This section describes technologies implemented both in FlowVision 2.xx.xx and FlowVision 3.xx.xx (FlowVision-HPC).

Import of surface meshes from CAD and finite-element systems

• Direct import of CAD/FEM geometry (surface mesh): VRML, STL, INP- Abaqus
• Indirect import of CAD/FEM geometry (via 3DTransVidia): DEFORM, Abaqus, ANSYS and NASTRAN, IGES, VDAFS and PARASOLID, CATIA V4/V5, Pro/E, UGS

Body-fitted Cartesian meshing

• Grid:
  • hexahedral fluid cells, polyhedral boundary cells
  • Cartesian
  • unstructured
  • non-staggered
• Grid generation concept: no simplifications of geometry (a mesh is built in/around the original geometry imported from a CAD or FEA system)
• Geometry complexity: arbitrary
• Moderate number of cells
• No block matching

Body-fitted Cartesian mesh

Automatic grid generation

Sub-Grid Geometry Resolution (SGGR) method:
Triangulated surfaces naturally cut Cartesian cells

Sub-Grid Geometry Resolution (SGGR) method:
Only 3 cells is generated around thin body

• Grid generation method: SGGR
• Grid generation process: completely automated
• Grid generation time: minutes

Àutomatic grid adaptation

• Adaptation to geometry
• Adaptation to solution
• Dynamic splitting and merging cells

Moving bodies in computation domain

• Easy import of additional bodies into the computation domain
• A 'moving body' built on an imported object has 6 degrees of freedom
• Accurate and fast Euler method for computing body motion relative to the computation domain
• Body kinematics: user-defined motion laws
• Body dynamics: gravity, buoyancy, hydrodynamic, or user-defined forces
• Coupled calculations of body motion and free surface evolution (ships)

Efficient Navier-Stokes solver

• Finite-Volume approach
• Accurate numerical scheme based on original reconstruction method:
  • 2-order approximation of convective operator in space
  • upwind
  • monotone
• Explicit and implicit time integration
• Velocity-Pressure implicit algorithm:
  • easy calculations of incompressible flows
  • large time steps (CFL ~ 10 - 1000)
• One method for all Mach numbers
• Non-skew and skew schemes
• Algebraic solver:
  • Lanczos method with second order incomplete ILU (ILU2) factorization
  • Modified method of successive point over-relaxation (SOR) for nonlinear systems of equations
  • Newton method

Free surfaces in computation domain

 

VOF (Volume Of Fluid) variable is the volume fraction of fluid 1 in a cell
VOF=1 - the cell contains only fluid 1
VOF=0 - the cell contains only fluid 2
0<VOF<1 the cell contains fluid 1 and fluid 2

 

Calculated wave pattern around ship hull

• A high-accuracy version of the VOF method: high accuracy is achieved by solving the governing equations in the 'free surface' cells (the cells partly filled with liquid)
• Reconstructing free surfaces: SGGR method

Clearance flow modeling

‘Gap cell’ is a polyhedral cell resulting from cutting a Cartesian (red) cell
by clearance walls

• Only 1 cell is required across the clearance to resolve the clearance flow, hence, the model enables simulation of the flows in thin channels (characteristic of compressors, bearings, etc.) on coarse meshes
• The ‘gap cells’ are automatically identified
• The governing equations are automatically modified in the ‘gap cells’
• The Gap model is thorougly verified

Fluid-structure interaction (FSI)

Force exerted by fluid on finite-element face j is the sum of forces
acting on the face parts found in different cells:
F_j = f_jk + f_ji + f_jm

• Direct two-way coupling with FEA system Abaqus (no intermediate softwear like MpCCI is required)
• Automatic exchange by computed data between FlowVision and Abaqus
• Easy creating and tuning a coupled multi-physic project in MP Manager (a module specially designed for FSI)
• Automated matching the finite-volume (FlowVision) and finite-element (Abaqus) meshes: SGGR method

Network licensing the software capabilities

• Independence on dongle
• Installation flexibililty

C++ implementation

• Object-oriented structure of the code
• Easily extendable solver (easy adding specialized modules, models, equations, functions)
• Easily extendable interface (easy adding new features, interface parameters, and visualization methods)

OpenGL-based graphics

• High visual quality and performance
• Most widely adopted graphics standard
• Reliability
• Hardware acceleration