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.

scholarly journals Effects of Material Rheology and Die Walls Translational Motions on the Dynamics of Viscous Flow during Equal Channel Angular Extrusion through a Segal 2θ-Die: CFD 2D Solution of a Curl Transfer Equation

2017 ◽  
Vol 2017 ◽  
pp. 1-26 ◽  
Author(s):  
Alexander V. Perig ◽  
Nikolai N. Golodenko
Keyword(s):  
Viscous Flow ◽  
Present Article ◽  
Physical Simulation ◽  
Stokes Equations ◽  
Equal Channel Angular Extrusion ◽  
Dead Zone ◽  
Numerical Approach ◽  
Theoretical Description ◽  
Local Flow ◽  
Angular Extrusion

The present article is focused on a phenomenological description of a polymer workpiece Equal Channel Angular Extrusion (ECAE) through 2θ-dies of Segal and Iwahashi geometries with a channel intersection angle 2θ = 105° with fixed and movable external inlet and outlet die walls. The local flow dynamics, including the formation of macroscopic rotation and a dead zone appearance during the flow of plasticine, paraffin, and wax workpiece models through the subject die configuration was studied using physical simulation techniques. The present article utilizes a Computational Fluid Dynamics (CFD) numerical approach to a theoretical description of 2D viscous flow of incompressible Newtonian continuum through the stated die geometries. The boundary value problem for the Navier-Stokes equations in the curl transfer form for the local viscous flow was formulated and numerically solved with a finite-difference method. Theoretical CFD-derived plots with computational flow lines, dimensionless flow and curl functions, flow velocities, and tangential stresses for viscous material flow through the stated die geometries have been generated and described. As a first rheological approximation the derived computational results provide the theoretical description of physical simulation experiments and visualize the formation of ECAE-induced rotational modes of large deformations like macroscopic rotation and rotational inhomogeneity.

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.

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.

Modeling and simulation of membrane process

2017 ◽  
Vol 2 (6) ◽  
Author(s):  
Maciej Staszak
Keyword(s):  
Fluid Dynamics ◽  
Stokes Equations ◽  
Polymer Membranes ◽  
Lattice Models ◽  
Network Models ◽  
Navier Stokes ◽  
Neural Network Models ◽  
Navier Stokes Equations ◽  
Different Types ◽  
Boltzmann Lattice

AbstractThe article presents the different approaches to polymer membrane mathematical modeling. Traditional models based on experimental physicochemical correlations and balance models are presented in the first part. Quantum and molecular mechanics models are presented as they are more popular for polymer membranes in fuel cells. The initial part is enclosed by neural network models which found their use for different types of processes in polymer membranes. The second part is devoted to models of fluid dynamics. The computational fluid dynamics technique can be divided into solving of Navier-Stokes equations and into Boltzmann lattice models. Both approaches are presented focusing on membrane processes.

A Survey of General Purpose Computation of GPU for Computational Fluid Dynamics

2013 ◽  
Vol 753-755 ◽  
pp. 2731-2735
Author(s):  
Wei Cao ◽  
Zheng Hua Wang ◽  
Chuan Fu Xu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Performance ◽  
Stokes Equations ◽  
Gpu Computing ◽  
Graphics Processing Unit ◽  
General Purpose ◽  
Navier Stokes ◽  
Processing Unit ◽  
Gpgpu Computing

The graphics processing unit (GPU) has evolved from configurable graphics processor to a powerful engine for high performance computer. In this paper, we describe the graphics pipeline of GPU, and introduce the history and evolution of GPU architecture. We also provide a summary of software environments used on GPU, from graphics APIs to non-graphics APIs. At last, we present the GPU computing in computational fluid dynamics applications, including the GPGPU computing for Navier-Stokes equations methods and the GPGPU computing for Lattice Boltzmann method.

Modelling Immunomagnetic Cell Capture in CFD

2008 ◽  
Author(s):  
Tobias Baier ◽  
Swaty Mohanty ◽  
Klaus Stefan Drese ◽  
Federica Rampf ◽  
Jungtae Kim ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Magnetic Particles ◽  
Magnetic Beads ◽  
Stokes Equations ◽  
Type Equation ◽  
Standard Technique ◽  
Binding Kinetics ◽  
Navier Stokes ◽  
Target Cells ◽  
Cell Capture

