Internal Wave Produced By Moving Submarine And Simulation Of SAR Remote Sensing Of Its Wake

Based on theoretic analysis, this thesis has made an in-depth study of the internal wave and the turbulent wake produced by submarine, as well as the mechanism that they modulate the gravity-capillary waves. The simulation model of synthetic aperture radar remote sensing of internal and turbulent wake of submarine is built up, and the effect of the remote sensing parameter to radar cross section and the condition on which the submarine can be detected are investigated by computer simulation. It is the fundamental research work of the submarine detection by SAR remote sensing, and has an important practical significance.Firstly, departing from hydrodynamic equations and based on linear theory, the integrated theoretic model of internal wave produced by a moving point source is presented. The internal wave generated by moving submarine is investigated by substituting source and sink for it, and the calculation method of the perturbation velocity is given. The outstanding trait of this model is that the wave height can be obtained because the linear boundary condition on the free surface is used. The theoretic results obtained by this model are consistent with experiment results.Secondly, in terms of the theory of turbulent boundary layer and propeller theory, the mean turbulent velocity distribution is acquired. Based on the experiment result of the momentumless wake, the method of predicting the dimension of submarine is presented. Subsequently, the evolvement characteristic of submarine wake, as well as the condition on which the turbulent wake can extend to the sea surface, is discussed.Finally, departing from three-dimension hydrodynamic model, taking account of the current modulation and the turbulence modulation to the surface gravity-capillary waves simultaneity, and using full-spectrum modeling of SAR (synthetic aperture radar) remote sensing, the simulation model of SAR remote sensing of the internal wave and the turbulence wake generated by submarine is built up. The trait of this model is that the effect of the turbulence to the gravity-capillary waves, which taking the form of source function in the action spectral density equation, is considered. The surface current is approximately considered as the superposition of the flow field of the internal wave and that of the turbulent wake, and the turbulence includes that produced by the shear velocity and by the internal wave. The source function is determined by applying the model of turbulence with internal wave mixing, and adopting Nasmyth spectrum of oceanic turbulence. The simulation analysis shows that the turbulence has an important effect to the surface gravity-capillary waves.