CFD Simulations of a Semi-Submersible With Absorbing Boundary Conditions

The CFD tool COMFLOW is suitable for simulations of two-phase flows in offshore applications. COMFLOW solves the Navier-Stokes equations in both water and (compressibl e) air. The water surface is advected through a Volume-of-Flui d method, with a height-function approach for improved accur acy. By employing Absorbing Boundary Conditions (ABC), boundaries can be located relatively close to an object, wit hout influencing outgoing waves or generating numerical reflections that affect the waves inside the flow domain. Tradition ally, boundaries are located far from the obstacle to avoid reflect ions; even when numerical damping zones are used. Hence, with the ABC approach less grid points are required for the same accuracy, which reduces the computing time considerably. Simulations of a semi-submersible model are compared to measurements. The overall agreement is reasonably good, fo r a wide range of wave conditions. The ABC performs well; numeri cal reflections are almost absent. Moreover, computing time s reduce with a factor four compared to damping zone techniques.

[1]  J. H. Westhuis.  The numerical simulation of nonlinear waves in a hydrodynamic model test basin , 2001 .

[2]  Patrick Joly,et al.  Absorbing Boundary Conditions for Linear Gravity Waves , 1994, SIAM J. Appl. Math..

[3]  Arthur Veldman,et al.  A Volume-of-Fluid based simulation method for wave impact problems , 2005 .

[4]  Arthur Veldman,et al.  AN IMPROVED VOLUME-OF-FLUID (IVOF) METHOD FOR WAVE IMPACT TYPE PROBLEMS , 2004 .

[5]  John D. Fenton,et al.  A Fourier approximation method for steady water waves , 1981, Journal of Fluid Mechanics.

[6]  Arthur Veldman,et al.  The numerical simulation of liquid sloshing in microgravity , 2006 .

[7]  Arthur Veldman.  The Simulation of Violent Free-Surface Dynamics at Sea and in Space , 2006 .

[8]  Tim Bunnik,et al.  Prediction of Green Water and Wave Loading Using a Navier-Stokes Based Simulation Tool , 2002 .

[9]  L YoungsD,et al.  Time-dependent multi-material flow with large fluid distortion. , 1982 .

[10]  C. W. Hirt,et al.  Volume of fluid (VOF) method for the dynamics of free boundaries , 1981 .

[11]  Arthur Veldman,et al.  Dynamics of liquid-filled spacecraft , 2003 .

[12]  Tim Bunnik,et al.  The numerical simulation of green water loading including vessel motions and the incoming wave field , 2005 .

[13]  Embrecht W. C. van Groesen,et al.  Modelling and simulation of surface water waves , 2002, Math. Comput. Simul..

[14]  Roel Luppes,et al.  The numerical simulation of liquid sloshing on board spacecraft , 2007, J. Comput. Phys..

[15]  Tim Bunnik,et al.  Application of a VOF Method to Model Compressible Two-Phase Flow in Sloshing Tanks , 2008 .

[16]  Arthur Veldman,et al.  Modeling two-phase flow with offshore applications , 2005 .

[17]  Tim Bunnik,et al.  Numerical Simulation of Sloshing in LNG Tanks With a Compressible Two-Phase Model , 2007 .

[18]  A. Veldman,et al.  Symmetry-preserving discretization of turbulent flow , 2003 .

[19]  A. Majda,et al.  Absorbing boundary conditions for the numerical simulation of waves , 1977 .

[20]  Dan Givoli,et al.  High-order nonreflecting boundary conditions for the dispersive shallow water equations , 2003 .

[21]  Jaap-Harm Westhuis.  Approximate Analytic Solutions And Numerical Wave Tank Results For the Reflection Coefficients of a Class of Numerical Beaches , 2000 .

[22]  Arthur Veldman,et al.  HYDRODYNAMIC WAVE LOADING ON OFFSHORE STRUCTURES SIMULATED BY A TWO-PHASE FLOW MODEL , 2006 .

[23]  Tim Bunnik,et al.  COMPRESSIBLE TWO-PHASE FLOW IN SLOSHING TANKS , 2008 .