Suppression of irregular frequency effects in fluid–structure interaction problems using a combined boundary integral equation method

Lau, Siew Ming; Hearn, Grant E.

doi:10.1002/fld.1650090703

Cited by 25 publications

(7 citation statements)

References 12 publications

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“…This accounts for why some methods originally developed for acoustical problems were adopted by researchers for dealing with surface-wave}body interaction problems. For example, Lee and Sclavounos [49] utilized Burton and Miller's method [50] and Lau and Hearn [51] utilized Schenck's method [52] for predicting related hydrodynamic quantities. The "rst method linearly combines the standard integral equation with its normal derivative and assigns a coupling constant of a non-zero imaginary part as well.…”

Section: A Brief Introductionmentioning

confidence: 99%

On the singularities of Green's formula and its normal derivative, with an application to surface-wave-body interaction problems

Yang¹

2000

Int. J. Numer. Meth. Engng.

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SUMMARYThe paper presents the non-singular forms of Green's formula and its normal derivative of exterior problems for three-dimensional Laplace's equation. The main advantage of these modi"ed formulations is that they are amenable to solution by directly using quadrature formulas. Thus, the conventional boundary element approximation, which locally regularizes the singularities in each element, is not required. The weak singularities are treated by both the Gauss #ux theorem and the property of the associated equipotential body. The hypersingularities are treated by further using the boundary formula for the associated interior problems. The e$cacy of the modi"ed formulations is examined by a sphere, in an in"nite domain, subject to Neumann and Dirichlet conditions, respectively.The modi"ed integral formulations are further applied to a practical problem, i.e. surface-wave}body interactions. Using the conventional boundary integral equation formulation is known to break down at certain discrete frequencies for such a problem. Removing the &irregular' frequencies is performed by linearly combining the standard integral equation with its normal derivative. Computations are presented of the added-mass and damping coe$cients and wave exciting forces on a #oating hemisphere. Comparing the numerical results with that by other approaches demonstrates the e!ectiveness of the method.

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Section: A Brief Introductionmentioning

confidence: 99%

On the singularities of Green's formula and its normal derivative, with an application to surface-wave-body interaction problems

Yang¹

2000

Int. J. Numer. Meth. Engng.

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“…6. Lau and Hearn (1989) present a review of different methods for removal or irregular frequencies. In Table 2 gives the comparison for S 1 r dS evaluated using the different approximations above for a square panel with side 5 m. We notice that using (126) gives erroneous values for z < 0, as indicated by the values enclosed in the blue box.…”

Section: Considerations For Improvementmentioning

confidence: 99%

An Open-Source Python-Based Boundary-Element Method Code for the Three-Dimensional, Zero-Froude, Infinite-Depth, Water-Wave Diffraction-Radiation Problem

Viswanathan¹,

Holden²,

Egeland³

et al. 2021

MIC

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In this paper, a new open-source implementation of the lower-order, 3-D Boundary Element Method (BEM) of solution to the deep-water, zero Froude-number wave-body interaction problem is described. A validation case for OMHyD, the new open-source package, is included, where the outputs are compared to results obtained using the widely used frequency-domain hydrodynamic analysis package ANSYS-AQWA. The theory behind the solution to the diffraction-radiation problem is re-visited using the Green function method. The Hess and Smith panel method is then extended to the case of a floating object using the image-source to impose the wall condition at the free-surface, and a wavy Green function component to account for presence of free-surface waves. An algorithm for computer implementation of the procedure is developed and subsequently implemented in PYTHON. The wavy part of the Green function is determined using a verified and published FORTRAN code by Teleste and Noblesse, wrapped for PYTHON using the Fortran to Python (F2PY) interface. Results are presented for the various stages of implementation viz. panelling, body in infinite fluid domain, effect of the free-surface, and effect of surface-waves. The hydrodynamic coefficients obtained from this preliminary frequency-domain analysis are shown to be in satisfactory agreement with ANSYS-AQWA results. Conclusions are drawn based on the performance of the code, followed by suggestions for further improvement by including the removal of irregular-frequencies, multi-body interactions, and bottom interference, which are not considered in the present implementation.

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“…This method originates from Ref. [20]. Therefore, by applying Green's theorem in the interior domain of the floating body, an additional boundary integral equation is introduced in a combined application with Equation 7:…”

Section: Removal Of Irregular Frequenciesmentioning

confidence: 99%

HAMS: A Frequency-Domain Preprocessor for Wave-Structure Interactions—Theory, Development, and Application

Liu

2019

JMSE

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This paper presents the theoretical background, the numerical implementation, and the applications of a new software that has been developed in recent years for the analysis of wave-structure interactions. The software is developed in the frequency domain, as a preprocessor of computing the wave excitation force, the added mass, and the wave radiation damping, for input to a time-domain solver via the Fourier cosine and sine transforms. In addition, it can also predict the motion responses of a marine structure with sufficient accuracy, with or without the presence of the mooring system. Unlike other frequency-domain software, such as WAMIT® and Hydrostar®, the present software currently employs the least squares method in association with a partially extended boundary integral equation method to remove the so-called “irregular frequencies”. Calculation of the free-surface Green’s function employs a combination of fast-convergent series expansions in different parametric sub-regions. The solution of the resultant linear algebraic system employs the lower-upper (LU) decomposition method. Symmetry properties can be exploited, and the open multi-processing (OpenMP) parallelization technique can be applied to reduce the computation burden. The accuracy and the efficiency of the developed software are finally confirmed by numerical validations on a floating ellipsoid benchmark case and the OC4 DeepCwind semisubmersible floating wind turbine in practice. A free executable version of the software is available to the research communities with the hope of facilitating advancements in the researches that are relevant to ocean engineering and marine renewable energies.

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Suppression of irregular frequency effects in fluid–structure interaction problems using a combined boundary integral equation method

Cited by 25 publications

References 12 publications

On the singularities of Green's formula and its normal derivative, with an application to surface-wave-body interaction problems

On the singularities of Green's formula and its normal derivative, with an application to surface-wave-body interaction problems

An Open-Source Python-Based Boundary-Element Method Code for the Three-Dimensional, Zero-Froude, Infinite-Depth, Water-Wave Diffraction-Radiation Problem

HAMS: A Frequency-Domain Preprocessor for Wave-Structure Interactions—Theory, Development, and Application

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