New Features and Enhancements in CFD
Autodesk has added some new functionality to Autodesk Simulation CFD (Computational Fluid Dynamics) as well as adding more learning resources. The most noteworthy items are probably the new ribbon, free surface, better view navigation, and finally support for Autodesk Vault. There is something for everyone in this year’s improvements.
Outline of the New Features
- Simulation Capabilities
- Results & Visualization
- CAD Formats & Direct Import
- Autodesk Vault and Autodesk 360
- Learning Resources
Autodesk has enhanced the user experience, focusing primarily on consistency with the Autodesk product line.
- Ribbon interface only
- Standard navigation bar and view cube added
Standard Autodesk Mouse Navigation
Mouse navigation is finally consistent with other Autodesk products.
Figure 1: Autodesk consistent view navigation implemented
- Rotate – Shift + middle mouse button
- Zoom – Roll mouse scroll wheel (this can be reversed)
- Pan – Middle mouse button
You can revert the mouse behavior back to CFDesign style through Interface Preferences, but I won’t waste your time mentioning how.
New Ribbon Interface
As you might have expected, the new interface has gone ribbon. This is fine as long as Autodesk kept the ‘easy-to-follow’ organization the CFD always employed.
Figure 2: The new ribbon
New tabs include:
- Vault – Archive as a .cfz. You can associate checked-in geometry files with your CFD design studies.
- Autodesk 360
- Start & Learn – Includes tutorials, videos, Wiki help, IdeaStation
- Community – exchange ideas, post questions
- IdeaStation – online system for communicating with the Autodesk product design team. Share ideas, request product enhancements, provide feedback
This new portion of the API permits CFD to launch scripts when specific events occur. These can be customized through the Setup tab and allow things such as specific data save upon completion of a simulation, automate the setup process, and so on.
Automatic Mesh Sizing includes several exciting improvements that further streamline the simulation meshing process. These improvements primarily affect four aspects of meshing: adaptation, independence, volume-based auto-sizing, and enhancement layer thickness growth control.
Mesh Adaptation Improvements
Mesh Adaptation worked well in CFD, but not for all things. Many limitations have been lifted and the overall process is faster
- Automatic layer adaptation has been removed from the Mesh Enhancement dialog, eliminating Y+ Adaptation conflict.
- Mesh distribution for each adaptation cycle requires less time to compute.
- Adaptation error indicator uses an alternative method that more selectively refines the mesh. In many cases, the resultant mesh is smaller, which leads to reduced simulation times.
- The auto-sizing function was refined to reduce the time required to compute the mesh distribution.
Mesh Adaptation now supports:
- Internal fan/pump
- Centrifugal pump/blower
- Distributed resistance
- Heat exchanger
- Check valve
Mesh Adaptation unfortunately still does not support extruded meshes or transient simulations, including rotating turbo-machinery and motion simulations.
Mesh Independence Indicators
- CFD now indicates how close the mesh is to a mesh independent solution.
- It evaluates pressure, velocity, and temperature (for heat transfer simulations) and displays the unchanged quantity of the previous mesh in the output bar after each adaptation step:
Mesh Independence: Pressure: 85% Velocity 98% Temperature 97%
Volume-Based Mesh Auto-sizing
CFD now supports volume-based auto-sizing, eliminating the need for nested volume strategies in areas not adjacent to geometric boundaries.
User-defined Mesh Enhancement Layer Thickness Growth
A new setting provides control of how the enhancement layer thickness grows. This allows users to affect the layers nearest the wall, making them smaller than those closest to the neighboring unstructured elements.
Provides improved heat flux and new turbulence model accuracy along walls.
Figure 3: Layer thickness enhancement near structure walls
- Two quick convection heat transfer models have been removed.
- Temperature results improvements in PCB Materials – permits better accuracy with temperature distribution in printed circuit board materials when not aligned with the Cartesian axes.
CFD now offers the ability to dynamically simulate the interface between liquids and gases. This includes movement such as sloshing, agitation, and mixing, and permits the application of open flow channels.
Figure 4: Sloshing study using Free Surface
Advanced Turbulence Models
New turbulence models are available:
- SST k-omega – recommended for flows with separation or detachment as well as for adverse pressure gradients, and is robust across a wide range of flow types.
- Detached Eddy Simulation (SST k-omega DES) – a Hybrid between SST k-omega and large eddy simulation (LES), which produces accurate results for separated, high Reynolds external aerodynamics flow applications.
- Scale Adaptive Simulation (SST k-omega SAS) – recommended for transient flow applications.
Distributed Resistance Accuracy Improvements
Distributed resistance formulation in CFD is improved in order to accurately predict pressure drop and velocity distribution in these two situations:
- Radially shaped resistance regions –including large variations in directional K values and regions not aligned with the Cartesian axes.
