What would be the type of methodology you would recommend for the interaction with CFD calculations ? Do teams usually completely try to match the Gomboc foils using the K-Lift property with the CFD calculations result or do they try to dissociate them ?
Gomboc uses potential flow theory to model lift and drag on appendages in real time, which doesn’t always give great agreement with RANS. In particular, there are usually quite significant differences for parts of an appendage that are operating very close to the surface, where the assumptions of potential flow are less accurate.
A good quality RANS analysis will generally be more accurate in terms of the lift that a specific geometry or rake angle produces, but the lift:drag ratio is usually represented well by Gomboc. As such, although rake or flap angles to achieve a certain lift may differ, overall results in terms of craft performance are usually less affected by the difference between RANS and potential flow.
If determining the incidence angles of appendages is important, it is certainly good practice to validate against RANS, but we don’t recommend adjusting Gomboc’s prediction of lift as it would have downstream consequences which may produce bigger errors.
Ultimately, for the most accurate results, users can run an appendage matrix in RANS and swap out Gomboc’s appendage model for that. However, this is not typically done, and most users use Gomboc’s appendage models as they are, bearing in mind the above limitations.