MoorDyn dynamic relaxation and fixed bodies

[RyanDavies19]

Feature or improvement description
Dynamic relaxation fix:

• Fixes an indexing error in MoorDyn that caused the fairlead tensions in the dynamic relaxation step to not be properly compared to the previous 9 values when checking for stability.
• Cleans up some output statements to look cleaner

Fixed body fix:

• Previously fixed bodies were not initialized and so their locations and orientation defaulted to 0's
• This update allows users to use fixed bodies at any location specified in the input file

Related issue, if one exists
FloatingArrayDesign/MoorDyn#160
FloatingArrayDesign/MoorDyn#156

Impacted areas of the software
MoorDyn

Additional supporting information
n/a

Test results, if applicable
Dynamic relaxation for a single catenary chain:

• Before:
  

• After:
  

Two fixed bodies with connecting line (made of three line segments connected with free points):

• Before:
  

• After:
  

[andrew-platt]

The following regression tests had some changes in the results and were updated accordingly. Below are some samples of the results and the effects they had on the regression tests.

5MW_OC4Semi_WSt_WavesWN & 5MW_OC4Semi_WSt_WavesWN_py

Slight difference in early transients for the mooring lines. This causes really small differences in platform sway. `StC_test_OC4Semi` changes similarly.

py_md_5MW_OC4Semi & md_5MW_OC4Semi

Slight changes in mooring line tensions. Note that there are some differences between these two test cases, likely due to motions that have not been updated.

MHK_RM1_Floating

Line tensions are a bit different leading to slightly different motions of the platform.