Open Source Seakeeping Evaluation and Analysis software suite

OpenSEA is an open source full featured seakeeping software suite.
The software suite can calculate hydrodynamic properties for any arbitrary body, or combination of bodies. It can then evaluate those hydrodynamic properties along with user defined forces to calculate frequency-based body responses, resonant frequencies and mode shape, time-based body responses, and Fourier analysis of time histories to determine non-linear responses.

What are the major differences between OpenSEA and other seakeeping programs?

• Open source: Completely free with all source available for use.
• Arbitrary body shapes: Many seakeeping software uses Lewis section based methods, which require ship-shaped bodies. OpenSEA uses full hydrodynamic radiation-diffraction evaluations to allow any arbitrary body shape, and any number of bodies.
• Simplified hydrodynamic methods: Many of the full radiation-diffraction suites were developed in the 1970′s – 1980′s. The developers at that time were keenly aware of the limits of computer power. To compensate for limited computing power, the mathematics for those software packages were highly analytical. This required using multiple bezel functions to simulate the presence of fluid domain boundaries, instead of physically meshing the boundaries. Why does this matter? Bezel functions are tough! They take a large amount of computational effort to evaluate and are usually approximated with simpler functions. This introduces inaccuracy. OpenSEA recognizes the advancement in computer technology and instead meshes all fluid boundaries for direct evaluation of the boundary conditions. This creates a more robust and expandable approach.
• Modern object oriented programming: Computer programming was very different in the 70′s-80′s when many of the other seakeeping programs were developed. FORTRAN was the popular language for scientific computing. This legacy language can inhibit continued development of these programs. OpenSEA uses modern object oriented programming techniques with C++ programming language.

You can learn more about OpenSEA on the software's website: www.opensea.dmsonline.us

Opensea is composed of multiple appliccations, listed below.

1. ohydro - hydrodynamic diffraction

• ofreq - frequency based dynamics analysis
• oTime - time base non-linear dynamics analysis
• oFourier - convert time based analysis into frequency domain
• oBatch - batch runs of all the above programs
• GUI - graphical interface to control all programs.
• Utilities - various small utilities to suppor the other applications.

We like all developers to use the same set of software for development. This keeps all the file-types compatible and limits headaches for everyone. Please goto to the wiki to learn which software is required. Standard Software

We try to keep the project organized. Please go to the wiki to learn how the project directories are structured, and please follow that directory structure. Directory Structure

The actual released binaries also have a structure. This was planned out to ensure file references remain compatible in the future. Please maintain the prescribed structure. Details are on the wiki. Application Structure

We maintain three separate project branches. Mast is the main development branch. Actual releases are held in the release_windows and release_linux branches. Further details are on the wiki. Release Branches

The software suite is comprised of five major software packages. The major features for each package are listed below.

oHydro calculates properties for hydrodynamic radiation and diffraction. It supports multiple bodies, hydrodynamic interaction between bodies, forward speeds, wave drift force calculations, and much more. The program operates multi-threaded to take advantage of modern multi-core computer systems. The program also supports deformation of the surface mesh to incorporate non-linear free surface conditions.

oFreq has two modes of operation. It performs frequency based linear response analysis. Or, it calculates resonant frequencies and mode shapes. The program incorporates user forces and hydrodynamic forces. Response amplitude and phase are calculated for each individual degree of freedom The program is flexible enough to allow definition of any system of motion, with unlimited degrees of freedom.

oTime is used to calculate fully non-linear dynamic responses. oTime includes hydrodynamic forces and user defined forces. All forces are resolved for each individual time step, which allows fully non-linear response calculations.

oFourier performs frequency transformations of time histories. It has two main applications.

1. Frequency analysis of output from oTime
2. Frequency analysis of experimental output from wave buoys or seakeeping trials

• OpenSEA has several different programs in it’s suite. oBatch allows automated execution and control of other programs in the OpenSEA suite. When combined with a table of parameter variations, oBatch can be used to repeat and automate a complicated seakeeping analysis for any number of seakeeping conditions.

• oBatch also aggregates and summarizes results for easily evaluation of a vessel’s seakeeping performance.