# Discussion Forum

## welding simulation

 Topics: CFD Module, 4.2, Heat Transfer Module
RSS feed   |   Turn on email notifications   |   3 Replies   Last post: October 5, 2011 1:56pm UTC

Kartikeyan Ramachandran

October 4, 2011 6:55am UTC

welding simulation

hi,
i am trying to process model tig welding of metal. i solved for temperature profile in my 3d comsol 4.2 model. Now how can i define the elements which are greater than melting temperature as fluid,can i export the data to matlab then identify the nodal points and then define separate physical properties for molten metal.

Earlier reply will be very useful to our progress.

Thanku in advance.

JiYoung Park

October 5, 2011 4:21am UTC in response to Kartikeyan Ramachandran

Re: welding simulation

Hi,

If i understood right, I think you need not to export file to define properties.

Is that for phase change and fluid flow?

First, you can use effective heat capacity method directly in comsol for melting

then,

add laminar flow study to marangoni effect.

Add carman-kozeny approximation in volume force term and weak contribution for surface tension effect

best regrads.

Kartikeyan Ramachandran

October 5, 2011 8:54am UTC in response to JiYoung Park

Re: welding simulation

sir,

thank you for your reply

the problem i am facing is how can i select only a particular nodes(which are greater than the melting temperature) as fluid and solve for the fluid equations in that domain alone... can i define the whole geometry as fluid(assuming solid to be a high viscous fluid) and then solve for heat transfer and fluid flow equations.

Earlier reply will be very useful 4 our progress

Thank u in advance

Karti Keyan

JiYoung Park

October 5, 2011 1:56pm UTC in response to Kartikeyan Ramachandran

Re: welding simulation

You mean

"Fluid flow in only molten region"

right?

The whole region is considered as liquid.

Firstly, you should solve phase transition with "heat transfer module" by effective heat capacity method

In that way, you can define liquid volume fraction which range from 0 to 1. (1 for liquid, 0 for solid)

Then, you want to see the velocity profile only in molten region( fl=1), right?

Therefore you need to "porosity method" with "laminar flow module"

You can easily find the paper related to porosity method in google,

in brief, porosity=0 for solid, porosity=1 for liquid.

It can be defined in volume force term in "laminar flow module"

Fx = -C*((1-fl)^2)/(fl^3+b)*u
Fy = -C*((1-fl)^2)/(fl^3+b)*v+rho*g*beta*(T-Tinf)

fl : liquid volume fraction
C : sufficiently large number (ex) 1e12
b : constant for not divided by zero (ex) 1e-3
rho : density
g : gravity

This equation makes velocity zero in solid.

best regards

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