Hi,
The MOSES provide many samples for users in C:\Program Files\Bentley\Engineering\MOSES CONNECT Edition V10.10\hdesk\runs\samples. One about CALM system mooring analysis is CALM.CIF & CALM.DAT in MOORING folder. In default, it does a time domain analysis of 600 seconds with a time step as 0.5. But when I change total time to 6000 and time step to 0.1. Something happens, Simulation Terminated Due to Instability at event about 2100.
That confuses me, Why does it give a non-convergent result with a smaller time step?
Hi Ju Peng,
Attached is a calm.cif and a calm.dat with change in time domain settings. My analysis ran to 2500 seconds without problems. The time step is .1.
I included the log file in the attachment.
This is not what you are getting?
Georgina Maldonadocalm.zip
Thanks for your reply.
Your files have a little difference from mine. It's about -cs_current setting and -period setting in g_pressure. My -cs_current is 0 0 1 and -period is omitted.
With your files, I do 2 analysis.
First one, I change the total time to 10000 with time step as 0.1. The result shows that the tanker has very big yaw after about 5300. (first picture)
Second one, the total time is still 10000 and time step is set to 0.5. The result shows no big yaw occurs. (second picture)
Which one should I believe?
Another question is,
In your calm.dat, the command "#tanker 300" is used to calculate current and wind force, and the tanker's piece has an option -cs_current 1 1 1 which will calculate the current force too.
Does it mean that the current force will be calculated twice?
HI Ju Peng,
The purpose of the files in the samples directory is to show some common command sequences. Many times we have changed the values so that the files will take a short time to run. These files are not intended as project ready.
You asked two questions in your previous post.
Question 1: Which one should I believe?
I cannot answer that question. I am not part of project support. Choosing a time step is an engineering decision and is different for every project. I can tell you that when I worked as an engineer we would start with a time step of 0.25 and start reducing it from there. We would compare from the reduction. When the numbers stopped changing we would consider that for the timestep for the analysis.
Questions 2: Does it mean that the current force will be calculated twice?
Yes, the files have both #tanker and -cs_curr and -cs_wind turned on. Current force will include that defined with #tanker and that defined with -cs_curr. Wind force will include that defined with #tanker and -cs_wind.
I hope this helps.
Georgina Maldonado