Transient Wave Packets: New Application in CFD-Methods

Wang

Clauss

et al. 2023

J. Marine. Sci. Appl.

This paper presents a comprehensive experimental study on the effect of extreme waves on a LNG carrier. The LNG carrier model was equipped with a variety of sensors to measure motions, green water height on deck as well as local and global loads. Experiments in transient wave packets provided the general performance in waves in terms of response amplitude operators and were accompanied by tests in regular waves with two different wave steepness. These tests allowed detailed insights into the nonlinear behavior of the vertical wave bending moment in steep waves showing that green water on deck can contribute to a decrease of vertical wave bending moment. Afterwards, systematic model tests in irregular waves were performed to provide the basis for statistical analysis. It is shown that the generalized extreme value distribution model is suitable for the estimation of the extreme peak values of motions and loads. Finally, model tests in tailored extreme wave sequences were conducted comparing the results with the statistical analysis. For this purpose, analytical breather solutions of the nonlinear Schrödinger equation were applied to generate tailored extreme waves of certain critical wave lengths in terms of ship response. Besides these design extreme waves, the LGN carrier was also investigated in the model scale reproduction of the real-world Draupner wave. By comparing the motions, vertical wave bending moment, green water column and slamming pressures it is concluded that the breather solutions are a powerful and efficient tool for the generation of design extreme waves of certain critical wave lengths for wave/structure investigations on different subjects.

Section: Transient Wave Packetmentioning

confidence: 99%

Experimental Study on the Effect of Extreme Waves on a LNG Carrier

Wang

Clauss

et al. 2023

J. Marine. Sci. Appl.

“…Transient wave packets have been introduced for the efficient experimental determination of the hydrodynamic behaviour of ships and offshore structures e.g., [38,39,[51][52][53][54][55]. TWPs are characterised by a synthesised task-related wave spectrum with tailored phase distribution.…”

Section: Transient Wave Packetsmentioning

confidence: 99%

Note on the Application of Transient Wave Packets for Wave–Ice Interaction Experiments

Hartmann

Polach

2021

Water

This paper presents the transient wave packet (TWP) technique as an efficient method for wave–ice interaction experiments. TWPs are deterministic wave groups, where both the amplitude spectrum and the associated phases are tailor-made and manipulated, being well established for efficient wave–structure interaction experiments. One major benefit of TWPs is the possibility to determine the response amplitude operator (RAO) of a structure in a single test run compared to the classical approach by investigating regular waves of different wave lengths. Thus, applying TWPs for wave–ice interaction offers the determination of the RAO of the ice at specific locations. In this context, the determination of RAO means that the ice characteristics in terms of wave damping over a wide frequency range are obtained. Besides this, the wave dispersion of the underlying wave components of the TWP can be additionally investigated between the specific locations with the same single test run. For the purpose of this study, experiments in an ice tank, capable of generating tailored waves, were performed with a solid ice sheet. Besides the generation of one TWP, regular waves of different wave lengths were generated as a reference to validate the TWP results for specific wave periods. It is shown that the TWP technique is not only applicable for wave–ice interaction investigations, but is also an efficient alternative to investigations with regular waves.

“…TWP's are deterministic wave groups, where both the amplitude spectrum and the associated phases are tailor-made manipulated. One major benefit of TWP's is the possibility to determine the response amplitude operator (RAO) of a structure in a single test run being well established in ocean engineering e.g., [40][41][42][43][44][45][46]. In the context of wave-ice interaction investigations, RAO denotes the determination of ice characteristics in terms of wave damping between two locations (measuring points) over a wide frequency range.…”

Section: Experimental Program and Generated Wavesmentioning

confidence: 99%

A New Model Ice for Wave-Ice Interaction

Polach

Hartmann

2021

Water

The interaction of waves and ice is of significant relevance for engineers, oceanographers and climate scientists. In-situ measurements are costly and bear uncertainties due to unknown boundary conditions. Therefore, physical laboratory experiments in ice tanks are an important alternative to validate theories or investigate particular effects of interest. Ice tanks use model ice which has down-scaled sea ice properties. This model ice in ice tanks holds disadvantages due to its low stiffness and non-linear behavior which is not in scale to sea ice, but is of particular relevance in wave-ice interactions. With decreasing stiffness steeper waves are required to reach critical stresses for ice breaking, while the non-linear, respectively non-elastic, deformation behavior is associated with high wave damping. Both are scale effects and do not allow the direct transfer of model scale test results to scenarios with sea ice. Therefore, the alternative modeling approach of Model Ice of Virtual Equivalent Thickness (MIVET) is introduced. Its performance is tested in physical experiments and compared to conventional model ice. The results show that the excessive damping of conventional model ice can be reduced successfully, while the scaling of the wave induced ice break-up still requires research and testing. In conclusion, the results obtained are considered a proof of concept of MIVET for wave-ice interaction problems.