Using Computational Fluid Dynamics to Model and Predict Sediment Dynamics and Scour In the Irish Sea

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Title: Using Computational Fluid Dynamics to Model and Predict Sediment Dynamics and Scour In the Irish Sea
Authors: Littler, Gary
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Date: 2022
Online since: 2022-08-02T11:32:49Z
Abstract: Ireland’s expansive marine resources have the potential to provide significant economic growth through the development of critical infrastructure such as offshore renewable energy installations. However, seabed hydrodynamics, morphodynamics, sediment mobility and, in particular, scour (the process of seabed erosion due to shear stresses generated by currents/waves) represent significant geological risks to the stability of such infrastructure from an environmental and engineering perspective. Such infrastructure can introduce seafloor obstacles that perturb the local environment inducing scour that can cause structural instability, or deposition resulting in the burying of structures. Understanding the processes that drive these complex patterns of sediment erosion and deposition over varying timescales is critical to the sustainable development of critical offshore infrastructure. Traditionally, assessments for such issues have utilised time-lapse bathymetric surveys and scaled physical testing. The former fails to capture the nuance of these processes between data collection surveys and cannot predict how the seabed will react to an obstacle, whilst the latter is costly and limited in recreating the marine environment. Predicting scour can be difficult due to vagaries about hydrodynamic conditions. Computational Fluid Dynamics (CFD) is an advanced modelling technique that solves problems of fluid flow and offers an effective means of investigating the complex interaction between hydrodynamics and manmade objects on the seafloor. Similarly, shipwrecks offer natural laboratories with which to validate models using CFD approaches. In this thesis, CFD simulations are generated for a high-resolution bathymetric survey dataset of two shipwreck sites and assessed for application in future scour prediction studies. Shipwrecks offer novel in-situ features with which to test theories of hydrodynamics and sediment transport around seabed objects, with CFD modelling offering a robust tool to do so. The aim of this thesis is to develop a CFD model at a shipwreck site in order to simulate current flow patterns and magnitudes with which to better understand seabed morphological patterns of sediment erosion and deposition caused by the wreck’s obstruction. When combined with other high-resolution seabed survey data, these outputs and understandings could potentially be applied to other critical offshore engineering as part of a robust methodology to assess the impacts of sediment dynamics and prevent scour and other adverse impacts. Modelled outputs for current flow and stress patterns correspond well with known seabed signatures for sediment erosion and deposition from survey data. The outputs from this approach can also be used in conjunction with repeat and physical (i.e. grab sample) survey data in order to understand temporal sediment dynamics and morphological change at a localised level. Ultimately, this approach can be adapted and applied to other man-made structures (such as offshore wind turbine foundation structures) on the seabed as part of engineering design studies to mitigate against the risk of scour causing instability.
Type of material: Master Thesis
Publisher: University College Dublin. School of Civil Engineering
Qualification Name: M.Eng.Sc.
Copyright (published version): 2022 the Author
Keywords: ScourShipwreckCFDDe-risk
Language: en
Status of Item: Peer reviewed
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Appears in Collections:Civil Engineering Theses

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