Openfast: Visualize mooring lines with VTK

Dear @bartoszstachowicz,

Good question. The inability to visualize the mooring lines is an unfortunate limitation of the current visualization capability of OpenFAST. And not just for MAP++, but also for the other mooring modules of OpenFAST: MoorDyn and FEAMooring. Just a few comments:

• The mooring lines are not currently visualized because the mooring modules currently interact with other modules through their fairlead connections only (for the mooring-substructure interaction), so, displacement and loading of points along each mooring line are not known by the OpenFAST glue code.

• To add the visualization capability, it would likely be best to add an output of the mooring modules related to the displacement of nodes along each mooring line (even if this output does not have an associated interaction with other modules). A line2 mesh should be used to ensure that visualization functionality can interpret the interconnection between the point elements.

• MAP++ solves each mooring line analytically, and so, each line is not numerically discretized (of course, there are nodes at the interconnections between each mooring line). This may make it difficult to visualize the catenary shape of each line in MAP++, unless nodes are artificially added to the solution. MoorDyn and FEAMooring do involve discretization of each mooring line into multiple line segments.

I'll let others comment on how much effort it would be to develop this new functionality.

Best regards,

Dear OpenFAST team,
I gave a try this weekend and it kind of works. In MAP C++ there is a routine already to evaluate the coordinates of a given number of points along the line: map_plot_x_array
I had to modify outputs, to create a single mesh for all the lines in the simulation, and initial inputs to be able to set the element length.
However, there is a shift in connect nodes, in the local line x-direction, when plotted. I hope this is only true for the plotting routine :).
Maybe someone knows why this is? I couldn't figure this out yet.
I'm attaching some pictures of the shift.

Kindest regards,

B.S.

@bartoszstachowicz, That's a really nice addition! I'm not entirely sure why there is a shift in the x-direction of the cables. I would have to look at your implementation to tell if it is an artifact of the VTK export, or a bug in MAP++.

Is this feature something you would like to contribute to the OpenFAST community? If so, would you like to create a pull request to the dev branch with your code addition?

@andrew-platt , Hello, yes sure, as soon as I have a moment to tidy it up a bit and learn how this works with pull requests.