Topic for open discussion: Dynamic
Stall
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October 30, 2020, post by Dave Santos Dutch-Roll with Dynamic-Stall and Vortex-Lift components are proposed identified as ideal megascale kite flight modes for AWE. A few "kite notes" that apply as well to aircraft, insect, and bird flight-
These
are substantially scale-invariant effects given constant "most probable
wind velocity". They will manifest with simple km-scale AWE sail-wings. More than mathematical-physics benchtop curiosities, these aerodynamic principles could power the world. |
November 1, 2020, post by Dave
Santos Enhanced Dynamic Stall by Load-Motion Shock When a skydiver pops open her parachute, there is an "opening shock." Similarly, when a kitesurfer jumps, she is "powering up" the kite (increasing AoA) while moving crosswind as fast as possible, away from the kite. These are special cases of Dynamic-Stall, where fast opposed Load-Motion momentarily boosts dynamic stall. For the purposes of an optimal pumping AWES, momentarily-opposed load-motion can greatly increase cyclic dynamic-stall force amplitude. In the context of power kite inscribing a figure-8 (lemiscate) on a spherical surface ("kite window"), the moment to maximize dynamic stall is after right crossing the mid-point in the dive/side-slip phase and progressively swinging forward, more into the wind, for a compounded dynamic-soaring (DS) dynamic-stall boost. Weaker flight phases at the tops of the 8 are high L/D low Cl/Cd. The high amplitude difference in force between these kite flight modes is maximally energetic. Many cases of biological flight are dynamically similar. Specific aerodynamic-factor scale-invariance to mega-scale challenges mathematical physics research starting from benchtop scale experiments and numbers. There are no formal go or no-go predictions yet. The heuristic predictions posed here remain open. Note that mega-scale air-volumes are non-dimensionally less viscous than micro-scale Re assumption, and non-dimensionally less inertial than meso-scale high velocity. These are key mega-scale AWES aero-engineering factors. |
Dynamic Stall
--------------------------- Jane Wang | Department of Physics Cornell Arts & Sciences "Research"I am fascinated by the physics of living organisms, with a focus on understanding insect flight. How does an insect fly, why does it fly so well, and how can we infer its ‘thoughts’ from its flight dynamics? The movement of an insect is not only dictated by the laws of physics, but also by its response to the external world. We have been seeking mechanistic explanations of the complex movement of insect flight. Starting from the Navier-Stokes equations governing the unsteady aerodynamics of flapping flight, we worked to build a theoretical framework for interpreting and predicting the functions of an insect’s internal machinery for flight. In this approach, the physics of flight informs us about the internal computing scheme for a specific behavior. Our most recent work makes new connections to neural science. We build physical models for quantitative analyses of flight reflexes, and relate our findings to the underlying neural feedback circuitries for flight." |