Seakeeping and optimized nozzle design for a stern trawler

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CUSTOMER: NODOSA

RELATED SERVICES: CFD SIMULATIONS, HULL OPTIMIZATION, SEAKEEPING, POWERING PREDICTION, NOZZLE DESIGN

SCOPE OF WORK:

  • Viscous CFD ship resistance calculation
  • Nominal wake calculation
  • Bow shapes optimization, with resistance reduction
  • Stern shape optimization, improving wake and hull-nozzle interaction on both free running and trawling conditions.
  • Bilge keels alignment
  • Nozzle optimization, using self-propulsion calculation with CFD, adapting design accordingly with vessel operational profile.
  • Production drawings

 

RESULTS:

The optimization study was focused in seakeeping performance improving, considering different hull shapes (conventional, vertical bow…) under two sea states and various loading conditions, aiming to decide which was the most adequate one for the vessel operational profile. In order to do so, pitching and acceleration in several points were evaluated.

Calculations have been performed using a sliding mesh and two degrees of freedom (heave and pitch) in such way that both accelerations and added resistance are measured under regular waves.

The evaluation of pitching, acceleration and wave added resistance was performed considering different wave configurations (height and period) aiming to reflect the future operation of the vessel and reflect owner’s requirements.

Subsequently, an optimization study was conducted for both bow and stern shapes, where significant improves in resistance were achieved, taking into consideration various loading conditions.

Regarding the nozzle, the behavior of several profile geometries was analyzed, both in free running and trawling conditions, focusing on this last one for the optimum design goal. After comparing power predictions for each case, production drawings corresponding to the best geometry were delivered.

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