Search found 18 matches

by Matt.Hall
Fri Aug 30, 2019 10:44 am
Forum: Structural Analysis
Topic: Response in Long term simulations and different MoorDyn time step
Replies: 4
Views: 89

Re: Response in Long term simulations and different MoorDyn time step

Hi Francisco, Thanks for providing the plots that show the problem, and also checking with the similar problem noted by a user last year. What you're showing isn't a behavior I'm familiar with, and I haven't been able to think of what could cause it within the MoorDyn model. To help eliminate possib...
by Matt.Hall
Fri Aug 23, 2019 4:29 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Compile MoorDyn C++ source files in Linux and some error of calculations
Replies: 1
Views: 233

Re: Compile MoorDyn C++ source files in Linux and some error of calculations

Sorry to not have responded sooner. Here are some answers: (1) Yes, this is the right way to compile it. (2) You would need to share with me the specifics of the outputs you are looking at and what their values are for me to be able to offer a suggestion about this. (3) If you would like to use this...
by Matt.Hall
Fri Aug 23, 2019 4:13 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Steps to compile MoorDyn
Replies: 4
Views: 498

Re: Steps to compile MoorDyn

This is an interesting problem that I haven't figured out yet. I see that you're using the standard OC4-DeepCwind mooring system description and it was a surprise to me that the simulation was unstable (the NaN value errors). These errors don't occur in MoorDyn v1.01.00 but do occur in v1.01.01, whi...
by Matt.Hall
Fri Aug 23, 2019 10:27 am
Forum: Structural Analysis
Topic: MoorDyn Response in Pitch/Roll
Replies: 2
Views: 65

Re: MoorDyn Response in Pitch/Roll

Hi Francisco, The frequency of those tension oscillations could be affected by hydrodynamic drag as well as the internal damping that you mentioned, so I'd double check drag coefficients just to be safe. That said, because the oscillations seem to decay more rapidly than the pitch motion, I wonder i...
by Matt.Hall
Mon Jul 01, 2019 5:39 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Steps to compile MoorDyn
Replies: 4
Views: 498

Re: Steps to compile MoorDyn

Hi, If you are simply looking to use MoorDyn, I'd recommend downloading the already compiled libraries rather than the source code. If you are looking to edit the code, please see below. For Windows, the makefiles provided with MoorDyn were set up for use with MinGW. If you don't already have it, I'...
by Matt.Hall
Wed Apr 03, 2019 7:07 pm
Forum: General
Topic: Lay length of Mooring line
Replies: 6
Views: 978

Re: Lay length of Mooring line

Hi Krishnaveni, I agree with Jason that your proposed approach is a good solution. Because MoorDyn is a lumped-mass model, the calculated touchdown length will change abruptly as a node touches down or lifts off. However, if you have enough nodes (short enough segments) the jumps in touchdown length...
by Matt.Hall
Fri Dec 14, 2018 3:06 pm
Forum: Airfoils
Topic: Making fault
Replies: 24
Views: 7836

Re: Making fault

Hi Yichau.Liu, Simulating mooring line failures would be an interesting capability. I've thought of the idea itself, but never how to go about realizing it in MoorDyn. Here are a few initial thoughts in case they are of help. Most of MoorDyn's information about the mooring system is stored in "...
by Matt.Hall
Fri Dec 14, 2018 2:01 pm
Forum: General
Topic: Available output channels from MoorDyn module
Replies: 5
Views: 2653

Re: Available output channels from MoorDyn module

Hi Paul,

Yeah, that sounds like the right approach. Summing the Con#fZ outputs (where # is connection number) for all the fairlead ("vessel") connections should give the total vertical force you're looking for. Glad there's a solution available for what you're looking for.

Best,
Matt
by Matt.Hall
Thu Dec 13, 2018 12:04 pm
Forum: General
Topic: Available output channels from MoorDyn module
Replies: 5
Views: 2653

Re: Available output channels from MoorDyn module

Hi Paul, MoorDyn in FAST isn't currently set up to output the net force components along the line - mostly because I wasn't sure this sort of output would be useful and have a clear physical meaning. The net forces on a node internal to the line would include tensions pulling in opposite directions ...
by Matt.Hall
Tue Oct 18, 2016 10:29 am
Forum: General
Topic: Problems with units in the outputs
Replies: 16
Views: 2711

Re: Problems with units in the outputs

Dear Luigia, The outputs directly from MoorDyn, including the "N" units, seem to be the correct ones in this case. 9E5 N is the right order of magnitude. I'll look through the code and see if I have an error in how MoorDyn passes the fairlead tensions to FAST. Did you mention that there wa...
by Matt.Hall
Tue Aug 16, 2016 8:29 am
Forum: General
Topic: Available output channels from MoorDyn module
Replies: 5
Views: 2653

Re: Available output channels from MoorDyn module

Hi, What version of FAST and MoorDyn are you using? I didn't have all the output channels set up in the first MoorDyn versions, but the "Con4pX"-type outputs should be working in the latest version. If updating doesn't solve the problem or you're already using the latest version, let me kn...
by Matt.Hall
Wed Jun 03, 2015 1:50 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Compiling FAST under Windows 7 with gfortran
Replies: 16
Views: 7433

Re: Compiling FAST under Windows 7 with gfortran

I know this is an old thread now, but just as an update: I too encountered the internal error problem with my installed version of gfortran, but the latest version from http://sourceforge.net/projects/mingw-w64/ (gfortran version 5.1.0) seems to have it solved.
Cheers,
Matt
by Matt.Hall
Mon Oct 17, 2011 5:18 pm
Forum: Computer-Aided Engineering Software Tools
Topic: MCrunch issue with Rainflow Cycle Exceedance plot
Replies: 7
Views: 5618

Re: MCrunch issue with Rainflow Cycle Exceedance plot

Hi Subin or Marshall, I know it's been some time since this thread was active, but I am also confused as to what "typeLMF" could mean in the MCrunch input files, and was hoping one of you might be able to tell me. Cheers.

Matt
by Matt.Hall
Thu Aug 25, 2011 2:31 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Irregular wave kinematics from FAST
Replies: 2
Views: 1571

Re: Irregular wave kinematics from FAST

Thanks, Jason. That was just what I needed to get things working. For some reason following equation (6) from the paper I still had discrepancies in the results, but using WaveElevC0 in the equation you typed out worked perfectly.

Best regards,
Matt
by Matt.Hall
Wed Aug 24, 2011 5:16 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Irregular wave kinematics from FAST
Replies: 2
Views: 1571

Irregular wave kinematics from FAST

Hi Jason, In my efforts to couple in different mooring models, I've been working to transmit the discrete wave spectrum generated by FAST to an external model. I am using values from within subroutine InitWaves of height, period, wave number, and phase of each discrete frequency component. These val...

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