Multi Level Meshing for a Handing-node Geometry using Ansys-Icepak

Objective :

The main objective of this challenge is to improve the mesh resolution on and around the CAD objects by using the multi-level meshing technique. And the procedure must start with a coarse background mesh and resolves fine level features through a series of successive mesh refinements.

1.Problem Description:

The Icepak model was given for this assignment. Open and unpack the given hanging_node.tzr model.

Without any modifications, the model results in about 700,000 elements. Noting that this mesh count results from using the non-conformal meshing technique, which reduces mesh bleeding and mesh, count.

However, this mesh does not fully resolve the fine-level geometric features of the CAD objects. we can reduce the mesh count and improve the mesh resolution on and around the CAD objects by using the multi-level meshing technique. This procedure starts with a coarse background mesh and resolves fine level features through a series of successive mesh refinements.

By using multi-level meshing and the uniform mesh parameters feature, you can reduce the mesh count to approximately 500,000 elements and improve mesh resolution.

Generate the Mesh:

1. Create non-conformal mesh assembly

we have generated the non-conformal mesh with the mesh parameter of refinement with a slack value then we can see the number of the elements was 714139 and the no of the nodes is 917885.

2. Use mesh separately option with slack values

When the Mesh separately options for an assembly is turned on, the offset added to Assembly in respective direction is called Slack Values. By default, the slack values are zero in all directions.

However, in order to use non-conformal mesh, the slack values should always be a positive number except it can be zero when the non-conformal boundary touches a hollow object or cabinet boundary.

The Slack values should be specified in such a way that cells on both sides of the interface are either fluid or solid, with the same material, and it does not violate any of the \"Non-Conformal Assembly Rules\" given in the attachment.

3. Use object parameters

Object parameters:

• Icepak offers the capability of assigning a parameter to almost any input such as power value, object size, flowrate, object active or inactive, etc.
• These parameters can be defined using the Parameters and Optimization in Icepak (under Solve and select Run Optimization).

The object parameters were set accordingly for the geometry object to get the good mesh parameter.

4. Use set uniform parameters and use average on 1 assembly, in multi-level meshing tab allow multi-level meshing up to level 2 for the objects.

We have grouped all collective parts which are important to the simulation and made them into assembling parts.

The assembled parts are shown above.

We have used a multi-level meshing on the assemble objects and the max level on the object was set to 2 on the level scale.

5. Use the same technique of 1

Considering the assemble-2 The same technique has been used for this process as the point that has been considered above. We have used a multi-level meshing on the assemble objects and the max level on the object was set to 2 on the level scale.

6. Generate mesh.

Mesh generation is the practice of creating a mesh, a subdivision of a continuous geometric space into discrete geometric and topological cells. Often these cells form a simplicial complex. Usually, the cells partition the geometric input domain. Mesh cells are used as discrete local approximations of the larger domain. Meshes are created by computer algorithms, often with human guidance through a GUI, depending on the complexity of the domain and the type of mesh desired. The goal is to create a mesh that accurately captures the input domain geometry, with high-quality (well-shaped) cells, and without so many cells to make subsequent calculations intractable. The mesh should also be fine (have small elements) in areas that are important for the subsequent calculations

Meshes are used for rendering to a computer screen and for physical simulation such as finite element analysis or computational fluid dynamics. Meshes are composed of simple cells like triangles because, e.g., we know how to perform operations such as finite element calculations (engineering) or ray tracing (computer graphics) on triangles, but we do not know how to perform these operations directly on complicated spaces and shapes such as a roadway bridge. We can simulate the strength of the bridge, or draw it on a computer screen, by performing calculations on each triangle and calculating the interactions between triangles.

Cut plane through the x-axis:

Cut plane through the y-axis:

Cut plane through the z-axis:

Mesh surface for the domain:

7.Observe in mesh reduction

Mesh reduction at the fan and heat sink assembly.

The slack value and minimum gap values are maintained as it is. The mesh type value is not changed and kept constant in the XYZ direction. Multi-level meshing is ON and an initially level 2 is set to guide sweep. Uniform mesh parameters are on with this setting mesh is generated and it is noted that the mesh count is 714139.

Multi-level meshing is ON and an initially level 2 is set to guide sweep. Uniform mesh parameters are on with this setting mesh is generated and it is noted that the mesh count is 652276 and the mesh resolution is also improved.

In the next step, mesh level is increased to 3, and mesh is generated. At this time the mesh count is further reduced to 527717.

A similar way is tried to heat sink assembly and found the mesh count and mesh resolution is improved when multi-level meshing is implemented

8. Do visual inspection

Visual inspection is a common method of Quality control, Data acquisition, and data analysis. Visual Inspection, used in the maintenance of facilities, means inspection of equipment and structures using either or all of raw human senses such as vision, touch, and with any non-specialized inspection equipment.

Visual inspection was done for the total body there was no intersection or overlapping bodies in the total domain.

9. Check for quality

The quality of the mesh plays a significant role in the accuracy and stability of the numerical computation. The attributes associated with mesh quality are node point distribution, smoothness, and skewness. Regardless of the type of mesh used in your domain, checking the quality of your grid is essential. Depending on the cell types in the mesh (tetrahedral, hexahedral, polyhedral, etc.), different quality criteria are shown below.

Face alignment:

The maximum face alignment that has been obtained in the geometry was one in the domain and the detailed profile of the face alignment is shown below.

Volume:

Volumetric meshes are a polygonal representation of the interior volume of an object. Unlike polygon meshes which represent only the surface as polygons, volumetric meshes also discretize the interior structure of the object.

Skewness:

Skewness is defined as the difference between the shape of the cell and the shape of an equilateral cell of equivalent volume. A general rule is that the maximum skewness for a triangular/tetrahedral mesh in most flows should be kept below 0.95, with an average value that is less than 0.33.

Conclusion:

Using the multi-level meshing mesh resolution can be improved at a time and the mesh count can be reduced. This approach significantly reduces run time without compromising the accuracy of the simulation.