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-   -   High speed planing hulls - prediction of drag force (https://www.cfd-online.com/Forums/openfoam-solving/206456-high-speed-planing-hulls-prediction-drag-force.html)

amh@inventas.no September 7, 2018 03:27

High speed planing hulls - prediction of drag force
 
I am running simulations on a planing hull at 30 knots, and I have done this with my own custom CFD settings in v1712 (based on ITTC recommendations etc.) and I have run this on a web-based platform(also openfoam, but different version). I have also run the same hull/speed in Starccm and I am getting large deviations on drag force which I am unable to explain.
The web-based platform uses a different version (I do not know which one).
However, the web-based platform and starccm do agree on the drag force being ca. 15kN, however my custom CFD simulations show 20,5kN with 1,5millions cells. I have tried different mesh refinement between 205k and 5,6M cells but get ca. the same results around 20kN. I have tried many different settings to try and find the cause of the large deviation, but so far no good.

I think now the only things I have not checked are: different openfoam versions, and effect of ventilation (I have some ventilation in my simulations). However I cannot believe that ventilation can play such a large role. And also, the web-based platform predicts a lower heave which would normally mean a higher drag, but it is the opposite way around.

Do you have any thoughts on this subject? Ps: I am still running more simulations to try and identify the cause (i.e running on both v1612 and v1712). Could there be a large difference between v1712 and per se v5.0 or v4.0?


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