At the 26th International Towing Tank Conference (ITTC), held 28 Aug – 03 Sep 2011, their specialist committee on CFD presented conclusions and suggestions for current and future CFD applications, respectively.
Specifically with regard to the difficulties and limitations of CFD that must be overcome to achieve wider use and acceptance, the challenges posed by meshing (cited by 42% of respondents) were a close second to concerns about the accuracy of CFD results (44%).
The report is not explicit about why meshing ranks so highly as a difficulty but the issue of geometric complexity in the form of fully appended and realistic hull forms is repeatedly mentioned in various other contexts. One can therefore infer geometric complexity as the source of complaints about meshing. Complexity of CFD (noted on the bar chart above as “Complexity”) may also include these concerns and it’s likely that turnaround time (noted as “Turnaround”) is also influenced by the time to mesh complicated shapes.
As with most things in engineering, this is part of a good news/bad news situation. The good news is that the application of unstructured, hybrid, and overset meshing techniques to marine hydrodynamics, a field that had been dominated by structured gridding for decades, has enabled the timely application of CFD to realistic geometries. The fact that realistic geometries are also more complex is the bad news side of the situation. Meshing giveth and meshing taketh away.
What’s almost more interesting than the meshing news is the fact that practitioners are mostly concerned about the accuracy of their CFD results (“Accuracy”). It’s interesting because the survey results indicate that users, 71% of whom claim to be have at least intermediate proficiency with CFD, apply quality checks to computations quite often. In fact, 61% claim to do so “as often as I can.” Yet despite this, accuracy remains the top concern.
Perhaps contributing to this is the fact that these same practitioners use three other quality check methods over the ITTC’s own guidelines. This is not to say that the ITTC has superior procedures to all other organizations or that best practices are somehow faulty but there might be some correlation. After all, the ITTC has a large body of benchmark cases available for validation and verification. However, the report also cites the lack of good quality, detailed data for full-scale and fully-appended hulls as an impediment to future progress.
Overall, the report provides fantastic insight into the state of marine hydrodynamic CFD and covers topics from physical modeling (e.g. free surfaces and turbulence) to numerical modeling (e.g. numerical algorithms and grids).
- Main International Towing Tank Conference (ITTC) website
- The Specialist Committee on Computational Fluid Dynamics, Final Report and Recommendations to the 26th ITTC (PDF)
- The full list of ITTC reports
- ITTC Recommended Procedures and Guidelines, Practical Guidelines for Ship CFD Applications (PDF)
Pointwise and Marine CFD
Pointwise has a long history of working with customers on applied CFD for marine hydrodynamics, from surface ships and submarines to hydrology. To see what’s possible, check out the marine applications on our website and then start your no-cost, no-obligation trial of the software.