Numerical Simulations of the Effects of a Tidal Turbine Array on Near-Bed Velocity and Local Bed Shear Stress

Abstract

Abstract:We apply a three-dimensional hydrodynamic model to consider the potential effects of energy extraction by an array of tidal turbines on the ambient near-bed velocity field and local bed shear stress in a coastal channel with strong tidal currents. Local bed shear stress plays a key role in local sediment dynamics. The model solves the Reynold-averaged Navier-Stokes (RANS) equations on an unstructured mesh using mixed finite element and finite volume techniques. Tidal turbines are represented through an additional form drag in the momentum balance equation, with the thrust imparted and power generated by the turbines being velocity dependent with appropriate cut-in and cut-out velocities. Arrays of 1, 4 and 57 tidal turbines, each of 1.5 MW capacity, were simulated. Effects due to a single turbine and an array of four turbines were negligible. The main effect of the array of 57 turbines was to cause a shift in position of the jet through the tidal channel, as the flow was diverted around the tidal array. The net effect of this shift was to increase near-bed velocities and bed shear stress along the northern perimeter of the array by up to 0.8 m·s −1 and 5 Pa respectively. Within the array and directly downstream, near-bed velocities and bed shear stress were reduced by similar amounts. Changes of this magnitude have the potential to modify the known sand and shell banks in the region. Continued monitoring of the sediment distributions in the region will provide a valuable dataset on the impacts of tidal energy extraction on local sediment dynamics. Finally, the mean power generated per turbine is shown to decrease as the turbine array increased in size.

A Numerical Design of Marine Current for Predicting Velocity and Kinetic Energy

“…On the contrary, when high tide current (Figure 4), current enters from section D go to section A and a small part flow to section B which previous happened eddy at center east area near Bangka Island whereas current from section Tables 2 and 3), we can see that the values of velocity can be used to design profile of the marine current turbine. The results if we compare the results of marine currents numerical simulation in the Bunaken Starit that presented by [6] which at flow rate of 1 Sv, the average velocities at enter of Bunaken Strait is 1.46 m/s when low tide currents and 0.85 m/s when high tide currents. It shows difference in the boundary conditions.…”

“…Gillibrand et al [6] have proposed numerical simulations which used the 3D shallow water equations derived from the RANS equations by using the hydrostatic assumption. Rodriguez-Cuevas, et al, [7] have been conducted a number of numerical experiments through test various turbulence models for shallow fluxes with recirculation of wakes produced by an island with a slight slope in their numerical simulations.…”

“…It would express the variations in temperature, especially in account dissipation by friction, will ignore and temperature will later appear as a tracer only liable for the effects of buoyancy. Conservative of the fluid mass based on the following equation [5][6], [13][14].…”

UoNGBR: A Regional Assimilation Barotropic Tidal Model for the Great Barrier Reef and Coral Sea Based on Satellite, Coastal and Marine Data

“…The hydrodynamics of shallow water regions, estuaries, straits and bays is affected by uncertainties in both bottom friction and bathymetric data [57][58][59][60][61]. Bathymetric data has been known as an important input to shallow water hydrodynamic modelling [62,63], while the influence of the drag coefficient value on tides in coastal regions has been reported by other studies [64,65].…”

Study on Impact of Turbine Location on Hydrodynamics in Tidal Farm

“…Jeyar et al investigated the hydrodynamic impacts of whole lagoon due to tidal waves using a 2-D, depth-averaged hydrodynamic model based on the shallow water equations. Gillibrand et al [11] adopted a three-dimensional (3-D) hydrodynamic model to consider the potential effects of energy extraction by an array of tidal turbines on ambient near-bed velocity field and local bed shear stress. Yamamoto et al [12] exploited ANSYS to select the best shape of oscillator, in order to efficiently harness the tidal flow energy in a cost-efficient manner.…”