SESAM
Postresp
SESAM User Course in Hydrodynamics Postresp workshop Long term statistics - Semi-submersible
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The workshop is based on the presentations given on long term statistics using Postresp
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In this workshop the old Postresp model from the basic workshop must be re-opened Start Postresp from HydroD HydroD as in the first workshop. You will be asked if you want to
overwrite the database. Answer No to this. Postresp will then open with the old database. Read wave climate from the file, scatter.jnl file, scatter.jnl , i.e. a scatter diagram called WORLDWID Define probabilities for which the fitting to the Weibull distribution is performed. Use
levels 10-2, 10-4, 10-6, 10-8, 10-10. Create and assign wave spreading function. Use cosine square spreading for
0.01 < Tz <= 9.99 and long crested seas for Tz > 10. Assign wave heading probabilities, as suggested: Assign scatter diagram to headings Create responses for long term calculations of air gap, AG2,. Compare results from
motion relative to total wave and motion relative to incoming wave only. Display long term response
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The files to be used are listed below: postresp_in2_semi.jnl
Complete input for this workshop
SCATTER.jnl
Input file for definition of a scatter diagram, worldwid
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Postresp
Detailed procedure Step 1: Start Postresp •
In the workshop the old Postresp model from the basic workshop must be re-opened
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Open the HydroD workspace used in the HydroD workshop.
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File – Recent Workspaces … Start Postresp from HydroD as in the first workshop. You will be asked if you want to
overwrite the database. Answer No to this. Postresp will then open with the old database.
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Postresp
Step 2: Read wave climate •
Read wave climate from the file scatter.jnl , i.e. a scatter diagram called WORLDWID Click the button for “Read command input file”
Locate and open the file SCATTER.JNL. (This file is normally distributed on a CD,
together with other training course files.)
Please notice some feedback in the bottom of the Postresp window. The last lines
should be similar to the following:
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Postresp
Step 3: Define Long Term Probabilities •
Define probabilities for which the fitting to the Weibull distribution is performed
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Define – Long Term Probability … Use levels 10-2, 10-4, 10-6, 10-8, 10-10. These are also default levels; just click OK
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Step 4: Create/Assign Wave Spreading Function •
Create wave spreading function
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Create – Wave Spreading Function … Give a name & description: COS2 – Cosine squared Select type: Cosine Power Give Power: 2
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Assign wave spreading function. We want to use wave spreading for the shortest waves only.
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Assign – Wave Spreading Function 1. Select Scatter diagram, WORLDWID
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Select NONE
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Select Part
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Give Hs=0.01 through 30
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Give Tz=10 through 40
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Apply
2. Select WORLDWID
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Select COS2
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Give Hs=0.01 through 30
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Give Tz=1 through 9.999
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OK
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Postresp
Step 5: Assign Wave Heading Probabilities •
Assign wave heading probabilities to all headings, as suggested
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Assign – Wave Direction Probability … Select direction, give probability, click Apply Repeat for all directions End with OK for the last direction
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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dir 0.0 15.0 30.0 45.0 60.0 75.0 90.0
prob 0.05 0.1 0.15 0.4 0.15 0.1 0.05
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Step 6: Assign Wave Statistics •
Assign scatter diagram to all headings
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Assign – Wave Statistics … Select direction, select Scatter diagram, click Apply Repeat for all directions End with OK for the last direction
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DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
Click Apply to keep the menu available for the next operation, end with OK to close the menu
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Postresp
Step 7: Assign Wave Spectrum Shape •
Assign wave spectrum to scatter diagram
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Assign – Wave Spectrum Shape… Select Worldwid Select Pierson Moskowitz Press OK
DNV Software - Postresp Workshop 1 Semi Revised 13 May 2012
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Postresp
Step 8: Create Long Term Response •
Create responses for long term calculations of relative motion, AG1, AG2, SUB1, SUB2. Compare results from motion relative to total wave and motion relative to incoming wave only.
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Create – Long Term Response … Select the wanted response variable
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AG2
Select all directions
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Postresp
Step 9: Display Long Term Response •
Display long term response. Display for 0° for the relative motion at the bow (AG1, AG2) and for 45° for the relative motion at the stern (SUB1, SUB2).
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Display – Long Term Response … Display AG2 for wave direction 0°, 45°, 90° Display AG2 for wave direction 15°, 30°, 60°, 75°
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The resulting plots are displayed on the next page
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Step 9: Display Long Term Response, cont.
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Step 10: Print Long Term Response •
Print the long term response to the screen. Remember that in the old database print was sent to a file
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Set – Print Select Screen , click OK
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Print – Long Term Response … Print all available response variables
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The resulting print for SUB2 is displayed on the next page
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Step 10: Print Long Term Response, cont.
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