Impact of Tsunamis on Near Shore Wind Power Units

With the number of wind power units (WPUs) on the rise worldwide, it is inevitable that some of these would be exposed to natural disasters like tsunamis and it will become a necessity to consider their effects in the design process of WPUs. This study initially attempts to quantify the forces acting on an existing WPU due to a tsunami bore impact. Surge and bore heights of 2m, 5m and 10m are used to compute the forces using the commercially available full 3D Navier Stokes equation solver FLOW3D. The applicability of FLOW3D to solve these types of problems is examined by comparing results obtained from the numerical simulations to those determined by small scale laboratory experiments. The simulated tsunami forces on the WPU are input into a simplified numerical structural model of the WPU to determine its dynamic response. The tsunami force is also used to obtain base excitation which when applied on the WPU would be equivalent dynamically to the tsunami forces acting on it. This base excitation is useful to obtain the response of the WPU experimentally, the setup for which is available at University of California, San Diego's (UCSD) Large High Performance Outdoor Shake Table (LHPOST). The facility allows full scale experimental setup capable of subjecting a 65kW Nordtank wind turbine to random base excitations. A stress analysis of turbine tower cross section is performed in order to assess the structural integrity of the WPU. It has been determined that the WPU is unsafe for bore/surge heights above 5 m. It has also been postulated that the structural responses could be considerable in case of the taller multi megawatt wind power units of present day.