ANSYS MESHING (CUTCELL) AND LOCAL MESH SIZING ON A BODY

The Sizing group available in Ansys meshing allows you to control the following options:

(1) Use Advanced Size Function

(2) Relevance Center

(3) Element Size

(4) Initial Size Seed

(5) Smoothing

(6) Transition

(7) Span Angle Center

(8) Minimum Edge Length


We already discuss 1st option 'Use Advanced Size Function' in the previous blog ( click here )

In this blog, we discuss another option of 'Sizing group'.
 
CUTCELL MESH
CUTCELL MESHING OF FORK TYPE CONNECTOR




Element Size


Element Size allows you to specify the element size used for the entire model. This size will be used for all edge, face, and body meshing. This option does not appear when the Use Advanced Size Function is on.




fine meshing



image show the element size = 2 mm. As shown in the image, meshing is created uniformly all over an object ( all topology like edge, face, vertex...). it is the most simple method of meshing any object but it is not accurate for all. Sometimes analysis at the boundary is important, our first priority, In this situation, we can use inflation or cutcell mesh with suitable element size.

Minimum Edge Length


Minimum Edge Length provides an indication of the smallest edge length in the model.

Cutcell Meshing :


The CutCell Meshing group of global mesh controls appears only when Physics Preference is set to CFD and Solver Preference is set to Fluent. Cut cell is hex dominant meshing method. 


It is used when boundary analysis of a large model (Aerodynamics analysis) is carried out. It will create automatically inflation type mesh on all over the boundary of the body. 

The CutCell Meshing group allows you to control these options:


(1) Active 

(2) Feature Capture 

(3) Tessellation Refinement




Cutcell Meshing



The main advantage is that you can easily get a predominantly hexa mesh with inflation layers on all over the boundary to capture viscous boundary effects. by cutcell method, the model converges more quickly and accurately than with tetra/prism meshes. 


The main disadvantage is that it works only with the Fluent solver. CFX, ANSYS Mechanical, AUTODYN, etc. 

Statistics Group :


The Statistics group give view and information about the following options:



(1) Nodes 

(2) Elements 



Nodes


FEM is a numerical method in which an object is meshed (Discretized) in small size depending upon element size. The node is the corner point of this small region. The governing equation is solved at each of these nodes and the solution is obtained.




computational nodes



The Nodes option gives a read-only indication of the 'number of nodes' in the meshed model. If the model contains multiple parts or bodies, you can view the 'number of nodes' in an individual part or body by selecting it under the Geometry object in the Tree Outline. Generally, more no of nodes & elements give accurate result but increase solution time & CPU cost. 

Elements


An element is the basic building block of finite element analysis. There are some basic types of elements. The use of different types of elements for finite element analysis depends on the type of object that is to be modeled or analyze for finite element analysis.


computational elements

An element is a mathematical region or planer area that defines how the degrees of freedom of a node related to the next. These elements may can be lines, areas (2-D or 3-D plates and membranes), or solids (bricks or tetrahedral).

The Elements option gives a read-only indication of the 'number of elements' in the meshed model. If the model contains multiple parts or bodies, you can view the 'number of elements' in an individual part or body by selecting it under the Geometry object in the Tree Outline. For bellow geometry, The no of nodes and no. of elements is shown...







statistics : nodes and elements



Body Meshing or Defining Local Mesh Sizing on a body :

The following table gives information or an overview of how to define body meshing or local mesh sizing on a body.

Sphere of influence

  • It is a very common option available in face sizing and vertex sizing and similar to face sizing and vertex sizing. Mesh will modify inside the sphere region. In the sphere of influence option, first, we select sphere center then sphere radius and last element size for region inside the sphere. Here I choose the sphere center as a global coordinate system which is CG of the body. Sphere radius 100 mm and element size for region inside the sphere is 1 mm. Follow the below fig.

Sphere of influence in ansys

Sphere of influence in ansys

Body of influence

  • It is a very interesting & useful feature in Ansys meshing, available in the sizing option. It is similar to the sphere of influence. In the sphere of influence, the mesh will modify the inside sphere region. similarly, in the body of influence, the mesh will modify inside the influence body region.

  • To apply the body of influence, two bodies will be created. 1st body is our primary body on which mesh modification is applied. The second body will be influence the body which is removed automatically after successful creation or modification of mesh. Follow the below fig.


selection of body in ansys
primary body

  • selection of body in ansys
    influence body

Note : Green color indicate selection of body...

Here The default element size is 5 mm and influence elements size is 0.5 mm.


Resulted Body of influence
Resulted Body of influence

  • Body of influence is used when we analyze any specific critical region is the given body and the condition of accuracy level is high then it is not required to create fine mesh on all over the whole body. just create influence body that has a shape like specific critical region in which meshing will finer.

  • From this option, We achieve two advantages (1) Demand of high accuracy level is fulfilled without compromising in a result. (2) Computational time is reduced without compromising in results.

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