A Condensed Phase Computational Fluid Dynamics Model for Polymer Melt Flow

2008 ◽  
Author(s):  
Qing Tang ◽  
Michael Bockelie
Keyword(s):  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Condensed Phase ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Polymer Materials ◽  
High Heat Flux ◽  
Time Step ◽  
Temperature Dependent Viscosity

This paper presents a condensed phase computational fluid dynamics (CFD) based tool for modeling the processes of melting, flow and gasification of thermoplastic materials exposed to a high heat flux. Potential applications of the tool include investigating the behavior of polymer materials commonly used in personal computers and computer monitors if exposed to an intense heat flux, such as occurs during a fire. The finite-volume based model uses a three-dimensional body-fitted time dependent grid formulation to solve the unsteady Navier Stokes equations. A multi-grid method is used to accelerate convergence at each time step. Sub-models are included to describe the temperature dependent viscosity relationship and in-depth gasification and absorption of thermoplastic materials, free surface flows and surface tension. A series of test cases have been performed and the model results are compared to experimental data to investigate the impacts of different sub-models, boundary conditions, material properties and problem configurations on the accuracy, efficiency and applicability of the modeling tool.

Sailing Yacht Rig Improvements Through Viscous Computational Fluid Dynamics

2005 ◽  
Author(s):  
Vincent G. Chapin ◽  
Romaric Neyhousser ◽  
Stephane Jamme ◽  
Guillaume Dulliand ◽  
Patrick Chassaing
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
High Speed ◽  
Stokes Equations ◽  
Wind Tunnel Test ◽  
Physical Modelling ◽  
Optimized Design ◽  
Linear Interaction ◽  
Sailing Yacht

In this paper we propose a rational viscous Computational Fluid Dynamics (CFD) methodology applied to sailing yacht rig aerodynamic design and analysis. After an outlook of present challenges in high speed sailing, we emphasized the necessity of innovation and CFD to conceive, validate and optimize new aero-hydrodynamic concepts. Then, we present our CFD methodology through CAD, mesh generation, numerical and physical modelling choices, and their validation on typical rig configurations through wind-tunnel test comparisons. The methodology defined, we illustrate the relevance and wide potential of advanced numerical tools to investigate sailing yacht rig design questions like the relation between sail camber, propulsive force and aerodynamic finesse, and like the mast-mainsail non linear interaction. Through these examples, it is shown how sailing yacht rig improvements may be drawn by using viscous CFD based on Reynolds Averaged Navier-Stokes equations (RANS). Then the extensive use of viscous CFD, rather than wind-tunnel tests on scale models, for the evaluation or ranking of improved designs with increased time savings. Viscous CFD methodology is used on a preliminary study of the complex and largely unknown Yves Parlier Hydraplaneur double rig. We show how it is possible to increase our understanding of his flow physics with strong sail interactions, and we hope this methodology will open new roads toward optimized design. Throughout the paper, the necessary comparison between CFD and wind-tunnel test will be presented to focus on limitations and drawbacks of viscous CFD tools, and to address future improvements.

Optimization of Biomimetic Propulsive Kinematics of a Flexible Foil Using Integrated Computational Fluid Dynamics–Computational Structural Dynamics Simulations

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Jiho You ◽  
Jinmo Lee ◽  
Seungpyo Hong ◽  
Donghyun You
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Young’S Modulus ◽  
Phase Angle ◽  
Structural Dynamics ◽  
Stokes Equations ◽  
Young's Modulus ◽  
Immersed Boundary ◽  
Computational Structural Dynamics ◽  
Dynamics Simulations

A computational methodology, which combines a computational fluid dynamics (CFD) technique and a computational structural dynamics (CSD) technique, is employed to design a deformable foil whose kinematics is inspired by the propulsive motion of the fin or the tail of a fish or a cetacean. The unsteady incompressible Navier–Stokes equations are solved using a second-order accurate finite difference method and an immersed-boundary method to effectively impose boundary conditions on complex moving boundaries. A finite element-based structural dynamics solver is employed to compute the deformation of the foil due to interaction with fluid. The integrated CFD–CSD simulation capability is coupled with a surrogate management framework (SMF) for nongradient-based multivariable optimization in order to optimize flapping kinematics and flexibility of the foil. The flapping kinematics is manipulated for a rigid nondeforming foil through the pitching amplitude and the phase angle between heaving and pitching motions. The flexibility is additionally controlled for a flexible deforming foil through the selection of material with a range of Young's modulus. A parametric analysis with respect to pitching amplitude, phase angle, and Young's modulus on propulsion efficiency is presented at Reynolds number of 1100 for the NACA 0012 airfoil.

