scholarly journals Parallel graph-grammar-based algorithm for the longest-edge refinement of triangular meshes and the pollution simulations in Lesser Poland area

2021 ◽  
Author(s):  
Krzysztof Podsiadło ◽  
Albert Oliver Serra ◽  
Anna Paszyńska ◽  
Rafael Montenegro ◽  
Ian Henriksen ◽  
...  
Keyword(s):  
Time Integration ◽  
Three Dimensional ◽  
Reaction Model ◽  
Graph Grammar ◽  
Diffusion Reaction ◽  
Integration Scheme ◽  
Triangular Meshes ◽  
Time Integration Scheme ◽  
Parallel Graph ◽  
Refinement Algorithm

AbstractIn this paper, we propose parallel graph-grammar-based algorithm for the longest-edge refinements and the pollution simulations in Lesser Poland area. We introduce graph-grammar productions for Rivara’s longest-edged algorithm for the local refinement of unstructured triangular meshes. We utilize the hyper-graph to represent the computational mesh and the graph-grammar productions to express the longest-edge mesh refinement algorithm. The parallelism in the original Rivara’s longest edge refinement algorithm is obtained by processing different longest edge refinement paths in different three ads. Our graph-grammar-based algorithm allows for additional parallelization within a single longest-edge refinement path. The graph-grammar-based algorithm automatically guarantees the validity and conformity of the generated mesh; it prevents the generation of duplicated nodes and edges, elongated elements with Jacobians converging to zero, and removes all the hanging nodes automatically from the mesh. We test the algorithm on generating a surface mesh based on a topographic data of Lesser Poland area. The graph-grammar productions also generate the layers of prismatic three-dimensional elements on top of the triangular mesh, and they break each prismatic element into three tetrahedral elements. Next, we propose graph-grammar productions generating element matrices and right-hand-side vectors for each tetrahedral element. We utilize the Streamline Upwind Petrov–Galerkin (SUPG) stabilization for the pollution propagation simulations in Lesser Poland area. We use the advection–diffusion-reaction model, the Crank–Nicolson time integration scheme, and the graph-grammar-based interface to the GMRES solver.

Computational Analysis of Characteristics and Mach Number Effects on Noise Emission From Ideally Expanded Highly Supersonic Free-Jet

2007 ◽  
Author(s):  
Taku Nonomura ◽  
Kozo Fujii
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Acoustic Noise ◽  
Time Integration ◽  
Three Dimensional ◽  
Integration Scheme ◽  
Noise Emission ◽  
Sonic Jet ◽  
Time Integration Scheme ◽  
Seventh Order

In this study, aero-acoustic noise from super-sonic jet plume is computationally investigated. Three-dimensional Navier-Stokes equations are solved with seventh order weighted compact non-linear scheme and total validation diminishing Runge-Kutta time integration scheme. At first, the noise from Mach 2.0 ideally expanded super-sonic jet is computed and validated with the past experimental study. Then the noises from various Mach number (2.0–3.5) ideally expanded jet plumes are computed. Noise source positions, directivity and convective Mach numbers are discussed.

scholarly journals IMPACT: an implicit time integration scheme for chemical species and families

2000 ◽  
Vol 18 (3) ◽  
pp. 337-346 ◽  
Author(s):  
G. D. Carver ◽  
P. A. Stott
Keyword(s):  
Middle Atmosphere ◽  
Time Integration ◽  
Three Dimensional ◽  
Chemical Species ◽  
Atmospheric Composition ◽  
Implicit Time ◽  
Integration Scheme ◽  
Implicit Time Integration ◽  
Time Integration Scheme ◽  
Complex Chemistry

