Optical method for detecting local velocity distribution of the flow field based on a vortex beam with anisotropic distribution of the topological charge number.

The velocity measurement of the flow field is of great significance in various fields such as navigation and aerospace. By detecting the velocity of the flow field around navigation bodies such as wings and ship propellers, it can realize the identification and detection of aircraft, ships, and other objects. Since the vortex beam carries orbital angular momentum due to its helical phase, it has a particularly wide range of applications in the field of flow field detection. In this paper, a vortex beam with topological load anisotropy distribution is proposed to detect the local velocity distribution of the flow field, and a two-dimensional fluid model is established for simulation verification. The results show that the vortex beam with topological load anisotropy distribution can measure the motion velocity at multiple locations in the local region of fluid, which provides, to our knowledge, a new way and theoretical support for fluid velocity detection.