Learning Forum

[sunil.voleti]

Hello everyone,

I am simulating melting behaviour of glass substrate with laser as heatsource.can anyone please explain How can I simulate melting and solidification of glass in Ansys fluent.

[Rob]

Assuming it's a normal viscosity model without any plastic or viscoelastic properties then the melting/solidification model ought to do it. Do you need the laser, or can you just add heat into the domain? 

[sunil.voleti]

Hey,

I have glass as substrate and I am moving laser as heatsource. I want to know the melting behaviour of glass due to the effect of laser power.

[Rob]

OK, so how does the glass flow and do you need the laser or just a heat source? 

[sunil.voleti]

It does not matter laser or heatsource but need to define properties of laser to heatsource in terms of heatflux,etc and also different viscocity for different temperatures, I want to see the melting of glass after reaching melting point during simulation or after the simulation.

for example melting point of glass is 1700 deg.celcius.if my substrate temperature exceeds melting temperature after some time then i have to see melting behaviour of glass 

[Rob]

So you'll need the melting/solidification model in Fluent.  But check with your supervisor what the glass properties are. 

[sunil.voleti]

yes, I need melting and solidification model in fluent for glass material.please help me melting simulation with some glass properties later I will use your model and simulation settings by changing material properties which I need.

[Rob]

We don't supply models, we're here to guide you to solutions. Read up on the melting & solidification model in the manuals (click on Help to access) and also look through the tutorials: the one on solidification should cover most of what you need. 

[sunil.voleti]

 can you help with one simulation example how to simulate melting of glass because I could not find examples related to melting in fluent 

[Rob]

Have you looked at the tutorial I suggested? 

[sunil.voleti]

I tried different examples with vof and without vof, and with solidification but I cannot see any melting effect and temperature distribution from heatsource to substrate.

[Rob]

If there's no heat transfer then there's something else wrong. Are the various volumes connected?

[sunil.voleti]

here I attached my 2D model sketch I defined heatflux for heatsource and also I tried with udf please help me with the melting simulation for this model.

[sunil.voleti]

hello rwoolhou

could you please help me with melting simulation for this model

[Rob]

So, heat is added to the domain, and the glass should get hot.  What's happening in your model?

[sunil.voleti]

I cannot see any melting of glass and I cannot see any temperature transmission from heatsource to glass

[Rob]

OK, can you see heat transfer to the domain? 

[sunil.voleti]

no I cannot see any temperature change 

[Rob]

So, even with heat added the domain isn't getting warmer?  If that's the case how are you adding heat, and are you adding it in the right place? 

[sunil.voleti]

if possible could you please simulate that model and attachhere I will be most thankful to you 

[Rob]

No, we can advise but are not permitted to give out models or detailed advice. Start with a model assuming the glass is solid and examine the heat transfer. Once that works, swap the solid for "solid" glass using the VOF model and solidification. 

[sunil.voleti]

Hey,ni tried every thing as you said but i cannot see any melting behaviour of my material. I can see only heat transfer between heat source and material. I added link here please see it, I need exactly like that to see how my material melts could you please say how can I achieve

[Rob]

OK, so you modelled the glass as a VOF fluid material, and it's warming up but not melting? n

[sunil.voleti]

I modelled glass and aluminium I tried with solidification and melting also. I tried different models with 3D and 2D geometries.n

[Rob]

Any pictures showing temperature contours through a plane? n

[sunil.voleti]

Hai,nplease see the attached video. I simulated with solidification and melting with energy on.I could some temperature change and melting of material inside the block. I would like to see flow of melting liquid to sides of block.n

[Rob]

I'm still not allowed to download attachments, please post some images. n

[sunil.voleti]

n

[Rob]

OK, so it's warming up OK. What boundary do you have to cause the red banding on the last image? What is the cell condition for the block?n

[sunil.voleti]

i defined as wall and i defined temperature for wallsn

[sunil.voleti]

n

[DrAmine]

Do you see Wall/WallShadow connection on the wall separating the air from glass? Or interfaces in case of non-conformal mesh?n

[sunil.voleti]

yes i can see wall shadowsn

[DrAmine]

Nice!nnAre you now using the melting model? Can you add screenshots showing all relevant aspect of the setup? And the material property for the glass fluid please.n

[sunil.voleti]

