Sequential Multiphysics Coupling: Data transfer and interpolation methods François Chapuis Sadek Cherhabili ANSYS FRANCE

Transcription

1 Sequential Multiphysics Coupling: Data transfer and interpolation methods François Chapuis Sadek Cherhabili ANSYS FRANCE 1

2 Agenda General context Comprehensive Multiphysics Method of coupling physics Mapping status in WB Overview of existing mapping tools (R13) New mapping algorithms In R14 Additional practical tools in R14 Imported load functionality External data component Mechanical/Thermal Demo1 Fluid Structure interaction (FSI one-way) Demo2 Two-way FSI System coupling (Fluent/ANSYS) in R14 2

3 General context Comprehensive Multiphysics 3

4 Comprehensive Multiphysics What is Multiphysics? Simulation of multiple physics! 1 Way FSI 2 Way FSI Deformation/Stress increase ~15% Mulitphysics is not new Part of core technology for decades Thermal Stress Complex thermoelectric-fluidic calculation 4

5 ANSYS Multiphysics : Built on a Strong Foundation Paramterization Meshing MULTIPHYSICS Fluids BREADTH Structural Thermal DEPTH CAD Import In-house Solution Emag Workflow ANSYS technical depth and breadth, provides the foundation for true multiphysics simulation. Postprocessing 5

6 ANSYS Multiphysics : Robust, Scalable, Proven ANSYS Multiphysics Advantages Highly scalable and robust solutions Built on proven simulation technology Single simulation environment Flexible simulation methods for many applications Supports parameterization and design optimization Proven fluid-structure interaction Structural Fluids Thermal Emag Multi-Field Solver Sequential solution Separate model & mesh Separation of expertise Structural Thermal Fluids Emag Direct Coupled Field Element-level coupling Highly coupled physics Single model & mesh 6

7 Multiphysics Simulation Portfolio Product Capabilities ANSYS Multiphysics ANSYS Mechanical/ CFD-Flo ANSYS Mechanical/ Emag ANSYS Mechanical ANSYS CFD Structural Heat Transfer Fluid Flow Low Frequency Electromagnetics High Frequency Electromagnetics Acoustics Direct Coupling Multi-field Solver Multi-field solver is available when purchased in conjunction with an ANSYS Mechanical license. 7

8 Methods of Coupling Physics 8

9 Methods of Coupling Physics Direct Coupling A single analysis employing a coupled-field element containing all the necessary DOFs to solve the coupledfield problem. Structural Thermal Fluids Emag Direct Coupling Element-level coupling Highly coupled physics Single model & mesh Load Transfer Two or more analysis are coupled by applying results from one analysis as loads in another analysis. Structural Fluids Thermal Emag Load Transfer Sequential solution Separate model & mesh Separation of expertise 9

10 Direct Coupling Options Continuum Elements 2-D and 3-D solid elements General analysis Discrete Elements Electromechanical transducer, thin fluid film elements, discrete circuits General analysis Reduced order modeling MEMS Switch - actuation voltage, mechanical contact and fluid damping effects are simulated using electromechanical transducer and thin fluid film elements. Silicon Ring Gyroscope Harmonic response including thermoelastic damping solved with direct coupledfield elements. 10

11 Load Transfer Options One-way Load Transfer One-way data exchange sufficient Temperatures Two-way Load Transfer Two-way data exchange required Implicit sequential coupling 11

12 Mapping status in ANSYS Workbench 12

13 Global mapping options (in release 13) Data type conservative data: force, heat flow, heat generation, etc. non-conservative data: displacement, velocity, temperature, heat flux, force density, etc. Type Surface-Surface Volume-Volume Method Point-Point (point cloud method) Point-element (Bucket search) Element-element (GGI based) 13

14 Overview of available mapping tools (R13) Point cloud mapping 2D &3D surface and volumetric Point-Point Bucket search based 2D&3D surface or volume mapping Point-element GGI (general grid interface) 3D surface mapping Element-element 14

15 Point cloud mapping (triangulation) Algorithm Binary search algorithm creates intermediate triangle(2d) or tetrahedral element on the source side use the distance of the target node to source nodes as interpolation weights Advantages Robust no element needed no element type restrictions Disadvantages Less accuracy in case of very different node densities between the source side and target side 15

