Workshop plan. From zero to results

Transcription

1 Lecture-0 ANSYS in how to start From zero to results 2014 W0-1 Schedule WEiP Workshop plan Week 1 - Quick start in ANSYS Week 2 Geometry DesignModeler (DM) Week 3 Mesh Meshing Week 4 Solver FLUENT/CFX Week 5 - Post Processing Week 6 Import/Export, Data Visualisation Week 7 Exam W0-2

2 ANSYS WEiP Exercise plan Week 1 Steady problems Week 2 Unsteady problems Week 3 Convection Week 4 Turbulent Flows Week 5 Turbomaschinery Week 6 Complex tasks, multiphase flows Week 7 Exam W0-3 Goals WEiP Goals: ANSYS in 45 minutes Workbench Overview Navigate through the GUI viewing controls ANSYS DesignModeler (DM) Overview Draw and dimension a 2-D sketch on the new plane (dimensioning will adequately specify the size and location of the sketch) ANSYS Meshing (AM) Overview Solution- Tutorial #1: 2D plate Post-processing W0-4

3 Runing ANSYS WEiP Uruchamianie systemu ANSYS Program ANSYS, jako dość wszechstronne i złożone narzędzie, może pracować w różnych trybach, począwszy od trybu wsadowego, poprzez różne interfejsy graficzne, a skończywszy na najbardziej rozbudowanym interfejsie graficznym ANSYS Workbench, umożliwiającym modelowanie złożonych struktur przestrzennych w środowisku przypominającym systemy CAD Poniżej omówiony zostanie standardowy tryb pracy interaktywnej dostępny w każdej instalacji i konfiguracji ANSYSa Warto w tym miejscu nadmienić, że w zaawansowanych zastosowaniach dość przydatny jest również na pozór przestarzały już tryb wsadowy We are going tu work in most advanced ANSYS Workbench W0-5 ANSYS Workbench What is Workbench? WEiP Platform for integration of all ANSYS analysis tools Solid mechanics, fluid dynamics, EM, optimization, etc Entire project contained in common platform: geometry creation, meshing, analysis, and post-processing W0-6

4 Starting Workbench WEiP To start Workbench - Double click on ANSYS Workbench 15 icon W0-7 Workbench Overview WEiP W0-8

5 The Workbench Graphical User Interface WEiP Geometry under component systems This will create a Geometry component in the Project Schematic area W0-9 DesignModeler (DM) Overview WEiP W0-10

6 Launching DM WEiP Right click on and select Import Geometry >Browse, and select link1agdb from the list Double click on and DesignModeler will be launched W0-11 DesignModeler (DM) Overview WEiP W0-12

7 Mesh WEiP Next task to geometry is mesh W0-13 What is the ANSYS Meshing Application? WEiP ANSYS has been working to integrate best in class technologies from several sources: ICEM CFD TGrid GAMBIT CFX ANSYS Prep/Post Etc W0-14

8 ANSYS Meshing Application Overview WEiP The objective of the ANSYS Meshing Application in Workbench is to provide access to common ANSYS Inc meshing tools in a single location, for use by any analysis type: FEA Simulations Mechanical Dynamics Simulation Explicit Dynamics Simulation AUTODYN ANSYS LS DYNA Electromagnetic Simulation CFD Simulation ANSYS CFX ANSYS FLUENT W0-15 Mesh Specification Purpose WEiP For both CFD (fluid) and FEA (solid) modelling, the software performs the computations at a range of discrete locations within the domain The purpose of meshing is to decompose the solution domain into an appropriate number of locations for an accurate result The basic building-blocks for a 3D mesh are: Tetrahedrons (unstructured) Hexahedrons (usually structured) Pyramids (where tet and hex cells meet) Prisms (formed when a tet mesh is extruded) Manifold Example: Outer casting and internal flow region are meshed for coupled thermal/stress gas flow simulation W0-16

9 ANSYS Meshing (AM) Overview WEiP W0-17 ANSYS Meshing (AM) Overview WEiP W0-18

10 WEiP W0-19 Different Mesh Methods WEiP W0-20

11 Fluent/Setup WEiP Next tasks are Setup and SOLUTION W0-21 How Does CFD Work? ANSYS CFD solvers are based on the finite volume method Domain is discretized into a finite set of control volumes General conservation (transport) equations for mass, momentum, energy, species, etc are solved on this set of control volumes Control Volume* WEiP Fluid region of pipe flow is discretized into a finite set of control volumes Unsteady Convection Diffusion Generation Partial differential equations are discretized into a system of algebraic equations All algebraic equations are then solved numerically to render the solution field * FLUENT control volumes are cell-centered (ie they correspond directly with the mesh) while CFX control volumes are node-centered W0-22 Equation Variable Continuity 1 X momentum u Y momentum v Z momentum w Energy h

