SISSA - International School for Advanced Studies

mathLab

Free Surface Flows: Numerical Methodologies and Application to Naval Architecture

When: 
Thursday, 23 February, 2012 to Friday, 24 February, 2012
Where: 
SISSA - Santorio A - Meeting Room VII Floor

The workshop has two main purposes:

  • To connect several research groups which study free surface flow problems with different
    numerical methodologies.
  • To discuss some of the modeling aspects related to this field (physical and
    mathematical models, numerical methods and their analysis, numerical simulations) and their
    applications to naval architecture problems.

Scientific Committee:

  • Prof. Antonio DeSimone (SISSA MathLab)
  • Prof. Alfio Quarteroni (EPFL - Politecnico di Milano)
  • Prof. Enrico Nobile (University of Trieste)
  • Prof. Giorgio Contento (University of Trieste)

Organizing Committee:

  • Dr. Luca Heltai (luca.heltai at sissa dot it)
  • Dr. Andrea Mola (andrea.mola at sissa dot it)

Confirmed Invited Speakers:

  • Prof. Carl-Erik Janson (Chalmers)
  • Prof. Hrvoje Jasak (University of Zagreb)
  • Prof. Giorgio Contento / Prof. Enrico Nobile (University of Trieste)
  • Prof. Andrea di Mascio (IAC Roma)
  • Prof. Ruben Scardovelli (University of Bologna)
  • Dr. Edie Miglio (MOX - Politecnico di Milano)
  • Dr. Nicola Parolini (MOX - Politecnico di Milano)
  • Dr. Luca Heltai / Dr. Andrea Mola (SISSA)

Schedule:

Thursday 23 February 2012

14:00 —14:15 Welcome (SISSA mathLab)
14:15 —15:15

Naval Hydrodynamics CFD Simulations with OpenFOAM

Prof. Hrvoje Jasak

Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Croatia and Wikki Ltd, United Kingdom

OpenFOAM (Field Operation And Manipulation) is an open source object-oriented numerical simulation library aimed at complex physics modelling. It handles continuum models by mimicking partial differential equations in software. Polyhedral Finite Volume discretisation is implemented in operator form (eg. temporal derivatives, gradient, divergence, source and sink terms), and operators are combined to form equations. Efficiency and elegance in implementation is achieved through layered development and extensive code re-use, where various components (eg. mesh handling, field algebra and calculus, discretisation, linear algebra and solvers, dynamic meshing etc.) are developed and validated in isolation.
In this talk, we shall present the capabilities of the Naval Hydrodynamics application suite using OpenFOAM. Surface capturing techniques used by the solver include compressive numerics and relative velocity formulation, using either implicit solution or explicit flux-limited scheme MULES. Two alternative forms of the momentum equation are used: cell-averaged momentum or cell-averaged velocity formulation, with optional ``single-phase VOF'' formulation. Dynamic mesh support, dealing with moving, deforming and topologically changing meshes is implemented and interacts with the library of dynamic mesh classes. Auxiliary capability, including incoming wave conditions, numerical beach, accurate reconstruction of the absolute pressure field and post-processing utilities are included in the solver.
Dynamic mesh classes implement "use-cases" for typical simulations: steady resistance, sinkage and trim, sloshing, slamming and 6-DOF sea-keeping dynamic meshes are implemented, illustrated in tutorial examples and validated on relevant cases.
In conclusion, two recent developments are presented, including the work on Overset grid technology and phase compressibility in under-water explosion simulations, both developed in collaboration with partners.

15:15 —16:15

Free-surface hydrodynamics of racing yachts

Dr. Nicola Parolini

MOX - Politecnico di Milano

In this talk, we review the numerical methodologies that have been developed and applied to America's Cup yacht design during the last few years. In particular, we will discuss the numerical simulations related to the free-surface hydrodynamics of mono- and multi-hull and their dynamics in calm water and waves.
A critical comparison between commercial RANS codes and the recent developments on open-source platforms will also be provided.

16:15 —16:45

Coffee Break

16:45 —17:45

A review of the geometrical VOF method

Prof. Ruben Scardovelli

DIENCA - Università di Bologna

In this talk we review the basic features of the geometrical VOF method in Cartesian grids: a) the interface reconstruction, from Young's method to the height function technique, and its geometrical properties, normal and curvature, b) the interface advection, split and unsplit schemes. Then we will discuss the multilevel implementation of the VOF algorithm in the in-house FEMuS code and in the open-source Gerris Flow Solver with AMR.

17:45 —18:45

Numerical modelling of competition rowing boats

Dr. Edie Miglio

MOX - Politecnico di Milano

In this talk we will describe the derivation of mathematical and numerical models for the simulation of rowing boats. Rowing boats are a complex dynamical system strongly affected by the rowers action and movements. Indeed a rowing boat hardly moves with constant speed, but it is instead subject to a complex system of secondary movements: horizontal and vertical accelerations as well as pitching are the main ones. These in turn generate gravity waves which dissipates part of the rowers power.
A numerical model may help a boat manufacturer to foresee the behaviour of new a boat design, and a trainer to better understand how crew composition and rowing style may affect performance. We present the results of the research carried out in the last years concerning the development of a complete mathematical model of the boat dynamics and of its interaction with the free surface flow.

