柔性筏的波浪驱动推进

中文摘要 AI 辅助

流体中的惯性推进通常源于动量通量的不平衡。对于波浪驱动推进的情况，动量以自激表面波的形式从振荡的筏上输运出去。虽然这一机制此前已针对刚性筏进行了分析，但柔性的作用尚未被研究。在本工作中，我们开发了一个流体-结构相互作用模型，用于描述周期性驱动的二维柔性筏，该筏静置于流体自由表面。筏被建模为欧拉-伯努利梁，并与下方流体的弱耗散准势模型耦合。改变弯曲刚度和施力位置揭示了与引入柔性相关的新特征，包括推力增强和反向的可能性。通过将筏的响应投影到其自由刚体和弹性模态上，流体载荷可以表示为模态阻抗，从而为计算高效的降阶模型提供信息。对模态响应及其对称性的分析有助于对我们关键发现的物理解释。对于均匀筏，单独激发任何单一模态都无法产生净推力，因此高效的波浪推进需要具有适当协调幅度和相位的干扰模态的混合。

英文摘要

Inertial propulsion in fluids generally arises from an unbalanced flux of momentum. For the case of wave-driven propulsion, momentum is transported away from an oscillating raft in the form of self-excited surface waves. While this mechanism has previously been analyzed for rigid rafts, the role of flexibility has yet to be investigated. In this work, we develop a fluid-structure interaction model for a periodically driven two-dimensional flexible raft resting at the free surface of a fluid. The raft is modeled as an Euler--Bernoulli beam and is coupled to a weakly dissipative quasi-potential model of the fluid beneath. Varying the flexural stiffness and forcing position reveals new features associated with the introduction of flexibility, including the possibilities of thrust enhancement and reversal. By projecting the raft response onto its free rigid-body and elastic modes, the fluid loading can be represented as a modal impedance, informing a computationally efficient reduced-order model. Analysis of the modal response and its symmetries facilitates physical interpretation of our key findings. For a uniform raft, excitation of any single mode in isolation is incapable of producing a net thrust, and thus efficient wave propulsion requires a blend of interfering modes with appropriately coordinated amplitudes and phases.

发表机构

• School of Engineering, Brown University（布朗大学工程学院）

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