Efficient implementation of a numerical model for flexible net structures

Martín, Tobías; Schacht, Stephan; Riesen, P.; Paschen, Mathias

doi:10.1016/j.oceaneng.2017.12.064

Cited by 14 publications

(11 citation statements)

References 8 publications

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“…Any restriction on time stepping is removed and no initial shape of the line has to be given. It is also noticed that the method was originally developed for nets 20 and direct coupling of both system matrices is now possible for applications in aquaculture technology.…”

Section: Resultsmentioning

confidence: 99%

“…The development of the new quasistatic mooring model based on finite elements which were originally developed for quasistatic modeling of more complex tensile structures 20,40 …”

Section: Numerical Modelsmentioning

confidence: 99%

“…The hydrodynamic forces are assigned to knots by equally distributing the net amount. As indicated in Reference 20, hydrodynamic forces can also be written as the partial sum of hydrodynamic drag, lift, and shear forces. The coefficients then depend particularly on the local angle between the fluid and bar unit vector and have to be found experimentally for each mooring configuration.…”

Section: Numerical Modelsmentioning

confidence: 99%

“…This article aims at developing such a quasistatic mooring model, which is disregarded in research so far. The finite element method for tensile structures, 20 which is based on a discrete representation of the structure using knots connected with trusses, is taken as the basis of the presented developments. Here, a linear system of equations is generated using force equilibria at each knot of the discrete line and a geometrical constraint preventing unphysical correlation of tension forces and bar deformation.…”

Section: Introductionmentioning

confidence: 99%

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Accurate modeling of the interaction of constrained floating structures and complex free surfaces using a new quasistatic mooring model

Martín

Kamath

Bihs

2020

Numerical Methods in Fluids

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SummaryA new approach for the coupled simulation of moored floating structures in a numerical wave tank using CFD is subject of this article. A quasistatic mooring model is derived by dividing the cable into finite elements and solve force equilibria in each time step. A successive approximation is applied to solve the problem most efficiently. Here, the unknown internal and external forces are separated, and the system is corrected iteratively using the intermediate results for the unit vectors until convergence is reached. An improved algorithm based on the directional ghost‐cell immersed boundary method is utilized for modeling floating objects in a three‐dimensional numerical wave tank. It is based on an implicit representation of the body on a stationary grid using a level set function. The motion of the rigid body is described using Euler parameters and Hamiltonian mechanics. Dynamic boundary conditions are enforced by modifying the ghost points in the vicinity of the structure. A special procedure for staggered grids is included in the article. The mooring model is coupled to the fluid‐structure interaction solver to simulate physically constrained floating bodies in waves. Several validation cases provide an overview of the accuracy of the mooring model and the floating algorithm. In addition, the comparison of the numerical results for the motion of a moored floating barge in regular waves with experiments is presented.

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Section: Resultsmentioning

confidence: 99%

“…The development of the new quasistatic mooring model based on finite elements which were originally developed for quasistatic modeling of more complex tensile structures 20,40 …”

Section: Numerical Modelsmentioning

confidence: 99%

Section: Numerical Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Accurate modeling of the interaction of constrained floating structures and complex free surfaces using a new quasistatic mooring model

Martín

Kamath

Bihs

2020

Numerical Methods in Fluids

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“…Simulation of a slender structure (such as the moorings in this study) at low tension is in itself a research subject. The tension element method, for instance, is one of the numerical methods developed to simulate slender structures with low pre-stressing or high flexibility (Paschen et al 2004;Martin et al 2018). Other simulation approaches have also been proposed by, e.g.…”

Section: Regular Wave Casesmentioning

confidence: 99%

Experimental and numerical investigation of a taut-moored wave energy converter: a validation of simulated mooring line forces

Yang

Ringsberg

Johnson

et al. 2020

Ships and Offshore Structures

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A reliable simulation model to calculate the motion and force responses of wave energy converters (WECs) is imperative to ensure the reliability and long-term performance of WEC systems; these aspects are fundamental to achieving full commercialisation of wave energy. A simulation model was developed and validated concerning the simulated WEC buoy motions in a previous study; this study validated the mooring force calculations for the same model. The example WEC system comprises a buoy, a power takeoff (PTO) system, and a three-leg mooring system wherein each leg is divided into two taut segments joined by a submerged float. A 1:20 physical model was built and tested in the Deepwater Offshore Basin at Shanghai Jiao Tong University. Numerical models were developed to simulate the coupled hydrodynamic and structural responses of the WEC system, primarily using potential flow theory, the boundary element method, the finite element method, and the Morison equation. The simulated and measured axial force results at the top ends of the six mooring segments were compared; the results agreed best in the lower segments of each mooring leg and in the moorings on the downwind side because of the PTO system uncertainties and the uncalibrated damping in the numerical model. Nonetheless, the numerical model reasonably predicted the moorings' accumulated fatigue damage, demonstrating that the model can be reliably used for mooring structural analyses. The study also used the validated numerical model to simulate a full-scale WEC system installed in Runde, Norway. A comparison of the results from the full-scale measurements and simulations shows that the numerical simulation model exhibited a good predictive capability for the mooring forces of the full-scale WEC system.

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Experimental and Numerical Investigations of the Hydrodynamic Characteristics, Twine Deformation, and Flow Field Around the Netting Structure Composed of Two Types of Twine Materials for Midwater Trawls

Thierry

Tang

Achile

et al. 2021

J. Ocean Univ. China

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Efficient implementation of a numerical model for flexible net structures

Cited by 14 publications

References 8 publications

Accurate modeling of the interaction of constrained floating structures and complex free surfaces using a new quasistatic mooring model

Accurate modeling of the interaction of constrained floating structures and complex free surfaces using a new quasistatic mooring model

Experimental and numerical investigation of a taut-moored wave energy converter: a validation of simulated mooring line forces

Experimental and Numerical Investigations of the Hydrodynamic Characteristics, Twine Deformation, and Flow Field Around the Netting Structure Composed of Two Types of Twine Materials for Midwater Trawls

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