SOFTWARE. Sesam user course. 20 February 2017 HydroD Global Analysis Wadam. Ungraded SAFER, SMARTER, GREENER DNV GL 2014

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1 SOFTWARE Sesam user course DNV GL 1 SAFER, SMARTER, GREENER

2 Scope of presentation Describe commands needed for performing a global analysis of a panel model, and their folders Environment modelling Analysis models Roll damping Sectional loads Loading conditions Offbody points Execution directives 2

3 Wave Modeling It s a Wave Body Interaction problem Regular Waves in Wadam Wind generated gravity Waves Linear (Airy) Wave Theory Monochromatic (1 st Order) and Bi-chromatic (2 nd order) Unidirectional Input of Sea State information for: Stochastic Linearization of: Drag loads on Morison members Roll Damping 3

4 Definition of waves Wadam Incoming wave defined as ( x, y, t) Acos( t ( kx cos ky sin )) Y A Wave amplitude X Wave number = Angular frequency = Wave direction ( going to direction) Input to Wadam: Wave direction + Wave length or Wave period or Angular frequency 4

5 Environment folder Locations, (one ore more objects) Depth, density, gravity Referring to frequencies, directions, spectrum etc., defined in Directions and Water (hydrodynamic analysis) Air Wind profiles (hydrostatic analysis) Directions Direction set, directions (hydrodynamic analysis) Water Frequency set, spectrum, current, wave spreading etc. (hydrodynamic analysis) 5

6 Directions folder Define wave propagating angles Direction Specification of one single direction Used when specifying the main direction in a sea state to combine with wave spreading Used to specify direction of current Direction Set Define a list of directions Used in frequency domain analysis 6

7 Water folder Contains wave spectrums spreading functions current profiles frequency sets phase sets wave height functions regular wave sets (Wasim) 7

8 Locations A location is a complete description of all environmental data necessary to compute the environmental loads on your structure or vessel This includes Directions for wave and current Wave, current and depth data Sea state data used for stochastic linearization & roll damping in Wadam Irregular time conditions used in time domain analysis in Wasim 8

9 Frequency domain condition Created by right-clicking on a location object Combines a set of M frequencies with a set of N directions, i.e. loads will be calculated for M N waves. NOTE: The wave amplitude is not relevant for a Wadam analysis (only for Wasim) 9

10 Sea State Used in drag linearization and stochastic roll damping Contains data required to produce an irregular sea Wave spectrum, spreading, sea state duration A spectrum is used from the given start heading and up to the next start heading 10

11 Restoring matrix 11

12 General Damping The damping can be frequency independent or not by selecting Interpolate 12

13 Critical Damping 13

14 Critical damping and natural period The equation ξ ξ ξ 0 will have harmonic solutions only when 2 The natural period is approximately 2 14

15 Display of strip model The Roll damping model is valid for monohull ships with XZ symmetry only 15

16 Quadratic Roll damping For stochastic linearization a quadratic coefficient can also be used Roll for both Wadam and Wasim Pitch for Wasim only 16

17 Offbody points Points Grid or From File Animation in Xtract Specified Postprocessing in Postresp 17

18 Compartment effects Options in Mass model setup 18

19 Creating a Wadam run Select a Single body or Multi-body analysis 19

20 Run dialog: Models to be used in run Reset dialog to default settings Selecting condition implicitly also selects location 20

21 Run dialog: Execution directives Select if data check only Acceptance criteria for static balance 21

22 Run dialog: Execution directives - Drag Additional definitions needed in Execution directives for drag linearization Constant drag velocity (used for all waves) Stochastic linearization Wave height linearization Define convergence criteria (similar to roll damping calculations) 22

23 Run dialog: Drift Forces & Solver Expensive Cheap If number of panels is larger than maximum matrix size (default = 5000) the direct solver is replaced by a block-iterative solver. Use direct solver if sufficient RAM (Increase the number) 23

24 Run dialog: Roll damping Roll damping strip model is valid for ships only Automatic iteration for short term statistics Option for quadratic roll damping Start values in iteration process if stochastic iteration (strip model) 24

25 Run dialog: Print switch This controls the amount of print in the print file from Wadam, WADAM1.LIS For most cases use Normal print. When using a roll damping model, the Model data switch may be useful. 25

26 Run dialog: Result Files Global Response Normally not changed, use default values. For second order analysis only (Separate license required) The Motion reference point may be user specified 26

27 Run dialog: Advanced Normally not changed Automatic meshing of waterplane (not recommended) Wave/current interaction Normally not used Restart files from different models can be stored using different file names Note the option for calculation of the mass model in HydroD (default) or Wadam 27

28 Run dialog: Output directory (optional) Output files can be directed to a different directory than the run directory, e.g. the directory of a Sesam Manager project. 28

29 Execute Wadam Start from the Activity Monitor May include both Stability analyses and Wasim analyses Possible to execute multiple activities (Threads) in parallel 29

30 Execute Wadam File handling (1) HydroD will create new folders in the workspace directory Typical folder names are: conv_files (offbody surface file) save_restart (wadam.rsq) tmp_files WadamRun1 (analysis files) WadamRun2 etc. HydroD will copy the selected T#.FEM files from the specified location into the workspace. The original files will not be moved Workspace files: <name>.hyd, <name>.sat Journal/log file: <name>.js 30

31 Execute Wadam File handling (2) The analysis Wadam folder, e.g. WadamRun2 (default) will contain all the files for one Wadam run Model interface files: T#.FEM Print files (should be checked) WADAM1.LIS poten.log force.log Results files Global response: G1.SIF Load files: L#.FEM, S#.FEM Actual panel model: panelt1.fem.bak files and WSAV.SIN may be deleted 31

32 Multibody Wadam analysis The WadamRun dialog contains a Multi-body option to be selected 32

33 The world-leading provider of software for a safer, smarter and greener future DNV GL Software software.support@dnvgl.com SAFER, SMARTER, GREENER 33