12 CFD Modeling Overview Problem Identification 1 Define goals WEiP Problem Identification 1 Define your modeling goals 2 Identify the domain you will model 2 Identify domain Pre-Processing 3 Geometry 4 Mesh 5 Physics 6 Solver Settings Solve 7 Compute solution Post Processing 8 Examine results 9 Update Model PreProcessing and Solver Execution 3 Create a solid model to represent the domain 4 Design and create the mesh (grid) 5 Set up the physics (physical models, material properties, domain properties, boundary conditions, ) 6 Define solver settings (numerical schemes, convergence controls, ) 7 Compute and monitor the solution Post-Processing 8 Examine the results 9 Consider revisions to the model W0-23 SOLVER Parallel processing can be used to run FLUENT on multiple processors to decrease turnaround time and increase simulation efficiency Critical for cases involving large meshes and/or complex physics FLUENT is fully parallelized and capable of running across most hardware and software configurations, such as compute clusters or multi-processor machines Parallel FLUENT can be launched either using the system command prompt or using the FLUENT Launcher panel For example, to launch an n-cpu parallel session, use the command fluent 3d tn The mesh can be partitioned either manually or automatically using a number of different methods Non-conformal meshes, sliding mesh interfaces and shell conduction zones require partitioning in serial A web-based lecture is available on the FLUENT User Services Center WEiP W0-24

13 FLUENT 12 GUI Navigation WEiP The FLUENT GUI is arranged such that the tasks are generally arranged from top to bottom in the project setup tree Selecting an item in the tree opens the relevant input items in the center pane General Models Materials Boundary Conditions Solver Settings Initialization and Calculation Postprocessing W0-25 Scaling the Mesh and Selecting Units When FLUENT reads a mesh file (msh), all physical dimensions are assumed to be in units of meters If your model was not built in meters, then it must be scaled Verify that the Domain Extents are correct after scaling the mesh WEiP When importing a mesh under Workbench, the mesh does not need to be scaled; however, the units are set to the default MKS system Define Units Any mixed units system can be used if desired By default, FLUENT uses the SI system of units (specifically, MKS system) Any units can be specified in the Set Units panel, accessed from the top menu W0-26

14 Material Properties FLUENT provides a standard database of materials and the ability to create a custom user-defined database WEiP Your choice of physical models may require multiple materials and dictate which material properties must be defined Multiphase (multiple materials) Combustion (multiple species) Heat transfer (thermal conductivity) Radiation (emissivity and absorptivity) Material properties can be directly customized as function of temperature/pressure Use of other solution variable(s) requires UDF W0-27 Operating Conditions WEiP The Operating Pressure with a Reference Pressure Location sets the reference value that is used in computing gauge pressures The Operating Temperature sets the reference temperature (used when computing buoyancy forces Specified Operating Density sets the reference value for flows with widely varying density W0-28

15 Changing Boundary Condition Types WEiP Zones and zone types are initially defined in the preprocessing phase To change the boundary condition type for a zone: Choose the zone name in the Zone list Select the type you wish to change it to in the Type pulldown list W0-29 Setting Boundary Condition Data WEiP Explicitly assign data in BC panels To set boundary conditions for particular zone: Select Boundary Conditions in the project tree Choose the boundary name in the Zone list Click the Edit button Boundary condition data can be copied from one zone to another Boundary conditions can also be defined by UDFs and profiles Profiles can be generated by: Writing a profile from another CFD simulation Creating an appropriately formatted text file with boundary condition data W0-30

16 Velocity Inlet Velocity Specification Method Magnitude, Normal to Boundary Components Magnitude and Direction WEiP Applies a uniform velocity profile at the boundary, unless UDF or profile is used Velocity inlets are intended for use in incompressible flows and are not recommended for compressible flows Velocity Magnitude input can be negative, implying that you can prescribe the exit velocity W0-31 Wall Boundary Conditions WEiP Five thermal conditions Heat Flux Temperature Convection simulates an external convection environment which is not modeled (user-prescribed heat transfer coefficient) Radiation simulates an external radiation environment which is not modeled (user-prescribed external emissivity and radiation temperature) Mixed Combination of Convection and Radiation boundary conditions Wall material and thickness can be defined for 1D or shell conduction calculations heat transfer calculations W0-32

