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HPDC Simulation of Binary Alloy

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Old   March 11, 2009, 06:19
Default HPDC Simulation of Binary Alloy
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Nitin Pathak
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Hi, I want to simulate High Pressure Die Casting for a binary alloy (simultaneous filling and solidification). I m using FLOW 3D V9.2. Flow 3D has the segregation model that can simulate the solidification of binary alloy. Actually i have to simulate the filling and solidification of a cavity simultaneously. As there can be some solidification occurring even during the filling process. So for my problem i m enabling filling, solidification model (with segregation), air entrapment model. The simulation tuns smoothly upto the complete filling of the cavity. But once filling is completed and again i restart the simulation for further solidification (closing the inlet of my cavity) it does not solve my problem. The error that comes is.."No reference pressure" I want to know whether FLOW 3D can simulate filling and solidification simultaneously for Binary alloy or not??? Yes i m able to do simulation without using the segregation model where only solidification is coming..but i have to see how the filling of cavity (the residual flow generated due to filling of cavity) affects the segregation pattern in case of binary alloy solidification. If anybody has tried ....Please try to reply asap.

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Nitin Pathak
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Old   March 11, 2009, 15:27
Default Re: HPDC Simulation of Binary Alloy
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MC
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Hi~ When running the restart are you selecting Numeric Tab>Fluid flow solver options>check the Use zero velocity field radio button? MC
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Old   March 11, 2009, 23:30
Default Re: HPDC Simulation of Binary Alloy
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Nitin Pathak
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Well, I m not choosing zero velocity field. Because in that case the residual flow velocities that are generated due to filling of cavity will set to be zero and in that case i wont get how the filling velocity is affecting the transport of species (binary alloy) within the cavity. I m trying to solve full equations continuity and momentum. I don't know whether FLOW3D is capable enough to simulate with this method. If filling velocity is neglected then indirectly we are assuming that there is no residual flow inside the cavity initially which is not correct to assume...!!!

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Old   March 13, 2009, 15:18
Default Re: HPDC Simulation of Binary Alloy
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MC
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Hi~ This can be done. Just ensure that you leave air entrainment and defect tracking on for restart so it is easier to keep track of the scalar's. Also rememeber to add the concentration at the inlet boundary. I suggest getting v93 as it is easier to implement this. MC
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Old   March 15, 2009, 00:12
Default Re: HPDC Simulation of Binary Alloy
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Nitin Pathak
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Hello MC, Thanks a lot for ur reply. But if would be nice if u can please write the steps right from starting. i will tell u what i m doing.. 1. Starting filling simulation with enabling the physical models (air entrainment, defect, solidification with segregation, heat transfer)

2. In boundary condition panel the inlet is at constant velocity say 5 m/s and with initial solute concentration and initial temperature.

3. i m using default numerical schemes with GMRES scheme.

4. There is no problem in filling part and when i restart the solution i m putting continuitive boundary condition at the inlet instead of constt velocity and using full momentum and continuity equations.

5. U told me to leave the air entrainment and defect tracking (is this should be done right from starting or i should leave it when i m restarting the solution for solidification)

It will be good if u can write step be step procedure mentioning physical models, BCs and the corresponding solver schemes..

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Old   March 17, 2009, 15:53
Default step by step
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You may want to go to FLOW 3-D(R) user's website for examples of set-ups.
MC
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Old   March 20, 2009, 00:58
Default Material properties used for Binary alloy solidification
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Hi,

