CN-121981016-A - Island wake induced electromagnetic field simulation method based on magnetohydrodynamics

Abstract

The application relates to the technical field of marine geophysical exploration, and provides a magnetic fluid dynamics-based island wake induced electromagnetic field simulation method. The method comprises the steps of constructing a three-dimensional island wake fluid dynamic model, coupling an equation describing sea water motion with a Maxwell equation set describing electromagnetic field evolution to construct a magnetohydrodynamics control equation set, modeling turbulence effects of sea water motion, and solving the magnetohydrodynamics control equation set to obtain a sea current velocity field and an induction electromagnetic field strength, wherein the induction electromagnetic field strength comprises an induction electromagnetic field strength and an induction magnetic field strength. The three-dimensional island wake flow fluid dynamic model constructed by the method comprehensively considers the vertical layered flow velocity profile of the sea water and the background geomagnetic field parameters, and the constructed magnetohydrodynamic control equation set fully considers the sea water movement, so that the model can truly reflect the multi-scale coupling mechanism of the topography-flow field-electromagnetic field.

Inventors

• PEI JIANXIN
• WANG ZHI
• LI YUGUO
• LUO MING
• LIU LANJUN
• CHEN JIALIN
• Duan Shuangmin
• WANG QI

Assignees

• 中国海洋大学

Dates

Publication Date

20260505

Application Date

20260403

Claims (10)

1. 1. The island wake induced electromagnetic field simulation method based on magnetohydrodynamics is characterized by comprising the following steps of: step S1, island topographic features and background ocean current conditions are obtained, and a three-dimensional island wake fluid dynamic model is constructed based on the island topographic features, the background ocean current conditions and the earth rotation effect; Step S2, coupling an equation describing sea water motion with a Maxwell equation set describing electromagnetic field evolution to construct a magnetohydrodynamics control equation set; Step S3, modeling turbulence effect of sea water movement; And S4, solving the magnetohydrodynamic control equation set to obtain a sea current velocity field and an induction electromagnetic field intensity, wherein the induction electromagnetic field intensity comprises an induction electromagnetic field intensity and an induction magnetic field intensity.
2. 2. The method of claim 1, wherein the three-dimensional island wake fluid dynamics model comprises an island geometry model, a sea water vertical stratified flow velocity profile, and a background geomagnetic field.
3. 3. The method of claim 2, wherein the vertical stratified flow velocity profile of seawater is expressed as: (1) Wherein, the Is a vertical layered flow velocity profile of seawater, For the current velocity at the reference depth, To describe the function of the stratification characteristics of the sea water, Is the sea water depth.
4. 4. A method according to claim 3, wherein the reference depth is 10m below the sea surface.
5. 5. The method of claim 1, wherein the equation describing the motion of sea water is expressed as: (4) Wherein, the In order to be a current velocity field, Is the density of the seawater, and the seawater is the density of the seawater, In the case of a pressure force, the pressure, Is the coefficient of dynamic viscosity of the material, In order to be a coriolis force term, Is Hamiltonian, t is time.
6. 6. The method of claim 5, wherein the coriolis force term The expression of (2) is: (5) Wherein, the In order to be a current velocity field, Is a coriolis force parameter; the Coriolis force parameter The method meets the following conditions: (6) Wherein, the Is the rotation angular velocity vector of the earth, Is the geographical latitude.
7. 7. The method of claim 6, wherein the maxwell's equations describing the evolution of an electromagnetic field are: (7) (8) Wherein, the In order to be of magnetic permeability, In order to induce the electric field strength, For the total magnetic field strength, In order to induce a current density in the current sensor, The Hamiltonian operator is adopted, and t is time; The induced current density The expression of (2) is: (9) Wherein, the Is the conductivity of the seawater and is used for the treatment of the seawater, In order to be a current velocity field, In order to induce the electric field strength, Is the total magnetic field strength.
8. 8. The method of claim 7, wherein the total magnetic field strength The expression of (2) is: (12) Wherein, the As the intensity of the geomagnetic field in the background, Is the strength of the induced magnetic field.
9. 9. The method of claim 8, wherein the set of magnetohydrodynamic control equations is: (17) Wherein, the In the form of a hamiltonian, In order to be a current velocity field, Is the density of the seawater, and the seawater is the density of the seawater, In the case of a pressure force, the pressure, Is the coefficient of dynamic viscosity of the material, In order to be a coriolis force term, In order to induce the electric field strength, In order to be of magnetic permeability, Is the conductivity of the seawater and is used for the treatment of the seawater, As the intensity of the geomagnetic field in the background, For the induced magnetic field strength, t is time.
10. 10. The method according to claim 1, wherein the calculation formula for modeling the turbulence effect of the sea water movement by using the large vortex simulation method is: (18) Wherein, the In order to be a current velocity field, For the resolved large-scale velocity component, Is a sub-lattice scale velocity component.

