The GHS SeaKeeping Optional Module is based upon a linear, 6-degree-of-freedom, rigid-body, frequency-domain, strip-theory method with variable heading and forward speed terms. The module is fully integrated with GHS, meaning loading condition and hydrostatic information is automatically accessed by the module. This means SK requires only a few input parameters, offering unmatched ease of use.
SeaKeeping offers an excellent and economical integrated option for seakeeping and hydrodynamic analysis that is well suited to the following applications:
Seakeeping output is organized by mode (i.e. Surge, Sway, Heave, Roll, Pitch, Yaw) so it is very easy to reference specific RAOs or response results. In addition, SeaKeeping offers an optional summary table which displays the most probable extreme position, velocity, or acceleration amplitude components in the x (Surge), y (Sway), z (Heave) translational directions, and the X (Roll), Y (Pitch), Z (Yaw) angular directions for a specified confidence level. This table is an ideal "one-location" reference for design values that may be added to the end of the report.
- Motion Studies: Compute 6-DOF motion RAOs, statistics, periods and amplitudes, with or without forward speed in long-crested seas.
- Rigging and Sea-Fastenings: Forecast accelerations at rigging and fastening points on the ship, supporting the calculation of rigging loads, fatigue, etc.
- Habitability: Estimate the periods and accelerations encountered under way in a variety of sea ways to ensure crew comfort and safety.
- Crane Operations: Estimate absolute and relative responses at crane booms and lift points.
Seakeeping reports are comprehensive, and include an initial section that summarizes input parameters, condition information, and specified critical points. A wave component summary table is also included, and if wave spectra are used, a wave spectra plot is included that shows both the continuous wave spectrum and the discrete wave samples used by SeaKeeping.
The module offers users the following features:
Don't see a specific feature on the list? Contact Customer Support to inquire about current and prospective feature updates. SeaKeeping is always being updated and improved.
- Integration with GHS command language and run files
- Included graphical user interface for setting up complex analyses
- Use of GHS geometry files (.GF) for seakeeping analysis with little or no modification
- Minimal input and ease of use compared to other commercially available software
- Recognizes vessel loading condition as specified in GHS, no need to specify hydrostatic parameters, it is all done automatically
- Full support for monohull vessels
- 6-DOF motions including displacements, velocities, accelerations, amplitudes and phase angles
- Absolute and relative motions
- Motions computed at vessel CG and at specified critical points
- Response amplitude operators (RAOs) for all DOF at any point
- Statistical response data including response variance, RMS, average and significant response amplitudes, average periods, and extreme maxima
- Acceleration amplitudes may be given in Ft/Sec2, m/Sec2, or gravitational units "G's"
- User specified confidence limits and time intervals
- Optional summary table for position, velocity, or acceleration amplitudes at default or specified confidence limits at any point is an ideal "one-location" reference table for design values
- Robust linear, rigid-body, frequency domain, strip-theory method
- Boundary element method for computing 2D hydrodynamics can accomodate most ship geometry, including anti-symmetric geometric sections (i.e. non-zero heel)
- Advanced parameterization of hydrodynamic panel mesh
- Parameterized wave spectra sampling using a constant variance or frequency bandwidth method
- Long-crested waves at any wave heading
- Short-crested waves with Cosine-Squared and Cosine-Power spreading functions
- Regular or irregular waves
- Non-zero vessel speed
- Deck immersion or "shipping water" probabilities and frequencies computed at any point (or all critical points)
- Single wave or spectra wave input (via WAVE command extension)
- Built in wave spectra include:
- Bretschneider (General, Narrow-band, and ITTC 1984)
- JONSWAP (general form)
- JONSWAP (ITTC 1978)
- Ochi-Hubble (6-parameter)
- Ochi-Hubble (most probable, single-parameter via Hs)
- Data file
- Five optional comma-separated output data files:
- Response Data: includes RAOs and response amplitudes and phase angles for all modes and all wave samples
- Forcing Data: includes total, inertial, and diffraction wave excitation forcing amplitudes per unit wave amplitude and phase angles
- Hydrodynamics Data: includes hydrodynamic and hydrostatic coefficients (i.e. A, B, and C's)
- Wave Data: includes wave sample characteristics such as periods, frequencies, spectral ordinate, sample amplitudes, etc.
- Variance Data: includes response variance (m0, m2, m4) for all modes and all critical points
- Full-featured GHS report file organized by mode including:
- All response amplitudes and phase angles tables and plots
- RAO tables and plots
- Response statistics tables
- Wave component summary table
- Continuous and sampled spectra table and plot
- Extreme amplitude summary
- Shipping water table
See the Version 16.00 Update for more information on the SEAKEEPING command.
2D Coefficients and Forces
3D Forces and Moments
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