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1-Polyflow_intro-to-cfd.pdf

This document outlines an agenda and introduction for a POLYFLOW training over two days. Day 1 will cover introductions to CFD and POLYFLOW, tutorials, and examples. Day 2 will cover time dependent flows, rheology, CFD post-processing, and workshops. The introduction defines CFD and the governing equations solved. It describes the CFD modeling process including defining goals, geometry, meshing, setting physics models and boundary conditions, and examining results. It covers topics like mesh types, setting up multi-zone meshes, and non-conformal interfaces.

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Chapter 1 Chapter 1 Introduction to CFD Introduction to Introduction to ANSYS Polyflow 1-1 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Agenda Day 1 8:30 Introduction to CFD 14:00 Polyflow B 8:30 Introduction to CFD 14:00 Polyflow B 9:30 Polyflow A 14:30 Tutorial 5 11:00 Example 15:30 Evolution 11:30 Tutorial 1 16:30 Tutorial 8 12:30 Lunch 17:00 Break for the day 12:30 Lunch 17:00 Break for the day 1-2 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual 8 30 Ti d d t Fl 14 00 I t d ti t Rh l Agenda Day 2 8:30 Time dependent Flows 14:00 Introduction to Rheology 9:30 Tutorial 7 15:00 CFD Post 10:30 Adaptive meshing 16:00 Workshop 11:30 Tutorial 9 17:00 Break for the day 12:30 Lunch 12:30 Lunch 1-3 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual What is CFD? • Computational fluid dynamics (CFD) is the science of predicting fluid flow, heat and mass transfer, chemical reactions, and related phenomena by solving numerically the set of governing mathematical equations Conservation of mass – Conservation of mass – Conservation of momentum – Conservation of energy – Conservation of species p – Effects of body forces (e.g. gravity) – Etc. • The results of CFD analyses are relevant in: – Conceptual studies of new designs – Detailed product development – Troubleshooting – Redesign • CFD analysis complements testing and experimentation by reducing total 1-4 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 • CFD analysis complements testing and experimentation by reducing total effort and cost required for experimentation and data acquisition.
Introduction to POLYFLOW training Training Manual How Does CFD Work? • ANSYS Polyflow solver is based on the finite element method – Domain is discretized into a finite set of Control elements – General conservation (transport) equations for mass, momentum, energy, species, etc. are solved on this set of control volumes Volume* are solved on this set of control volumes Fluid region of pipe flow is discretized into a finite set of control volumes. – Partial differential equations are Equation Variable Continuity 1 X momentum u Unsteady Convection Diffusion Generation discretized into a system of algebraic equations – All algebraic equations are then solved numerically to render the solution field Y momentum v Z momentum w Energy h 1-5 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 numerically to render the solution field
Introduction to POLYFLOW training Training Manual CFD Modeling Overview • Problem Identification 1. Define your modeling goals 2. Identify the domain you will model Problem Identification 1. Define goals • PreProcessing and Solver Execution 3. Create a solid model to represent the domain 2. Identify domain Pre-Processing domain 4. Design and create the mesh (grid) 5. Set up the physics (physical models, material properties, domain properties, 3. Geometry 4. Mesh 5. Physics p p p p boundary conditions, …) 6. Define solver settings (numerical schemes, convergence controls, …) 7 Compute and monitor the solution 6. Solver Settings Solve e Model 7. Compute and monitor the solution • Post-Processing 8 Examine the results 7. Compute solution Post Processing 9. Update 1-6 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 8. Examine the results. 9. Consider revisions to the model. Post Processing 8. Examine results
Introduction to POLYFLOW training Training Manual 1. Define Your Modeling Goals • What results are you looking for (i e pressure drop mass flow rate Problem Identification 1. Define goals 2. Identify domain • What results are you looking for (i.e. pressure drop, mass flow rate, extrudate shape, flow balance, ..), and how will they be used? – What are your modeling options? • What physical models will need to be included in your analysis? – temperature, gravity, viscous heating, free surface)? • What simplifying assumptions do you have to make? – E.g. simplify the geometry – 2d vs. 3d – Symmetry • What degree of accuracy is required? M h l ti – Mesh resolution • How quickly do you need the results? 2d 3d h l ti t 1-7 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – 2d vs. 3d, mesh resolution, etc.
