University of Twente Student Theses


Modelling the equilibrium height of offshore sand waves

Gerwen, W. van (2016) Modelling the equilibrium height of offshore sand waves.

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Abstract:Tidal sand waves are dynamic bed forms found in shallow seas, reaching heights of several meters and migration rates of several meters per year. Because of their dynamic behavior, unraveling the physical processes behind the growth of these bed forms is of particular interest to offshore industries. Various modelling efforts looking into the linear formation processes of sand waves already give a good description of the initial stages of formation. However, the non-linear evolution, causing sand waves to grow towards an equilibrium, is not yet fully understood. To further increase our understanding of the processes controlling the non-linear evolution of sand wave fields, a numerical shallow water model (Delft3D) is used. This is the first model study which shows the growth of a sand wave field towards a stable equilibrium. It is shown that both suspended load transport and tidal asymmetry reduce the equilibrium sand wave height. A residual current results in the formation of asymmetrical bed forms that migrate in the direction of the residual current. By including suspended load transport and tidal asymmetry, the predicted equilibrium wave heights approximate wave heights as found in the field.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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