Tool Test 2 Challenge Task: Solid (3D) MESHING OF intake manifold cad MODEL USING ANSA PREPROCESSOR TOOL

Course: Preprocessor for Structural Analysis using ANSA

NOVEMBER 18, 2020

Submitted by: Amanpreet Singh Whan

Supervisor: David Nirmal Paul

Abstract

The intake manifold is an arrangement of tubing with several intake or outlet passages, through which a gas or liquid is gathered or distributed. The design of the intake manifold has a significant effect on engine performance characteristics. The report presents a strategy that was adopted to mesh the automobile engine intake manifold CAD design using the ANSA Pre-Processor tool for the fulfillment of the Tool Test 2 Challenge task. Solid meshing is a four-step process that includes importing a given CAD model, geometry clean-up, Tria meshing, and finally performing tetra meshing of generated volumes using setting quality and mesh parameters. The max quads elements are found to be 0 while 48318 tria elements (100%) and 108209 tetra elements (100%) are present in the meshed model.

Table of Contents

Abstract.

List of Figures.

1 Introduction.

2 Aims.

3 Methodology and Results.

3.1 Import CAD Model and do Geometry Clean-Up.

3.2 Meshing.

4 Discussion.

5 Conclusion.

6 Learning Outcomes.

Appendix.

List of Figures

Figure 1-Workflow overview of ANSA Pre Processor.

Figure 2-Imported given Intake Manifold CAD Model.

Figure 3-Topo performed and oriented Intake Manifold CAD Model.

Figure 4-Intake Manifold presentation before Length parameters command activated.

Figure 5- Intake Manifold model presentation resolution after Length parameters command activated.

Figure 6- Geometry Check-Up command executed resulting error-free CAD model.

Figure 7- Mesh Parameters and Quality set as per challenge requirements.

Figure 8- Intake Manifold tria meshed scene in PID mode.

Figure 9- Intake Manifold tria meshed shadow scene in PID mode.

Figure 10- Tetra or Unstructured Mesh scene for Intake Manifold CAD Model.

Figure 11- List of volumes created for Tetra Rapid Mesh for the given Model.

Figure 12- An example representing deploying of tria and ortho tria mesh on planar and curved surfaces respectively.

Figure 13- Manipulated construction lines for a given intake manifold CAD design.

Figure 14- Tetra Mesh cut scenes of different regions.

1 Introduction

An air intake manifold system is an essential part of the automobile engine. It supplies the fuel/air mixture to the cylinders. An intake manifold is an integrated assembly that sits on the top of the engine, consisting of a series of tubes that distribute fresh outside air to each cylinder. Intake manifold contains a chamber to the inlet of which run off the accelerator with the certain feeds to pipes it leads to each cylinder. The air intake manifold increases engine efficiency by feeding the amount of air to the combustion chamber of an IC engine.

2 Aims

• Check and fix all the geometry errors of the given Model for Geometry Clean-up purposes.
• Set the length perimeters and the type of mesh required.
• Perform 3D or Solid Meshing of the components of the model as per the given Mesh Quality Criterion to generate an overall good mesh flow for the entire model.
• Investigate and Improve the mesh quality wherever required.

3 Methodology and Results

The section describes the different stages that were performed using an engineering tool, ANSA Pre-Processor for the successful generation of an overall good mesh of the Intake Manifold CAD model for the completion of the Tool Test 2 Task. These stages can be further broadly sub-categorized into four key steps, starting from importing of cad model to geometry clean-up, carrying out of meshing as per asked quality requirements, and finally generating a volume mesh using tetra rapid mesh algorithm for the given CAD model.

ANSA Pre Processor is an advanced computer-aided engineering tool extensively used for FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics) analysis in the automotive and aerospace industry. ANSA pre-processor is a CAE software developed by BETA CAE Systems and follows a strict workflow when numerically solving a given problem. Figure 1 represents the workflow overview implemented in the software.

3.1 Import CAD Model and do Geometry Clean-Up

After opening the ANSA Pre-processor software, the first and the foremost step is to import the CAD geometry and perform topology using the topo command in the faces section of Topo Module Buttons for the entire model.

The model can be refined either using Auxiliaries-> fine in Topo Module Buttons or by simply setting a value of length for the entire model in the Perimeters section of Mesh Module Buttons. Considering the complexity of the fine operation, Mesh perimeters-> Length was chosen to be the easiest and preferable choice.

