محسن صفی خانی

Before sailing, submarines with ferromagnetic hulls are demagnetized to avoid damage and detection by sea mines and airborne systems. The increase in the residual magnetization of the submarine body after demagnetization due to the rising and falling can reduce the effect of demagnetization. This study aimed to investigate how internal hydrostatic pressure affects the magnetic signatures of a demagnetized submarine model. Magnetic sensors were placed at specific points under the body, and the changes in magnetic signatures were recorded when pressure was applied from 0 to 60 bar. The results show that by increasing the pressure up to 60 bar before demagnetization, the magnetic field components originating from the sample's internal stresses showed a linear increase. After depressurization, there was an exponential decrease followed by a subsequent increase in permanent magnetization of about 6%. However, after demagnetization, as the pressure increased up to 60 bar, the magnetic field generated by internal stresses in the sample increased by about 27%, but upon decreasing pressure, this magnetic field did not decrease but remained unchanged. This phenomenon negatively impacted the performance of the deperming process. Also, for further investigation, the increasing trend of magnetic signatures was evaluated at pressures of 30, 45, and 60 bar.

One way of detecting ships or submarines is the observation of magnetic field signature around the object. Ships or submarines can be assumed as a collection of closed circuit of electrical currents. The electrical current of each close circuit must be properly regulated. The main purpose is production of a magnetic field equal to the magnetic field around the ship but with the opposite direction. By using this method, the magnetic field can be effectively reduced. This simulator is designed in C# language and it was named General Magnetic Compensation. The inputs of this software are geometry, location and magnetic field and the output is electrical currents of each closed loop, thus making the magnetic field reduced around the submarine. Accuracy and validity of the new software was investigated by analytical relation of magnetic field for proper geometry. Then a submarine was simulated in COMSOL and data of this simulation were used in General Magnetic Compensation software. The results were in great agreement with the results of the COMSOL software and could predict the magnetic field well.

Detecting by the means of the marine magnetic anomaly maps is one of the detection and passive controlling methods for the surface and subsurface equipments including the submarines. Considering the point that nowadays, that submarines are made very silent in an acoustic view, detection and recognition of them by using acoustic detector in the sea has become hard and almost impossible. Thus, using magnetic anomaly methods seems to be necessary. By using this method, the fluctuation in the earth's magnetic field due to a ferromagnetic object is detected and by the help of computer processing, the magnetic map of the area is prepared. In this study, by processing and analyzing magnetometric data, a magnetic anomaly map was created in the region of the Persian Gulf near the Genaveh coast, after necessary corrections. Magnetic anomalies were first used to highlight superficial anomaly using the first-order derivative filter. The maps are further processed using Euler de-convolution method to determine the depth of anomalies. Both methods show surface abnormalities with low depth in the north and south in the lower and middle regions of the study area.