16 Bucket search based mapping Algorithm node to element mapping linear interpolation Advantages Mesh only needed on one side support more element type than GGI method suitable for non-conservative data transfer Disadvantages Can not guarantee both profile preserving and global conservation for conservative data (compare with GGI based) 16

17 GGI based 3D surface mapping (exclusive to CFD) Algorithm Octree search method element-element mapping through control surface Advantages Robust and accurate Able to handle non-overlap interpolation Profile preserving and global conservative for conservative quantities Disadvantages Need element information on both sides complicated and cost more memory and computing times Mapping information can not directly used for constrain conditions Very limited element shapes 17

18 New enhancements in Release 14 18

19 New Mapping/interpolation Methods At R14, we have expanded the weighting options to include: Point Cloud/Triangulation Works well in many cases. Can give poor results if target points not found within the source point cloud -> More options in R14 Kriging (R14) Regression-based interpolation technique that can give smoother mapping Distance Based Average (R14) Simple robust method give a mapping when other weightings fail 19

20 Mapping onto surface with default settings (R13) 20

21 New triangulation transfer type (R14) Volumetric Previously only option available in R13 Uses tetrahedrons during mapping Not good for shells and surface mapping Surface Uses triangle during mapping Produces smoother contours when mapping to shells or surfaces 21

22 Surface transfer type effect on mapping nodal temperature Volumetric mapping (R13) Surface Transfer (R14) 22

23 Triangulation with projection for outside nodes (R14) Projection of outside nodes using 8 closest points 23

24 More Outside options for Triangulation (R14) Triangulation weighting attempts to locate a target point inside tetrahedrons constructed from the source points Sometimes the target points may lie outside Several options to handle this situation Options to handle Outside Points include Projection back into the volume Use distance weighted average Ignore outside points Extrapolation limits can be set 24

25 Kriging (R14) Regression-based interpolation technique that assigns weights to surrounding source points according to their spatial covariance values 25

26 Example: Kriging vs. Triangulation In this example, due to curvature, the nodes fall outside on the ends Smooth contours R13 26

27 Distance based average mapping (R14) Using 3 point Using n closest points and use the distance from the target node to the source node(s) to calculate a weighting value Using 8 points 27

28 Distance based average for outside nodes (R14) Using 1 point Using 4 points Using 8 points Increasing the number of points to use for distance based average of nodes found outside improves quality of mapping 28

29 Additional practical tools in R14 29

30 New mapping validation options Added new tree object (right mouse click on External Load or Imported Thickness and select Insert -> Validation Reverse Mapping Validation Map results of mapping back onto source and compare to original inputs Distance Based Average Comparison Compare results to distance based average mapping results Source Values Plots the source data which can allow for visual comparison against mapped data (done in preview 3) Invoked by right mouse click on Validation and select Analyze 30

31 Validation settings File Identifier Choose identifier (i.e. variable imported) Items provided by parent external load or external thickness object Type Reverse Mapping Distance Based Average Comparison Output Type Absolute Difference Relative Difference 31

32 Validation settings: Graphics Controls Display Colored Points (default) or Colored Spheres are drawn using 6 colors based on Display Minimum and Display Maximum inputs Scaled Spheres are spheres drawn based on Display Minimum and Display Maximum inputs Scale Colored Spheres and Scaled Spheres sizes are controlled by this input Display Minimum and Display Maximum Must be within the range of the Minimum and Maximum statistics. Items outside these boundaries will not be drawn Display In Parent When On, items will be drawn on the parent object in the tree (i.e. External Load or External Thickness) Number Of Items Currently displayed number of items shown in the graphics window. This number will change based on the Display Minimum and Display Maximum values 32

33 Validation Example for Reverse Mapping Validation showing relative difference of reverse mapping back on the source points Displayed in Parent 33