In the next step, go to the Checks Manager and select geometry from the options list. The main function of the Checks geometry is to locate geometrical issues such as unmeshed macros, unchecked faces, needle faces, collapsed cons, triple cons, and cracks. Even though most of these errors can be easily eliminated using the Auto-Fix command but issues concerning triple cons must be fixed manually by releasing Cons or Hot-points (nodes) and joining cons/ nodes back again using the topo command. Before executing the Checks geometry operation, make sure to turn on the most essential above stated geometry issues.

What follows hereafter is the set of images showing different results obtained before and after the completion of geometry clean-up for the given model using ANSA Pre-Processor software.

3.2 Meshing

Meshing is a phase where the CAD geometry is discretized to represent the computational domain in which the solver will discover a solution. A refined mesh helps to achieve better results.

The meshing conducted for the given model is explained in the following steps:

• The Perimeters length was set to 3 mm in the perimeters section of the Mesh module buttons. This will help to generate a mesh of constant element size.

• In the next step, the values of Quality Criteria and Mesh Parameters were entered as per challenge requirements to get a good flow of the mesh over the model. The values used for the quality criteria and mesh parameters are presented in the following tables.

Table 1-Quality criteria and its respective assigned values

Quality Criteria
Criteria	Value
Min length	1
Max length	5
Tet Collapse	0.2

Table 2- Mesh Parameters and its assigned values

Mesh Parameters
Parameters	Value
Target length	3
Minimum target length	1
Maximum target length	5
Distortion distance	20%
Distortion angle	0

• ‘Spot Mesh’ Mesh Generation algorithm was used to produce mesh for the model.

• Next, a volume was generated for the meshed intake manifold CAD model and then the generated volume was meshed using Tetra Rapid Mesh algorithm.

• Quality failing elements were eliminated using multiple approaches which include Reconstruction of mesh, Moving & Pasting Grids and Splitting and Swapping of the elements.

The results of the meshed intake manifold are presented in the following pictures.

4 Discussion

ANSA Pre-Processor was used to mesh the Intake Manifold model as per asked Quality Criteria and Mesh Parameters to generate a good overall mesh flow for the successful completion of the Tool Test 2 task. To fulfill the requirements of the challenge, geometry clean-up, initial tria/ortho tria meshing, and finally 3D meshing using tetra rapid mesh algorithm for the generated volume was performed and the obtained results are presented in the figures shown above.

In Figure 6, it can be seen that the provided CAD model had almost zero geometry errors such as needle faces, cracks, unchecked faces, and triple cons.

The solid or 3D meshing is a two-step process. In the initial step, the given model has to be meshed using either a tria or ortho tria mesh algorithm, and later after generating volume for the model it has to be meshed using tetra rapid mesh algorithm. Tria mesh algorithm cannot be applied on curved and circular surfaces as it leads to distortion of the surface by generating kinks and dips on it. Therefore, the ortho tria mesh algorithm was used for the curved surfaces and tria mesh algorithm was used for planar surfaces while generating mesh for the given Intake manifold CAD model. The following figure represents an example showing surfaces where the ortho tria and the tria mesh algorithm was implemented.

The construction lines were manipulated by a certain amount in some critical areas of the geometry where quality could possibly fall to generate an overall good flow of the mesh for the entire model. Following are the figures that represent the areas of the given model where manipulation of the construction lines has been completed to generate a good mesh flow.

Figures 8 and 10 instruct that there are not any off and collapsed elements existing within the meshed Intake Manifold CAD model. Moreover, a total of 48318 tria elements and 108209 tetra elements are present in the meshed model.

5 Conclusion

In conclusion, the main aim of the challenge was to do a geometry clean-up of the automobile Intake Manifold and generate tetra or unstructured mesh using tetra rapid mesh algorithm. The max quads elements were found to be 0 whereas 48318 tria elements and 108209 tetra elements are present in the meshed model.

6 Learning Outcomes

Throughout this challenge, I have gained knowledge about different commands that are used to fix geometry errors and are used to generate the mid surface of any CAD Model with both auto and manual options. I have learned about different commands that are required to generate Solid meshing. I have also learned that the Mesh Quality can be fixed using several operations like ‘mesh reconstruction’, ‘mesh smoothing,’ ‘grids move or paste’, and ‘elements split and join’.

Appendix

• It took me 3 hours to mesh this given Intake Manifold CAD Model.

Here is the link to access the tetra meshed intake manifold CAD model file:

https://drive.google.com/file/d/1yzxrMjSuAAvC4SrHDs39yvRUu9ZCQy6Z/view?usp=sharing