The separation of cells from a complex sample by immunomagnetic capture has become a standard technique in the last decade and has also obtained increased attention for microfluidic applications. We present a model that incorporates binding kinetics for the formation of cell-bead complexes, which can easily be integrated into a computational fluid dynamics (CFD) code. The model relies on the three equation types: Navier-Stokes equations governing the fluid dynamics, convection-diffusion equations for non-magnetic cells and a Nernst-Planck type equation governing the temporal evolution of cell-bead complex concentrations. The latter two equations are augmented by appropriate ‘reaction’ terms governing the binding kinetics which is formulated as a population rate balance between creation and annihilation of cell-bead complexes. First, the simulation results show, that by means of the developed approach appropriate parameter sets can be identified which allow for a continuous separation of tagged cells (cell/bead complexes) from non-magnetic particles such as non-target cells entering with the target cells. Moreover tagged cells can be, to a certain extend, separated from unbound beads. Second, the computed concentrations at the outlet show a drastic drop for higher cell/bead complexes beyond a certain number of beads per cell. We show that a critical number of beads per cells exists where the binding is considerably reduced or the reaction cascade ceases completely. This occurs when cell/bead complex have a similar magnetic mobility as the free magnetic beads. The presented CFD model has been applied to the simulation of a generic continuous cell separation system showing that the method facilitates the design of magnetophoretic systems.

scholarly journals A Massively Parallel Hybrid Finite Volume/Finite Element Scheme for Computational Fluid Dynamics

Mathematics ◽  
2021 ◽  
Vol 9 (18) ◽  
pp. 2316
Author(s):  
Laura Río-Martín ◽  
Saray Busto ◽  
Michael Dumbser
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Finite Element ◽  
Mach Number ◽  
Finite Volume ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Massively Parallel ◽  
Navier Stokes ◽  
Navier Stokes Equations

In this paper, we propose a novel family of semi-implicit hybrid finite volume/finite element schemes for computational fluid dynamics (CFD), in particular for the approximate solution of the incompressible and compressible Navier-Stokes equations, as well as for the shallow water equations on staggered unstructured meshes in two and three space dimensions. The key features of the method are the use of an edge-based/face-based staggered dual mesh for the discretization of the nonlinear convective terms at the aid of explicit high resolution Godunov-type finite volume schemes, while pressure terms are discretized implicitly using classical continuous Lagrange finite elements on the primal simplex mesh. The resulting pressure system is symmetric positive definite and can thus be very efficiently solved at the aid of classical Krylov subspace methods, such as a matrix-free conjugate gradient method. For the compressible Navier-Stokes equations, the schemes are by construction asymptotic preserving in the low Mach number limit of the equations, hence a consistent hybrid FV/FE method for the incompressible equations is retrieved. All parts of the algorithm can be efficiently parallelized, i.e., the explicit finite volume step as well as the matrix-vector product in the implicit pressure solver. Concerning parallel implementation, we employ the Message-Passing Interface (MPI) standard in combination with spatial domain decomposition based on the free software package METIS. To show the versatility of the proposed schemes, we present a wide range of applications, starting from environmental and geophysical flows, such as dambreak problems and natural convection, over direct numerical simulations of turbulent incompressible flows to high Mach number compressible flows with shock waves. An excellent agreement with exact analytical, numerical or experimental reference solutions is achieved in all cases. Most of the simulations are run with millions of degrees of freedom on thousands of CPU cores. We show strong scaling results for the hybrid FV/FE scheme applied to the 3D incompressible Navier-Stokes equations, using millions of degrees of freedom and up to 4096 CPU cores. The largest simulation shown in this paper is the well-known 3D Taylor-Green vortex benchmark run on 671 million tetrahedral elements on 32,768 CPU cores, showing clearly the suitability of the presented algorithm for the solution of large CFD problems on modern massively parallel distributed memory supercomputers.

Computational Fluid Dynamics of Four-Quadrant Marine-Propulsor Flow

1999 ◽  
Vol 43 (04) ◽  
pp. 218-228
Author(s):  
Bin Chen ◽  
Frederick Stern
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Ring Vortex ◽  
Reynolds Averaged Navier Stokes ◽  
Four Quadrant ◽  
Marine Propulsor

Computational fluid dynamics results are presented of four-quadrant flow for marine-propulsor P4381. The solution method is unsteady three-dimensional incompressible Reynolds-averaged Navier-Stokes equations in generalized coordinates with the Baldwin-Lomax turbulence model. The method was used previously for the design condition for marine-propulsor P4119, including detailed verification and validation. Only limited verification is performed for P4381. The validation is limited by the availability of four-quadrant performance data and ring vortex visualizations for the crashback conditions. The predicted performance shows close agreement with the data for the forward and backing conditions, whereas for the crashahead and crashback conditions the agreement is only qualitative and requires an ad hoc cavitation correction. Also, the predicted ring vortices for the crashback conditions are in qualitative agreement with the data. Extensive calculations enable detailed description of flow characteristics over a broad range of propulsor four-quadrant operations, including surface pressure and streamlines, velocity distributions, boundary layer and wake, separation, and tip and ring vortices. The overall results suggest promise for Reynolds-averaged Navier-Stokes methods for simulating marine-propulsor flow, including offdesign. However, important outstanding issues include additional verification and validation, time-accurate solutions, and resolution and turbulence modeling for separation and tip and ring vortices.

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