Increase Hydrodyn and Subdyn Element Segments

Hi, Have Good Time

I wanted to increase the number of pile element divisions in both Hydrodyn and Subdyn, also my goal is to output the wave force at the depth of the pile in more nodes.

I modified the Hydrodyn module as shown below and entered the specifications of the new elements
But when running, I encountered the following error, which shows that adding new lines to the Hydrodyn module causes problems.
There is a place, please help me.

Best Regards

Dear @Mohammadreza.Akbarza,

It looks like you’ve defined 33 joints in HydroDyn but left NJoints = 2; setting NJoints = 33 should solve this issue. Note that for a given member of HydroDyn, you can change the discretization by setting MDivSize at the member level rather than be adding more joints and members.

Best regards,

Dear Jankam

Thank you for your reply

As you said, I looked for the MDivSize setting in the HydroDyn input files and I couldn’t find it, what I found out is that probably in the new version, this setting no longer exists.
If possible, I would be happy to introduce a link or a reference so that I can be sure

Dear @Mohammadreza.Akbarza,

MDivSize still exists in the HydroDyn primary input file. You can find the input in the table of member-level properties (column 6) in the MEMBERS section of the input file. And the input is documented in the online HydroDyn documentation on readthedocs here: Input Files — OpenFAST v3.5.0 documentation.

Best regards,

Dear Jason

Thanks for your tip, I found MDivSize.
At this stage, I want to output the outputs related to the drag and inertia forces on the nodes, according to the OpenFast documentation, I entered the outputs into the HydroDyn input file, but all the outputs are zero.
I think I have not defined the inputs correctly, if possible, check the figure below

Of course, I checked a number of topics in this field, but I did not find this case

Best Regards.

Dear @Mohammadreza.Akbarza,

It looks like you are requesting to output the lumped hydrodynamic loads at joints. But these are only useful for the axial hydrodynamic loads applied at member ends. To output the distributed (force per unit length) hydrodynamic loads along the member, you should use MαNβFDxi and MαNβFIxi for the drag and inertia forces, respectively, at output node Nβ of output member Mα.

Best regards,