from http://cn.comsol.com/blogs/improving-your-meshing-with-swept-meshes/
By means of meshing improved swept mesh
Frei Walter 2015 Nian 9 Ri Yue 2
Finite element analysis is concerned, to model the geometry high aspect ratio is one of the more challenging tasks. We hope to be able to accurately characterize the geometry and mesh solution, but do not want too many grid cells, otherwise it will take a lot of computing resources when solving model. Here, we will analyze how to generate accurate and efficient means of finite element mesh meshing sweep in some common modeling cases.
Starting pipe exemplary network
In the network shown below, it is assumed that you need to calculate the fluid flow therethrough. We can see a lot of elbow connected by a long straight section.
Pipe Network. Photo by Hervé Cozanet, and by Wikimedia Commons share.
The figure is a geometric model of fluid flow in a pipe network.
A tubular body CAD model of fluid flow analysis.
Continuing to use the default physical field control grid functionality of the geometric meshes are, you will be shown below the grid. Note: Application of the boundary wall grid, and the grid size in the long straight pipe sections relatively uniform.
Finite element mesh default the fluid flow boundary layer problem is included in all the grid no slip boundary.
Analysis of the fluid flow in terms of an experienced, soon realized that the flow field in the long straight section of the main duct in parallel with, and along the slow axis variation. Meanwhile, the rate of change of the cross-section of the elbow and is quite obvious. Learn before we can use the knowledge to geometry is divided into different domains.
Field is divided into a plurality of pipeline sub-domains, and displayed in a different color.
After the geometric partitioning is completed, we can apply the mesh free tetrahedral features. This grid can only be used in a field in the pipe longitudinal direction, as shown below, this domain represents a bend. Note: We have not yet applied boundary layer mesh feature.
In applications where only one domain tetrahedral mesh.
From this domain subdivision mesh grid along straight segments to perform the sweep function, as shown below. We can also "sweep" assigns a feature distribution unit size sub-features, to explicitly control distribution unit, and set the non-uniformity in the longitudinal direction. Since foreseen longitudinal direction of the flow changes very slowly, axially stretching unit.
Swept along the straight section of the grid also includes a non-uniform cell distribution.
Now, we can apply nested tetrahedral meshes to two curved sections, and the rest of the straight segment sweep. The final step is the use of meshing sequence boundary mesh feature.
Tetrahedral grid in combination with a sweep, the application of the boundary layer at the wall.
It can be observed from the figure, the sweep can significantly reduce the size of the mesh of the fluid flow model problem. Water course 90 degrees bend in it demonstrates the use of this swept meshing techniques.
The second example: the coil and the surrounding environment
We will focus conversion, consider a similar lower induction coil of FIG.
Induction coil. Photo by Spinningspark, and by Wikimedia Commons share.
The coil is made of wire comprising a gently curved long. To calculate the inductance therein, also we need to consider the core material and the surrounding air. Such default mesh geometry of the model and as shown in FIG.
Air core surrounding coil domain.
The default application wherein the free tetrahedral mesh for the entire model.
You may have noticed that the coil itself is very suitable for the implementation of sweeping meshing operations. A long coil, and a uniform cross-section. Thus, we can start the application from the triangular surface mesh at one end, and then perform a sweep along the entire length of the coil to create a triangular prism unit.
Application of triangular mesh (in blue) in the cross-sectional surface of the coil end, and along the entire length of the sweep performed.
But we still need to use a grid around the body. The body can be applied only around the tetrahedral meshes are not swept meshing. To use meshing body of tetrahedral units, you can use all the boundaries are triangular surface elements. Thus, the grid must be added in sequence conversion characteristics, and applied to the upper surface between the coil and the surrounding body. The contact unit is split operation object boundary, to create a triangular face element.
Conversion operation triangular element is introduced in the coil boundary.
Triangulation using the rest of the mesh domain.
We found from the figure, as compared with the default setting grid, used herein to describe a fewer coil unit. Heat transfer by anisotropic carbon fiber woven tutorial is one such example, which combines sweep tetrahedral mesh and meshing body around performed, although involving different physical fields.
The last example: MEMS
Finally, let us consider a microelectromechanical system (MEMS) structure, which comprises a micro-scale structural features bendable. If different potentials applied on different objects, you will be able to measure the change in the inductance of the structural perturbations. Applying an electrical potential change will cause deformation of the system. Similar electric comb drive , accelerometers and gyroscopes and other devices to use this type of effect.
Resonant MEMS cantilever. Photo by Pcflet01, and by Wikimedia Commons share.
A common characteristic of these is that the MEMS structure: they are composed of a variety of flat sheet, the layers need to be meshing together with the air surrounding the domain. Gap structure can also be very elongated. FIG simplified model characterizes the portion of the MEMS structure, comprising interdigitated finger structure.
The exemplary simplified model characterizing portion of the MEMS structure.
When using the default settings of the grid, the insertion of cell (as shown) in a narrow air gap between the parts. But we know exactly the different potentials of both sides of the finger structure, the gap between the ground plane and the straight section of the fingers to maintain a uniform electric field.
The default grid display setting unit area smaller than the actual demand, substantially uniform electric field in these areas
The configuration shown is not suitable for use swept meshing, because the model is not included in the field uniform cross section. But if we introduce some division plane, it can be divided into the field for use prismatic field sweep of meshing. First, we will introduce the two divided planes are located top and bottom surfaces of the fingers, and to divide the two air-domain solid domains. These plane as the planar working add features to the geometric sequence, and consists of two segmented object feature as an input to divide the solid.
The introduction of two planes divided solid and air field domain.
Subsequently, the other can be introduced to describe the long straight segment of the fingers division plane, as shown below. This is important, because we know that the electric field and the displacement of these areas will change very slowly.
Two other planar structure is divided into the finger domain prisms.
Now, the new rectangle can be applied to the surface by dividing the introduced map meshes are mesh feature. Non-rectangular surface on the same plane may be split by triangular grid units, as shown below.
Surface mesh applied on a split plane.
Application of these two thin layers domains surface mesh, referring finger domain and domain-like structure with an air gap between the surface composition, and as a sweep start point grid. After application surface adjacent rectangular unit converting operation can be performed meshing with the air domain tetrahedral units.
The final grid and grid combines the freedom swept grid.
We observed that the total number of elements in the finite element model is reduced. You can read our " surface-micromachined accelerometers tutorial " blog, which describes the use of split planes and swept meshing techniques.
Grid sweep summary
For many types of COMSOL Multiphysics model, the sweep is a meshing powerful techniques that can help minimize the computational complexity of the model. Based on engineering judgment and your knowledge to each question, you can quickly obtain highly accurate results, while compared to the default grid settings, lower computing costs.
Of course, this does not mean that you should always use this method, which is suitable for containing relatively thin or thick areas of high aspect ratio geometry, and you should also determine the solution can be characterized better by sweeping the grid.
