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The “C-Plane” is a submerged variable depth ocean current turbine that is tethered to the sea floor and uses sustained ocean currents to produce electricity. As part of the development of a th scale physical model of the C-Plane, a mathematical model and dynamics simulation of the prototype was developed and is presented in this paper. This three-dimensional mathematical model represents the C-Plane as a rigid body with moveable control surfaces that is moored with three linear elastic cable elements. Gravitational, buoyancy, hydrodynamic, cable, gyroscopic, and inertial forces are included and a PC-based dynamics simulation is created. The simulation demonstrates that the C-Plane is stable and capable of changing depth in all expected operating conditions. The C-Plane prototype can fly level from a height of 3 to 6 m using the configuration suggested in this paper. The maximum ascent rates of the C-Plane with a water speed of 0.3 m/s are 0.015 m/s when the pitch is fixed at 0° and 0.030 m/s when the pitch is fixed at 4°. The maximum descent rates of the C-Plane are 0.018 m/s when the pitch is held at 0° and 0.031 m/s if the pitch is held at −4°. 相似文献
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A realistic-geometry global baroclinic tidal model forced with a single tidal constituent is used to investigate the generation of the internal tide and the associated radiated baroclinic energy flux. The model internal wave spectrum is populated at discrete frequency multiples of . The subharmonic is particularly energetic at its turning latitude of . Poleward only integer superharmonics of are significantly excited. The subharmonic turning latitude (SHTL) disturbance has high vertical wavenumber and shear, provided that internal tide energy level exceeds a threshold value. Under these circumstances, Richardson numbers smaller than 1/4 occur in the upper few hundred meters in both the realistic-geometry model and in a complimentary idealized geometry two-dimensional (2D) model. In the 2D model, the disturbance enables Richardson number dependent diapycnal entrainment to effect a modification of the stratification of the upper 400 m of the ocean, and poleward cross-SHTL energy flux falls to 10% of its pre-instability value due to energy transfer to the non-propagating (i.e., inertial) subharmonic. Realistic-geometry simulations suggest a more modest 40% decrease in net flux, although the strongest beams are almost entirely shut down. The predicted energy flux-convergence implies a thermocline dissipation rate in the 28.5–30.0°N latitude band of , with an associated diapycnal diffusivity of . North of Hawaii the implied regional dissipation rate reaches with an associated thermocline diffusivity of . Investigations of subgridscale parameterization and resolution sensitivity suggest that the basic character and magnitude of the predictions are robust to details of the numerical solutions. The present results are taken as further evidence that an increase in shear-driven turbulent mixing in the upper ocean is predicted at special latitudes. It is suggested that the search should be directed to regions where intense low-mode internal tide beams cross their subharmonic turning latitude. 相似文献
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