34 Source Value Validation New Source Value validation draws source load values directly on model. 34

35 Source Value Validation (cont) Displaying In Parent helps show how well mapping performed. 35

36 External data Component 36

37 Importing External Load into Mechanical 1 Edit 2 3 Edit 37

38 External Load - Details 38

39 3D Face & Body Temperature Mapping 2 3D Face 1 3D Body 39

40 2D Edge & Body Temperature Mapping 2 1 2D Bodies 2D Edge 40

41 3D Face Pressure Mapping Using Magnitude & Normal Using X Y Z Components 41

42 2D Edge Pressure Mapping 2 1 Using Magnitude & Normal Using X Y Z Components 2 42

43 Convection Load Mapping 3D Face 1 43

44 Mapping 2D Results onto 3D Model 2D Results 2D Results Mapped on 3D Model using cylindrical coordinate system 44

45 Thermal-Stress Analysis (Dissimilar Mesh) Temperature distribution bleed across the body boundary with All bodies selected With Manual option user can choose the body using material IDs to produce more accurate results 45

46 Multiple File Mapping Often users need to map multiple sets of data WB must provide a way for users to easily setup whether mapping 1 file or a 100 External Data now supports Ability to handle multiple files Multi-edit to specify file formatting Ability to designate Master File to re-use XYZ data(leads to much faster mapping) 46

47 Multi File Mapping : multiple select By Multiselecting the files, properties for all files can be set at once Columns can be sorted for more efficient editing 47 Multi row specification can be set at once Data Identifiers can be copied into Mechanical

48 Multiple File Mapping: Example Source results taken from two separate analyses Geometry is oriented on arbitrary coordinate system Results from each analysis are generated in separate files and added to a single External Data System Transformations are applied to get source data into target system 48

49 Multiple File Mapping: Example (cont) Multiple imported loads can be inserted to correspond with files from External Data System. Target Geometry Identifiers are available for each file contained in upstream External Data system. Imported Loads from each file 49

50 Multiple File Mapping with Master Transient results exported to separate files. Each file contains all nodes with results at different time points. Master file selected. Nodes from all other files will not be read. Single connection from External Data to Mechanical 50

51 Multiple File Mapping with Master (cont) Single Imported Load from External Data. Since master file is selected, nodes will be read only once reducing memory footprint and much quicker mapping Multiple loads can be imported and applied at different time steps. 51

52 Activation/Deactivation Support for Imported Loads Ability to allow activation or deactivation of Imported Loads per load step. This allows the user to turn off an imported load in a subsequent load step. User can choose to activate/deactivate the loads using the RMB option that is available in the timeline (Graph) and tabular data Available for all imported loads 52

53 Imported Data Export Functionality New Export option allows writing tab delimited data to a file. Accessible from Imported Loads and Imported Thicknesses. Nodal Data Element Centroid Data 53

54 Demonstration 54

55 External Data For FSI one-way 55

56 One-way Data Transfer (R13) In Workbench both thermal and structural loads can be transferred from CFX/Fluent to ANSYS Temperature Either as a surface or a body load Wall Heat Transfer Coefficient As a surface convection coefficient Pressure Surface load which includes both normal (Pressure) and tangential (Shear) components In fact, force data that comes directly from the solution of the momentum equations is used The data is interpolated in the background using CFD-Post 56

57 Pressure/temperature/HTC Transfer to Mechanical Systems (R13) Mechanical/thermal nodal values are transferred by linear interpolation from the surrounding CFD nodes If interpolation process cannot find a face to map to, then closest point is chosen Mapping can be slow for large cases Octree mapper or external data can be used instead, discussed later 57

58 One-way data: Integrated Process in Workbench (R13) Example Project Schematic Geometry CHT Mesh CFD CHT Solution Thermal Loads Pressure Loads Thermal Stress Solution 58

59 New Octree mapping CFD-Post (R14) 1-way FSI (β) New Octree mapping method Significantly faster algorithm Improved handling of nodes outside selected region Need to set Option in CFD-Post 1-way FSI in ANSYS Workbench uses CFD-Post under-the-hood Will use mapping option set by user in CFD-Post (which is stored in user preferences) Status message with diagnostics report will indicate use of new mapping method is being used 59

60 External Data Component for FSI (R14) Allows pressure, temperature and heat transfer coefficient to be imported into ANSYS Mechanical from an external ASCII file Can be used as an alternative to the standard 1-way mapping Export a data file from CFD-Post, then import via External Data 60