17 Problem Setup Heat Source WEiP An energy (heat) source is added to the solid zone to simulate the heat generation by the heat-generating electronic components W0-33 Temperature Distribution (Front and Top View) WEiP Temp (ºF) 426 Flow direction Air (fluid zone) Front View Convection boundary 15 W/m 2 K 298 K free stream temp Flow direction Board (solid zone) Elect Component (solid zone) 2 Watts source Top View (image mirrored about symmetry plane) Convection Boundary 15 W/m 2 K 298 K free stream temp W0-34

18 Convergence Monitors Residuals WEiP Residual plots show when the residual values have reached the specified tolerance All equations converged W0-35 Results WEiP NOW We are going to the last step RESULTS W0-36

19 Starting CFD-Post WEiP Within ANSYS Workbench Drag the CFD-Post icon in the Component Systems list to the project tree OR, create a standalone CFD-Post session From the Start Menu or Command Line Start > Programs > ANSYS 120 > ANSYS CFD-Post CFD-Post can also be started from the CFX-Solver Manager or the CFX Launcher W0-37 GUI Layout WEiP Additional tabs (various tools) Outline tab ( model tree ) Details view Various Viewers (3D, Chart, ) W0-38

20 CFD-Post General Workflow WEiP 1 Prepare locations where data will be extracted from or plots generated 2 Create variables/expressions which will be used to extract data (if necessary) 3 i) Generate qualitative data at locations ii) Generate quantitative data at locations 4 Generate Reports W0-39 Creating Locations WEiP Locations are created from the Insert menu or from the toolbar Once created, all Locations appear as entries in the Outline tree Use the check boxes next to each object in the Outline tree to quickly control visibility Double-click objects in the Outline tree to edit Right-click objects in the Outline tree to Duplicate or Delete W0-40

21 Location Types WEiP Planes XY Plane, Point and Normal, etc Can define a circle or rectangle to bound the plane, otherwise it s bounded only by the solution domain(s) Point XYZ: At coordinates Can pick from Viewer Node Number: Some solver error messages give a node number Variable Max / Min: Useful to locate where max / min values occur Point Cloud Create multiple points Usually used as seeds to streamlines, vectors W0-41 Location Types WEiP Lines Straight line between two points Usually used as the basis for an XY Chart Polylines Also used for Charts Read points from a file Use the line of intersection between a boundary and another location Extract a line from a contour plot W0-42

22 Location Types WEiP Volumes Elements are either in or out No cut volumes From Surface A volume is formed from all elements touching (or above / below) the selected location Can be useful for mesh checking Isovolume Base on a variable at, above or below a given value, or between two values W0-43 Location Types Isosurfaces Surface of a variable at a specified value WEiP Isosurface of pressure behind a flap valve Iso Clip An Iso Clip takes a copy of any existing location and then clips it using one or more criteria Eg a outlet boundary plot which is then clipped by Velocity >= 10 [m/s] and Velocity <= 20 [m/s] Can clip using any variable, including geometric variables W0-44

23 Other Tools Timestep Selector Transient results are post-processed by loading in the end results file, then selecting different timesteps from the Timestep Selector WEiP Timestep Animation Quick Probe Selector Editor Animation Animate objects, create MPEGs More on next slide Quick Editor Provides a very quick way to change the primary value associated with each object Probe Pick a point from the Viewer and probe a variable value at that point W0-45 Case Comparison WEiP When multiple files are loaded you can select Case Comparison from the Outline tree Automatically generates difference variables and plots SST k-e Difference Plot Expression syntax: function()@case:#location Eg: areaave(pressure)@case:1inlet W0-46

24 Files Results ANSYS CFD Post can read ANSYS results for temperature, velocity, acceleration, magnetic forces, stress, strain, and mesh deformation WEiP Import Locations csv files which contain point data which defines a polyline or surface ANSYS Surface Mesh (cdb): To allow for export of data on a surface for use as a boundary condition in ANSYS Export Profile Boundary Data: for use in CFX-Pre General formatted results data ANSYS Load Data: Written onto an imported ANSYS cdb file W0-47