Introduction to POLYFLOW training Training Manual 2. Identify the Domain You Will Model • How will you isolate a piece of the Problem Identification 1. Define goals 2. Identify domain • How will you isolate a piece of the complete physical system? • Where will the computational Where will the computational domain begin and end? – Do you have boundary condition information at these boundaries? Domain of Interest as Part of a Larger System (not modeled) – Can the boundary condition types accommodate that information? – Can you extend the domain to a point where reasonable data exists? y ( ) point where reasonable data exists? • Can it be simplified or approximated as a 2D or axisymmetric problem? Domain of interest isolated and meshed for CFD simulation. 1-8 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 y p
Introduction to POLYFLOW training Training Manual 3. Create a Solid Model of the Domain Pre-Processing 3. Geometry 4. Mesh 5. Physics Solid “steel” extrusion die geometry • How will you obtain a solid model of the fluid region? y 6. Solver Settings g – Make use of existing CAD models? • Extract the fluid region from a solid part? – Create from scratch? • Can you simplify the geometry? – Remove unnecessary features that would complicate meshing (fillets, bolts…)? Make use of symmetry or periodicity? Extracted fluid “cavity” – Make use of symmetry or periodicity? • Are both the solution and boundary conditions symmetric / periodic? • Do you need to split the model so that 1-9 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 boundary conditions or domains can be created?
Introduction to POLYFLOW training Training Manual 4. Design and Create the Mesh Pre-Processing 3. Geometry 4. Meshing 5. Physics A mesh divides a geometry into many elements. These are used by the CFD solver to construct control volumes • What degree of mesh resolution is required in each region of the domain? – The mesh must resolve geometric features of i t t d t di t f y 6. Solver Settings interest and capture gradients of concern, e.g. velocity, pressure, temperature gradients – Can you predict regions of high gradients? – Will you use adaption to add resolution? Triangle Quadrilateral • What type of mesh is most appropriate? – How complex is the geometry? – Can you use a quad/hex mesh or is a tri/tet or hybrid mesh suitable? Hexahedron Tetrahedron y – Are non-conformal interfaces needed? • Do you have sufficient computer resources? – How many cells/nodes are required? H h i l d l ill b d? 1-10 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – How many physical models will be used? Pyramid Prism/Wedge
Introduction to POLYFLOW training Training Manual Tri/Tet vs. Quad/Hex Meshes • For flow-aligned geometries, quad/hex meshes can provide higher-quality solutions with fewer higher quality solutions with fewer cells/nodes than a comparable tri/tet mesh – Quad/Hex meshes show reduced numerical diffusion when the mesh is aligned with the flow. – It does require more effort to t d/h h generate a quad/hex mesh 1-11 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Tri/Tet vs. Quad/Hex Meshes • For complex geometries, quad/hex meshes show no numerical advantage, and you can save meshing effort by using a tri/tet mesh or hybrid mesh – Quick to generate – Flow is generally not aligned with the mesh • Hybrid meshes typically combine tri/tet elements with other elements in selected regions – For example, use wedge/ prism elements to resolve b d l boundary layers. – More efficient and accurate than tri/tet alone. W d ( i ) h 1-12 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Tetrahedral mesh Wedge (prism) mesh
Introduction to POLYFLOW training Training Manual Multizone (or Hybrid) Meshes • A multizone or hybrid mesh uses different meshing methods in different regions. For example, – Hex mesh for fan and heat sink – Tet/prism mesh elsewhere TET • Multizone meshes yield a good combination of accuracy, efficient calculation time and meshing effort. HEX g • When the nodes do not match across the regions a non-conformal interface the regions, a non conformal interface can be used. 1-13 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Non-Conformal Meshes • Non conformal meshes are useful for meshing complex geometries – Mesh each part then join together Non-conformal interface 1-14 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Set Up the Physics and Solver Settings • For a given problem, you will need to: – Define material properties • Fluid Pre-Processing 3. Geometry 4. Mesh 5. Physics • Solid – Select appropriate physical models • Isothermal, non-isothermal, gravity, viscous heating etc For complex problems solving a simplified or 2D y 6. Solver Settings heating, etc. – Prescribe operating conditions – Prescribe boundary conditions at all boundary zones problem will provide valuable experience with the models and solver settings for your problem in a short boundary zones • Inlets, outlets, wall temperatures, heat fluxes, etc. – Provide initial values or a previous solution – Set up solver controls amount of time. p – Set up convergence monitors 1-15 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Compute the Solution • The discretized conservation equations are solved iteratively until convergence. C i h d h Solve 7. Compute solution • Convergence is reached when: – Changes in solution variables from one iteration to the next are negligible. • Residuals provide a mechanism to help monitor this trend monitor this trend. – Overall property conservation is achieved • Imbalances measure global conservation • The accuracy of a converged solution is dependent upon: – Appropriateness and accuracy of physical models. – Mesh resolution Mesh resolution – Numerical errors 1-16 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Examine the Results • Examine the results to review solution and extract useful data – Visualization Tools can be used to Post Processing 9. Update Model answer such questions as: • What is the overall flow pattern? • Are there recirculation zones? • What is the free surface shape? 8. Examine results 9 What is the free surface shape? – Is a blow molded part fully formed? • Are key flow features being resolved? Numerical Reporting Tools can be used – Numerical Reporting Tools can be used to calculate quantitative results: • Forces and Moments • Average heat transfer coefficients • Surface and Volume integrated quantities • Flux Balances • Flow Balance • Contact time Examine results to ensure property conservation and correct physical behavior. High residuals may be caused by just a few poor quality cells 1-17 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Contact time may be caused by just a few poor quality cells.