61 External Data Component for FSI R14 (cont) Consider using External Data when: You want to map a non-standard variable, e.g. a transient average You want to use lower resolution data from CFD results instead of mapping every node Create a Point Cloud in CFD-Post then export data Fluid and structural geometries are in different coordinate frames Export data using a local coordinate frame in CFD-Post A workflow based on a single project is not convenient E.g. fluid and structural groups You don t have a CFD-Post license available when importing the data into Mechanical The interpolation is too slow using the standard approach Could also use the Point Cloud method to speed up 61

62 External Data Component (cont) The main disadvantage of using External Data is that the workflow is disconnected no automatic data updates 62

63 Demonstration CFD Solution Standard transfer WB External Data 63

64 System Coupling 14.0 Two-way FSI with FLUENT and Mechanical 64

65 Fluid-Structure Interaction Applications Fluid-structure interaction problems encompass a wide range of applications in many different industries. Aerospace, automotive, power generation, biomedical, etc. 65

66 Fluid-Structure Interaction The solution to two-way fluid-structure interaction requires co-simulation between computational fluid dynamics and structural mechanics. Applications such as air foil flutter, flow induced vibration from wind loading, membrane valves, pumps, elastic artery modeling and fuel tank sloshing require a two-way fluid-structure interaction solution to accurately predict the behavior of the design. 66

67 Iterative Coupling* A transient 2-way FSI simulation has three levels of iterations: Time Loop Coupling / Stagger Loop Field Loop End Field Loop End Coupling / Stagger Loop End Time Loop The transient loop each loop/step moves forward in time, as in a standard CFD or FEA transient simulation. Loads / displacements are updated between the FEA and CFD solvers. The usual inner loop, used to converge the field(s) within a solver named Coefficient Loops in CFD and Equilibrium Iterations in FEA. Existing for ANSYS CFX since R11 Now for ANSYS FLUENT with System Coupling (R14) 67

68 System Coupling 14.0 Facilitates simulations that require tightly integrated couplings of analysis systems in the ANSYS portfolio Extensible architecture for range of coupling scenarios (one-, two- & n-way, static data, co-simulation ) ANSYS Workbench user environment and workflow Standard execution management and data interfaces 68

69 System Coupling 14.0 A Broad Range of Features Two-way surface force/displacement coupling with ANSYS Fluent and ANSYS Mechanical Steady/static and transient two-way FSI Workbench based setup and execution Windows and Linux Execution from command line outside of Workbench including crossplatform execution Integrated post-processing with ANSYS CFD-Post Parallel processing for both CFD and structural solutions with ANSYS HPC Restarts for fluid-structure interaction Parameterization, design exploration and optimization 69

70 System Coupling Schematic Setup 70

71 System Coupling Controls the Participant Solvers for Transient and Steady/Static Solutions Solution update can ONLY be done via System Coupling System Coupling ensures that the time duration and time step settings are consistent across all participant solvers 71

72 Setup Transient Structural Model Setup transient structural solution, structural boundary conditions and Fluid Solid Interface 72

73 Setup Fluid Flow (FLUENT) Model Setup transient fluid solution, fluid boundary conditions and specify System Coupling Dynamic Mesh Zone for fluid-structure interaction motion 73

74 System Coupling Motion Type System Coupling motion identifies zones that may participate in System Coupling Allows user-defined motion to be combined with System Coupling motion Defaults to stationary motion type when not connected to System Coupling 74

75 Update Setup Cells for Transient Structural and Fluid Flow (FLUENT) State of System Coupling setup cell will be Upstream data is now available for SC Setup 75

76 System Coupling Setup GUI Outline Chart Monitors Details Solution Information Text Monitors 76

77 System Coupling Analysis Settings Coupling End Time Coupling Step Size Minimum Number of Iterations per Coupling Step Maximum Number of Iterations per Coupling Step 77

78 System Coupling Participants are Transient Structural and Fluid Flow (FLUENT) Region and variable information is generated automatically via Update when analysis systems are first connected to System Coupling For FLUENT, all regions of type Wall are shown in SC Setup For Mechanical, all regions of type Fluid Solid Interface are shown in SC Setup 78

