Decoding ANSYS for better understanding of FEA/CFD analysis.

I am back with my second article in the series of "understanding FEA in Less than 10 minutes ". I want to give you the best way of understanding FEA analysis and the best way to understand anything is by giving an appropriate analysis example. Before we start with the example, it would be better to get some clarity about the working nature of the Ansys software because all my examples are going to performed using Ansys software. This is article is going to about the process happening inside Ansys software.

So let’s start then,

Ansys has a simulation tool inside it, and we are going to feed our input data into this simulation tool.

 What type of data are we going to feed anyway?

There are basically four things which are going into this simulation tool by the user; they are Geometry, Material property, Meshing and Boundary Condition (B.C). All of this information will be given to the Mechanical Design Engineer only in few cases, in most of case we may need to find or assume the input data. But in almost all of the FEA analysis the user input will be these four and they go into the simulation tool in the same order as I have mentioned.

So what happens inside the Ansys simulation tool?

From our physical problem we extract the input data and feed it into the simulation tool, where the input data gets converted into a Mathematical Model, the software uses key governing equations like equilibrium equations, conservation equations or momentum equations and etc. to create the mathematical model. Now the simulation tool analyzes this mathematical model, perform the required calculation to obtain the numerical solution. Once we have the numerical solution we can obtain our desired result by selecting variables at specific point. Let me explain what I mean by this in a moment.

Say for example we are performing thermal analysis, so our goal in performing a thermal analysis is to find the thermal loads such as temperature, heat flux, heat flow and etc. These thermal loads are the selected variables and we are going to calculate these variables at specific points of our choice in the geometry of the model and we mark out these specific points during our mesh generation.

I hope I have given you a clear picture of what happens inside the simulation tool of the Ansys software, this will be the process for all type of analysis, but the input data for each type of analysis will have a different type of input data depending upon its physical problem. Before I finish my article, I would like to give a brief explanation about the four user input which we feed into the simulation tool.

Geometry:

This is the very first and the essential input that we need. Geometry is nothing but the 3D CAD model of our physical problem. Say for example we are going to perform static structural analysis on a bridge to find its stress, strain and deformation. In order to do that, we need a 3D model to perform the analysis, so we design a 3D model of the bridge and import this geometry of our bridge into the Ansys simulation tool.

There are 2 ways in which you can bring your model into the simulation tool. One is by design your 3D model in other software’s such as solidworks, Creo, CATIA, Solidedge or any other 3D modeling Software's and importing them into the simulation tool. Second way is by creating the 3D model using your Ansys software itself, Ansys provides you with the option to build your 3D model; it comes with an interface for creating sketches and extruding them into CAD models, just like any other CAD developing software.

Material Property:

Material Property is very important this is where we select the type of material and all other properties of that chosen material. This step comes somewhere between geometry and meshing, sometimes even after setting up boundary conditions, It’s actually up to the user.

Meshing:

Out of these four input data, meshing is the easiest one to perform, but that does not make it the least important one, In fact the core of FEA is meshing. So what is mesh generation? Mesh generation is dividing a given domain into nodes and elements and in the process, we are going to mark out the specific location at which we want the Ansys tool to perform simulation and come up with numerical solution. In fact FEA is all about dividing your object into small finite elements, and that is how we got the name “FINITE ELEMENT" for this subject.

Boundary Condition:

The most integral part of any FEA analysis problem is the definition of it boundary conditions. It is very important that the Mechanical Design Engineer understand the role of B.C in the numerical algorithm, it play a vital role in constructing the mathematical model.

So far I have only explained about the process that happens inside the Ansys software. I haven’t explained anything about performing an analysis using the Ansys software. I will be doing that in all the other articles which I am going to write in this series of "understanding FEA in Less than 10 minutes". Feel free to share your comments and thoughts on my articles. I look forward to your comments.