Numerical and Experimental Modelling of Wave Loads on Thin Porous Sheets

Mackay, Ed; Johanning, Lars; Ning, Dezhi; Qiao, Dongsheng

doi:10.1115/omae2019-95148

Cited by 9 publications

(8 citation statements)

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“…However, a constant value of δ = 0.5 has been used in the present work. This value was found to give good agreement between experimental results and predictions from a potential-flow model by Mackay et al (2019).…”

Section: Theoretical Pressure-drop Modelsupporting

confidence: 65%

“…Since differences in the measured wave height between the deeper section and the raised section have been observed, it is hypothesized that it generates a diffracted wave field that interacts with the reflected wave from the porous sheet and cylinders. The effect is discussed further by Mackay et al (2019) who also found discrepancies with a potential-flow model.…”

Section: Physical Experimentsmentioning

confidence: 88%

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Using a porous-media approach for CFD modelling of wave interaction with thin perforated structures

Feichtner

Mackay

Tabor

et al. 2020

J. Ocean Eng. Mar. Energy

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This work presents the use of a porous-media approach for computational fluid dynamics (CFD) modelling of wave interaction with thin perforated sheets and cylinders. The perforated structures are not resolved explicitly but represented by a volumetric porous zone where a volume-averaged pressure gradient in the form of a drag term is applied to the Navier–Stokes momentum equation. The horizontal force on the structures and the free-surface elevation at wave gauges around the cylinder model have been analysed for a range of porosities and regular wave conditions. The CFD results are verified against results from a linear potential-flow model and validated against experimental results. The applied pressure gradient formulation produces good agreement for all porosity values, wave frequencies and wave steepnesses investigated. It is demonstrated that an isotropic macroscopic porosity representation used for large volumetric granular material can also be used for thin perforated structures. This approach offers greater flexibility in the range of wave conditions that can be modelled compared to approaches based on linear potential-flow theory and requires a smaller computational effort compared to CFD approaches which resolve the flow through the openings. The approach can therefore be an efficient alternative for engineering problems where large-scale effects such as global forces and the overall flow-behaviour are of the main interest.

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Section: Theoretical Pressure-drop Modelsupporting

confidence: 65%

Section: Physical Experimentsmentioning

confidence: 88%

Using a porous-media approach for CFD modelling of wave interaction with thin perforated structures

Feichtner

Mackay

Tabor

et al. 2020

J. Ocean Eng. Mar. Energy

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“…Therefore, the present work assumes the influence of KC to be negligible and uses δ = 0.5. This value was found to have good agreement between experimental results and numerical results from both previous CFD modelling, [33], and from a potential-flow model by Mackay et al [40].…”

Section: Theoretical Pressure-drop Formulationsupporting

confidence: 82%

“…This work focuses on the comparison between CFD models with different types of porosity implementations, but experimental results are included for reference. For detailed information and photos of the experiments, we refer to [33,40,41], but relevant aspects of the setup are outlined in the following.…”

Section: Wave Flume Experimentsmentioning

confidence: 99%

Comparison of Macro-Scale Porosity Implementations for CFD Modelling of Wave Interaction with Thin Porous Structures

Feichtner

Mackay

Tabor

et al. 2021

JMSE

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Computational fluid dynamics (CFD) modelling of wave interaction with thin perforated structures is of interest in a range of engineering applications. When large-scale effects such as forces and the overall flow behaviour are of interest, a microstructural resolution of the perforated geometry can be excessive or prohibitive in terms of computational cost. More efficiently, a thin porous structure can be represented by its macro-scale effects by means of a quadratic momentum source or pressure-drop respectively. In the context of regular wave interaction with thin porous structures and within an incompressible, two-phase Navier–Stokes and volume-of-fluid framework (based on interFoam of OpenFOAM®), this work investigates porosity representation as a porous surface with a pressure-jump condition and as volumetric isotropic and anisotropic porous media. Potential differences between these three types of macro-scale porosity implementations are assessed in terms of qualitative flow visualizations, velocity profiles along the water column, the wave elevation near the structures and the horizontal force on the structures. The comparison shows that all three types of implementation are capable of reproducing large-scale effects of the wave-structure interaction and that the differences between all obtained results are relatively small. It was found that the isotropic porous media implementation is numerically the most stable and requires the shortest computation times. The pressure-jump implementation requires the smallest time steps for stability and thus the longest computation times. This is likely due to the spurious local velocities at the air-water interface as a result of the volume-of-fluid interface capturing method combined with interFoam’s segregated pressure-velocity coupling algorithm. This paper provides useful insights and recommendations for effective macro-scale modelling of thin porous structures.

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“…The quadratic pressure drops were considered by researchers in prediction of the added mass and the damping coefficients for a porous stabilizer, plate, or disc undergoing forced motions as well as the wave force on thin porous sheets. Examples include Molin and Remy [13] and Mackay et al [14].…”

Section: Introductionmentioning

confidence: 99%

Local Enhancements of the Mean Drift Wave Force on a Vertical Column Shielded by an Exterior Thin Porous Shell

Cong

Liu

2020

JMSE

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The wave interaction with a vertical column shielded by an exterior porous shell is studied within the framework of potential flow theory. The structures are fixed rigidly at the sea bottom. The interior cylinder is impermeable, and the exterior shell is slightly porous and thin. Additionally, the exterior shell is assumed to have fine pores, and a linear pressure drop is adopted at the porous geometry. The mean drift wave force on the system is thereby formulated by two alternative ways, based respectively on the direct pressure integration, i.e., the near-field formulation, and the application of the momentum conservation theorem in the fluid domain, i.e., the far-field formulation. The consistency of the two formulations in calculating the mean drift wave force is assessed for the present problem. Numerical results illustrate that the existence of the porous shell can substantially reduce the mean drift wave force on the interior column. It also appears that the far-field formulation consists of a conventional part as well as an additional part caused by the energy dissipation through the porous geometry. The mean drift wave force on the system is dominated by the first part, which resembles that on an impermeable body. Local enhancements of the mean drift wave force are found at some specific wave frequencies at which certain propagation modes of the fluid satisfy a no-flow condition at the porous shell.

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Numerical and Experimental Modelling of Wave Loads on Thin Porous Sheets

Cited by 9 publications

References 0 publications

Using a porous-media approach for CFD modelling of wave interaction with thin perforated structures

Using a porous-media approach for CFD modelling of wave interaction with thin perforated structures

Comparison of Macro-Scale Porosity Implementations for CFD Modelling of Wave Interaction with Thin Porous Structures

Local Enhancements of the Mean Drift Wave Force on a Vertical Column Shielded by an Exterior Thin Porous Shell

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