Archimedes Function Error

[yman95]

My current process of using the Archimedes is as follows:

• Import .stl file
• Set mass on the 'Process' tab, then click on 'Mass' to set the numerical value
• Click the Archimede button on the 'Move' Tab

For example the geometry (attached) I'm working on right now, a hexagon with circumradius of 5m and height of 7.5m

If I set the mass to be 137909kg, the submerged volume should be 134.54 m^3 (rho=1025 kg/m^3)
137909g = -1025g*V

But BEMRosetta calculates submerged volume as 211.1 m^3?

Am I missing something or is the function not working properly?
Hexagon_10m_centered.zip

Best,
Yi

[izabala123]

Thank you Yi 😊

You are right. Hopefully, it is fixed now.

Best regards
Iñaki

[yman95]

@izabala123 I just downloaded the codes again, but it seems like it hasn't been updated?

[izabala123]

Hi Yi

Please download it from https://github.com/BEMRosetta/BEMRosetta/releases

It was uploaded some hour ago.
In some days I will update the source code.

Best regards
Iñaki

[yman95]

@izabala123 Got it, thanks.

On the same issue, clicking the Archimedes button multiple times will result in the geometry shifting every time, presumably taking the current unsubmerged part as the actual weight (total-buoyancy force) for the Archimedes calculation.

Also, setting a large enough mass (weight>buoyancy force), on the first click will set it to the default equilibrium and the following clicks will move the geometry underneath the water. It's probably a good idea to throw a message saying that the geometry will sink.
For example, I tried another material with (rho=7800kg/m^3), this will give my geometry a mass of 1132306.6kg, which will need 1104m^3 of submerged volume to be afloat. My geometry has a maximum of 487.14m^3, so it will sink.

Appreciate your work,
Yi

[izabala123]

Hi Yi

Thank you for your report. Yes, that was the behaviour of the function. It was a problem in the non-linear fitting function used to get the right draft. I have run you example and others and it works apparently perfect. Please download the exe from https://github.com/BEMRosetta/BEMRosetta/releases/download/November_2023/BEMRosetta.exe and give me your feedback. Thank you.

Iñaki