Development of SIMPLE-Like Algorithms for Incompressible Navier-Stokes Equations in Liquid Processing of Materials

2012 ◽  
Vol 184-185 ◽  
pp. 944-948 ◽  
Author(s):  
Hai Jun Gong ◽  
Yang Liu ◽  
Xue Yi Fan ◽  
Da Ming Xu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Incompressible Fluid Flow ◽  
Numerical Accuracy ◽  
Simple Scheme ◽  
Navier Stokes Equations ◽  
Computational Fluid Dynamics Cfd

For a clear and comprehensive opinion on segregated SIMPLE algorithm in the area of computational fluid dynamics (CFD) during liquid processing of materials, the most significant developments on the SIMPLE algorithm and its variants are briefly reviewed. Subsequently, some important advances during last 30 years serving as increasing numerical accuracy, enhancing robustness and improving efficiency for Navier–Stokes (N-S) equations of incompressible fluid flow are summarized. And then a so-called Direct-SIMPLE scheme proposed by the authors of present paper introduced, which is different from SIMPLE-like schemes, no iterative computations are needed to achieve the final pressure and velocity corrections. Based on the facts cited in present paper, it conclude that the SIMPLE algorithm and its variants will continue to evolve aimed at convergence and accuracy of solution by improving and combining various methods with different grid techniques, and all the algorithms mentioned above will enjoy widespread use in the future.

scholarly journals ECAP process improvement based on the design of rational inclined punch shapes for the acute-angled Segal 2θ-dies: CFD 2-D description of dead zone reduction

2015 ◽  
Vol 6 (1) ◽  
pp. 41-49 ◽  
Author(s):  
A. V. Perig ◽  
N. N. Golodenko
Keyword(s):  
Fluid Dynamics ◽  
Physical Simulation ◽  
Stokes Equations ◽  
Equal Channel Angular Extrusion ◽  
Dead Zone ◽  
Polymer Materials ◽  
Navier Stokes ◽  
Geometric Condition ◽  
Angular Pressing ◽  
Punch Shape

Abstract. This article is focused on a 2-D fluid dynamics description of punch shape geometry improvement for Equal Channel Angular Extrusion (ECAE) or Equal Channel Angular Pressing (ECAP) of viscous incompressible continuum through acute-angled Segal 2θ-dies with 2θ < 90°. It has been shown both experimentally with physical simulation and theoretically with computational fluid dynamics that for the best efficiency under the stated conditions, the geometric condition required is for the taper angle 2θ0 of the inclined oblique punch to be equal to the 2θ angle between the inlet and outlet channels of the Segal 2θ-die. Experimentally and theoretically determined rational geometric condition for the ECAP punch shape is especially prominent and significant for ECAP through the acute angled Segal 2θ-dies. With the application of Navier-Stokes equations in curl transfer form it has been shown that for the stated conditions, the introduction of an oblique inclined 2θ0-punch results in dead zone area downsizing and macroscopic rotation reduction during ECAP of a viscous incompressible continuum. The derived results can be significant when applied to the improvement of ECAP processing of both metal and polymer materials through Segal 2θ-dies.

