CFD Material interchange

[Anonymous]

Hello,

all of the time I'm interchanging the material of the same object,

the temperture results stays the same. Even if I interchange Steel

with Wood for example.

I guess it's not enough to change the material, looks like I have to

click somewhere else to tell the CFD that a different material has

to be calculated.

Does anybody have an idea?

Thank you!!!

Stephan

[Jon.Wilde]

I have moved this to the Sim CFD page.

It looks as though you have fixed temperature boundary conditions so this sounds like expected behaviour. What are you trying to achieve with the analysis and what are the input conditions you are using?

Thanks,

Jon

[Anonymous]

Dear John,

thank a ot for your reply.

This was my first start.

In general, I like to estimate a change of borings with cooling air through a steel mold.

Assume a steel mold that will be loaded by hot glass.

The Mold will be cooled down by cooling air.

I have to analyze the temperature influence in the mold by changing the cooling bores while the mold is head up by hot glass internally.

But even if I simulate a much simpler model: a tube with an tempered air flow through it, I see no results on the material of the tube and

especially no influence, if I change the material of the tube.

Looks like I'm making something basically wrong 😞

Tks and best regards from Germany,

Stephan 🙂

---

@wildej wrote:

I have moved this to the Sim CFD page.

It looks as though you have fixed temperature boundary conditions so this sounds like expected behaviour. What are you trying to achieve with the analysis and what are the input conditions you are using?

Thanks,

Jon

---

[Jon.Wilde]

Morning Stephan,

Are you running this transiently?

With initial temperatures applied to the mold you could then run a study where the passing air would cool it over time.

Will the model have the hot glass and cooling air applied simultaneously or just a cooling phase?

Thanks,

Jon

[Anonymous]

Dear Jon,

thank a lot for your help..!!

the cooling air is all of the time switched on, while the glass falls in, will be formed to a container and

then brought out. By changing the wholes, their position and passing air volumne, I like to find out the

influence to the mold / glass.

To find out step by step the right approach, I used only a tube last time, passed internally by air.

I did the following in CFD:

- tube material I set to steel

- inlet and outlet of the tube I do chose and close, fill the internal "space"

- this space I do specifiy as air

- for this air I do set the boundary condition as volumne flow, speed and zero pressure at the oulet

- the initinal temperature of the internal tube surface I set to 500 degrees

I expected that the tube will show a temperature profil depending on its material and the cooling air.

But if I eleminate the air or interchange the material of the tube, the temperature profil stays the same.

What am I doing wrong?

Tks for your help and sorry, if my English is not the best.

Tks and best regards from Germany,

Stephan

[Jon.Wilde]

Hi Stephan,

For any basic flow channel you would need a flow rate and temperature on the inlet and just a pressure on the outlet.

I would set an initial temperature condition to the volume(s)

Remmeber that if you are running steady state and just have one temperature in the model, by the time it is converged (assume at time = inifinity) then everything will just be the same temperature.

Maybe you need to run a transient study?

Does that help?

Kind regards,

Jon

[Anonymous]

Hi Jon,

yes, this already helps and the final result looks much more promising,

at least there's a a new temperature profil if I interchange the material.

Please, have a look for the attachement, showing the difference between

Steel and Wood.

I'm just wondering why Steel is not heated completely thru and the Air flow

is not shown at the outlet as this is the case for Wood.

Do you have an explanation?

Tks and best regards

Stephan

[Jon.Wilde]

Hi,

If you are running transiently, it would take a while for heat to propogate.

Your mesh also looks pretty coarse, which can throw the results.

Are you running with radiation on? Seems unnecessary.

Also think about the quality of the flow through the channel, it would not have time to properly develop (as the pipe is so short) and so may not be very representative of reality.

Can you share a CFZ file if you have further questions? I would be easier to troubleshoot.

Hope this is useful.

Thanks,

Jon

[Anonymous]

Hi Jon,

yes it help's and I'm coming pretty good further.

Unfort., the Solver is stopping calculation now.

Afterwards I have chosen "intelligent solving", but it did not help.

The file is attached, can you have a look?

Do you have an idea, how I can simulate dropping in Glas?

Yet in the attached file I have just set internal temp. to 500 Degrees, but the Glas Go usually

falls in with 1200 Degrees and will be blown out from bottom to top.

Tks and best regards

Stephan

[Jon.Wilde]

Hi Stephan,

Please can you share a support file (CFZ)?

I am not quite clear what you mean by 'dropping in glass' - might you be able to explain?

Thank you!

Jon

[Anonymous]

Hi Jon,

please find attached the file you are asking for.

Thank you so much!!

Best regards

Stephan

[Jon.Wilde]

Hi Stephan,

Thanks for sharing the file.

