Providing current forecasts for the 2012 Olympic Sailing Competition by means of a finite element based numerical flow model
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Abstract
This project focuses on studying and modelling the flow in the sailing area of the 2012 Olympic Sailing Competition, located partly in Portland Harbour and partly in Weymouth Bay, in order to provide accurate and reliable current forecasts for the Dutch Olympic Sailing Team. From literature it follows that the main flow in the area is the tidal flow. Wind- and wave-induced currents may have a significant influence on the flow as well. Since the available current data is considered outdated, sailed current measurements have been performed to obtain reliable current data. To provide for current forecasts, the two-dimensional depth-averaged numerical flow model FINEL2D, which has the finite element method (FEM) as numerical basis, has been used. FINEL2D adopts the discontinuous Galerkin method to solve the shallow water equations, complemented by a Riemann solver according to Roe to account for the fluxes trough the element boundaries. The TPXO model has been used to enforce boundary conditions on the model. A Nikuradse roughness of 0.035 m has led to model results which deviate least from the measured current. To overcome the phase shift that is still visible, the roughness around Portland Bill and the Shambles Bank has been increased to 0.25 m. By investigating the influence of wind and waves on the flow, it appeared that the wave-induced current in the area of interest is negligible. Wind does however have a significant influence on the flow. Since it is difficult to obtain accurate and reliable wind predictions, accounting for the wind in the current forecasts is difficult. In conclusion it can be stated that the flow in the sailing area of the 2012 Olympic Sailing Competition can be modelled well by means of the two-dimensional depth-averaged numerical flow model FINEL2D. The model results correspond well to the during the survey measured flow velocities and flow directions.