Model order reduction in aerodynamics: Review and applications

2019 ◽  
Vol 233 (15) ◽  
pp. 5816-5836
Author(s):  
Gonçalo Mendonça ◽  
Frederico Afonso ◽  
Fernando Lau
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Model Reduction ◽  
Adaptive Sampling ◽  
Stokes Equations ◽  
Order Reduction ◽  
High Fidelity ◽  
Least Mean Squares ◽  
Speed Up ◽  
Dynamics Models

The need of the aerospace industry, at national or European level, of faster yet reliable computational fluid dynamics models is the main drive for the application of model reduction techniques. This need is linked to the time cost of high-fidelity models, rendering them inefficient for applications like multi-disciplinary optimization. With the goal of testing and applying model reduction to computational fluid dynamics models applicable to lifting surfaces, a bibliographical research covering reduction of nonlinear, dynamic, or steady models was conducted. This established the prevalence of projection and least mean squares methods, which rely on solutions of the original high-fidelity model and their proper orthogonal decomposition to work. Other complementary techniques such as adaptive sampling, greedy sampling, and hybrid models are also presented and discussed. These projection and least mean squares methods are then tested on simple and documented benchmarks to estimate the error and speed-up of the reduced order models thus generated. Dynamic, steady, nonlinear, and multiparametric problems were reduced, with the simplest version of these methods showing the most promise. These methods were later applied to single parameter problems, namely the lid-driven cavity with incompressible Navier–Stokes equations and varying Reynolds number, and the elliptic airfoil at varying angles of attack for compressible Euler flow. An analysis of the performance of these methods is given at the end of this article, highlighting the computational speed-up obtained with these techniques, and the challenges presented by multiparametric problems and problems showing point singularities in their domain.

Computational Fluid Dynamics Analysis of Two Parallel Rectangular Jets Using OpenFOAM

2016 ◽  
Author(s):  
Han Li ◽  
Huhu Wang ◽  
Yassin A. Hassan ◽  
N. K. Anand
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulent Flow ◽  
Stokes Equations ◽  
Laser Doppler Anemometry ◽  
Physical Models ◽  
Shear Stresses ◽  
Turbulence Characteristic ◽  
Computational Fluid Dynamics Analysis ◽  
Simulation Results

Two or multiple parallel jets are an important shear flow that widely existing in many industrial applications. The interaction between turbulence jets enables fast and thorough mixing of two fluids. The mixing feature of parallel jets has many engineering applications, such as, in Generation IV conceptual nuclear reactors, the coolants merge in upper or lower plenum after passing through the reactor core. While study of parallel jets mixing phenomenon, numerical experiments such as Computational Fluid Dynamics (CFD) simulations are extensively incorporated. Validation of varied turbulent models is of importance to make sure that the numerical results could be trusted and served as a guideline further design purpose. Many commercial CFD packages in the market such as FLUENT and Star CCM+ can provide the ability to simulate turbulent flow with predefined turbulence model, however, such commercial solvers may lack the flexibility that allow users build their own models for R&D purpose. The existing solvers in OpenFOAM are developed to fulfill both academic and industrial needs by achieving large-scale computational capability with a variety of physical models. Moreover, as an open source CFD toolbox, OpenFOAM grants users full control of the source code with complete freedom of customization. The purpose of this study is to perform CFD simulation using OpenFOAM for two submerged parallel jets issuing from two rectangular channels. Fully hexahedron multi-density mesh is generated using blockMesh utility to ensure velocity gradients are properly evaluated. A generalized-multi-grid solver is used to enhance convergence. Based on Reynolds-Averaged Navier-Stokes Equations (RANS), the realizable k-ε and k-ε shear stress transport (SST) are selected to model turbulent flow. Steady state Finite Volume solver simpleFoam is used to perform the simulation. In addition, data from experiments run in Thermal-Hydraulic Lab at Texas A&M University using particle image velocity (PIV) and Laser Doppler Anemometry (LDA) methods are considered in order to compare and validate simulation results. A number of turbulence characteristic such as mean velocities, turbulent intensities, z-component vorticity were compared with experiments. It was found that for stream-wise mean velocity profile as well as shear stresses, the realizable k-ε model exhibits a good agreement with experimental data. However, velocity fluctuation and turbulence intensities, simulation results showed a certain discrepancy.

scholarly journals The application of CFD software in the explosive hazardous area classification

2018 ◽  
Vol 247 ◽  
pp. 00053
Author(s):  
Andrzej Krauze
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Linear Equations ◽  
Computer Software ◽  
Numerical Algorithms ◽  
Transport Equations ◽  
Time Step ◽  
Hazardous Area ◽  
Area Classification ◽  
Control Volumes