79 Recommended Way to Create Data Transfer Regions Use Ctrl key to select a FLUENT and Mechanical region pair and select Create Data Transfer from right-click pop-up menu Automatically fills in the details for the data transfer region Data transfers can be one-way (i.e. only transfer force or only transfer displacement) or twoway 79

80 Create Data Transfers 80

81 Data Transfer Defines the Details for the Source, Target and Data Transfer Controls Participant Region Variable Transfer At Start of Iteration only Under Relaxation Factor Convergence Target 81

82 Execution Control Co-Simulation Sequence Transient or Static Structural will always be first in the co-simulation sequence Debug Output Different levels of debug output for analysis and data transfers Intermediate Results File Output Controls the intervals for writing restart file information 82

83 Executing System Coupling 83

84 Alternative Method for Executing System Coupling From schematic select Update using right-click menu on System Coupling solution cell Solution progress (% complete) can be monitored using View Progress menu 84

85 Solution Information Build information Complete summary of coupling service input file Analysis details Participant summaries Data transfer details Mapping diagnostics Time step and iteration summary Solver field equation convergence summary Data transfer convergence summary FLUENT/MAPDL solver output 85

86 Chart Monitors X-axis can be coupling time, step or iteration. Default chart monitors show convergence history for all data transfers. 86

87 Adding Charts and Variables Add charts by selecting Create Convergence Chart Variables can be added or removed from charts Data transfers, CFD and structural convergence norms Chart properties are editable in same manner as other charts within ANSYS Workbench 87

88 Post Processing System Coupling Transient Structural or Fluid Flow (FLUENT) Results cell for solver-specific post-processing Add a Results System (ANSYS CFD-Post) for unified post-processing of structural and fluid results 88

89 Post Processing System Coupling Oscillating Plate Verification Excellent correlation between System Coupling, published data and MFX solver 89

90 Data Transfer Type Conservative CFX GGI technology. Locally and globally conservative and preserves profiles. Should be used when sending flows (Heat Flows, Total Force) Profile Preserving Used for non-conservative data and fluxes (Displacement, Temperature, Wall Heat Flux) The appropriate option is automatically chosen If defining your own data to send need to pick the appropriate option 90

91 System Coupling Examples 91

92 Fuel Tank Sloshing Transient free surface flow in a fuel tank with internal baffles. 92

93 Mitral Valve Transient blood flow through a three leaf mitral valve, non- Newtonian fluid and anisotropic hyperelastic tissue. Solution includes remeshing of the fluid domain and nonlinear contact. 93

94 Reed Valve Transient response of reed valve opening and closing. Solution includes remeshing of the fluid domain, large deformations and nonlinear contact. 94

95 Vibrating Rod Transient response of vibrating rod including vortex shedding. 95

96 Summary In Release 14: More options/enhancements for existing mapping methods New mapping/interpolation methods Extension to CFD users for FSI (Surface and Volume loads - One-way coupling) System Coupling for two-way FSI for CFD user s 96

97 Questions and Answers 97

98 Appendix A1 More on mapping 98

99 Mapping Diagnostics: Named Selection Creation Option to create nodal based named selections for mapped nodes, unmapped nodes, and outside nodes. Can help the user better understand the mapping. 99

100 Source Point Morphing Users desire to morph the locations of the source points. This allows more precise mapping between dissimilar geometries. External Data now exposes Morphing Can be done in X/Y/Z or R/th/Z. Default is no morphing(i.e. x=x) Morphing supports a number of intrinsic functions for moving nodal locations. Below is a list of supported functions: sin(arg) asin(arg) sinh(arg) cos(arg) acos(arg) cosh(arg) tan(arg) atan2(arg1,arg2) tanh(arg) atan(arg) exp(arg) log10(arg) log(arg) loge(arg) max(arg list) min(arg list) nint(arg) int(arg) abs(arg) fabs(arg) pow(value, exponent) sqrt(arg) sign(arg) floor(arg) ceil(arg) round(arg) PI, pi constant E, e constant 100

101 Source Point Morphing (using constants) Unmorphed nodes Source Results(cylinder) Target Model (ellipse) Morphed nodes External Data Morphing Inputs 101

