| Underwater vehicle is an important means to protect the sovereignty and security of our country territorial waters,and has important significance for border security.The research on the detection and tracking of underwater vehicle has always been valued by various powerful maritime states.The optical detection method based on the hydrodynamic characteristics of the wake of underwater vehicle has the advantages of long detection distance,strong anti-interference ability,and not easy to be deceived and induced.It is the current research focus of underwater vehicle detection technology.Based on the application requirements of non-acoustic detection of underwater vehicle,this paper conducts theoretical and experimental research on the hydrodynamic and optical characteristics of the wake of underwater vehicle.The research progress is as follows:Carry out theoretical research on the wake characteristics of underwater vehicle from two aspects of hydrodynamics and optics.In terms of hydrodynamics,the wake field of the DARPA SUBOFF model is simulated and calculated based on the governing equations of fluid flow,and the spatial evolution of the wake field under different speed conditions is analyzed.In terms of optics,the velocity magnitude of the wake field of the DARPA SUBOFF model is correlated with the fluctuation characteristics of the wake field’s refractive index through the kinetic energy dissipation rate,and the calculated refractive index power spectrum of the wake field under different speed conditions shows that the variation law of the velocity magnitude and the fluctuation characteristics of the refractive index was analyzed.According to the similarity law of flow in fluid mechanics,the experimental device for the wake characteristics of underwater vehicle is designed.The geometrical similarity and mechanical similarity theories are used to determine the model scale ratio and motion speed of the experimental device,and the analysis results are reflected in the design of the experimental program in the form of parameters,which provides the basis for the subsequent experiments on the wake characteristics of underwater vehicle.The hydrodynamic and optical characteristics of the wake field of an underwater vehicle under different speed conditions are studied experimentally.In the optical measurement experiment of the hydrodynamic characteristics of the underwater vehicle wake,the gray information shows that the fluctuation intensity of the wake field is positively correlated with the velocity of the model,and negatively correlated with the wake development time.In the measurement experiment of the optical power characteristics of the underwater vehicle wake,the optical power signal of the wake field presents the characteristic of damping motion in the time domain;the frequency signal above 0.3Hz is gradually added;in the time-frequency domain,the low-frequency signal below 0.2Hz occupies the entire time period,and the energy in the initial signal segment increases with the increase of the motion speed. |