Introduction to POLYFLOW training Training Manual Consider Revisions to the Model • Are the physical models appropriate? – Is the flow unsteady? – Are there 3D effects? Post Processing 9. Update Model Are there 3D effects? • Are the boundary conditions correct? – Is the computational domain large enough? 8. Examine results 9 p g g – Are boundary conditions appropriate? – Are boundary values reasonable? • Is the mesh adequate? – Can the mesh be refined to improve results? – Does the solution change significantly with a refined mesh or is the solution mesh independent? mesh, or is the solution mesh independent? – Does the mesh resolution of the geometry need to be improved? 1-18 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Effect of mesh resolution on exit velocity variation at a die exit
Introduction to POLYFLOW training Training Manual POLYFLOW Workflow under Workbench 2 • Start ANSYS Workbench • Drag the Fluid Flow (POLYFLOW) Drag the Fluid Flow (POLYFLOW) system from Analysis Systems group in the Toolbox onto preview drop target shown in the Project Schematic. – Same for the extrusion or blow molding 1-19 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Import the Geometry • Right-click on Geometry cell A2 and select Import Geometry • Import the geometry file (CAD model or a previous DesignModeler db fil ) .agdb file) • You can also link the POLYFLOW simulation to an existing DesignModeler session. 1-20 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Generate a Mesh • Right-click on Mesh cell and select Edit. – Meshing opens and loads geometry • Select Mesh under Model in Outline • Select Mesh under Model in Outline – Note that Preferences are automatically set for POLYFLOW, because Meshing was opened from a POLYFLOW system. from a POLYFLOW system. 1-21 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Define Boundary and Cell Zones • Create boundary zones using Named selections. – Select the surface which will represent the boundary you wish to set. – Right-click the selection and select Create Named Selection Create Named Selection. – Name the selection and click OK. • bs.1, bs.2, etc… die exit • You will also need to define the regions of the flow containing fluid and solid (if any) and solid (if any). – Fluid, solid regions – Different regions for different remeshing More details will be presented later 1-22 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – More details will be presented later • sd.1, sd.2, sd.3, etc…
Introduction to POLYFLOW training Training Manual Set Up and Run POLYFLOW • Edit the Setup cell to set up the model options – Boundary conditions – Solver settings – Solution – Post processing • Once run, the solution will be post processed in CFD-Post for post processing – Contour and vector plots – Profile plots – Calculation of forces and moments – Animation of unsteady flow results – Free surface shape – … 1-23 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Demonstration of POLYFLOW Software • Start POLYFLOW (assume the mesh has already been generated). – Set up a simple problem. – Solve the flow field. – Postprocess the results. • Online help and documentation is available 1-24 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
Introduction to POLYFLOW training Training Manual Navigating the PC at Fluent • Log in to your workstation – Login name: ansys – Password: ansys • Directories – Tutorial mesh/case/data files can be found in c:Student Filesfluenttut – We recommend that you save your work into a central working folder: c:users W ki f ld h th d kt i h t t t – Working folder shown on the desktop is a shortcut to c:users • To start POLYFLOW and/or Workbench, use the desktop icons. • Your support engineer will save your work at the end of the week. • It is recommended that you restart FLUENT and/or Workbench for each tutorial to avoid mixing solver settings from different 1-25 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 each tutorial to avoid mixing solver settings from different workshops.

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1-Polyflow_intro-to-cfd.pdf

  • 1.