102 Source Point Morphing (using functions) Original nodes in XY Plane Nodes morphed using function on z coordinate 102

103 Imported Thickness From External Data An Imported Thickness group is created for each External Data system linked to the Model cell under Geometry Support for 3D Shells and 2D Planar Additional Imported Thickness objects can be added to the group via the context-menu Mapping is performed to calculate the thickness on the mesh. Thickness value is mapped from imported data to each node on the scoped surface body/face. For a 2D analysis, an average thickness per element is calculated from the nodes which is sent to the solver as real constant for every element. User can modify final thickness via the Scale and Offset entries. Applied thickness = (Imported values * Scale) + Offset Shell Offset is only available for 3D Shell models only File containing point cloud data of thickness at various XYZ locations 103

104 Visualization of Imported Thickness(3D) Select Imported Thickness node in the tree to visualize contours Select Mesh node in the tree to visualize Thickness on the Mesh Note variation 104

105 Imported Thickness(2D Planar) Note 2D Geometry Contour on Imported Thickness Object Verify correct solve via user defined result(nmisc1 on PLANE182) 105

106 Shell thickness and offset when mapping data to shells Shell Thickness Factor property allows you to account for the offset and thickness at each target node (surface bodies) when mapping data from an upstream External Data system This value is multiplied by each target node s physical thickness and used along with the node s offset to determine the top and bottom location of each target node. A positive value uses the top location of each node during mapping, while a negative value uses the bottom location of each node. All target nodes projected to top and then mapped Target geometry overlay with source points All target nodes mapped at default surface body location Target shell elements overlay with source points top All target nodes projected to bottom and then mapped bottom Offset Type - Middle 106

107 User input thickness value for all unmapped nodes A thickness value can be applied to target nodes that fall outside the threshold of the mapping settings and cannot be mapped. Source points are from model with larger hole radius Unmapped nodes that will get default value 1.5e-2 (m) 107

108 User input thickness value for all unmapped nodes Contour plot of imported thickness Mesh shell thickness plot using imported thickness (nodes along hole are using 1.5e-2 (m) default thickness value) 108

109 Appendix A2: More Examples/illustrations 109

110 Solution comparison between 3D shells and 2D Plane Stress Elements 2d plane stress analysis provides almost same solution as 3d shells with same imported thickness with in plane loading Equivalent Stress 3D Shells Total Deformation 2D Planar 110 3D Shells 2D Planar

111 Input file for Imported thickness Global thickness Imported thickness 2D Plane Stress Sending global thickness per body Sending global thickness per body Overriding global thickness by sending imported thickness per element 3D Shell Model Sending global thickness per body Sending global thickness per body sending imported nodal thickness table 111 Overriding global thickness by sending imported nodal thickness table

112 Imported thickness restrictions for a 2D plane stress analysis: Imported thickness can be applied in a 2d analysis for a plane stress model only. It will be marked under defined if 2d behavior is not set to plane stress. Solving such an analysis will throw an error: Imported thickness values for all nodes should be positive. If imported data has negative values, then user may use appropriate offset so that imported thickness is positive. Importing non positive values will throw an error: User is not allowed to apply force load on an edge which is being shared by the scoping of an imported thickness. Solving such an analysis will throw an error: 112

113 Example: Triangulation with Projection Results in smoother mapping as compared to V Projection

114 Thermal results on curved surface to be used in mapping Thermal result to be transferred to Structural mesh Results are only on surface 114

115 Reverse mapping validation Absolute difference using Volumetric transfer type 0.04 C to C Absolute difference using Surface transfer type 0.04 C to C 115

116 Reverse mapping validation Relative difference using Volumetric transfer type 1.0e-2% to 7.9e-2% Relative difference using Surface transfer type 1.0e-2% to 2.6e-2% 116

117 Distance based average comparison Absolute Difference Volumetric transfer type Absolute Difference Surface transfer type 117

118 Distance based average comparison Relative Difference Volumetric transfer type Relative Difference Surface transfer type 118

119 Multiple File Mapping with Master (cont) Imported loads at 1, 3, and 5 seconds. 119