A hybrid grid-based finite-element approach for three-dimensional magnetotelluric forward modeling in general anisotropic media

Yu, Nian; Li, Ruiheng; Kong, Wenxin; Gao, Lei; Wu, Xialan; Wang, Enci

doi:10.1016/j.cageo.2022.105035

Cited by 6 publications

(3 citation statements)

References 32 publications

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“…MT responses are calculated in the frequency range of 1E5 Hz to 1E−1 Hz with hybrid mesh 20 of different orders. In total, 26 frequency points were calculated, of which 10 frequency points were equally spaced between 1E5 Hz and 1E4 Hz, and the other frequency points were equally spaced from 1E4 Hz to 1E−1 Hz.…”

Section: Advantages Of Hybrid Meshmentioning

confidence: 99%

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Hybrid mesh for magnetotelluric forward modeling based on the finite element method

Liu

et al. 2023

Sci Rep

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Unstructured tetrahedral grids have been applied in magnetotelluric (MT) forward modeling using the finite element (FE) method because of their adaptability to complex anomalies. However, high-quality results require an extreme refinement of the near-surface area, which leads to excessive meshes and an increased degree of freedom (DoF) of the governing equation of the finite element system. To reduce the computational cost, we have developed a hybrid mesh based on triangular prisms and tetrahedrons. The required elements in the near-surface area are reduced because the quality of the triangular prism is not limited by the element aspect ratio. The deep area is discretized by tetrahedral elements to ensure the flexibility of the unstructured grids. The superiority of this hybrid mesh has been tested on a layered model, the DTM1 model and terrain relief models. The results show that the modeling efficiency has been improved, especially for high-frequency data. The accuracy of the modeling using the hybrid mesh is significantly higher than that of the tetrahedral mesh with a similar DoF. Usage of the hybrid mesh can be easily adapted to complex geoelectric models with strong terrain fluctuations, which requires less computational cost than using conventional unstructured elements.

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Section: Advantages Of Hybrid Meshmentioning

confidence: 99%

“…Triangular prism elements can be used to build the stretched grid in the near surface area 20 . However, the accuracy of the numerical solution will be reduced when the stretched grid extension is too long.…”

Section: Introductionmentioning

confidence: 99%

Hybrid mesh for magnetotelluric forward modeling based on the finite element method

Liu

et al. 2023

Sci Rep

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“…First, the grid division has variability, and it is difficult for a single discrete element to meet the specific requirements. In view of the above problems to be solved, in this paper, a hybrid finite element method is proposed which can effectively improve the grid quality of the calculation area and obtain the numerical solution of the hybrid element [36,37]. The theoretical model given in this paper is equivalent to optimizing the grid structure, and it also expands the application range of the traditional finite element.…”

Section: Numerical Example Of 2d Thin-plate Deformation Solved By Hyb...mentioning

confidence: 99%

Thermal-Mechanical Coupling Model Based on the Hybrid Finite Element Method for Solving Bipolar the Plate Deformation of Hydrogen Fuel Cells

2022

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New energy is the focus of attention all over the world, and research into new energy can inject new vitality into the industrial system. Hydrogen fuel cells are not only environmentally friendly, but also rich in reserves that can be used as a strategic resource for the entire country. The difficulty lies in the safe design of application equipment and the batch generation and storage of hydrogen. In addition, fuel cells have the disadvantage of a slow start-up. Based on the above problems, this paper proposes a hybrid-element method to solve the thermal-mechanical coupling model of fuel cell plate, which can effectively solve the thermal stress change, temperature field distribution and displacement change of the battery plate when working. Firstly, the hybrid-element algorithm is given for 2D plate deformation. Then, the deformation application of a 3D fuel cell plate is given. The 2D numerical results show that the hybrid finite element method (FEM) is more flexible for realizing the flexible combination of sub-mesh and finite element basis functions, and has a better mesh quality compared to the traditional constant strain triangular element (CST) adaptive FEM and quadrilateral isoparametric element (Q4) adaptive FEM. This method achieves a balance between numerical accuracy and solving efficiency for the multi-porous elastic plate. In addition, a deformation control formula is given which can display the displacement deformation and stress merge to same graph, since it is convenient to quickly compare the regions where the displacement and stress extremum appear. In short, the hybrid finite element method proposed in this paper has good mesh evaluation results, and when the number of discrete elements is equivalent, the hybrid element converges faster and the solution efficiency is higher. This paper also provides a good numerical theory and simulation reference for industrial mechanics and new energy applications.

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Robust inversion of 1D magnetotelluric data using the Huber loss function

Desifatma,

Djaja,

Pratomo

et al. 2024

Comput Geosci

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In this study, a robust 1D inversion was performed on magnetotelluric (MT) data by utilizing the Huber loss function to avoid misleading interpretation of results, which is caused by the presence of outliers in the data. The MT method utilizes the ratio between the electric field (E) and the magnetic field (H), which are perpendicular to each other, to obtain impedance values (Z). These values are used to extract subsurface information in the form of electrical resistivity variations with depth. In the study, forward modeling of the 1D MT responses was conducted by recursively calculating Z values. Robust inversion was performed using the Huber loss function as an objective function to minimize the difference between the calculated and observed data. The Huber loss function combines the squared loss and the absolute loss to anticipate the presence of outliers in MT observation data. The robust inversion was performed on synthetic data with additional noise and field data. The inversion process utilized 50 layers with a thickness of 500 m, a hyperparameter $$\varvec{\delta }= 5\times {10}^{-2}$$ δ = 5 × 10 - 2 , $$\lambda =0.01$$ λ = 0.01 , and $${\lambda }_{t}=100$$ λ t = 100 . The number of iterations used was 500 for inversions that used synthetic data and 3000 for inversions that used field data. The robust inversion scheme using the Huber loss function successfully overcame the presence of outliers and accurately estimated the actual model parameters, both for synthetic data and field data that contained outliers. The misfit was relatively small and close to zero, indicating that the inversion code works well.

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A hybrid grid-based finite-element approach for three-dimensional magnetotelluric forward modeling in general anisotropic media

Cited by 6 publications

References 32 publications

Hybrid mesh for magnetotelluric forward modeling based on the finite element method

Hybrid mesh for magnetotelluric forward modeling based on the finite element method

Thermal-Mechanical Coupling Model Based on the Hybrid Finite Element Method for Solving Bipolar the Plate Deformation of Hydrogen Fuel Cells

Robust inversion of 1D magnetotelluric data using the Huber loss function

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