For a discussion about the boundary element method, see Theory for the Boundary Elements PDE in the COMSOL Multiphysics Reference Manual.
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If both The Electrostatics Interface and The Electrostatics, Boundary Elements Interface are available, the Electric Scalar-Scalar Potential Coupling node is available from the Multiphysics menu in the Physics toolbar or by right-clicking the Multiphysics Couplings node in Model Builder.
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The Electrostatics Interface and The Electrostatics, Boundary Elements Interface can also be coupled by using the same name for the dependent variable for both interfaces. Then Electric Scalar-Scalar Potential Coupling is not needed. How to set the name for the dependent variable is described in the Dependent Variables section.
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In the COMSOL Multiphysics Reference Manual see the Physics-Controlled Mesh section for more information about how to define the physics-controlled mesh.
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For more information about making selections, see Working with Geometric Entities in the COMSOL Multiphysics Reference Manual.
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For most applications it is simpler to sweep over terminals using the Stationary Source Sweep study step. See Stationary Source Sweep in the COMSOL Multiphysics Reference Manual and (for more details) Stationary Source Sweep in the Modeling with the AC/DC Module chapter of this manual.
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To correctly calculate the terminal charge and the corresponding capacitances, if voltage Terminal is used on boundaries between The Electrostatics Interface and The Electrostatics, Boundary Elements Interface, let the dependent variable for The Electrostatics, Boundary Elements Interface be the same as the dependent variable for The Electrostatics Interface and disable Electric Scalar-Scalar Potential Coupling. How to set the name for the dependent variable is described in the Dependent Variables section. Since the Electric Scalar-Scalar Potential Coupling is disabled, add manually a Fully Coupled node to the Stationary Solver below the Solution node in the Solver Configurations.
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For 3D components, from the Condition for the x = x0 plane, Condition for the y = y0 plane, and Condition for the z = z0 plane lists, choose Off (the default), Symmetric, or Antisymmetric. Then enter the value for the plane location x0, y0, or z0 (SI unit: m) as required.
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For 2D components, from the Condition for the x = x0 plane and Condition for the y = y0 plane lists, choose Off (the default), Symmetric, or Antisymmetric. Then enter the value for the plane location x0 or z0 (SI unit: m) as required.
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For more information about the Far Field Approximation settings, see Far-Field Approximation Settings in the COMSOL Multiphysics Reference Manual.
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For 3D components, select the Infinity condition — Total charge (the default) or Asymptotic value at infinity. Specify the Total charge Qtot (SI unit: C; the default value is 0 C) or Electric potential at infinity V∞ (SI unit: V; the default value is 0 V). If there is an antisymmetric symmetry in the potential field, it acts as an added infinite ground plane with a fixed value of the electric potential. The value at infinity is fixed to 0 by the presence of the infinite ground plane, so for this case there is a fixed Zero potential at infinity condition.
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For 2D components, select the Infinity condition — Total charge (the default) or Value at reference distance. Specify the Total charge Qtot (SI unit: C; the default value is 0 C) or Electric potential at reference distance Vref (SI unit: V; the default value is 0 V). If there is an antisymmetric symmetry in the potential field, it acts as an added ground line with a fixed value of the electric potential. The value at a reference distance is fixed to 0 by the presence of the ground line, so for this case there is a fixed Zero potential at reference distance condition.
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For more information about the Quadrature settings, see Quadrature in the COMSOL Multiphysics Reference Manual.
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