A new data-driven method for morphodynamic seabed modelling and prediction that is able to accoun... more A new data-driven method for morphodynamic seabed modelling and prediction that is able to account for morphological relationships across space is presented. The new method uses a two-dimensional spatial statistical model that first derives surfaces that are ...
The initial growth of mechanically generated small amplitude water waves below a laminar air stre... more The initial growth of mechanically generated small amplitude water waves below a laminar air stream was examined numerically and experimentally in order to explore the primary growth mechanism, that is, the interfacial instability of coupled laminar air and water flows. Measurements of the laminar velocity profile in the air over the water surface were found to be consistent with Lock’s [Q. J. Mech. Appl. Math. 4, 42 (1951)] theory. This profile was then used to calculate the spatial growth rates by solving the Orr-Sommerfeld equations. The simulation shows that the growth of the boundary layer affects the exponential growth of water waves along the fetch. The sensitivity of the growth rate is observed to vary by a factor of 2 for changes in the laminar velocity profile as small as 2% at the water surface. This indicates that the interfacial instability is strongly influenced by the wind-induced surface current. A laminar airflow was produced in the wind tunnel over mechanically gen...
Infiltration and exfiltration processes have a significant influence on the hydrodynamics of the ... more Infiltration and exfiltration processes have a significant influence on the hydrodynamics of the swash zone. Such processes need to be taken into account in the modelling of cross-shore sediment transport and the prediction of beach profile evolution. This paper presents a numerical study of the swash hydrodynamics using a 2D Volume-Averaged Reynolds-Averaged Navier-Stokes model, which was calibrated and validated against new experimental data. The model was used to simulate wave run-up from regular waves over permeable and impermeable fixed slopes. Swash flow velocities and water depth data were obtained from the simulations and used to estimate bed shear stresses at three different locations on the beach slope. The results show that infiltration can have opposing effects on the bed shear stress when compared to equivalent swash on an impermeable slope. During the uprush phase, stresses are directly increased due to boundary layer thinning, whereas, during the backwash phase, there...
This paper presents results of wave flume experiments on the interaction of a vertical, slender s... more This paper presents results of wave flume experiments on the interaction of a vertical, slender surface piercing cylinder with extreme waves in the presence and absence of sheared currents. Following, the new-wave approach according to which a deterministic wave group represents an extreme wave in a random sea, we employ focused waves to model extreme events. Using recently introduced experimental methodologies we accurately generate steep non-linear focused waves propagating over the sheared, inline and opposing currents. One of the comparative advantages of this methodological approach is the creation of focusing wave groups with the same linearized target spectrum for all conditions investigated. The focused waves interact with a slender cylinder placed at the focus point and a phase-base separation method is used to isolate the linear, quadratic sub- and super-harmonics and high frequency third-order spectral components of the wave/wave-current induced loads. Preliminary results...
Lagrangian formulation for surface waves with vorticity is used to create a numerical wave-curren... more Lagrangian formulation for surface waves with vorticity is used to create a numerical wave-current flume. The numerical flume is then used to reproduce a physical experiment on focused wave groups in sheared currents. The numerical results include evolution of the free surface of focused wave groups in still water and over in-line and opposing currents and flow kinematics under such waves. Numerical results are compared with experiment and demonstrate good agreement.
A new data-driven method for morphodynamic seabed modelling and prediction that is able to accoun... more A new data-driven method for morphodynamic seabed modelling and prediction that is able to account for morphological relationships across space is presented. The new method uses a two-dimensional spatial statistical model that first derives surfaces that are ...
The initial growth of mechanically generated small amplitude water waves below a laminar air stre... more The initial growth of mechanically generated small amplitude water waves below a laminar air stream was examined numerically and experimentally in order to explore the primary growth mechanism, that is, the interfacial instability of coupled laminar air and water flows. Measurements of the laminar velocity profile in the air over the water surface were found to be consistent with Lock’s [Q. J. Mech. Appl. Math. 4, 42 (1951)] theory. This profile was then used to calculate the spatial growth rates by solving the Orr-Sommerfeld equations. The simulation shows that the growth of the boundary layer affects the exponential growth of water waves along the fetch. The sensitivity of the growth rate is observed to vary by a factor of 2 for changes in the laminar velocity profile as small as 2% at the water surface. This indicates that the interfacial instability is strongly influenced by the wind-induced surface current. A laminar airflow was produced in the wind tunnel over mechanically gen...
Infiltration and exfiltration processes have a significant influence on the hydrodynamics of the ... more Infiltration and exfiltration processes have a significant influence on the hydrodynamics of the swash zone. Such processes need to be taken into account in the modelling of cross-shore sediment transport and the prediction of beach profile evolution. This paper presents a numerical study of the swash hydrodynamics using a 2D Volume-Averaged Reynolds-Averaged Navier-Stokes model, which was calibrated and validated against new experimental data. The model was used to simulate wave run-up from regular waves over permeable and impermeable fixed slopes. Swash flow velocities and water depth data were obtained from the simulations and used to estimate bed shear stresses at three different locations on the beach slope. The results show that infiltration can have opposing effects on the bed shear stress when compared to equivalent swash on an impermeable slope. During the uprush phase, stresses are directly increased due to boundary layer thinning, whereas, during the backwash phase, there...
This paper presents results of wave flume experiments on the interaction of a vertical, slender s... more This paper presents results of wave flume experiments on the interaction of a vertical, slender surface piercing cylinder with extreme waves in the presence and absence of sheared currents. Following, the new-wave approach according to which a deterministic wave group represents an extreme wave in a random sea, we employ focused waves to model extreme events. Using recently introduced experimental methodologies we accurately generate steep non-linear focused waves propagating over the sheared, inline and opposing currents. One of the comparative advantages of this methodological approach is the creation of focusing wave groups with the same linearized target spectrum for all conditions investigated. The focused waves interact with a slender cylinder placed at the focus point and a phase-base separation method is used to isolate the linear, quadratic sub- and super-harmonics and high frequency third-order spectral components of the wave/wave-current induced loads. Preliminary results...
Lagrangian formulation for surface waves with vorticity is used to create a numerical wave-curren... more Lagrangian formulation for surface waves with vorticity is used to create a numerical wave-current flume. The numerical flume is then used to reproduce a physical experiment on focused wave groups in sheared currents. The numerical results include evolution of the free surface of focused wave groups in still water and over in-line and opposing currents and flow kinematics under such waves. Numerical results are compared with experiment and demonstrate good agreement.
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Papers by Richard Simons