    Chapter 1 Chapter 1 Introductionto CFD Introduction to Introduction to ANSYS Polyflow 1-1 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 2.
    Introduction to POLYFLOWtraining Training Manual Agenda Day 1 8:30 Introduction to CFD 14:00 Polyflow B 8:30 Introduction to CFD 14:00 Polyflow B 9:30 Polyflow A 14:30 Tutorial 5 11:00 Example 15:30 Evolution 11:30 Tutorial 1 16:30 Tutorial 8 12:30 Lunch 17:00 Break for the day 12:30 Lunch 17:00 Break for the day 1-2 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 3.
    Introduction to POLYFLOWtraining Training Manual 8 30 Ti d d t Fl 14 00 I t d ti t Rh l Agenda Day 2 8:30 Time dependent Flows 14:00 Introduction to Rheology 9:30 Tutorial 7 15:00 CFD Post 10:30 Adaptive meshing 16:00 Workshop 11:30 Tutorial 9 17:00 Break for the day 12:30 Lunch 12:30 Lunch 1-3 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 4.
    Introduction to POLYFLOWtraining Training Manual What is CFD? • Computational fluid dynamics (CFD) is the science of predicting fluid flow, heat and mass transfer, chemical reactions, and related phenomena by solving numerically the set of governing mathematical equations Conservation of mass – Conservation of mass – Conservation of momentum – Conservation of energy – Conservation of species p – Effects of body forces (e.g. gravity) – Etc. • The results of CFD analyses are relevant in: – Conceptual studies of new designs – Detailed product development – Troubleshooting – Redesign • CFD analysis complements testing and experimentation by reducing total 1-4 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 • CFD analysis complements testing and experimentation by reducing total effort and cost required for experimentation and data acquisition.
  • 5.
    Introduction to POLYFLOWtraining Training Manual How Does CFD Work? • ANSYS Polyflow solver is based on the finite element method – Domain is discretized into a finite set of Control elements – General conservation (transport) equations for mass, momentum, energy, species, etc. are solved on this set of control volumes Volume* are solved on this set of control volumes Fluid region of pipe flow is discretized into a finite set of control volumes. – Partial differential equations are Equation Variable Continuity 1 X momentum u Unsteady Convection Diffusion Generation discretized into a system of algebraic equations – All algebraic equations are then solved numerically to render the solution field Y momentum v Z momentum w Energy h 1-5 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 numerically to render the solution field
  • 6.
    Introduction to POLYFLOWtraining Training Manual CFD Modeling Overview • Problem Identification 1. Define your modeling goals 2. Identify the domain you will model Problem Identification 1. Define goals • PreProcessing and Solver Execution 3. Create a solid model to represent the domain 2. Identify domain Pre-Processing domain 4. Design and create the mesh (grid) 5. Set up the physics (physical models, material properties, domain properties, 3. Geometry 4. Mesh 5. Physics p p p p boundary conditions, …) 6. Define solver settings (numerical schemes, convergence controls, …) 7 Compute and monitor the solution 6. Solver Settings Solve e Model 7. Compute and monitor the solution • Post-Processing 8 Examine the results 7. Compute solution Post Processing 9. Update 1-6 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 8. Examine the results. 9. Consider revisions to the model. Post Processing 8. Examine results
  • 7.
    Introduction to POLYFLOWtraining Training Manual 1. Define Your Modeling Goals • What results are you looking for (i e pressure drop mass flow rate Problem Identification 1. Define goals 2. Identify domain • What results are you looking for (i.e. pressure drop, mass flow rate, extrudate shape, flow balance, ..), and how will they be used? – What are your modeling options? • What physical models will need to be included in your analysis? – temperature, gravity, viscous heating, free surface)? • What simplifying assumptions do you have to make? – E.g. simplify the geometry – 2d vs. 3d – Symmetry • What degree of accuracy is required? M h l ti – Mesh resolution • How quickly do you need the results? 2d 3d h l ti t 1-7 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – 2d vs. 3d, mesh resolution, etc.
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    Introduction to POLYFLOWtraining Training Manual 2. Identify the Domain You Will Model • How will you isolate a piece of the Problem Identification 1. Define goals 2. Identify domain • How will you isolate a piece of the complete physical system? • Where will the computational Where will the computational domain begin and end? – Do you have boundary condition information at these boundaries? Domain of Interest as Part of a Larger System (not modeled) – Can the boundary condition types accommodate that information? – Can you extend the domain to a point where reasonable data exists? y ( ) point where reasonable data exists? • Can it be simplified or approximated as a 2D or axisymmetric problem? Domain of interest isolated and meshed for CFD simulation. 1-8 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 y p
  • 9.