20:30 —

Social Dinner

Friday 24 February 2012

09:00 —10:00

A fully nonlinear potential flow method for simulation of large amplitude ship motions

Martin Kjellberg

Department of Shipping and Marine Technology at Chalmers University of Technology, Gothenburg, Sweden

A fully nonlinear unsteady three-dimensional boundary element method for free surface flows is currently being developed at the Department of Shipping and Marine Technology at Chalmers University of Technology in cooperation with the Department of Engineering and Architecture at the University of Trieste. The aim of the development is the prediction of large amplitude wave induced motions and loads of ships with forward speed, thus taking into account all nonlinearities in the inviscid free surface flow and wave-body interaction. A boundary element method with raised free surface panels is coupled with a mixed Eulerian-Lagrangian technique for the evolution of the free surface. A technique for suppressing breaking waves is implemented for increased robustness in the simulations. A description of the method is given as well as some numerical results showing the current state of the development and its capabilities.

10:00 —11:00

A stable semi-Lagrangian potential method for the simulation of ship interaction with unsteady and nonlinear waves

Prof. Antonio De Simone, Dr. Luca Heltai, Dr. Andrea Mola

SISSA mathLab

We present preliminary results of a model for the simulation of three dimensional unsteady nonlinear water waves generated by a ship hull advancing in calm water. In the framework of potential flow theory, the continuity equation becomes a Laplace equation for the potential field, complemented by nonlinear boundary conditions on the unknown free surface.
To prevent downstream transport of the mesh nodes and avoid remeshing, such boundary conditions are written in semi-Lagrangian framework (also known as arbitrary Lagrangian Eulerian formulation). The resulting boundary value problem is a system of nonlinear integro-differential equations, in which the unknowns are the deformation field of the free surface, along with the corresponding potential and potential normal derivative. Upon discretization, we obtain a system of Differential Algebraic Equations (DAE), defined on a deforming grid. The spatial equation are discretized via an adaptive, collocation based, iso-parametric Boundary Element Method (BEM), while time advancing of the nonlinear differential-algebraic system is performed using implicit Backward Differentiation Formulas with variable step size and variable order. The semi-Lagrangian free surface boundary conditions are stabilized by means of a Streamwise Upwind Petrov–Galerkin (SUPG) method, and unstructured quadrilateral grids are automatically generated and adapted on arbitrary CAD hull geometries.
The entire code is based on the open source libraries Deal.II for the BEM framework and SUNDIALS for the DAE solution framework. It has been developed as part of the OpenSHIP project. The test cases considered are that of a Wigley hull and of the US Navy Combatant, DTMB 5415, advancing in calm water.

11:00 —11:30

Coffee Break

11:30 —12:30

Numerical predictions of ship and propeller hydrodynamics by CFD. Results from the OpenSHIP project.

Norman Del Puppo, Guido Lupieri, Mitja Morgut, Giorgio Contento, Enrico Nobile

Department of Engineering and Architecture - University of Trieste - Via A. Valerio, 10 34127 Trieste - Italy

We present a selection of CFD investigations on ship and propeller hydrodynamics performed in the frame of an extensive benchmarking presently undertaken within the undergoing Project OpenSHIP - Highly reliable CFD simulations for the prediction of the hydrodynamic performance of the hull-propeller system with OpenSource software - co-financed by the ERDF - European Regional Development Fund - Friuli Venezia Giulia Region Operational Programme 2007 - 2013, in the Call for industrial research projects in the field of shipbuilding industry and pleasure yachts. The simulations are conducted with the software OpenFOAM®.
The wavy viscous flow induced by a foil at constant speeds underneath the free surface with an angle of attack of 5 degrees is presented first. The numerical results from VOF-RANSE simulations are systematically compared with experimental data from the literature in terms of free surface profile, forces and velocity profiles. This test case on a relatively simple geometric shape has been selected for the highly conservative nature of the generated 2D wave pattern, allowing a detailed analysis of the coupling between the flow solver and the free surface treatment in the perspective of its application to the more complex ship-shapes.

The double model test case on the KCS Kriso hull is then presented with comparisons between the numerical results obtained and the experimental data available from the Gotheborg workshop 2010 on the wake at the propeller disk. The investigation has been mainly focused on the grid generation by means of snappyHexMesh.
Finally the numerical predictions of the flow around the model scale propellers E779A and PPTC are presented. The comparison between simulations and experimental data in steady state regime and the preliminary results from unsteady simulations are shown.

12:30 —13:30

Numerical simulation of free surface flows around ship hulls

Prof. Andrea di Mascio
IAC Roma

Some techniques used for the simulation of free surface flows around ship hulls will be reviewed in the talk.
Free surface–fitting approaches will be discussed first, with emphasis on the models developed for the simulation of spilling breaking waves. Then, interface–capturing techniques used for the computation of ship flows with plunging breaking waves will be reported, together with some examples in the context of naval architecture (sea– keeping, manoeuvrability). Issues regarding the coupling of level–set approaches with Lagrangian particle methods will be addressed.
Examples about the ongoing research activity for the simulation of free surface flows with strong fragmentation will be also briefly described.

Additional Informations:

  • Here you can find
    additional informations on the Venue of the Workshop.

Registration:

Due to limited size of the lecture room, participation is open
only to registered participants. Please use the link below to
register.

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