Speed loss in waves and wave-induced torsion of a wide-breadth containership

Abstract

Aspects relevant for operational and structural design of a wide-breadth, neo-panmax containership were addressed. First, speed loss in waves was investigated. Second, wave-induced global hull girder torsion was determined to assess the effects of the increased breadth on this load component, generally considered critical for the ship’s structural strength. An extended Reynolds-averaged Navier–Stokes (RANS) equations solver simulated the ship advancing in calm water as well as in selected regular head and bow waves. A boundary element method (BEM) computed transfer functions of wave-induced ship response. Before using spectral techniques to obtain long-term predictions of hull girder torsion, these transfer functions were corrected to account for non-linear effects. To assess the reliability of the computed long-term hull girder torsion, the extended RANS equations solver was used to perform additional simulations for this ship advancing at selected speeds in equivalent regular design waves that represent wave conditions considered critical for structural design. Except for the very forward part of the ship, long-term BEM-based predictions of wave-induced hull girder torsion did not exceed rule values. Comparative BEM and RANS predictions of hull girder torsion differed significantly, underlining the need to validate the predictions systematically.

The influence of nonlinearities on the symmetric hydrodynamic response of a 10,000 TEU Container ship

“…), the idealisation of the medium (e.g. water compressibility and density variability) and hull flexibility especially for slender vessels with large bow flare or beam can also be important factors in whipping, springing, impact problems and underwater explosions Rathje, 2011).…”

A regression and beam theory based approach for fatigue assessment of containership structures including bending and torsion contributions

“…Therefore, to capture the nonlinear characteristics (such as hull geometry and wetted surface), a 3D panel method is often used to the wave loads calculations for fatigue assessment [10e12]. Recently, computational fluid dynamics has also started to be applied for wave load analysis in large ships [13], but is still too time consuming for fatigue design purposes.…”

A Rankine Panel Method for Added Resistance of Ships in Waves

“…The design of cargo and passenger ships is usually performed on the basis of powering requirements in calm water without con sidering the actual operating conditions; the effect of the seaway is included using an experience-based allowance on the required power called the sea margin [1], This practice can lead to either unnecessary excessive power reserves or to underpowered ships that cannot sail against wind and waves in heavy weather [2], Because of the increased concern with fuel consumption, a reliable prediction of the power increase in waves becomes increasingly important for both ship designers (selection of the engine and propulsion system) and operators (prediction of the service speed and the associated fuel consumption along with the selection of speed and course). This issue is important for reg ulatory bodies, not only regarding the required redundancy to ensure maneuverability and course keeping in adverse environ ments, but also regarding the assumed ship speed in waves as a prerequisite for a global strength analysis of the ship's hull girder.…”

“…Computational fluid dynamics (CFD) methods based on the numerical solution of RANS or Euler equations demonstrated their ability to provide results of comparable or superior accuracy to model test measurements in many problems of ship hydrodynamics [6,7], but their applications to added resistance predictions are still rare [2,8,9]. Although such methods might, in principle, directly address the problem of power increase in irreg ular waves (if combined with an engine model), both long waves (and the corresponding large ship motions) and short waves (which contribute to the added resistance through diffraction) have to be simultaneously resolved, which significantly increases the required grid size and computational time.…”