    Introduction to POLYFLOWtraining Training Manual 3. Create a Solid Model of the Domain Pre-Processing 3. Geometry 4. Mesh 5. Physics Solid “steel” extrusion die geometry • How will you obtain a solid model of the fluid region? y 6. Solver Settings g – Make use of existing CAD models? • Extract the fluid region from a solid part? – Create from scratch? • Can you simplify the geometry? – Remove unnecessary features that would complicate meshing (fillets, bolts…)? Make use of symmetry or periodicity? Extracted fluid “cavity” – Make use of symmetry or periodicity? • Are both the solution and boundary conditions symmetric / periodic? • Do you need to split the model so that 1-9 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 boundary conditions or domains can be created?
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    Introduction to POLYFLOWtraining Training Manual 4. Design and Create the Mesh Pre-Processing 3. Geometry 4. Meshing 5. Physics A mesh divides a geometry into many elements. These are used by the CFD solver to construct control volumes • What degree of mesh resolution is required in each region of the domain? – The mesh must resolve geometric features of i t t d t di t f y 6. Solver Settings interest and capture gradients of concern, e.g. velocity, pressure, temperature gradients – Can you predict regions of high gradients? – Will you use adaption to add resolution? Triangle Quadrilateral • What type of mesh is most appropriate? – How complex is the geometry? – Can you use a quad/hex mesh or is a tri/tet or hybrid mesh suitable? Hexahedron Tetrahedron y – Are non-conformal interfaces needed? • Do you have sufficient computer resources? – How many cells/nodes are required? H h i l d l ill b d? 1-10 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – How many physical models will be used? Pyramid Prism/Wedge
  • 11.
    Introduction to POLYFLOWtraining Training Manual Tri/Tet vs. Quad/Hex Meshes • For flow-aligned geometries, quad/hex meshes can provide higher-quality solutions with fewer higher quality solutions with fewer cells/nodes than a comparable tri/tet mesh – Quad/Hex meshes show reduced numerical diffusion when the mesh is aligned with the flow. – It does require more effort to t d/h h generate a quad/hex mesh 1-11 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 12.
    Introduction to POLYFLOWtraining Training Manual Tri/Tet vs. Quad/Hex Meshes • For complex geometries, quad/hex meshes show no numerical advantage, and you can save meshing effort by using a tri/tet mesh or hybrid mesh – Quick to generate – Flow is generally not aligned with the mesh • Hybrid meshes typically combine tri/tet elements with other elements in selected regions – For example, use wedge/ prism elements to resolve b d l boundary layers. – More efficient and accurate than tri/tet alone. W d ( i ) h 1-12 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Tetrahedral mesh Wedge (prism) mesh
  • 13.
    Introduction to POLYFLOWtraining Training Manual Multizone (or Hybrid) Meshes • A multizone or hybrid mesh uses different meshing methods in different regions. For example, – Hex mesh for fan and heat sink – Tet/prism mesh elsewhere TET • Multizone meshes yield a good combination of accuracy, efficient calculation time and meshing effort. HEX g • When the nodes do not match across the regions a non-conformal interface the regions, a non conformal interface can be used. 1-13 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Non-Conformal Meshes • Non conformal meshes are useful for meshing complex geometries – Mesh each part then join together Non-conformal interface 1-14 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 15.
    Introduction to POLYFLOWtraining Training Manual Set Up the Physics and Solver Settings • For a given problem, you will need to: – Define material properties • Fluid Pre-Processing 3. Geometry 4. Mesh 5. Physics • Solid – Select appropriate physical models • Isothermal, non-isothermal, gravity, viscous heating etc For complex problems solving a simplified or 2D y 6. Solver Settings heating, etc. – Prescribe operating conditions – Prescribe boundary conditions at all boundary zones problem will provide valuable experience with the models and solver settings for your problem in a short boundary zones • Inlets, outlets, wall temperatures, heat fluxes, etc. – Provide initial values or a previous solution – Set up solver controls amount of time. p – Set up convergence monitors 1-15 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Compute the Solution • The discretized conservation equations are solved iteratively until convergence. C i h d h Solve 7. Compute solution • Convergence is reached when: – Changes in solution variables from one iteration to the next are negligible. • Residuals provide a mechanism to help monitor this trend monitor this trend. – Overall property conservation is achieved • Imbalances measure global conservation • The accuracy of a converged solution is dependent upon: – Appropriateness and accuracy of physical models. – Mesh resolution Mesh resolution – Numerical errors 1-16 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Examine the Results • Examine the results to review solution and extract useful data – Visualization Tools can be used to Post Processing 9. Update Model answer such questions as: • What is the overall flow pattern? • Are there recirculation zones? • What is the free surface shape? 8. Examine results 9 What is the free surface shape? – Is a blow molded part fully formed? • Are key flow features being resolved? Numerical Reporting Tools can be used – Numerical Reporting Tools can be used to calculate quantitative results: • Forces and Moments • Average heat transfer coefficients • Surface and Volume integrated quantities • Flux Balances • Flow Balance • Contact time Examine results to ensure property conservation and correct physical behavior. High residuals may be caused by just a few poor quality cells 1-17 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Contact time may be caused by just a few poor quality cells.
