Hull form optimization of a mega-boxer

dsme_megaboxer
MSC Danit. Source: DSME

With a capacity of 14,000 TEUs, an overall length of 365.5 meters and a deadweight of 165,517 metric tons, the MSC Danit became the world’s largest container vessel when finished by Korean shipyard Daewoo Shipbuilding & Marine Engineering (DSME). A New Panamax design, the ship offers excellent performance despite its record size. DSME used FRIENDSHIP SYSTEMSCAESES / FRIENDSHIP-Framework (FFW) for variation and optimization of proven parent ships to arrive at a design with maximum performance and efficiency. The final hull displayed less than 50% of the wave resistance of the baseline design, and the hydrodynamic optimization in CAESES/FFW had a favorable effect on propulsion performance.

Optimization overview—Design conditions for the carrier were:

  • LPP around 360m
  • Breadth just below 52m
  • Design draught of 14m
  • Guaranteed speed of 24 knots (Fn approx. 0.207)
  • 90% MCR with 15% sea margin at scantling draught of 15.5m

DSME approached design and optimization of the carrier in two phases:

  • Phase 1
  1. Selection of two proven parent ships with high nose type bulbs as starting point
  2. Scaling to principal dimensions
  3. CFD simulations for re-combinations of various fore- and aftbodies
  4. Identification of most promising candidate as baseline for further fine-tuning
  • Phase 2
  1. Investigation of a series of variants through parametric modeling and CFD
  2. Identification and selection of the influence of individual form parameters
  3. Selection of the best hull form for final model tests
  4. Model testing at HSVA (Hamburg ship model basin)

Systematic investigation and variation—In a systematic parameter study, the parent ships were varied by swinging the baseline’s sections using the Generalized Lackenby approach of CAESES/FFW. In this approach, the region of influence on the hull shape can be selected flexibly; in addition, the slopes of the shift functions can be defined freely at either end. Through this, variations may start well forward of the bossing and may end just aft of the forward perpendicular. With zero slopes at the beginning and end, transitions become very smooth. A series of variants was produced and numerically simulated for wave resistance. Here, the SHIPFLOW advanced CFD code of FRIENDSHIP SYSTEMS’ cooperation partner FLOWTECH was applied.

dsme_megaboxer_cfd
Baseline (top) vs. optimized (bottom). Source: FRIENDSHIP SYSTEMS

Variants indicated a beneficial modification of the parallel length of the mid-body from 5% to 15% LPP. Changes to the slope of the sectional area curve (SAC) as available with the Generalized Lackenby approach were applied in steps of 5deg, from minus 25deg to plus 25deg. Through the increase in the parallel mid-body, the wave resistance coefficient could be further reduced by up to 8%. Additional improvement was achieved through adjusted volume distribution at the forward perpendicular.

The hull form finally chosen for model testing featured a straight type and rather steep SAC with pronounced slope at entrance and run, and a comparatively long parallel mid-body. The design waterline displayed a small entrance angle and a relatively strong shoulder between stations 12 and 16.

Outcomes—In all, optimization with CAESES/FFW achieved:

  • Reduction in wave resistance by more than 50%
  • Modification of the mid-body
  • Adjusted volume distribution at forward perpendicular
  • Better propulsion
  • Stable wave patterns
  • Higher robustness of the vessel
  • Optimal trim

Benefits seen by DSME—“For DSME’s design process, we see three major advantages in applying CAESES / FRIENDSHIP-Framework,” explained Choi Young Bok from DSME’s Hydrodynamic R&D team: increased speed performance, increased automation, and speed-up of optimization.

For the vessel in operation, a major benefit of hull form optimization is the significant savings in fuel consumption. With an optimized hull, and powered by a 72,240kW engine, the ship makes the most of every ton of fuel.