MAE[577] Project 02-Mandeep

8/8/2019 MAE[577] Project 02-Mandeep

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[Project 02: Multi Physics

Simulation with

COMSOL]

[15 September ]

[2010 ]P

[Product

analysis usingCOMSOL]

By Mandeep Singh


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1 Introduction COMSOL is emerging as a new tool for the researchers. It concept of using multiphysics( applying multi environment simultaneously) is really a helping tool in analyzing the system with multi constraints. COMSOL focuses on to cut down unproductive operation and tries to adopt an environment that provides a better focus on the task to increase productivity. This feature along with a strong solver and flexibility are the key point for its popularity as a commercially available software packages for analyzing multiphysics models. COMSOL solver also works on

the similar pattern of problem solving like any other analysis software i.e., the use of Preprocessing, Solution and Post Processing.

In the Pre Processing the domain settings and boundary condition to the task are applied like geometrical parameters, Material and physics constraints.

During material selection, check points are provided to ensure that all the required material

properties are available. The material properties required during solving the problem are check marked and rest are left unmarked. After material selection, boundary conditions are applied using Joule Heating Node. This node contains the settings for defining the heat conduction and current conduction.

We will use the example of Busbar and will apply loading onto it and will analyze its behavior when Current is flown through it.

The first problem is to analyze a busbar heating . Before that we will understand the usage of a busbar.

A busbar is a metal strip generally of copper or aluminium that is used to transmit heavy currents inside a switch board or other current carrying devices. Hence choice of material is also an important aspect in design of busbar.

On the two ends of the busbar strip, wires are connected through bolts. The busbars carry huge current. Most of the heat occurs on the surface because of the skin effect of AC current. Hence heat dissipation becomes an important aspect in designing of busbar. Busbar are even designed

with hollow tubes so as to increase the surface area for better heat dissipation.

The second Problem The Wrench is a structural mechanics problem where we will analyze the system behavior with respect to the change in load and the mesh size.


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2 Problem definition / Problem statement

Part 1 of the assignment focuses to understand the heat dissipation and to understand the influence of change in the size of a mesh. Part 2 of the assignment asks to analyze a wrench

under different loads and hence again analyze the system with the variation of mesh size.

3 Result

3.1 Assignment Part 1 The Bus Bar

Our Busbar looks like as shown in the figure below.

Fig 1. Busbar

There is one hole in the top part and 2 holes on the base. In this problem the busbar is considered to be made of copper and the bolts of titanium.


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Assumptions taken :

1. Material is isotropic 2. Bolt cross section boundaries do not contribute to cooling or heating of the device.

Also the electric potential at the upper right vertical bolt surface is 20 mV, and that the potential at the potential at the two horizontal surfaces of the lower bolts is 0 V.

First we will apply the Pre processing parameters , then we will move towards solution and

then finally to Post processing.

3.1.1 PREPROCESSING :

This part involves modeling of the system, selection of the environment i.e. we apply the physics of the system i.e. what kind of system we want to analyze like structural mechanics, acoustic, fluid chemical etc. Since we are analyzing the heating of the busbar, we will apply Joules heating environment. Once this is defined then we move towards the geometrical part where we define the geometry of the system.

In this case we have used a predefined model of a busbar extracted from the COMSOL library.

After creating the model, we select the material from the database. We can also define the

properties of the material as per our requirements.

Here we have been given to use Copper as a material for Busbar and Titanium Beta 21S as the material for the bolts.

After defining this we apply the boundary condition to the system like temperature , Voltage

etc.

After the geometrical Part we apply the meshing to the model. There are several built in meshing sizes available in the COMSOL. One can customize it also as per the requirements. The

meshed geometry is shown below.


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Fig 2. Meshing of Bushbar

3.1.2 SOLUTIONS (Results)

Here we get the directly related primary quantities that can be derived from the current like

current density.


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Fig. 3 The temperature distribution over a the Busbar

We can also plot the current density plot and displacement graph or thermal stresses, that are indirectly related to the system parameters.

We also analyzed the system using Fluid flow environment where we studied the affect if air

flow over the model.


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0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 0.09 0.095 0.1 0.0050.01

0.0150.02

0.0250.03

0.035

308

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314

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324

mesh size(m)

Width of Busbar (m)

A v e r a g e

T e m p e r a

t u r e

( K )

Fig 8. The plot between computational time V/s Mesh Size is represented below :


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0.005 0.01 0.015 0.02 0.025 0.03 0.03550

60

70

80

90

100

110

120

130

140

mesh size (m)

C o m p u

t a t i o n a

l T i m e

( s )

Mosh Size Vs Computational Time

data1

Fig 9. The plot between computational time V/s Mesh Size is represented below :


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3.2 Assignment Part 2 The Wrench

The main motive of this problem is to understand the behavior of model under different mesh element sizes. The following figure below shows the wrench model to be analysed.

Figure 10 Showing Geometry to be analyses under Load


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First the bolt is fixed or constrained using Boundary condition and then meshing is done

Fig 11. Meshed geometry

Fig 12. Showing boundary being made constrained at the bolt location


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Fig. 13 Showing the Maximum Principal Stress Plot


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Fig. 14 Showing the Load(Xaxis), Mesh size(m) and Max Principle. Stress


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Fig 15

Showing

Computational

time

Vs

Mesh

Size

4 Conclusion

Through these graphs we came to know the affect of mesh size on the accuracy as well and computational size. More finer the mesh , more accurate is the solution. We have to optimize with the time limit, money and the accuracy importance for a particular solution.

For the 1st question we can figure out that even the coarse mesh size is able to provide the

solution considerably accurate. This is because our geometry is not complex. At the same time in the 2nd question we can see that only finer and normal give some consistent results and hence are recommended to be used.


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COMSOLs has the benefit of using so many environment at the same time. The main thing about the software is that when defining the problem , you are required to put many domains and constrains that make you aware of the output. Its versatility in multi physics is one of the major aspect in popularity. Ofcourse the user interface is also better among the other FEA packages. One can run their own differential equation to analyze the system is also a

compliment to the software.

5 References (Websites) 1. COMSOL Introduction to COMSOL Multiphysics

MAE[577] Project 02-Mandeep

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