Vertical-axis wind turbine (VAWT) configurations expose the airfoil sections of turbine blades to angles of attack between 0° and 360°. In designing new VAWT configurations or improving existing configurations, some knowledge of the aerodynamic forces at these angles must be known. This paper presents a model for predicting 360° of aerodynamic forces acting on the s1210 airfoil at two low Reynolds-number conditions. This model is based upon results from wind-tunnel experimentation and achieves a close approximation of the measured performance of the airfoil. Models such as this provide the means to predict airfoil lift and drag characteristics and use those results to predict the thrust capabilities of the airfoil as the turbine blades rotate. The model is presented and compared with other post-stall models within the literature. These comparisons show that this model is superior to previous models when applied to the s1210. The model shows that two angles of attack regions between 0 and 30° and then again those between 180° and 300° provide the highest thrust contributions of the airfoil. Using models such as these for system-level analysis provides the means to assess the feasibility of different VAWT configurations. Furthermore, it provides the means to assess the proper spacing and distance between turbine blades to generate the desired thrust. This enables the designer to determine the optimum turbine geometry in order to maximize performance.
The ability to predict earthquakes and tsunamis is becoming increasingly important as world population continues to grow in high-density coastal metropolitan areas. Earthquakes which occur in and near undersea subduction zones where the earth’s crust slides under continental masses generate highly destructive tsunamis. Deep ocean buoy systems and sensor implantation techniques are being developed to obtain seismic data from the earth’s crust in water depths of 6000 m. For the first time, deep-sea drilling, high-resolution seismic sensors, and long-term, deep-ocean mooring technology are being combined to provide systems which continuously monitor earthquake activity in the deep ocean. Such systems provide vital seismic research information to the scientific community.
Thirty-five deep ocean current profiles obtained by direct current meter measurements have been studied to determine their influence on buoy mooring systems. The total kinetic energy of each current profile has been calculated and the observed maximum determined to be 1 075 200 joules (1075.2 kJ) as contained in the Gulf Stream Current profile at 37 deg 12 min N, 67 deg W. A single graph is presented which delineates the observed natural bounds on shape, kinetic energy, and current speed of these profiles. Single point nylon moorings in 3000 meters of water are shown to be nearly insensitive to current profile shape when the total kinetic energy is concentrated in the upper 1/6 of the water column. Well developed, high energy profiles do exhibit this concentration. As a result, mooring analysis in the survival environment can be greatly simplified. Comparisons between real and idealized current profiles are provided to demonstrate this phenomenon.
The dynamic motion responses of buoy hulls employed in deep ocean systems are often a critical factor affecting the operability of data links, sensors, or other components. The degree of coupling between the buoy and the wave surface, and consequently the expected motion characteristics are commonly described in terms of “surface following” and “surface piercing” behavior. However, as a basis for buoy hull selection and design, it is necessary to fully evaluate the expected performance of the buoy, based on static and dynamic motion responses in a realistic seaway, in the context of the mission constraints as well as the wave properties at the deployment site. A comparison of several different buoy shapes is described, and it is shown that mission requirements, operational constraints, and location can significantly alter the selection of the best hull shape for each set of conditions.
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