A few comments on the model setup:

1. The Initial Conditions (I think) is not doing what you expect. What about what is in the cente? Should there be a part there in reality? What is the Initial Temperature of the entire solid before this cooling phase? That is what we need to assign really
2. I would say try a smaller timestep with  3 inner iterations (this is usually the most we need). Try 0.5s or even 0.1s
3. Not sure I would bother with radiation here, there is very little for anything to radiate from and to within the air channel - it will all be at nearly the same temperature

Hope this helps,

Jon

[Anonymous]

Hi Jon,

you have to imagine that there are two idential molds in the machine.

 By putting them opposie together, the center offers a "whole" which

will be loaded with a Glass Gob and then blown out from Bottom to

the top with that target that the Glass will have the same form as the

centre.

I have tried radiation off and smaler time steps. Now, the solver did

run through, great. But, do you have an idea why it's working now 

and it did not before? Does this belong to the smaller time step, shall

I use this small one all of the time now?

My next step will be to see changes by comparing different materials,

to simulate the glass drop in and bowing out.

So I'm sorry Jon, but I guess I will have to write you several more times

🙂

All the best and thank you so much,

Stephan

[Jon.Wilde]

Hi Stephan,

I would guess that this must be down to the timestep, yes. 

If this made such a difference I would run a quick test on a cloned scenario with an even smaller one, just to be sure the results are the same and we are fully capturing everything.

We will be here to help if you need it 🙂

Thanks,

Jon

[Anonymous]

Hi Jon,

once again its me, sticking at one point.

As once explained, you know that I have to simulate a gob fall into a mold

and to see the changes of the mold temperature by changing the cooling

air holes.

I have tried to simulate the gob in now and first run was pretty ok.

Even if I'm not sure whether I set the right timing and movement of the gob

at least it starts to fall and stop at the right positions.

Unfortunately, the second run with head flow on, failes. Solver stopped. I 

should as in Community for help.

Please, find attached the file.

Can you habe a look and share your ideas?

Thank you and best regards

Stephan

[Jon.Wilde]

Hi,

I am not sure we can run an analysis like this (I have never tried) but let's try. Typically we would have motion of a part within a fluid.

First things first, the basics.

There is a strange CAD overlap which I suggest needs cleaning up so the two parts have a nice clean surface where they meet. At the moment you have a very strange shaped part with motion assigned to it

All parts are going to need an initial temperature.

I am sure that we cannot have moving BC's so the 500C on the glass will need to be removed and an initial condition on the solid should take it's place.

If we are looking at purely conduction, switch to a laminar analysis (Solve -> Physics -> Turbulence).

Please let me know if these points help.

Thanks,

Jon

[Anonymous]

Good morning Jon,

I have simplified the model, changed all to initinal conditions and

tuned to laminar analysis.

Unfort. this model is crashing down now while solving.

Would you have a look whether you see a reason for it?

Strangely the previouse model with BC conditions worked, at least

the first run with temp. conditions only.

Tks and best regards

Stephan

[Jon.Wilde]

Morning,

This is a different model - there is no contact between the two parts until they meet at the bottom. So, nothing at all will occur until this point - seems like we could do without the motion and just run the bottom section?

Or, you could run with air inbetween the parts and then could account for radiation between them? This approach makes far more sense to me and I know it can work too 🙂

The question then is what BC's to apply to the air. You may need film coefficients to allow the warmer air to escape - what is the ambient air temp?

Thanks,

Jon

[Anonymous]

Dear Jon,

for the final version, of course it would be brilliant to see the gob falling in and to see the temperature

changing and different temperature profiles over time.

For time beeing, it's certainly good enough to fix the gob in the lower position and to see the impact

while changing the air holes.

The latter I will give it a try now and let you know the results asap.

Thank you so much, I'm happy to have someone in the background as yours since I'm working alone

from home at my dissertation and having no-one to ask for any help or comment is quiet difficult,

Tks again and best regards

Stephan

[Anonymous]

Hi Jon,

I'm well proceeding, but receiving strange results:

- I have fixed a Glass Parison (blown out Gob) in the Mold

- I have set initinal temp. to Mold and Gob

- I have entered new materials for each (Glass & GG)

- as the real process needs some time to head the machine up, I gave it a run with 300

- afterwards I increased the cooling air volumne and decreased the temp.

- I even increased the latter, but no real effect

- then I switched the cooling air to BC temperature

- now I have a huge impact. that high that the temp profile of the mold and gob is senseless as just as one

- in general, after heading up time, the whole process takes just 4 seconds and starts again all 20 seconds

- also usualls, the mold has a temperature profil from the beginning, after some working time, of approx.

  500 degrees internally and 300 degrees outernally. 

Please, find attached the file, divied in three scenarios.

Can you please have a look, why the cooling air is having no or too much influence and how do I bring the

test down to 4 seconds while proving realistic results as in reality? How can I give the Mold an initinal temp

profil?

Tks and best regards

Stephan