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DNV GL © 2014
Ungraded
HydroD Global Analysis Wadam20 February 2017 SAFER, SMARTER, GREENERDNV GL © 2014
Ungraded
SOFTWARE
20 February 2017DNV GL
HydroD Global Analysis Wadam
Sesam user course
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DNV GL © 2014
Ungraded
HydroD Global Analysis Wadam20 February 20172
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
DNV GL © 2014
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HydroD Global Analysis Wadam20 February 2017
Wave Modeling
It’s a Wave – Body Interaction problem Regular Waves in Wadam
– Wind generated gravity Waves– Linear (Airy) Wave Theory– Monochromatic (1st Order) and Bi-chromatic (2nd order)– Unidirectional
Input of Sea State information for:– Stochastic Linearization of:
– Drag loads on Morison members– Roll Damping
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HydroD Global Analysis Wadam20 February 2017
Definition of waves – Wadam
Incoming wave defined as
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X
YA Wave amplitude
Wave number =
Angular frequency =
Wave direction (“going to” direction)
Input to Wadam:Wave direction +
Wave length or Wave period or Angular frequency
))sincos(cos(),,( kykxtAtyx
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HydroD Global Analysis Wadam20 February 2017
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)
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HydroD Global Analysis Wadam20 February 2017
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
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HydroD Global Analysis Wadam20 February 2017
Water folder
Contains– wave spectrums– spreading functions– current profiles– frequency sets– phase sets– wave height functions – regular wave sets (Wasim)
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HydroD Global Analysis Wadam20 February 2017
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
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HydroD Global Analysis Wadam20 February 2017
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)
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HydroD Global Analysis Wadam20 February 2017
Sea State
Used in drag linearization and stochastic roll damping Contains data required to
produce an irregular seaWave spectrum, spreading, sea
state duration A spectrum is used from the
given start heading and up to the next start heading
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HydroD Global Analysis Wadam20 February 2017
Restoring matrix
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HydroD Global Analysis Wadam20 February 2017
General Damping
The damping can be frequency independent or not by selecting Interpolate
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HydroD Global Analysis Wadam20 February 2017
Critical Damping
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HydroD Global Analysis Wadam20 February 2017
Critical damping and natural period
The equation
ξ ξξ 0
will have harmonic solutions only when
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The natural period is approximately
2
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HydroD Global Analysis Wadam20 February 2017
Display of strip model
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The Roll damping model is valid for monohull ships with XZ symmetry only
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HydroD Global Analysis Wadam20 February 2017
Quadratic Roll damping
For stochastic linearization a quadratic coefficient can also be used – Roll for both Wadam and Wasim– Pitch for Wasim only
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HydroD Global Analysis Wadam20 February 2017
Offbody points
Points Grid or From File– Animation in Xtract
Specified– Postprocessing in Postresp
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HydroD Global Analysis Wadam20 February 2017
Compartment effects – Options in Mass model setup
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HydroD Global Analysis Wadam20 February 2017
Creating a Wadam run
Select a Single body or Multi-body analysis
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HydroD Global Analysis Wadam20 February 2017
Run dialog: Models to be used in run
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Selecting condition implicitly also selects location
Reset dialog to default settings
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HydroD Global Analysis Wadam20 February 2017
Run dialog: Execution directives
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Select if data check only
Acceptance criteria for static balance
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HydroD Global Analysis Wadam20 February 2017
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)
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Run dialog: Drift Forces & Solver
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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)
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Run dialog: Roll damping
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Automatic iteration for short term statistics
Start values in iteration process if stochastic iteration (strip model)
Roll damping strip model is valid for ships only
Option for quadratic roll damping
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Run dialog: Print switch
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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.
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HydroD Global Analysis Wadam20 February 2017
Run dialog: Result Files – Global Response
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Normally not changed, use default values.
For second order analysis only(Separate license required)
The Motion reference point may be user specified
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Run dialog: Advanced
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Restart files from different models can be stored using different file names
Normally not changed
Note the option for calculation of the mass model in HydroD (default) or Wadam
Automatic meshing of waterplane (not recommended)
Wave/current interaction
Normally not used
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Run dialog: Output directory (optional)
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Output files can be directed to a different directory than the run directory, e.g. the directory of a Sesam Manager project.
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HydroD Global Analysis Wadam20 February 2017
Execute Wadam
Start from the Activity Monitor May include both Stability analyses and
Wasim analyses
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Possible to execute multiple activities (Threads) in parallel
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HydroD Global Analysis Wadam20 February 2017
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
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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
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HydroD Global Analysis Wadam20 February 2017
Multibody Wadam analysis
The WadamRun dialog contains a Multi-body option to be selected
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HydroD Global Analysis Wadam20 February 2017
SAFER, SMARTER, GREENER
www.dnvgl.com
DNV GL – [email protected]
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