I am using solidification and melting with energy on I want to see melting behaviour of glass but my problem is I cannot see any flow of glass after it melted I mean I my model there is Glass surrounded by air. I could see melting inside Glass but I want to see flow of glass fluid to the sides.n

[DrAmine]

How the glass melt will flow across the walls?n

[sunil.voleti]

n

[DrAmine]

It is better to remove the walls, use VOF model with air as primary phase and the glass fluid as secondary phase. For the secondary phase the solidification / melting model will take care about melting. Once the liquidus fraction increases the ability of the glass fluid to flow will increase and flow..n

[sunil.voleti]

Yes I know glass will not flow across walls then what type of boundary I have to define. n

[sunil.voleti]

you mean VOF with Solidification and melting right?n

[sunil.voleti]

could you please help me what type of boundary conditions i have to define for my model if i use vof and solidification and melting?n

[Rob]

Yes, with an interior surface type. The glass looks to be melting but can't flow because of the wall. n

[sunil.voleti]

could you please help me what type of boundary conditions i have to define for my model if i use vof and solidification and melting?.

[sunil.voleti]

n

[sunil.voleti]

what type of boundary conditions i need to define for glass fluid to see flow of materialn

[DrAmine]

Do not define any wall. Go back to Fluent and just switch wall to interior or in Meshing just call the Wall of the Glass Box interiorn

[sunil.voleti]

where i need to define temperature because in fluent if i need to define temperature it should be wall rightn

[sunil.voleti]

I defined interior in meshing and it shows as interior in fluent when the material is solid but if I change if I am changing as fluid in cell zone conditions its showing as walls againn

[sunil.voleti]

n

[sunil.voleti]

I simulated with interior as you said I could not see any melting of glassn

[DrAmine]

How did you define the temperature at the beginning? At the walls? What will drive melting: I think the warm air flow.Check the phase glass material properties.n

[sunil.voleti]

I defined temperature in cell zone conditions for Air block with fixed values option n

[DrAmine]

Are you doing a demo? I would rather patch it as ini value and let it run and adapt itself. For the glass cell zone patch a temperature below solidus.n

[sunil.voleti]

yeah I did patch alson

[sunil.voleti]

I need to define gravity or not?n

[DrAmine]

Yes.n

[sunil.voleti]

ok i will try with it.n

[DrAmine]

okn

[sunil.voleti]

hai Dr Amine thanks alot for your valuable sugessions. How we can calculate angle of glass before melting and after melting. is it contact angle.if yes how to calculate itn

[sunil.voleti]

could you please help me with defining contact anglen

[DrAmine]

Which contact angle?n

[sunil.voleti]

Hai DrAmine,nAs you said If I patch temperature for interior is it constant or it changes during the time.n

[Rob]

Patch is the initial condition, it will change with time when you run the model assuming the solver is set up correctly. n

[sunil.voleti]

Is there any option to define initial condition in terms of watts or else we can patch only with temp.n

[DrAmine]

Only with Temperature as we are solving for Temperature/Enthalpy Equation.n

[sunil.voleti]

how can i patch different temperatures for interior I mean for different areas of interior different temperatures n

[DrAmine]

if not explicitly already defined as cell zones you will need to create cell registers for the areas.n

[sunil.voleti]

In my simulation i can see only volume fraction but not liquid fraction what might be the problem.nIf I turn on gravity I am getting error that floating point error.n

[sunil.voleti]

Hi DrAmine,ncould you please help me how we can define heatsouce (Laser) instead of temperature.n

[DrAmine]

You see liquidus fraction and phase volume fraction. n

[DrAmine]

Heatsource via a source term applied into energy equation.n

[sunil.voleti]

I did not understand can you please explain little clearn

[sunil.voleti]

if i define source term no need to again patch temperature for interior rightn

[DrAmine]

You can patch if initial condition should be required.n

[sunil.voleti]

In source term to define energy source for 2D model its showing w/m3 units but we use that unit for 3D model because it is volume. how can I change units as w/m2 for 2D model.n

[Rob]

It's still W/m3 in 2d. If you've not touched the reference values the domain is 1m deep: axi symmetric is Pi radians (check that) sector. If you have changed the reference values, change it back to 1m depth. n

[sunil.voleti]

you mean if I use axisymmrtric no depth in reference values then it will be correct for 2d model right n

[Rob]

