Wave resistance determination by pressure integration and wave cut analysis using non-linear rankine panel method

This study demonstrates that a bounded, physically relevant solution does exist at the so-called T = Uω/g = 1/4 resonance in the linear seakeeping problem for a realistic ship with forward speed, U, frequency of encounter, ω, and gravitational acceleration, g. The solution of the seakeeping problem by a linear, three dimensional, time-domain Rankine panel method, validated through numerical analysis, testing, and comparison to physical experiments, supports this claim. The solution can also be obtained with equal validity through frequencies both above and below the critical frequency.

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On Numerical Treatments of the Infinite Condition in the Frequency-Domain Rankine Panel Method

Journal of the Japan Society of Naval Architects and Ocean Engineers ◽

10.2534/jjasnaoe.24.105 ◽

2016 ◽

Vol 24 (0) ◽

pp. 105-127

Author(s):

Hidetsugu Iwashita

Keyword(s):

Frequency Domain ◽

Panel Method ◽

Rankine Panel Method ◽

Numerical Treatments

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Application of a Boundary Element Method for Wave-Body Interaction Problems Considering the Non-Linear Water Surface

Volume 7A: Ocean Engineering ◽

10.1115/omae2017-61852 ◽

2017 ◽

Author(s):

Daniel Ferreira González ◽

Jonas Bechthold ◽

Moustafa Abdel-Maksoud

Keyword(s):

Water Surface ◽

Three Dimensional ◽

Free Water ◽

Numerical Approach ◽

Panel Method ◽

The Body ◽

Time Step ◽

Non Linear ◽

Wigley Hull ◽

Tank Test

In this paper an existing time domain panel method, which was originally developed for propeller flow simulations, is extended by implementing the mixed Eulerian-Lagrangian approach for the computation of the non-linear free water surface. The three-dimensional panel method uses a constant source and doublet density distribution on each panel and a Dirichlet boundary condition to solve the velocity potential in every time step. Additionally, a formulation for the acceleration potential is included in order to determine the hydrodynamic forces accurately. The paper gives an overview on the governing equations and introduces the numerical approach. Validation results of the developed method are presented for the wave resistance of a submerged spheroid and a wigley hull. Additionally, the wave diffraction due to a surface piercing cylinder in regular waves is validated regarding the forces and the water surface elevation around the body. Here, the computations are compared with other numerical methods as well as tank test results. Apart from this, the paper deals with an application example showing simulations of an artificial service vessel catamaran in waves. The forces on the hull with and without forward speed are presented. The paper concludes with a discussion of the presented results and a brief outlook on further work.

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Waves’ Numerical Dispersion and Damping due to Discrete Dispersion Relation

Volume 8A: Ocean Engineering ◽

10.1115/omae2014-23152 ◽

2014 ◽

Author(s):

Babak Ommani ◽

Odd M. Faltinsen

Keyword(s):

Free Surface ◽

Dispersion Relation ◽

Surface Waves ◽

Boundary Integral ◽

Panel Method ◽

Numerical Dispersion ◽

Finite Difference Schemes ◽

Rankine Panel Method ◽

Free Surface Waves ◽

The Waves

In linear Rankine panel method, the discrete linear dispersion relation is solved on a discrete free-surface to capture the free-surface waves generated due to wave-body interactions. Discretization introduces numerical damping and dispersion, which depend on the discretization order and the chosen methods for differentiation in time and space. The numerical properties of a linear Rankine panel method, based on a direct boundary integral formulation, for capturing two and three dimensional free-surface waves were studied. Different discretization orders and differentiation methods were considered, focusing on the linear distribution and finite difference schemes. The possible sources for numerical instabilities were addressed. A series of cases with and without forward speed was selected, and numerical investigations are presented. For the waves in three dimensions, the influence of the panels’ aspect ratio and the waves’ angle were considered. It has been shown that using the cancellation effects of different differentiation schemes the accuracy of the numerical method could be improved.

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