Trans RINA, Vol 153, Part B2, Intl J Small Craft Tech, 2011 Jul-Dec COUPLING OF RANSE-CFD WITH VPP METHODS: FROM THE NUMERICAL TANK


TO VIRTUAL BOAT TESTING (DOI No: 10.3940/rina.ijsct.2011.b2.116)


C Boehm, Delft University of Technology, Netherlands / Yacht Research Unit Kiel, Germany K Graf, University of Applied Sciences Kiel / Yacht Research Unit Kiel, Germany SUMMARY


The paper proposes a new method to evaluate the performance of sailing yachts. It is based on the idea to directly implement the calculation of sail force equilibrium in a RANSE flow solver. This is done by coupling an empirical prediction of sail forces with hydrodynamic forces calculated by the flow code and solving the equations of motion within an transient RANSE solution. The paper discusses implementation steps for the inclusion of the sail forces into the flow code as well as calculation and grid setup. Some first results of the method christened RVPP are shown for a generic yacht design and are compared with results from a classical VPP approach on the same design. The paper finishes with a discussion of the pros and cons of the method.


NOMENCLATURE 


 


Leeway angle (°) Heel angle (°)


Rudder angle (°)


 Dynamic viscosity (Pa s)  Kinematic viscosity (m² s-1) T


Turbulent viscosity (m² s-1)


 Density of water (kg m-3)  Tab angle (°) i


Viscous stress (Pa)


 Control Volume (m³)  Specific turbulent dissipation (s-1)  Angular velocity of rigid body (rad s-1)


AW Apparent wind vector (m s-1) AWA Apparent Wind Angle (°) AWS Apparent Wind Speed (m s-1) B


ASails Total Sail Area (m²)


BOA Breadth over all (m) c


cD Drag Coefficient (-)


cDTotal Aggregate Drag Coefficient (-) CE


Efficiency coefficient (-)


CE Aerodynamic Centre of Effort (m) CG Centre of Gravity (m) cL


Lift Coefficient (-)


cLTotal Aggregate Lift Coefficient (-) cM


CV FHß


Added mass coefficient (-) Control Volume (m³)


DWL Design Water line (m) FH


Hydrodynamic Lift normal to span and incident flow (N)


Hydrodynamic Lift due to leeway (N)


FH Hydrodynamic Lift due to rudder (N) FH Hydrodynamic Lift due to trim tab (N) FAero Total Sail Force Vector (N) FHydro Hydrodynamic Fluid Force (N) FExt External Force (N) FSail Sail Force (N) FSA Added mass Force sails (N)


Body forces, normalized by mass (m s-2) Volume-of-Fluid Fraction (-)


FD Hydrodynamic Drag Force (N) flat g I k


Flattening factor of sails (-) Gravity vector (m s-2)


Tensor of moment of Inertia (kg m²) Turbulent kinetic energy (m s-1)


LOA Length over all (m) LCG Longitudinal Centre of Gravity (m) m


Mass (kg)


MHydro Hydrodynamic Fluid Moment (Nm) MExt External Moment (Nm) n p


Surface normal (-) Pressure (N m-2 )


rH


RH RI


RPP RTot RU


Si T


Added Resistance due to Heel Ratio (-) Added Resistance due to Heel (N) Induced Resistance (N) Parasitic profile drag (N) Total Resistance (N) Upright Resistance (N)


RWaves Added Resistance due to sea state (N) Reef


Reefing factor (-)


Control Volume Face Surface (m²) Total draft (m)


T Transformation matrix from local into global coordinate system (-)


TCB Draft Canoe Body (m) TCG Transverse Centre of Gravity (m) TWA True Wind Angle (deg) TWS True Wind Speed (m s-1) u


Flow velocity (m s-1)


ux,uy Components of boat velocity (m s-1) VCG Vertical Centre of Gravity (m) v


us uB


xi xG


Linear velocity (m s-1) CV face centre vector (m)


Vector to centre of gravity (m) zceAero Aerodynamic vertical centre of efficiency (m)


Sail Measurement Definitions P


Vertical Distance between boom and hoist point of main (m)


BAD Vertical Distance between Deck and boom (m) ©2011: The Royal Institution of Naval Architects B-81


velocity of sails due to rotation (m s-1) Boat velocity (m s-1)


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