Description

Island wake induced electromagnetic field simulation method based on magnetohydrodynamics Technical Field The application relates to the technical field of marine geophysical exploration, in particular to a magnetic fluid dynamics-based island wake induced electromagnetic field simulation method. Background In the science of the earth system, the interaction of the ocean with the earth's magnetic field is an important topic of research for cross-layer coupling. The induced electromagnetic field excited by the motion of the conductive sea water in the geomagnetic field not only provides a unique electromagnetic view angle for detecting the ocean power process, but also brings challenges to modeling of the earth main magnetic field and accurate interpretation of satellite magnetic measurement data. In the earth's main magnetic field, the motion of the conductive sea water generates induced electromotive force due to the cutting of the magnetically induced lines, which in turn forms induced current and excites the secondary electromagnetic field. Since Faraday proposed the hypothesis that sea water motion cut earth induction lines can generate induced electromotive force, the research paradigm in the field underwent an evolution process from early theoretical analysis to high-precision numerical simulation which is accompanied by the development of computing power and numerical algorithms, to the assimilation fusion of current multi-source remote sensing and field observation data. Despite the recent significant advances in numerical simulation techniques, current research has focused on idealized flow fields or global scale circulation, and the electromagnetic effects generated by forced flow fields on medium and small scale terrains still lack systematic cognition. Taking wake vortex (ISLAND WAKE) caused by island and other topographical obstacles as an example, the nonlinear flow field disturbance has obvious unsteady characteristics (such as vortex cycle shedding and turbulence energy dissipation) and can excite electromagnetic response with a specific space-time structure. Numerical simulations based on computational fluid dynamics (Computational Fluid Dynamics; CFD) indicate that the lee side of an island is prone to periodic karman vortex shedding, resulting in flow velocity fields exhibiting strong spatial gradients and temporal instability. Theoretical analysis indicates that the flow field disturbance can generate magnetic field fluctuation of 1-10 nT magnitude at the sea surface, the fluctuation amplitude of the magnitude is far higher than the noise substrate of the ocean magnetotelluric instrument, but the actual detectability still depends on the correlation between the signal frequency and the noise characteristics of the instrument. Such fluctuations may not only interfere with interpretation of marine magnetotelluric detection data, but also present challenges to inversion and interpretation of satellite magnetic measurement data. However, current marine electromagnetic models focus on the electromagnetic induction process itself, and the input field based on is typically a simplified parameter. While coriolis forces are key kinetic factors that regulate many ocean flow fields (especially large-mesoscale processes such as tidal, inertial, etc.), their effects are not typically involved in the calculation of electromagnetic models. The model is difficult to truly reflect a multi-scale coupling mechanism of a terrain-flow field-electromagnetic field, so that the generation and evolution mechanism research of related induction electromagnetic fields still has obvious blank, and deep exploration and perfection are needed. Disclosure of Invention Aiming at the problems in the prior art, the application provides a magnetic hydrodynamics-based island wake induced electromagnetic field simulation method, which aims to solve the problem that an electromagnetic model in the prior art is difficult to truly reflect a multi-scale coupling mechanism of a topography-flow field-electromagnetic field. The application provides a magnetohydrodynamic island wake induced electromagnetic field simulation method, which comprises the following steps: step S1, island topographic features and background ocean current conditions are obtained, and a three-dimensional island wake fluid dynamic model is constructed based on the island topographic features, the background ocean current conditions and the earth rotation effect; Step S2, coupling an equation describing sea water motion with a Maxwell equation set describing electromagnetic field evolution to construct a magnetohydrodynamics control equation set; Step S3, modeling turbulence effect of sea water movement; And S4, solving the magnetohydrodynamic control equation set to obtain a sea current velocity field and an induction electromagnetic field intensity, wherein the induction electromagnetic field intensity comprises an induction electromagnetic field intensity a