If it's axi-symmetric the domain is assumed to be a sector, of Pi or 2Pi radians (I can never remember which so tend to use an area calc to check). If you change the depth value in the reference values you risk the boundary retaining a hard coded depth but you reporting based on the reference. n

[sunil.voleti]

if i change depth as zero what it represents? Is it 2D or 3Dn

[sunil.voleti]

As I am using asisymmetric all the interior walls are becoming axis automatically in fluentn

[DrAmine]

You are using axiss-ymmetric with the x-axis being the axis of rotation: you cannot modify the way Fluent is storing the volume here.n

[sunil.voleti]

Do i need to define any axis or just I have to choose axi symmetric instead of planarn

[DrAmine]

Fluent expects that the x-direction is your axis of rotation. You need to make that happen. (Gravity if enabled should be in parallel to that direction too)n

[Rob]

If you change the reference depth to zero (in 2d) it's still 2d but all the calculations that require an area (or volume) could return interesting results. How about leaving the reference depth alone and instead use the results to see what's going on in your model? nIf you set the domain to be zero thickness in 3d (no idea how as you'll no longer have a volume) the cells will either have an aspect ratio of infinity and/or the mesh will fail to read into Fluent. n

[sunil.voleti]

my problem is I want to simulate 2D model with planar. I need to define energysource with source term options but the units are in W/m3. how i can define w/m2 insted of W/m3. n

[sunil.voleti]

As ROB said me before its still W/m3 in 2D. if i define 2D energy value in energy source does fluent calculates solution correctly?n

[Rob]

It does, because you assume the 2d domain is 1m thick (if you've not been messing with the reference) when working out the source volume. If you initialise the model & do a volume check on the fluid it'll give a volume in m3. n

[DrAmine]

You need to provide the sources in terms of W/m?. The depth is under reference values. Default is one meter.n

[sunil.voleti]

what type of viscosity I need to define in ansys fluent I mean LOG viscosity or dynamic viscosity?n

[Rob]

Have a look at the units, that'll give you a good idea. n

[sunil.voleti]

if I define energy with source terms in ansys I cannot see any contour change in terms of temperature. Is it possible to get temperature or its not possible. n

[Rob]

You should, how much energy are you adding when compared to how much mass? n

[sunil.voleti]

I did not understand what you mean exactly could you please expain in detail ?n

[Karthik R]

What means is - how does your total input energy (in J) compare to the sensible and latent heat added to your fluid. This is a simple hypothetical energy balance.nm x Cp x del_T vs. Total input energynCompare these two quantities and see how much del_T you should expect if all the heat were added to increase the temperature. If this is small, then if you have phase change in your simulation, this temperature change would be further reduced.nKarthikn

[sunil.voleti]

Hello,nHow we can define radiation (Emmisivity coefficient) in fluent to our model?n

[Rob]

Absorption is is a material property, emissivity is a surface value and is set in the boundary conditions. n

[sunil.voleti]

hello Karthik nI could see temperature in simulation but I cannnot see temperature where I have defined my energy I could see some where in my model could you please help me with this. n

[Rob]

What can and can't you see? n

[sunil.voleti]

I mean its showing temperature but as not expected its showing very less temperature could you help me what might the problem. I defined energy in source terms.n

[Karthik R]

What is your input energy? What does your flow look like and what temperatures are you seeing? You need to give us this data so we can help. nPlease check the overall energy balance in your simulation and make sure that you are conserving energy.nKarthikn

[sunil.voleti]

Hey,nI patched temperature and I want to see the temperature change during the simulation. I have defined equation by using field function. As per equation the temperature has to decrease during the time but it increasing very fast in the simulation. could you please help me.nn

[Rob]

Do a hand calculation of the source and plot that in Excel.n

[sunil.voleti]

I have calculated with same equation in excel it shows correct results with decreasing temperature but in simulation temperature was increasing n

[Rob]

If you're adding more energy than is leaving it'll heat up. Where is the heat going, and does it balance? n

[sunil.voleti]

I am patching for example 2400?c at the start of simulation and I have set in properties as 1500?c is solidus temperature and 1700?c as liqudious temperature. Is it true what I am defining?n

[sunil.voleti]

I want to see melting of material during the timen

[Rob]

OK, and you're also adding heat into the domain. How does that heat leave the domain? n

[sunil.voleti]

I have outletn

[Rob]

OK, and does heat leave through the outlet faster or slower than you're adding it through the source? What about any walls in the domain? n