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Advanced
Analysis > Computational Fluid
Dynamics
STX Canada/US Marine (STXM) has been on the cutting edge of CFD use in the marine industry since 2002 for a wide range of fluid flows including:
- Hull powering calculations
- Hullform optimization and appendage alignment
- Engine room ventilation
- Exhaust particle tracking
- Heli-deck turbulence calculations
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- Tank sloshing loads
- LNG tank cooldown analysis
- Combustion dynamics
- Frequency and time domain seakeeping simulations
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Aerodynamic analysis of turbulence levels over the helicopter flight deck
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Resistance tests using CFD to optimize hullform
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The new ducktail getting a final coat of paint
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CFD Model of the original hull stern (top) and with fitted ducktail (bottom) showing the improvement in the transom wave and aft shoulder wave
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Potential Flow Seakeeping Simulation of a Patrol Vessel in an irregular seaway using Precal
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For most CFD calculations, STXM uses the state-of-the-art commercial CFD code Star CCM+, while for most seakeeping calculations STXM typically uses the codes ShipMo or Precal, depending on the vessel under study.
STXM has been involved in a number of large CFD projects over the years. Notable recent projects include:
Design of an Arctic Offshore Patrol Vessel for the Canadian Navy:
For this project STXM has optimized the hullform for both open water performance and ice breaking capabilities. Extensive CFD and model tests were used to design a hull that blended the hull features required for ice breaking, with those required for high open water speed and good seakeeping operability. The superstructure was also modeled using CFD to ensure the turbulence levels were acceptable over the heli-deck. Time domain simulations were conducted to measure the standard deviation of fluctuations in the vertical velocity, and ensure they were within acceptable limits for helicopter operations.
Upgrades to the MS Veendam
As part of a recent refit to the MS Veendam, STXM designed a ducktail appendage for the ship. The purpose of this appendage was to raise the GM of the vessel to offset topside weight additions, and to decrease the resistance of the vessel. The appendage was designed in a fashion similar to other ducktails designed by STXM, and was tested entirely using CFD methods. Following the refit, side by side trials of the MS Veendam against a sister vessel without the ducktail showed an increase in top speed of ½ a knot for the Veendam, and that to achieve the same speed, a 6% reduction in power demand was achieved.
Seakeeping Calculations
As a result of our participation in the MARIN Cooperative Research (CRS) program, STXM has access to a couple of advanced seakeeping programs developed by MARIN. By making use of these state-of-the-art 3-D potential flow seakeeping codes, PRECAL and PRETTI, we can offer accurate seakeeping predictions for a wide variety of hull forms including monohulls, SWATHs and trimarans.
STXM also uses the strip theory based code ShipMo for seakeeping calculations of monohulls. This code has been developed by DRDC and is well validated by numerous sea trials.
These software tools also improve our ability to calculate the structural loads imposed on ships in a seaway and enable STXM to conduct a completely non-linear time domain analysis of the ship’s motions and structural loads. Real time visualizations of seakeeping predictions provide our clients with accurate representations of the motions of their designs in any sea state.
Time Domain Seakeeping Simulations using Star CCM+
Viscous damping plays an important role in damping resonant roll motions, and for the unique hullform of the Compact Semi-Submersible (CSS), this is also the case for heave and pitch motions. To ensure the accuracy of panel code simulations, STXM conducted CFD time domain seakeeping simulations for the CSS using Star CCM+.
Ventilation and Exhaust
Exhaust
flows on the exterior deck of a cruise ship, automobile emissions
the car deck of a ferry, or ventilation in a ship’s engine room
are all important safety and comfort issues for passengers and
crew. CFD provides valuable, minimum cost solutions to
model any exhaust or ventilation problem.
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Time domain seakeeping simulations of a Compact Semi-Submersible using Star CCM+
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Hull form Optimization and Powering Calculations of a Tanker Using CFD
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Modeling an engine room to ensure adequate ventilation and heat rejection
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Thermal loads from the cooldown
of LNG tanks
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