Abstract. The implicit time integration scheme of Stott and Harwood (1993) was proposed as an efficient scheme for use in three-dimensional chemical models of the atmosphere. The scheme was designed for chemistry schemes using `chemical families', in which species with short lifetimes are grouped into longer-lived families. Further study with more complex chemistry, more species and reactions showed the scheme to be non-convergent and unstable under certain conditions; particularly for the perturbed chemical scenarios of polar stratospheric winters. In this work the scheme has been improved by revising the treatment of families and the convergence properties of the scheme. The new scheme has been named IMPACT (IMPlicit Algorithm for Chemical Time-stepping). It remains easy to implement and produces simulations that compare well with integrations using more accurate higher order schemes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry; lioposphere - composition and chemistry; instruments and techniques)

scholarly journals An investigation of stress inaccuracies and proposed solution in the material point method

2019 ◽  
Vol 65 (2) ◽  
pp. 555-581 ◽  
Author(s):  
José Leόn González Acosta ◽  
Philip J. Vardon ◽  
Guido Remmerswaal ◽  
Michael A. Hicks
Keyword(s):  
Shape Function ◽  
Time Integration ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Material Point Method ◽  
Material Point ◽  
Point Method ◽  
Implicit Time ◽  
Integration Scheme ◽  
Time Integration Scheme

AbstractStress inaccuracies (oscillations) are one of the main problems in the material point method (MPM), especially when advanced constitutive models are used. The origins of such oscillations are a combination of poor force and stiffness integration, stress recovery inaccuracies, and cell crossing problems. These are caused mainly by the use of shape function gradients and the use of material points for integration in MPM. The most common techniques developed to reduce stress oscillations consider adapting the shape function gradients so that they are continuous at the nodes. These techniques improve MPM, but problems remain, particularly in two and three dimensional cases. In this paper, the stress inaccuracies are investigated in detail, with particular reference to an implicit time integration scheme. Three modifications to MPM are implemented, and together these are able to remove almost all of the observed oscillations.

scholarly journals Fluid/Structure Coupled Aeroelastic Computations for Transonic Flows in Turbomachinery

2002 ◽  
Author(s):  
Hirofumi Doi ◽  
Juan J. Alonso
Keyword(s):  
High Performance ◽  
Load Transfer ◽  
Time Integration ◽  
Three Dimensional ◽  
Convergence Acceleration ◽  
Integration Scheme ◽  
Fluid Structure ◽  
Flow Solver ◽  
Operational Conditions ◽  
Time Integration Scheme

The present study demonstrates the capabilities of a fluid/structure coupled computational approach which consists of an unsteady three-dimensional Navier-Stokes flow solver, TFLO, and a finite element structural analysis package, MSC/NASTRAN. The parallelized flow solver relies on a multi-block cell-centered finite volume discretization and the dual time stepping time integration scheme with multigrid for convergence acceleration. High accuracy is pursued with respect to load transfer, deformation tracking and synchronization between the two disciplines. As a result, the program successfully predicts the aeroelastic responses of a high performance fan, NASA Rotor 67, over a range of operational conditions. The results show that the unsteady pressure generated at the shock may act to damp or excite the blade motion mainly depending on the inter-blade phase angle. It is concluded that the level of sophistication in the individually sophisticated disciplines together with an accurate coupling interface will allow for accurate prediction of flutter boundaries of turbomachinery components.

Modeling of 3D Magnetostrictive Systems with Application to Galfenol and Terfenol-D Actuators

2012 ◽  
Vol 77 ◽  
pp. 11-28
Author(s):  
Marcelo J. Dapino ◽  
Suryarghya Chakrabarti
Keyword(s):  
Finite Element ◽  
Time Integration ◽  
Three Dimensional ◽  
Nonlinear Dynamic System ◽  
Element Model ◽  
Implicit Time ◽  
Integration Scheme ◽  
Modeling Framework ◽  
Time Integration Scheme ◽  
Parametric Analyses

This work presents a unified approach to model three dimensional magnetostrictive transducers. Generalized procedures are developed for incorporating nonlinear coupled constitutive behavior of magnetostrictive materials into an electro-magneto-mechanical finite element modeling framework. The finite element model is based on weak forms of Maxwell's equations for electromagnetics and Navier's equations for mechanical systems. An implicit time integration scheme is implemented to obtain nonlinear dynamic system responses. The model is implemented into a finite element (FE) solver and applied to two case studies, a Galfenol unimorph actuator and a magnetohydraulic Terfenol-D actuator for active engine mounts. Model results are compared with experiments, and parametric analyses are conducted which provide guidelines for optimization of actuator design.