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    Introduction to POLYFLOWtraining Training Manual Consider Revisions to the Model • Are the physical models appropriate? – Is the flow unsteady? – Are there 3D effects? Post Processing 9. Update Model Are there 3D effects? • Are the boundary conditions correct? – Is the computational domain large enough? 8. Examine results 9 p g g – Are boundary conditions appropriate? – Are boundary values reasonable? • Is the mesh adequate? – Can the mesh be refined to improve results? – Does the solution change significantly with a refined mesh or is the solution mesh independent? mesh, or is the solution mesh independent? – Does the mesh resolution of the geometry need to be improved? 1-18 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 Effect of mesh resolution on exit velocity variation at a die exit
  • 19.
    Introduction to POLYFLOWtraining Training Manual POLYFLOW Workflow under Workbench 2 • Start ANSYS Workbench • Drag the Fluid Flow (POLYFLOW) Drag the Fluid Flow (POLYFLOW) system from Analysis Systems group in the Toolbox onto preview drop target shown in the Project Schematic. – Same for the extrusion or blow molding 1-19 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Import the Geometry • Right-click on Geometry cell A2 and select Import Geometry • Import the geometry file (CAD model or a previous DesignModeler db fil ) .agdb file) • You can also link the POLYFLOW simulation to an existing DesignModeler session. 1-20 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 21.
    Introduction to POLYFLOWtraining Training Manual Generate a Mesh • Right-click on Mesh cell and select Edit. – Meshing opens and loads geometry • Select Mesh under Model in Outline • Select Mesh under Model in Outline – Note that Preferences are automatically set for POLYFLOW, because Meshing was opened from a POLYFLOW system. from a POLYFLOW system. 1-21 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
  • 22.
    Introduction to POLYFLOWtraining Training Manual Define Boundary and Cell Zones • Create boundary zones using Named selections. – Select the surface which will represent the boundary you wish to set. – Right-click the selection and select Create Named Selection Create Named Selection. – Name the selection and click OK. • bs.1, bs.2, etc… die exit • You will also need to define the regions of the flow containing fluid and solid (if any) and solid (if any). – Fluid, solid regions – Different regions for different remeshing More details will be presented later 1-22 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 – More details will be presented later • sd.1, sd.2, sd.3, etc…
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    Introduction to POLYFLOWtraining Training Manual Set Up and Run POLYFLOW • Edit the Setup cell to set up the model options – Boundary conditions – Solver settings – Solution – Post processing • Once run, the solution will be post processed in CFD-Post for post processing – Contour and vector plots – Profile plots – Calculation of forces and moments – Animation of unsteady flow results – Free surface shape – … 1-23 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Demonstration of POLYFLOW Software • Start POLYFLOW (assume the mesh has already been generated). – Set up a simple problem. – Solve the flow field. – Postprocess the results. • Online help and documentation is available 1-24 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010
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    Introduction to POLYFLOWtraining Training Manual Navigating the PC at Fluent • Log in to your workstation – Login name: ansys – Password: ansys • Directories – Tutorial mesh/case/data files can be found in c:Student Filesfluenttut – We recommend that you save your work into a central working folder: c:users W ki f ld h th d kt i h t t t – Working folder shown on the desktop is a shortcut to c:users • To start POLYFLOW and/or Workbench, use the desktop icons. • Your support engineer will save your work at the end of the week. • It is recommended that you restart FLUENT and/or Workbench for each tutorial to avoid mixing solver settings from different 1-25 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. Release 12.1 June 2010 each tutorial to avoid mixing solver settings from different workshops.