It has been demonstrated that sound waves carrying orbital angular momentum undergo frequency modulation after being reflected by a rotating object. In this paper, we, observed the rotational Doppler shift phenomenon of the acoustic vortex in an underwater environment by using a Fresnel-spiral zone plate for the construction of the focused acoustic vortex with controllable topological charge. The positive and negative rotation speeds of the spinning object are precisely determined with the rotational frequency shift and the acoustic vortex's topological charge. The rotational Doppler effect of acoustic vortex provides a possibility to improve the detection and recognition accuracy of Autonomous Underwater Vehicles with propellers.

中文翻译：

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基于菲涅尔螺旋波带板的声涡流观察旋转物体的旋转多普勒频移

已经证明，携带轨道角动量的声波在被旋转物体反射后会发生频率调制。在本文中，我们通过使用菲涅尔螺旋波带板构建具有可控拓扑电荷的聚焦声涡流，观察了水下环境中声涡流的旋转多普勒频移现象。旋转物体的正负旋转速度由旋转频移和声涡的拓扑电荷精确确定。声涡流的旋转多普勒效应为提高螺旋桨自主水下航行器的检测和识别精度提供了可能。