With all of the buzz of what’s new in SOLIDWORKS 2016, and even SOLIDWORKS Simulation 2016, many engineers that specialize in computational fluid dynamics (CFD) might feel left out. However, the team at SOLIDWORKS has created a series of updates to their CFD tool, SOLIDWORKS Flow Simulation, in the 2016 release.

Meshing Is Key to SOLIDWORKS Flow Simulation 2016

Lotfi Derbal, product portfolio manager for SOLIDWORKS Flow Simulation at Dassault Systèmes, notes that perhaps the most important improvement to the software is its meshing enhancements.

“For any simulation, the time spent on meshing is important to the user,” said Derbal. “When you have a large model, it means more CPU time. The compromise is: do you want a quick automatic mesh, or should you spend time to optimize the size of the global mesh?”

Typically, an automatic mesh will yield a less desirable computational model than one that is manually optimized by the user. However, Derbal notes that “with current enhancement of the mesh, even with manual operation, you can optimize the mesh very fast … faster than the last version.”

Flow Simulation also has the ability to create more uniform meshes for improved convergence and accuracy. This meshing ability can be used for both internal and external flows. Users are able to set local mesh domains within which the mesh is optimized. To define these domains more easily, Flow Simulation 2016 allows users to directly create domains around a specific design detail without adding a geometric feature, which was previously needed. Each domain can be set to have either a particular cell size or cell number for local optimization of the mesh to capture all the detail of the model while still maintaining a uniform mesh around that model.

Another added tool to SOLIDWORKS Flow Simulation is the mesh plot. This tool creates a quick reference the engineer can use to see where the mesh still needs to be refined.

The plot shows how many levels of refinement a mesh cell has undergone from the initial global mesh size. The higher the number, the more times a cell’s size has been reduced and thus finer the mesh. This information is useful in understanding if the mesh is well suited for its purpose of capturing both the geometry and the resulting flow field.

Nested Iterations Reduce CFD Computations for Transient Analysis

A significant time saver for engineers will be the ability to use nested iterations when computing a transient analysis. Derbal explained that simulations that traditionally need small time steps can take days or weeks to solve.

“If the simulation requires a time step of say 0.1 milliseconds and you want to investigate a range of 5 seconds total, then you are looking at 50,000 time steps,” said Derbal. “A compressible gas flow in a vessel, for example, can take days to calculate.”

With the nested iterations, however, much larger time steps are permissible, reducing your computational time considerably. Derbal noted that the new computation will not be able to capture tiny transient details in the results, so the accuracy may be reduced by a small percentage. However, if that accuracy level is good enough for your simulation, then the time savings is well worth it.

Using nested iterations, SOLIDWORKS Flow Simulation can solve the same problem with larger time steps, thereby reducing overall computational time. Image courtesy of SOLIDWORKS.

“The problem with transient flow is that you have to follow the changing flow field,” said Derbal. “The goal of nested iterations is to get a value at a specific time stamp, where there is no interest in intermediate values. Overall, fewer time steps are needed and you get the desired time results faster.”

However, users should be aware that this new transient solver isn’t compatible with all CFD models in the 2016 version. Although full integration is expected for the 2017 release, nested iterations will currently not work on simulations with:

• Cavitation
• High mach numbers
• Rotation
• Condensation, humidity, steam and real gases

Other improvements to the transient solver include the ability to reduce the size of result data files by saving only specific parameters and the ability to produce time-averaged results.

Mirroring Symmetrical Simulations without Cutting Geometry

Solving a model in Flow Simulation with symmetry isn’t a new feature. Users were able to cut the computational domain in half, declare that domain face as a plane of symmetry and then perform their analysis.

What is new in SOLIDWORKS Flow Simulation 2016 is that now results from a simulation using symmetry can be mirrored to display the results of a full model.

Even though only half of the wing was analyzed with symmetry, results can be mirrored to show the full model. Image courtesy of SOLIDWORKS.

Considering that you can cut the computational domain not only in half but again to solve only a quarter of the geometry of a cylindrical pipe, for example, there is significant time savings to gain by employing symmetry in an analysis.  But you don’t have to sacrifice displaying the results on only a portion of the model for unknowing observers who might ask where the rest of the model has gone.

Importing Sunlight Properties for Analysis and Photo Realism

Another interesting feature in SOLIDWORKS Flow Simulation is the ability to import a Solar Access study from SOLIDWORKS into solar radiation simulations.

Solar data is not just for rendering shadows on your presentation images anymore, because there is direct applicability in simulations as well.

“Users can directly import the sunlight properties for CFD calculations so that the flow simulation doesn’t need to recalculate the view factor and then use that to deal with the radiation effect,” said Derbal.

The solar heat gain on the face of a body is a critical piece of information when looking into, for example, the air conditioning system in a car or assessing the HVAC loads of a skyscraper.

“When one part of a body is in the sunlight and the other parts are partially or fully shaded, there are different thermal values on each face,” explained Derbal. “So to calculate the flow simulation properly, knowing about the solar rays is important in getting the right thermal flux on each face.”

For more information on what is new in SOLIDWORKS 2016, follow this link.

About the Author

Shawn Wasserman (@ShawnWasserman) is the Internet of Things (IoT) and Simulation Editor at ENGINEERING.com. He is passionate about ensuring engineers make the right decisions when using computer-aided engineering (CAE) software and IoT development tools. Shawn has a Masters in Bio-Engineering from the University of Guelph and a BASc in Chemical Engineering from the University of Waterloo.