Dynamic Positioning - Deepwater Application

Hello Haydar,

There are several files available for DP analysis in the test directory.  The basic DP capabilities can be analyzed with the commands in the file cont_mean.cif.  This file can be found in the following directory.  (Assuming you did the default MOSES installation.)

C:\Program Files\Bentley\Engineering\MOSES CONNECT Edition V11\hdesk\runs\tests\conn

The topic of dynamic positioning usually requires a thread.  Some analyses include a time domain analysis and some analyses include multiple bodies.  If you would like to continue the thread outside of Bentley Communities, please contact me at georgina.maldonado@bentley.com to continue the conversation.

Georgina Maldonado

Hello Haydar,

There are several files available for DP analysis in the test directory.  The basic DP capabilities can be analyzed with the commands in the file cont_mean.cif.  This file can be found in the following directory.  (Assuming you did the default MOSES installation.)

C:\Program Files\Bentley\Engineering\MOSES CONNECT Edition V11\hdesk\runs\tests\conn

The topic of dynamic positioning usually requires a thread.  Some analyses include a time domain analysis and some analyses include multiple bodies.  If you would like to continue the thread outside of Bentley Communities, please contact me at georgina.maldonado@bentley.com to continue the conversation.

Georgina Maldonado

Hello Georgina,

I'm interested in DP analysis, too. Especially, estimating whether vessel can keep its position under certain weather condition.

I saw cont_mean.cif you recommended above, i understood almost every command written in there.
But I cannot find information of command prop_max in line 52.
Can you tell me the directory of the macro prop_max.mac or explain how does it works?

And is there any sample file using command 'propulsion' noted in 'MOSES REFERENCE MANUAL XVI.F Obtaining Propulsion/Weather Envelopes'?
I cannot find sample for this command.

thanks.

Hi Kim Hyun Joong,

It appears your thread is inside the thread for Haydar.  You can start your own thread if you prefer.

I wanted to let you know we are having a SIG (Special Interest Group) presentation on this topic.  Please see the below link.  The command prop_max is one of the commands that will be discussed.

Here is a short description of the prop_mas command.

The environment command defines a wave, wind, and current.  The prop_max starts with what is defined with the &ENV command.  The prop_max command does three loops.  Let us take the order: wave, wind, then current.

The first is the wave loop.

The wind and current are held constant during the wave loop.  I mean the velocity and global direction are held constant.  The wave global direction is also held constant.  The height of the wave changesin this loop.  The wave height is increased until one of the propellers reaches a maximum.  The wave height that resulted in a propeller having a maximum is reported.  This is first done for a rotation of 0 degrees.  Then the vessel is rotated 10 degrees.

For the 10 degree rotation the same calculations are done.

The wind and current velocity and global direction are held constant. The wave global direction is also held constant.  The height of the wave is changed in this loop.  The wave height is increased until one of the propellers reaches a maximum

The calculations for wave continue for 10 degree rotations until the rotation is 360 degrees.

After the wave calculation are complete the wind calculations begin.

Now we are in the wind loop.

The wave and current are held constant during the wind loop. The velocity and global direction for the current is help constant.  The wave spectrum and the global direction is held constant.  The wind global direction is also held constant.  The wind velocity changes in this loop.  The wind velocity is increased until one of the propellers reaches a maximum.  The wind velocity that resulted in a propeller having a maximum is reported.

The vessel is then rotation 10 degrees and the wind calculation is repeated.

Once the wind calculations reach a rotation of 360 degrees the current force calculations begin.

The current force calculations are done similar to the wind calculation.

I hope this helps. 

Please sign up for the below SIG presentation.

Cheers,

Georgina Maldonado

https://event.on24.com/eventRegistration/EventLobbyServlet?target=reg20.jsp&partnerref=Email&eventid=2185844&sessionid=1&key=5EFB2237E734808E948090DEC0C4017F&regTag=&sourcepage=register

Hello Georgina,

Thanks for your answer
I understood how prop_max works, but i still have a question for this command.

I think prop_max should be affected by characteristic of propulsion connector.
(~prop in cont_mean.cif)

To prove this idea, I analyze examples with changing Max_thrust value of connector '~prop'.
I test 4 condition, Max_thrust 100, 200, 300, 400.
The Analysis result shows that As Max_thrust increases, Max wind and Max current result increases. And those results show various values for each condition.

But Max wave result shows only 10(input value) and 715.54

Column below is my assumption through this output. I think 715.54 is maximum value of iteration. If input value of current and wind can move the barge, Max wave value printed 10(input value).
But when current and wind cannot move the barge, wave iteration reaches maximum value 715.54 and print it as output. So wave does not affect x,y direction displacement of barge.

Does my assumption right? I cannot sure it is right.

I want to attend SIG you suggested, but 10:00 AM EST is 12:00 AM for Korean standard time, it is hard to attend on time.
If there is some way to listen SIG for later, please tell me.

Thanks.

Hi Hyunjoong, 

It has been a whole. How are you? You posted the part of output but it seems something went wrong. 

I am speculating you incremented the maximum capacity of the thrust then check the variation of the result. If so, the wave profile reported in the out file should change for every heading, not only with two values. 

Please let me know if I misunderstand you and you can email me if you want to show me your output.

Thank you.

Best regards,

Bitna

Hello Bit-na,

Glad to see you again.

It is first time i use this command, there might be some mistakes.
I upload cont_mean.cif and cont_mean_100.cif which Max_thrust of ~prop modified as 100.
cont_mean_100.txt(output file) shows 10 and 715.54 for max wave.200205_DP_TEST.zip

And another minor question, Max_thrust of propulsion connector means maximum thrust of the unit in bforce units. According to Reference Manual For MOSES, XII.M.6

Then which one does max_thrust value mean? engine power (kW) or Bollard pull performance (ton)

Since I had not attended MOSES lecture, i have lots of miscellaneous question.
I try to solve them by reference manual and examples, but i could not find clarified solution.
Thank you for your kind reply despite the low level of questions.

Thanks.