Dynamic Modeling of Viscoelastic Body in Multibody System

2011 ◽  
Vol 105-107 ◽  
pp. 587-594
Author(s):  
Da Zhi Cao ◽  
Zhi Hua Zhao ◽  
Ge Xue Ren
Keyword(s):  
Fractional Derivative ◽  
Multibody System ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Time Integration ◽  
Three Dimensional ◽  
Viscoelastic Body ◽  
Integration Scheme ◽  
Large Rotation ◽  
Time Integration Scheme

Dynamic equations of viscoelastic bodies with fractional constitutive are derived base on the principle of virtual work and the theory of continuum mechanics. The three-dimensional fractional derivative viscoelastic constitutive model is implemented into the flexible multibody system (FMBS), using the 3D solid element based on the absolute nodal coordinate formulation (ANCF), which can exactly describe the geometric nonlinearities due to large rotation and large deformation. The BDF time integration scheme in conjunction with the Grünwald approximation of fractional derivative and the Newton-Raphson algorithm are used to solve the equations of motion. Several numerical examples are presented to demonstrate the use of the modeling procedure presented in this investigation and the effects of parameters in the fractional derivative model.

scholarly journals Structural Reliability Sensitivities under Nonstationary Random Vibrations

2013 ◽  
Vol 2013 ◽  
pp. 1-21 ◽  
Author(s):  
Rita Greco ◽  
Francesco Trentadue
Keyword(s):  
Structural Reliability ◽  
Structural Parameters ◽  
Time Integration ◽  
Structural Response ◽  
Integration Scheme ◽  
Structural Systems ◽  
Frame Building ◽  
Time Integration Scheme ◽  
Noise Input ◽  
The Time Domain

Response sensitivity evaluation is an important element in reliability evaluation and design optimization of structural systems. It has been widely studied under static and dynamic forcing conditions with deterministic input data. In this paper, structural response and reliability sensitivities are determined by means of the time domain covariance analysis in both classically and nonclassically damped linear structural systems. A time integration scheme is proposed for covariance sensitivity. A modulated, filtered, white noise input process is adopted to model the stochastic nonstationary loads. The method allows for the evaluation of sensitivity statistics of different quantities of dynamic response with respect to structural parameters. Finally, numerical examples are presented regarding a multistorey shear frame building.

scholarly journals Numerical Simulation of the Coagulation Dynamics of Blood

2008 ◽  
Vol 9 (2) ◽  
pp. 83-104 ◽  
Author(s):  
T. Bodnár ◽  
A. Sequeira
Keyword(s):  
Blood Coagulation ◽  
Computational Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Clot Formation ◽  
Diffusion Reaction ◽  
Numerical Code ◽  
Injured Region ◽  
Reaction Equations

The process of platelet activation and blood coagulation is quite complex and not yet completely understood. Recently, a phenomenological meaningful model of blood coagulation and clot formation in flowing blood that extends existing models to integrate biochemical, physiological and rheological factors, has been developed. The aim of this paper is to present results from a computational study of a simplified version of this coupled fluid-biochemistry model. A generalized Newtonian model with shear-thinning viscosity has been adopted to describe the flow of blood. To simulate the biochemical changes and transport of various enzymes, proteins and platelets involved in the coagulation process, a set of coupled advection–diffusion–reaction equations is used. Three-dimensional numerical simulations are carried out for the whole model in a straight vessel with circular cross-section, using a finite volume semi-discretization in space, on structured grids, and a multistage scheme for time integration. Clot formation and growth are investigated in the vicinity of an injured region of the vessel wall. These are preliminary results aimed at showing the validation of the model and of the numerical code.

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