The Hamburg Ship Model Basin

Setting the Standard in Ship Optimisation

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CFD - FreSCo+

The Finite-Volume Navier-Stokes solver FreSCo+ (“Free Surface Code”) is HSVA’s multi-purpose CFD code. The code is developed jointly with Hamburg Technical University (TUHH) with a strong focus on maritime applications. Additional Information can also be found at the FreSCo+ web site.

  • Two-phase flows are addressed by interface-capturing methods based upon the Level-Set or Volume-of-Fluid (VOF) technique. Specific interface sharpening techniques in line with a conservative interpolation for face-based pressures are available for two-phase flow simulations.
  • In order to simulate cavitating flows, the VOF-method can be combined with a selection of mass-transfer models. Optionally, more accurate Lagrangian bubble-techniques can be used to determine the vapor content.

    CFD FreSCO 01
  • Various turbulence-closure models are available with respect to statistical (RANS) or scale-resolving (LES, DES) approaches.
  • The software supports the solution of the segregated, pressure-based adjoint system in order to determine a continuous sensitivity distribution ready to be employed in an optimisation strategy. The adjoint approach is a very efficient and powerful tool in order to design hydrodynamically favorable ship hulls and appendages. HSVA and its research partners are the first to apply this innovative optimisation tool in a maritime context.
  • A robust and accurate overset-mesh technology enhances the state-of-the-art possibilities of hydrodynamic simulation tools and might facilitate a significant speed up during the design and optimisation cycle. These benefits are traded against an enhanced data-management effort and mass and momentum conservation challenges. As an alternative approach for moving grids the sliding interface method is implemented as well

    CFD FreSCO 02
  • FreSCo+ allows simulating the motion of a floating body with an implicit coupling of the Flow solver with the dynamic rigid motion (6-DOF).
  • Following the example of geometrical modeling and computer animation applications, the Free-form deformation (FFD) method implemented into FreSCo+ is a geometric shape modification technique. The underlying geometry is manipulated by moving the control points. (Optional: The relationship between the lattice grid and the mesh is illustrated in the figure below. The original grid around a circle is shown on the left hand side. The control points are connected in a lattice grid shown in red. By moving the four inner lattice points to new positions the circle and the grid are deformed accordingly.)  Coupled with the adjoint method, the Free Form Deformation method both methods add up to an efficient automated optimisation tool.

    CFD FreSCO 03
  • Seaway boundary conditions are implemented to implicitly force the simulation towards far-field seaway conditions along all far-field boundaries of the domain.
  • The solver can be coupled with the in house inviscid flow solver QCM using the body force concept in an iterative fashion.  This RANS-BEM Coupling –method allows for a good balance of computational effort and accuracy.
  • The code is efficiently parallelized to run on HSVA’s computation cluster as well as other state of the art parallel computers with more than 1000 processors.
  • The choice of arbitrary polyhedral cells also with hanging nodes as topological basis, the modern modular design of the code and the use of standard file formats facilitates the broadening of the application range. The code can be used structured and unstructured grid from state of the art grid generators.