- Planar regions not aligned with a Cartesian axis.
Results & Visualization
Visualization capabilities in CFD have been expanded and, in the case of heat transfer, the results can be reused:
- Use CFD heat transfer results in Autodesk Simulus and Autodesk Simulation Mechanical.
- Display wall heat flux as a vector (direction and magnitude).
- Model walk-through visualization – view the results as if you were physically inside the model.
Figure 5: Model walk-through
Wall Results Accuracy Improvements
Improvements to the force and heat flux computations on wall surfaces include:
- Results computed while the simulation is running and after it is complete are more consistent.
- Weighting functions are improved in order to account for forces and fluxes near surface boundaries and to improve accuracy.
- Wall force runtime results account for shear forces.
CAD Formats & Direct Import
Autodesk Simulation CFD doesn’t import generic CAD models, but instead has always handled CAD imports though a very nice application hand-off process. After working through the process a few times you don’t mind this at all. However, Autodesk has gone further and now offers direct geometry imports as well as more application pass-through options.
New CAD application support
- PTC Creo 1.0 and 2.0
- Siemens PLM NX 8 (UG NX 8)
Direct Import Formats
- Autodesk Inventor® parts and assemblies
- Autodesk Shape Manager (.smt)
- Parasolid (.x_t)
- ACIS (.sat) (Version 7 and earlier) – this will affect old Simulation CFD studies as well, should they include newer ACIS model versions
- Pro/E assembly and part files (using the Granite kernel)
- SolidWorks parts and assemblies
- Siemens PLM NX 8 part files (UGNX)
- CAD Doctor (.sdy)
The new import/study creation process is as easy as picking ‘New Design Study’ and browsing to the file that you want to import. Additional studies can be added to a project using direct import as well.
Inventor Fusion File Preparation and Conversion
Fusion is still part of the Simulation workflow process. Two CAD formats have to continue to use Fusion as their means of importation:
- Pro/E Wildfire 3 and previous
- CATIA v5
There is a twist. The following formats must be exported to neutral formats before opening with Fusion:
- Solid Edge – export to Parasolid
- SpaceClaim – export to ACIS v7.0 or earlier
- CoCreate One Space Designer – export to ACIS v7.0 or earlier
Autodesk Vault and Autodesk 360
Autodesk Vault and Autodesk 360 support are now included.
CFD to Vault compatibility is restricted to the CFD Share File and is only compatible with Autodesk Vault 2014. While this option has some limitations, it follows the basic outline we presented at Autodesk University 2012 for manually archiving to Vault. The Share File option is very good in the respect that:
- Vault will track the version when the same name is used.
- Users can choose from four levels of study information.
- Studies are gathered into a single file.
- File compression is automatic.
- This is the same file you can use to send the study for others to use.
- Existing studies can be updated directly from Vault.
The downside to this methodology is that the geometry versions (CAD models used in the study) will not be tracked in Vault.
CFD now offers a direct connection to Autodesk 360. With this you can:
- manually upload the design study as a share file.
- manually save images of simulation results.
- automatically save your simulation data to Autodesk 360.
Image results can be automatically uploaded, allowing users to check the results remotely as soon as the simulation is complete without needing to open the design study. I like this, especially when the study takes a lot of time and you have to move on with other activities.
A new, simplified set of controls are available for accessing help and documentation in the Start & Learn ribbon tab. This tab is consistent across the other Simulation products, and makes it easier for you to find these resources when you need them.
Figure 6: Start & Learn tab
Start Here (Quick Start)
This opens an all-new section in the WikiHelp that contains a new collection of videos, articles, and tutorials designed to help new users learn the basics as quickly as possible. These are organized into three steps:
Step 1: Watch 5 Quick Start Videos
Each is approximately 1 minute long, and includes:
- CFD Story
- The Process
- Interaction Basics
- User Interface
- Keep Learning
Step 2: Perform 3 Quick Start Tutorials
These are focused on different applications, and include:
- Flow Control
- AEC Ventilation
- Electronics Cooling
Figure 7: New electronics cooling tutorial
Step 3: Apply What You've Learned
The learning map graphically organizes the information needed to learn the essentials of Simulation CFD. These are organized into nodes and roads that delineate the path you should take to learn the product as quickly as possible.
Each node is clickable and contains a collection of one or more articles, videos, or tutorials to help you learn about the selected topic. Higher-level nodes are arranged according to the typical user-process within the product. Each node can then be marked as ‘read’ in order to keep you on-track.
Note: An Internet connection is required as the Learning Map is only hosted on the Autodesk servers.
Sources: Some images and information was sourced from the online Autodesk Simulation CFD Wiki.