Dear All,
I am naval architect currently working on Jackup Barge stability .usually all the stability jobs are performed on Autoship. but for performing MODU stability , we are required to run the stability in different wind direction.this is not possible in auto ship and therefore i was trying to find a way around by simulating the stability in Moses.
I have prepared Hull Model in .DAT file. and I could compare the existing Hydrostatic and Tank particulars with the My model and is found to be fairly Matching. However , I couldn't compare the KN values in Moses since i was not able to simulate the KN values in Moses.
QUERY NO.1
HOW TO GET KN VALUES IN MOSES.
Refer attached mu .CIF file Commands used to run MAX Allowable VCG.
&device -oecho no -pri device -g_def device &style output -lpi 9&title STABILITYINMODELHSTATICS
&status nwt_down&status wt_down kg_allow -draft 2.4 \ -wind 100 50 \ -damage SWB1P \ -yaw 0 \ -i_gm 0.15 \ -i_ar_ratio 1.4 \ -i_dang_t1 0 \ -d_gm 0 \ -d_range 10 \ -d_dwt_t1 0 END&finish
QUERY NO.2
HOW TO WIND HEELING MOMENT IN DIFFERENT WIND DIRECTIONS
Also attaching my.DAT FILE for reference
0488.NOUF.DAT
Hello Adith,
Via a separate post I gave you details how to contact me directly. But let me try to respond to your questions.
Question 1
Calculating righting arm curves via KN is a historical method. With today’s software, MOSES, the righting arm calculations can be done quickly and accurately.
KN curves are:
KN = GZ – KG*sin(theta)
MOSES computes GZ. KG is usually an input value. Calculating KG*sin(theta) is all user input and can be done in your spreadsheet. The difficult math is in computing GZ. If you plan to compare KN curves via the equation above, you are comparing MOSES’es ability to calculation sin(theta). You would be using the GZ from MOSES then subtracting the manually input values to get KN.
You need the GZ at several drafts for a heel of 0 degrees from MOSES. You can calculate the KG*sin(theta).
Question 2
You can change the direction of the wind with the "-yaw" option on the "kg_allow" command. You can put a list. For example "kg_allow -options -yaw 0 10 30 80 90 ".
I hope this helps.
Georgina Maldonado
1) for Calculation GZ , I suppose " RARM " command may be used for various displacement . and KN to be compared for various heel angles via excel sheet.
2) am able to run wind in different direction, but i am not able to get the wind heeling moment reports.i want to know how much is the wind moment acting in different wind direction and displacement.
example attached for ref.
/cfs-file/__key/communityserver-discussions-components-files/343374/wind-heeling-moment.pdf
Hi Adith,
Attached please find stability.zip. This is a set of files to show how to use the commands. The files are not intended to demonstrate an engineering analysis. These files use the dat file you sent earlier.
In the ans directory there is the output file. Please see out00001.txt. Page 1 and 2 of the output is the curves of form. Page 3 is the righting arm and heeling arms for a wind speed of 100 knots. Please see the line that reads "Arms About Axis Yaed 0.0 Deg from Vessel X". This means the wind is from the positive y axis toward the negative axis. It is conventional to say this is starboard to port. Of course, this depends on the model.
Please see the columns labeled "Heeling". Those are the wind heeling moments.
Page 4 is the results for a very simple stability check. The checks are not meant to be regulation checks.
Pages 5 and 6 are similar to pages 3 and 4. In pages 5 and 6 the wind direction is 45 deg from the vessel X.
Pages 7 to the end are for the calculated allowable KG. Please look for the reading "Arms About Axis Yawed." This line wind direction.
Georgina Maldonadostability.zip
THANK YOU
Hi Georgina,
want to ask related to this, so for Axis yawed 90 deg means wind from stern to bow?
kind regards
Hi Nafuat,
Thank you for your question.
I have attached a sample file showing righting arms for 90 and -90 degrees. Please see the attached files. I am following the standard convention that the bow is at x = 0 and stern is positive x values.
This files has a body that has the stern transverse dimension smaller in comparison to the bow transverse dimension. I did this to compare the value of the righting arm for +90 and -90 degrees.
For yaw = 90 degrees the rotation is stern to bow. Bow goes into the water.
For yaw = -90 degrees the rotation is bow to stern. Stern goes into the water.
I hope my description is good.yarm.zip
Thanks for this.
It is clear.
Kind regards,