Seawater is generally considered as an electrical conductor with rather weak electrical conductivity. As a moving electrical conductor in an electromagnetic field, seawater motions induce weak electromagnetic field in surrounding environment. The movement of vessels in seawater leads to the variations of electromagnetic field pattern, called as magnetic wake. In order to detect a moving object through the induced magnetic wake, a magnetometer can be placed under the seawater surface. In this paper, we present a mathematical model through which we can study the magnetic wake in water of finite depth and, explore its behavior with respect to environmental parameters and geometric characteristics of the moving object. More specifically, we show through mathematical expressions and numerical results that there always exists an optimal depth under the sea surface wherein if amagnetometer isplaced, maximum amplitude of magnetic wake can be captured. Several key properties are verified for the optimal magnetic wake detection through numerical results. Firstly, the optimal depth is increased by increasing the speed of the moving vessel. Secondly, the optimal depth is not influenced considerably by the variation of sea depth, and thirdly, in the case wherethe Froude number of the vessel is lower than 0.5, the optimal depth is below 15 m.
"Optimal Magnetic Wake Detection in Finite Depth Water," Progress In Electromagnetics Research M,
Vol. 106, 25-34, 2021. doi:10.2528/PIERM21091504
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