There are three products: CFD-OHMUGA, Overset-OHMUGA and Optimization-OHMUGA.  The first is CFD solver, the second is dynamic overset grid solver serving for CFD solver, both of these two solvers can run independently or couple together.  The third is optimization solver working for ship hull optimization using CFD results and  surrogate  model. 

CFD-OHMUGA is a copyrighted, unstructured grid, MPI parallel, CFD viscous flow solver developed with world leading-edge numerical methods and multi-functions, which is designed to provide reliable simulation methods and tools for the researches and engineering designs about complex, challenged and new marine hydrodynamics and aerodynamic problems, addressing for fast, robust and accurate computation. 

CFD-OHMUGA is designed to simulate broad CFD problems, especially marine hydrodynamics (or aerodynamics) problems, such as ship resistance and propulsion (autopilot), maneuvering (e.g. zigzag using propeller and rudder controllers), seakeeping (e.g. pitch-heave, course-keeping in waves), etc. for single or group of ships. Thanks for the powerful function of dynamic overset grid solver, it can deal with the problems of  relative motions, very complicated geometries (wing, fin, skeg, bilge keel, etc.), and refinement grids. 

CFD-OHMUGA has three versions, Version 1 can predict free surface flow using parallel unstructured grid method, Version 2 is implemented with the new function of 6DOF by solving rigid body dynamic equations, version 3 is a coupled solver of CFD and overset grids solvers (coupled with Overset-OHMUGA). The latest version is making the coupled parallel computation and prediction for fluid flow, free surface, body forces, moments, and 6dof motions (captive or free-body) and controllers, for fluid-body (or wave-body) interaction problems, of multi-bodies (floating or submerged bodies) with independent 6dof motions and their multi-appendages (controllers) with independent motions (rotation along an axis, or 3dof rotations).

Main models: Inertia or non-inertia coordinate systems;  Single-phase incompressible viscous flow;  Free surface model including level set transport and reinitialization model; RANS (BSL, SST) and DES turbulence models; Multi-body (1-6DOF motions) and multi-appendage (1-3DOF rotations) rigid body dynamic models; Incident linear regular or irregular waves; Body force propeller model; Linear mooring model; Active controllers for autopilot, heading control, etc.

Main numerical methods: Dynamic unstructured overset grids constructed by either multi-block, body-fitted, non-orthogonal curvilinear structured grids (automatically transformed to unstructured grid formation), or normal unstructured grids with four(4) different kinds of hybrid elements (tetrahedral, hexahedral, prismatic and pyramidal elements); Collocated grid (all variables are set at nodes based on element vertexes); Finite Volume (median-dual scheme); Projection or PISO method for velocity and pressure coupling; 2nd-order Implicit method for temporal and spatial discretization for momentum and level set governing equations to apply big time step; Upwind edge-conformed method, or line-extension method of shape function interpolation for fiction node in a tetrahedral element for convection term discretization; Limiter functions for convection term discretization (venkatakrishnan or barth jesperson limiter, or TVD method of Roe's minmod, Roe's superbee, van Albada, Van Leer, etc.); An option of variable gradient calculation based on local fiction orthogonal coordinates; Shape function (iso-parameter) interpolation method is used for discretization for the poison equation; Far distance water fiction points and fiction elements method for accurately calculating pressure gradient near free surface.; Narrow Band and Geometry method for level set equations (to keep fast calculation and accuracy in skewed grids); KD-Tree fast search and geometry method for calculating distance of close points for level set reinitialization; Efficient and compact stencil numerical treatments for pressure equation for hexahedral elements; Multi-body (object) 1-6DOF motions; Earth coordinate and body-fixed coordinate switch; ALE for grid motion; Multi-body forces, moments and motions are computed independently; multi-layer refinement overset grids can be set flexibly to follow all or part of body motions; Implicit method for time evolution for predicting 1-6DOF motions; Multi-appendages (controllers); Euler angle methods for 1-3DOF appendage rotations which is independent from body motions; Calculate motions in earth system by Composting the appendage 1-3DOF motions with their parents’ 1-6DOF body motions; HPC (High performance computation) of MPI parallel computation.

Overset-OHMUGA is a copyrighted, domain composition, MPI parallel, unstructured, dynamic overset grid solver for providing DCI (Domain Connectivity Information) and surface area weight coefficients for different CFD solvers (CFD-OHMUGA or others). Overset-OHMUGA is a library provided for CFD solvers, who includes two different solvers: one is DCI  (Domain Connectivity Information) solver, another is named as SURCLIP used to calculate surface area weight coefficients in order to generate an integral area for calculating force or moments on a rigid body. Overset-OHMUGA also provides a library DRTL (Donor Receptor Transaction Library) constructed by different kinds of functions used to communicate information with CFD solvers in MPI parallel way while the coupled solver is used. Main methods used in Overset-OHMUGA: 1) a new efficient method named Iterative Band Algorithm (IBA) for hole cutting is suggested .  2) Automatic process, watertight band, no grid hierarchies, no auxiliary geometries, no protected elements near boundaries. 3) Multi-level fringe nodes. 4) Multi-level appendages. 5) Efficient searching method. 5) Orphan nodes treatment by average method.

Optimization-OHMUGA is an optimization solver (independent from the CFD solver) used for ship hull shape optimization for multi-objects. It is constructed with two sub-solvers, one is CFD stencil solver, another is surrogate optimization solver. Wherein the former firstly uses CFD solver to calculate objects (e.g. ship resistances) and constraints (e.g. ship displacements) under the conditions of typical ship hull shapes, thus provides basic data stencils for latter usage. The latter then secondly performs the optimization process using a surrogate method based the data stencils. In Optimization-OHMUGA solver, NSGA- II method is suggested for calculating multi-objects and multi-constraints optimization, RBF (Radial Basis Function) method is advised for calculating grid displace, and RBF surrogate model is used for interpolating the variables based on stencils provided by CFD solver.

The CFD codes have been validated or demonstrated with different and necessary examples of marine hydrodynamics, including cases of 2D or 3D, laminar or turbulence flow, steady or unsteady, with or without free surface, forces, moments and motions, multi-body and multi-controllers, etc. 

OHMUGA products are convenient  to use. The users are required to set parameters in input files (user interface), and a grid file (or an additional boundary condition file if that is not included in the grid file), wherein, the formations of grid files (or boundary condition file) are compatible to Gridgen or FIELDVIEW, and output file formations are compatible to formation of Tecplot. Special design is possibly provided according to user's special formations.

In addition, Fortran and c compilers, MPI and PETSc  should be pre-installed. 

General Flow                            Ship