Author(s): Xiangfeng Lin
Linked Author(s):
Keywords: Scour; Tidal stream turbine; Tripod foundation; Flume experiment
Abstract: Tidal stream turbines may experience severe scour in marine environments, posing a threat to the safety of these structures. However, only limited research has been conducted on the scour process around tidal stream turbines. To gain a deeper understanding of the nature of scour around these energy converters, a series of tests were conducted in a closed-circuit flume. The tests focused on the temporal development of scour depth around a turbine model supported by a tripod foundation. The flow conditions considered included steady currents and simulated tidal currents. The effects of the alignment angle of the tripod foundation and the flow velocity were analyzed. The experimental results revealed that the scour pattern around the turbine model was greatly influenced by the alignment angle. This is because of the interactions between the approach flow and the tripod foundation under different alignment angles. In addition to local scour around each leg of the foundation, global scour occurred as a result of flow acceleration and streamline contraction beneath the structural elements of the tripod foundation. Remarkable scour holes also formed on the lateral sides downstream of the turbine model under steady current conditions, indicating high turbulence in this region. Under simulated tidal current conditions, fluctuations in the temporal development of scour were observed due to the reversing flow direction and migrating ripples. By approximating the root mean square velocity of the simulated tidal current to the mean velocity of the steady current, the scour depths were found to be comparable under both flow conditions. Additionally, it was observed that the flow velocity maintained a linear relationship with the scour depth. Taking into account the influence of the tripod foundation and the turbine rotor, a prediction equation based on the effective flow work was proposed for determining the final scour depth of the turbine model. This equation was found to be suitable for both steady current and simulated tidal current conditions in the laboratory experiment.
Year: 2023