Combination Of Surge Research Articles

Aerodynamic performance assessment of φ-type vertical axis wind turbine under pitch motion

The floating vertical axis wind turbine (VAWT) is considered as a competitive device in the utilization of offshore wind energy. However, the platform pitch motion would affect its aerodynamic behavior. In this paper, the aerodynamic performance of a floating φ-type VAWT under pitch motion is investigated by using the Improved Delayed Detached Eddy Simulation SST k−ω turbulence model. After verifying the feasibility of the numerical model, the effects of pitch motion amplitude and period on the aerodynamic characteristics were evaluated, and the impacts of these observations were elucidated. The results showed that the averaged net power coefficient increment of about 1.5%–15% could be obtained under platform pitch motions, and the fluctuation of aerodynamic loads was found to increase. Besides, the pitch motion pattern could be regarded as the combination of surge and heave motions, which explained the similarity of their effects on the wind turbine aerodynamics. Furthermore, it was found that the frequency of the peak torque coefficient would change under different periods of pitch motion, which should be noticed in the design of floating wind turbine. Finally, it was concluded that the current study provided additional information about the effect of pitch motion on wind turbine aerodynamics.

Recovering from Hurricane Rita at Lake Livingston Dam

On September 24, 2005, incredibly powerful winds on the dry side of Hurricane Rita caused a combination of surge and waves that damaged approximately 11,000 feet of the rip rap that provides upstream slope protection on the 13,480 foot long Lake Livingston Dam, north of Houston, owned and operated by the Trinity River Authority of Texas (TRA). Lake Livingston Project staff, responding immediately to the crisis, worked night and day during and after the storm to minimize further damage and initiate repairs. Quick funding, 75% by the Federal Emergency Management Agency (FEMA) and 25% by the City of Houston, combined with efficient work by TRA management, land surveyors, engineers, and the contractor, resulted in remarkably fast repair of the dam. This presentation documents the steps taken to move from the hurricane damaged dam back to full service within 7 months of the hurricane’s landfall.