You have four methods to bring the data from Fluent into EnSight
Reading the .cas.h5/.dat.h5 natively in EnSight.
Export EnSight Case Gold format from within Fluent.
Export Common Fluids Format (CFF Post) from within Fluent.
Export EnSight DVS (Data Visualization Store) from either a running session (in-situ), or to disk from within Fluent.
Which One to Choose
In general and common use cases requiring generic post processing needs, pick your variables of interest and export Common Fluids Format (.cas.post/.dat.post). In EnSight, use the Ansys Post File reader to import the .cas.post/.dat.post files.
For large data, where parallel is needed for capacity, pick your variables and export EnSight Case Gold nodal.
If you want to have a look at the raw restart data, you can load cas.h5/dat.h5, but be aware that some of the dat.h5 variable values are raw values intended for Fluent restart.
DVS export offers several advantages in key use cases. If you are attempting to post process the results of the simulation while it is running, using DVS in-situ export to EnSight allows for a direct memory transfer to EnSight for post-processing a running simulation. In addition, DVS provides great performance for large models (>100M cells) by utilizing pre-partitioned data exported from each solver process. Finally, DVS’s other main advantage is in efficient data storage. It provides data de-duplication to reduce duplicate data written, as well as using HDF5 compression to further reduce file size on disk.
This method of data transfer is under active development, with updates available in subsequent releases.
See Ansys Fluids Post Reader within the Ansys EnSight User Manual for current limitations and use-cases. Where these limitations are issues for your particular post processing needs, utilizing the EnSight Case Gold export should provide a workable method.
The CFF Post method has effectively replaced the use of the .cdat file method.
Note: For some datasets saved from a version of Fluent prior to 2020 R1, EnSight’s Fluent HDF5 Restart reader fails to read the .cas.h5/.dat.h5 file. Resaving these datasets using a version of Fluent of version 2020 R1 or later resolves the issue, and can be read into EnSight.
| Aspect | EnSight Case Format | Fluent HDF5 Reader (.cas.h5/.dat.h5) | Ansys CFF Post | EnSight DVS Format |
|---|---|---|---|---|
| Files | A lot of files and disk space - for each timestep, there will be one geometry file (if transient geometry) + one file for each variable. So, the number of files grows quickly for transient simulations | Less disk space and files than the EnSight Case Gold format | File size will depend heavily on how many variables are exported. One set of files for each timestep. | File size will depend upon how many variables written. A singular .dvs header file is written, along with one directory for each flow solver (both transient or steady state). |
| Performance | This is the native format of EnSight. The software is optimized for this format. Therefore, using this format will result in less CPU memory and ~ 3X quicker loading time | The Fluent reader is slower and requires more memory |
Both memory usage and performance will be in between EnSight Case Format and Fluent HDF5 Reader. | Memory usage will be larger than EnSight Case gold, but smaller than CFF Post or Fluent Restart reader. |
| Variables on Boundaries | Fluent does the extrapolation of the variables onto the boundary parts and exports them. Therefore, the values are present on the boundary parts and are correctly calculated | Fluent doesn't export the values of all variables onto the symmetry plane parts/boundary parts. |
Variables should be comparable to those shown within Fluent Post. | Variables should be comparable to those shown within Fluent Post. |
| Variables on Symmetry Planes | Similar to the point above, Fluent calculates the value of the variables on the symmetry plane parts and exports them into the Case Gold | Fluent doesn't export the values of all variables onto the symmetry plane parts/boundary parts. |
Variables should be comparable to those shown within Fluent Post. | Variables should be comparable to those shown within Fluent Post. |
| Discrete Phase | Discrete Phase can be exported from Fluent to Measured Format and included in the EnSight Case format. | No discrete phase |
Not available in CFF Post format yet. | Not yet available. |
| Computing Variables | For Volume-based calculations (for example Volume Weighted average), the most accurate method is to use Elemental Variables (not Nodal). Specify Elemental variables on export. | The elemental-only variables available in the .cas/.dat reader are well suited for volume based calculations. |
Currently, all the physics variables are nodal. All mesh and topology variables are elemental. | Same guidelines as EnSight Case Gold (choose Nodal or Elemental, depending upon the accuracy and comparisons required. |
Tip: Utilize the Fluent export to EnSight Case Format (nodal data) as the most appropriate, quickest, and most accurate method for getting your data from Fluent to EnSight.