Numerical simulation with a macroscopic CFD method and experimental analysis of wave interaction with fixed porous cylinder structures

Qiao, Dongsheng; Mackay, Ed; Yan, Jun; Feng, Changlong; Li, Bin Bin; Feichtner, Anna; Ning, Dezhi; Johanning, Lars

doi:10.1016/j.marstruc.2021.103096

Cited by 19 publications

(3 citation statements)

References 54 publications

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“…According to the aforementioned computational conditions and this paper's high-efficiency method, the hydrodynamic constraint loads of CP-VLFS's connectors in time-domain are determined under various wave angles, RIW excitation forces at SS6. The duration for an entirely stable sea state is maintained for nearly 1-2 h (Qiao et al, 2021), hence, this paper defines t=2 h as the computation time.…”

Section: Results Analysis and Discussionmentioning

confidence: 99%

Hydrodynamic constraint loads estimation on connectors of column-pontoon type very large floating structure (CP-VLFS) under wave stimulation

Han²,

Ji³

et al. 2023

Front. Mar. Sci.

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Column-pontoon type very large floating structure (CP-VLFS) operated at the deep and sea faraway areas are generally exposed to the extremely complex wave conditions. The connectors of CP-VLFS are generally subjected to complicated hydrodynamic constraint loads when the modules of CP-VLFS are stimulated by the long-tern wave forces. The general method for analyzing the hydrodynamic performances for marine floating structures and their components is almost on the basis of potential flow/fluid theory (PFT), but its algorithm principle is relatively complex and would consume plenty of computing time. During the preliminary design and scheme comparison stages for CP-VLFSs, the hydrodynamic results for CP-VLFSs’ modules and their connectors required to be rapidly determined. Hence, a rapid and high-efficiency estimating method for time-domain hydrodynamic constraint loads of connectors on CP-VLFS considering the mathematical and mechanical model of rigid module and flexible connector (RMFC) is developed via this paper. During this estimation method, the Morison theory of floating body is employed to assess the hydrodynamic excitation forces by random and irregular wave (RIW) on CP-VLFS structures, and a series of concise formulas for estimating the hydrodynamic constraint loads of CP-VLFS connectors are derived based on the geometrical relationship of the CP-VLFS modules’ motion. For this paper’s explorations, a three-module CP-VLFS model is considered as a case, and the time-domain hydrodynamic constraint loads of CP-VLFS’s connectors are determined under the RIW stimulations with different wave angles. Hydrodynamic constraint loads of CP-VLFS connectors estimated by this paper agree well with the results of PFT and those of physical experiment, validation the methodologies developed by this paper. Some useful conclusions may provide significant technical supports for hydrodynamic characteristics of CP-VLFS modules and their connectors optimization.

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Section: Results Analysis and Discussionmentioning

confidence: 99%

Hydrodynamic constraint loads estimation on connectors of column-pontoon type very large floating structure (CP-VLFS) under wave stimulation

Han²,

Ji³

et al. 2023

Front. Mar. Sci.

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“…Such an approach is erroneous as discussed in Section 2.4. Conversely, in [22], only the normal component of the flow is considered when establishing the value of the resistance coefficients, essentially resulting in f y = f z = 0. In fact, this lack of clarity about the role of the resistance coefficients in characterising permeable screen macro behaviours leads the authors of [23] to recommend the use of isotropic coefficients ( f x = f y = f z ) as they compare the performance of porous baffles to volumetric porous media with isotropic and orthotropic resistance coefficients, without sufficient insight on the differences in behaviour of the models considered on the fundamental level.…”

Section: Current Modelling Practicementioning

confidence: 99%

A Method to Evaluate Forchheimer Resistance Coefficients for Permeable Screens and Air Louvers Modelled as a Porous Medium

Marykovskiy,

Pomaranzi,

Schito

et al. 2024

Fluids

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Porous medium models are commonly used in Computational Fluid Dynamics (CFD) to simulate flow through permeable screens of various types. However, the setup of these models is often limited to replicating a pressure drop in cases where fluid inflow is orthogonal to the screen. In this work, a porous medium formulation that employs a non-diagonal Forchheimer tensor is presented. This formulation is capable of reproducing both the pressure drop and flow deflection under varying inflow angles for complex screen geometries. A general method to determine the porous model coefficients valid for both diagonal and non-diagonal Forchheimer tensors is proposed. The coefficients are calculated using a nonlinear least-squares optimisation based on an analytical solution of a special case of the Navier–Stokes equations. The applicability of the proposed method is evaluated in four different scenarios supplemented by local CFD simulations of permeable screens: wire mesh, perforated screens, air louvers, and expanded mesh panels. The practical application of this method is demonstrated in the modelling of windbreaks and permeable double-skin facades, which typically employ the aforementioned types of porous screens.

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“…This is believed to be the worst scenario in terms of wave/current loads on the tube net and thus will provide a conservative design for the seaweed ring structure and mooring lines. It is evidenced from the literature [34,35] that environmental loads on perforated cylinders are smaller than those on impermeable cylinders. The initial tube nets used for seeding have a diameter of 75 mm, whereas the tube nets containing mature seaweed ready for harvesting measure approximately 200 mm-300 mm in diameter [25].…”

Section: Modelling Of Seaweed Tube Netsmentioning

confidence: 99%

Hydroelastic Responses of a Submersible Ring Structure for Offshore Seaweed Cultivation under Wave Action

Nguyen,

Wang,

von Herzen

et al. 2023

JMSE

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This paper investigates the hydroelastic response of a submersible circular ring structure, designed for offshore seaweed cultivation, under wave action and during the submergence process. The ring structure comprises two circular HDPE pipes connected to each other by equally spaced brackets. The structure carries seaweed grow-out lines, and is kept in position by a mooring-line system used for fish pens. The HDPE collar is equipped with multiple inlet and outlet valves, allowing it to be submerged to avoid strong waves and to be raised to the water surface when the strong waves die down. The software AquaSim was used for the hydroelastic analysis of the moored structure. It is found that we can significantly reduce the von Mises stresses in the ring structure as well as the mooring-line forces by submerging. However, the structure can experience significant increase in stress during the submergence process due to bending from combined wave action and non-uniform distribution of filled water in the ring structure. This stress increase may cause structural damage or even failure. Therefore, it is important to submerge the ring structure in calm waves ahead of predicted storms and to control the distribution of seawater into the ring structure. For the latter, it is best to use at least two inlet valves and two outlet valves to minimize the likelihood of damage of the ring structure during the submergence process.

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Numerical simulation with a macroscopic CFD method and experimental analysis of wave interaction with fixed porous cylinder structures

Cited by 19 publications

References 54 publications

Hydrodynamic constraint loads estimation on connectors of column-pontoon type very large floating structure (CP-VLFS) under wave stimulation

Hydrodynamic constraint loads estimation on connectors of column-pontoon type very large floating structure (CP-VLFS) under wave stimulation

A Method to Evaluate Forchheimer Resistance Coefficients for Permeable Screens and Air Louvers Modelled as a Porous Medium

Hydroelastic Responses of a Submersible Ring Structure for Offshore Seaweed Cultivation under Wave Action

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