This article is devoted to the practical application of CFD Computational Fluid Dynamics software, as a tool helpful in the explosive hazardous area classification. The practical examples will be discussed, which show that use of computer software for the simulation of gas emissions or the simulation of vapors of flammable liquids, allows not only visualization, but also improvement the quality of following conclusions received during the explosive hazardous area classification. The Computational Fluid Dynamics is a branch of physics which deals with solving transport equations for given boundary conditions using numerical methods. The solution is found by dividing the analyzed space into a specified number of small control volumes (cells). At the same time, time period is divided into short steps. Then, for each of the cells at each time step, the transport equations are converted into the system of linear equations. Such systems are solved using appropriate numerical algorithms.

Computational fluid dynamics study of human-induced wake and particle dispersion in indoor environment

2016 ◽  
Vol 26 (2) ◽  
pp. 185-198 ◽  
Author(s):  
Yao Tao ◽  
Kiao Inthavong ◽  
Jiyuan Tu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Environment ◽  
Particle Dispersion ◽  
The Body ◽  
Wake Flow ◽  
Time Step ◽  
Directed Flow ◽  
Stagnant Region ◽  
The Impact

The impact of human-induced wake flow and particle re-dispersion from floors in an indoor environment was investigated by performing computational fluid dynamics simulations with dynamic mesh of a moving manikin model in a confined room. The manikin motion was achieved by a dynamic layering mesh method to update new grids with each time step. Particle transport from the floors and its re-dispersion was tracked by a Lagrangian approach. A series of numerical simulations of three walking speeds were performed to compare the flow disturbance induced by the walking motion. The significant airflow patterns included: an upward-directed flow in front of the body combined with a high velocity downward-directed flow at the rear of the body; a stagnant region behind the gap between the legs and counter-rotating vortices in the wake region. The airflow momentum induced by the moving body disturbed PM2.5 particles that were initially at rest on the floor to lift and become re-suspended due to its interaction with the trailing wake. The residual flow disturbances after the manikin stopped moving continued to induce the particle to spread and deposit over time. The spatial and temporal characteristics of the particle dispersion and concentration showed that higher walking speed was conducive to reducing human's exposure to contaminants in breathing region.

Spinoff Challenges for Computational Fluid Dynamics

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Francis H. Harlow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computational Models ◽  
Stokes Equations ◽  
Driving Forces ◽  
Experimental Studies ◽  
Big Bang ◽  
Stochastic Representation ◽  
Collective Behaviors ◽  
Agent Based

This paper describes extensions of computational fluid dynamics (CFD) to fields of analysis lying well beyond their current realms of application. In particular, three examples are presented. The first is to the collective behavior of mobs of people interacting with sources of danger and/or opportunity to which each individual responds by actions that depend strongly on the inducement of fear and/or excitement, depending on the intrinsic susceptibilities of the person. This behavior results in both individual activities (agent-based) and collective behaviors (crowd-based stochastic) with consequences of potentially great significance. Extensions are also described for which various other emotional developments are important to the behavior of a mob. The second example is to the processes of biological evolution, in particular to the driving forces that influence the directions of species alterations through a succession of characteristics that are tested for survivability in classical Darwinian fashion. The key to the analysis lies in the newly emerging field of epigenetics, in which numerous important experimental studies are producing astonishing results leading to major challenges to the creation of computational models of the collective fluid-like dynamics of interacting biological species. The third example explores an alternative to the Big Bang theory for describing the origin of our universe. The idea is that a parent universe exists, being composed of energy, matter, and antimatter in various forms. In some region a perturbation occurs, which locally has an excess of matter over antimatter. An enormous gravitational buildup of matter and energy in the region leads to a black hole, in which there is distortion in the fourth dimension. The result then leads to an offspring entity (universe) that becomes completely detached from the parent. To apply computational fluid dynamics to the analysis of this process requires formulations that include a major component of relevant physical representations. In all three of these examples, instabilities, fluctuations, and turbulence play major roles. These arise naturally in agent-based numerical formulations (the first and second of our examples), but are much more challenging to describe in a stochastic representation (e.g., the Navier–Stokes equations). Some promising spectral analysis extensions for stochastic formulations are included in this paper.

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