The Moving Mesh (ale) interface (
), found under the Mathematics>Deformed Mesh branch (
) when adding a physics interface, can be used to create models where the geometry, here represented by the mesh, changes shape due to some physical phenomena without material being removed or added. The difference between the Deformed Geometry and Moving Mesh interfaces is that the former defines a deformation of the material frame relative to the geometry frame, while the latter defines a displacement of the spatial frame relative to the material frame. The Moving Mesh interface can be used to study both stationary states and time-dependent deformations where the geometry changes its shape due to the dynamics of the problem. For example, it can be used for fluid domain deformations in fluid-structure interaction (FSI) or electrostatic domain deformations in MEMS.
), found under the Mathematics>Deformed Mesh branch () when adding a physics interface, can be used to create models where the geometry, here represented by the mesh, changes shape due to some physical phenomena without material being removed or added. The difference between the Deformed Geometry and Moving Mesh interfaces is that the former defines a deformation of the material frame relative to the geometry frame, while the latter defines a displacement of the spatial frame relative to the material frame. The Moving Mesh interface can be used to study both stationary states and time-dependent deformations where the geometry changes its shape due to the dynamics of the problem. For example, it can be used for fluid domain deformations in fluid-structure interaction (FSI) or electrostatic domain deformations in MEMS.When this interface is added, these default nodes are also added to the Model Builder: Fixed Mesh and Prescribed Mesh Displacement (the default boundary condition). Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Moving Mesh to select features from the context menu.
The Moving Mesh interface includes the following predefined variables, which can be of interest, for example, to monitor the quality of the mesh and define a stop criterion for remeshing (see Adding a Stop Condition):
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Maximum element distortion, ale.I1isoMax, is measured as the maximum of the first invariant of the isochoric mesh strain tensor, ale.I1iso, over the moving mesh domains. This measure is zero for a mesh that is identical to the original material frame mesh except for a uniform scaling, and increases with increasing element distortion. Any element where ale.I1iso is about 2 or greater must usually be considered severely distorted. By plotting this quantity while solving, you can monitor how the mesh deforms and where it might become too distorted.
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The local relative element volume, ale.relVol, is a quantity that measures the local volumetric distortion of the elements. When this measure approaches zero in some part of the mesh, frame transformations become singular causing solvers to fail.
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The minimum relative element volume, ale.relVolMin, must be > 0, otherwise the mesh elements are inverted. A suitable stop criterion using this variable is that the minimum relative element volume must be larger than a small positive number.
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The maximum relative element volume, ale.relVolMax, is a positive scalar number that represents the maximum value of the relative element volume.
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The minimum mesh quality, ale.minqual, must be > 0; an acceptable mesh quality is typically larger than 0.1 (where the quality measure is a number between 0 and 1).
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Sloshing Tank: Application Library path COMSOL_Multiphysics/Fluid_Dynamics/sloshing_tank
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The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
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Specify the names of the spatial coordinates of the base frame for the physics interface — the material frame — in the Material frame coordinates fields. The defaults are the coordinates of the spatial frame in uppercase letters (X, Y, and Z). You can change the names in the fields for the First, Second, and Third coordinate. The field labels include the default spatial coordinate names in parentheses.
The Geometry shape order setting controls the order of polynomials — 1 (linear), 2 (quadratic; the default), 3 (cubic), 4 (quartic), or 5 (quintic, 2D only) — used for representing the geometry shape in the spatial frame. The same order is used for Lagrange shape functions defining the mesh position in domains where Free displacement has been activated.
Select the smoothing type for freely deformed domains from the Mesh smoothing type list. Choose between Lagrange, Winslow, Hyperelastic, and Yeoh smoothing. The default is Laplace smoothing. For Yeoh smoothing, also specify a Stiffening factor (default: 100).
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