The Betz limit expresses the maximum proportion of the kinetic energy flux incident on an energy conversion device that can be extracted from an unbounded flow. The derivation of the Betz limit requires an assumption of steady flow through a notional actuator disk that is stationary in the streamwise direction. The present derivation relaxes the assumptions of steady flow and streamwise actuator disk stationarity, which expands the physically realizable parameter space of flow conditions upstream and downstream of the actuator disk. A key consequence of this generalization is the existence of unsteady motions that can, in principle, lead to energy conversion efficiencies that exceed the Betz limit not only transiently but also in time-averaged performance. Potential physical implementations of those unsteady motions are speculated.

中文翻译：

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使用非稳态流体力学超越贝兹极限的理论框架

贝兹极限表示入射到能量转换装置上的动能通量的最大比例，该动能通量可以从无限制的流中提取。贝兹极限的推导需要假设通过名义致动器盘的流量稳定，该致动器盘沿流向固定。本推导放宽了稳定流动和沿流方向的致动器盘平稳性的假设，这扩大了致动器盘上游和下游的流动条件的可物理实现的参数空间。这种概括的一个关键结果是，存在不稳定的运动，从原理上讲，它不仅可以瞬时地而且在时间平均性能上导致能量转换效率超过贝兹极限。推测了这些不稳定运动的潜在物理实现方式。