km2) spanning the transition from boreal forest to barren lands tundra. Bedrock geology of this region is complex and includes the Archean Slave Craton, the Archean and Paleoproterozoic Rae domain of the Churchill Province, the Paleoproterozoic Thelon and Taltson magmatic-tectonic zones, and the Paleoproterozoic East Arm sedimentary basin. The area has variable mineral potential for lode gold, kimberlite-hosted diamonds, VMS, vein uranium and copper, SEDEX, as well as other deposit types. A comparison of analytical methods was carried out after processing the field collected samples to acquire both the &lt; 2 mm and for the &lt; 0.063 mm size fractions for 241 surficial sediment (till) samples, collected using a 10 x 10 km grid. Analytical methods comprised: 1) aqua regia followed by ICP-MS analysis, 2) 4-acid hot dissolution followed by ICP-ES/MS analysis, 3) lithium metaborate/tetraborate fusion methods followed by ICP-ES for major elements and ICP-MS for trace elements and, 4) portable XRF on dried, non-sieved sediment samples subjected to a granular segregation processing technique (to produce a clay-silt proxy) for seventeen elements (Ba, Ca, Cr, Cu, Fe, K, Mn, Ni, Pb, Rb, Sr, Th, Ti, U, V, Zn, and Zr) Results indicate that pXRF data do not replicate exactly the laboratory 4-acid and fusion data (in terms of precision and accuracy), but the relationship between the datasets is systematic as displayed in x-y scattergrams. Interpolated single element plots indicate that till samples with anomalies of high and low pXRF concentration levels are synonymous with high and low laboratory-based analytical concentration levels, respectively. The pXRF interpolations thus illustrate the regional geochemical trends, and most importantly, the significant geochemical anomalies in the surficial samples. These results indicate that pXRF spectrometry for a subset of elements is comparable to traditional laboratory methods. pXRF spectrometry also provides the benefit of rapid analysis and data acquisition that has a direct influence on real time sampling designs. This information facilitates efficient and cost-effective field projects (i.e. where used to identify regions of interest for high density sampling), and to prioritize samples to be analyzed using traditional geochemical methods. These tactics should increase the efficiency and success of a mineral exploration and/or environmental sampling programs.
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She, Ruifeng, and Yanfeng Ouyang. Analysis of Drone-based Last-mile Delivery Systems under Aerial Congestion: A Continuum Approximation Approach. Illinois Center for Transportation, August 2023. http://dx.doi.org/10.36501/0197-9191/23-014.
Повний текст джерелаАнотація:
This paper presents a systematic analysis and design framework for a spectrum of last-mile delivery systems that leverage unmanned aerial vehicles (UAVs). Four distinct modes are considered: (1) direct drone deliveries from a fixed depot; (2) drone deliveries from parked trucks that carry bulk parcels to customer neighborhoods; (3) drone deliveries from nonstopping trucks that tour customer neighborhoods; and (4) as a benchmark, traditional truck-based home deliveries. We present a new continuum-approximation approach that is used for analysis of both truck routing and aerial-UAV traffic. We compared the operational cost and efficiency of different delivery schemes to reveal how a certain scheme is the most efficient under various scenarios. We demonstrate the applicability of our model on expansive real-world roadway networks and further conduct analysis on grid networks, yielding key analytical insights. The drone-based delivery is demonstrated to be superior to conventional truck-only delivery, suggesting a significant potential for socioeconomic benefit. It is observed that when servicing a relatively low demand over a small area, dispatching drones directly from the distribution facility is the most efficient method. As the demand grows or spans a wider area, collaborative strategies are preferred, as they better cope with certain aspects, such as the long line-haul cost or the ramping aerial congestion, by striking a balance between efficiency and flexibility.
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Lynk, John. PR-610-163756-WEB Material Strength Verification. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), April 2019. http://dx.doi.org/10.55274/r0011573.
Повний текст джерелаАнотація:
DATE: Tuesday, April 30, 2019 TIME: 11:00 a.m. ET CLICK THE DOWNLOAD/BUY BUTTON TO ACCESS THE WEBINAR REGISTRATION LINK Join the PRCI Integrity and Inspection technical committee for a pipeline operator driven discussion regarding PRCI research related to non-destructive technologies for the purpose of pipe material verification and how operators have applied this research in the field. This webinar will include; research project overview, operator case studies and analysis of current technology gaps. Panelists: Mark Piazza, Manager Pipeline Compliance and R and D, Colonial Pipeline Company Mike Kern, Director of Gas Transmission Engineering, National Grid Oliver Burkinshaw, Senior Materials Engineer, ROSEN Simon Bellemare, Founder and CEO of Massachusetts Materials Technologies John Lynk, Program Manager, Integrity and Inspection and Subsea Technical Committees, PRCI Expected Benefits/Learning Outcomes: - In-ditch non-destructive evaluation for material yield strength that has been utilized on in-service lines to confirm incomplete records of pipe grades and/or to evaluate acquired assets - How the data has been utilized to collect opportunistic data as part of external corrosion direct assessments to provide a basis for maximum allowable operating pressure, as well as prioritizing and setting criteria for further inspection and potential capital projects. - The ability to differentiate specific manufacturing processes, such as low frequency and high frequency electro-resistance welded longitudinal seams, have been successfully applied on a number of pipeline integrity projects - Enhancement of inline inspection technologies combined with verification digs have demonstrated the potential to apply pipe joint specific strength data in fitness-for-service, as opposed to lower minimum values set by pipe grade or by nominal conservative assumptions. Who should attend: - Pipeline integrity engineers, specialists and management - Pipe materials specialists Recommended pre-reading: PR-610-163756-R01 Hardness Stength and Ductility (HSD) Testing of Line Pipes Initial Validation Testing Phase I PR-335-173816-MV Validation of insitu Methods for Material Property Determination CLICK THE DOWNLOAD/BUY BUTTON TO ACCESS THE WEBINAR REGISTRATION LINK Not able to attend? Register anyway to automatically receive a link to the webinar recording to view on-demand at your convenience.