I m able to run simulation for HPDC for binary alloy. But the segregation model is predicting wrong values for solute concentration as a result of solidification.
My alloy is A-356 which is binary alloy (Al-Si 7%) i.e. initial solute concentration (Si) is 0.07.
The eutectic composition of this alloy is 0.126. But after running the simulation the segregation model predicts the solute concentration beyond eutectic concentration which is wrong. I have seen the example (in flow3d itself) file that simulates segregation model and based on that i have calculated the properties.
I have gone through the documentation for segregation model.
My data for alloys are.
Initial solute concentration 0.07; pure solvent melting temperature = 913 K; Eutectic Temperature = 850 K; Density 2420; Thermal Expansion coeff = 2.1e-05; solutal expansion coeff = 0.025; specific heat of fluid 1 = 1194; Thermal conductivity of fluid 1 = 86.9
Latent heat of fusion for fluid 1 = 4.29e+05; Eutectic concentration 0.126
I m taking reference solute concentration equal to initial solute concentration 0.07 and based on that i have calculated the liquidus TL1 and solidus TS1 temperature which are as follows:
TL1 = 878 K; TS1 = 643.79 K Partition coeff is 0.13 Diffusion coeff = 1e-09
But i m doubtful about solidus temperature value as it is lower than the eutectic temperature.
Actually my solute concentration is in that regime of phase diagram where if u calculate the TS1 based on initial solute concentration it comes out to be less than eutectic temperature so what values to be taken for TS1.
If anyone can come out with some suggestion or guidance so that i can predict correct segregation of alloy. I can also give my prepin file if anybody wants to see the complete material properties and data.
All properties i have choosen in SI units.
Thanks and Regards
NP
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Old   April 10, 2009, 19:19
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Hi~
Just out of curiosity did you preprocess the simulation to look at the phase diagram to ensure it is the one you are trying to capture? You can preprocess. To view the diagram Analyze>open results>Select existing radio button then select prpplt file then render.
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Old   April 13, 2009, 00:15
Default Michael Barkhudarov
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Hi Pathak,

I just want to say that the message about the absence of the reference pressure is just a warning. It means that the pressure values in the solution may drift with time, the magnitude of the 'drift' depending on the pressure solver used.

Michael
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Old   April 13, 2009, 00:49
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Quote:
Originally Posted by melissa View Post
Hi~
Just out of curiosity did you preprocess the simulation to look at the phase diagram to ensure it is the one you are trying to capture? You can preprocess. To view the diagram Analyze>open results>Select existing radio button then select prpplt file then render.
MC
Hi Melissa

I saw the phase diagram..The values which i m putting are defining correct phase diagram. But still the solute concentration is going beyond the eutectic range.
btw thanks a lot for this info of looking phase diagram actually i didnt know that.

Regards
NP
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Old   April 13, 2009, 00:54
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Quote:
Originally Posted by mike@flow3d.com View Post
Hi Pathak,

I just want to say that the message about the absence of the reference pressure is just a warning. It means that the pressure values in the solution may drift with time, the magnitude of the 'drift' depending on the pressure solver used.

Michael
Hello Sir,

Yupp it is warning. Actually i simulated with one geometry then i was able to solve for the segregation after filling of binary alloy was done.
But for a diiferent geometry i m not able to simulate for the segregation part. I mean the menu shows one warning " that regarding pressure thing"
but after that there is no progress observed in the code. Filling part is going ok but once i restart my file then it doesnt move.
So i just want to know whether i will be able to solve for HPDC simulation for a binary alloy or not?
Thanks & Regards

NP
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Old   April 13, 2009, 15:38
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Hi Pathak,

Yes, it is perfectly possible to do the filling and solidification with segregation in one pass. The problems you are having have nothing to do with the segregation model, but with the transition from filling to solidification. If you want to do it in one simulation, you need to turn off the inlet velocity when the mold is full, otherwise, the solver will not converge. If you are doing it using a restart simulation, then you need to reset the boundary condition too.

Does it make sense?
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Old   April 14, 2009, 01:02
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Quote:
Originally Posted by mike@flow3d.com View Post
Hi Pathak,

Yes, it is perfectly possible to do the filling and solidification with segregation in one pass. The problems you are having have nothing to do with the segregation model, but with the transition from filling to solidification. If you want to do it in one simulation, you need to turn off the inlet velocity when the mold is full, otherwise, the solver will not converge. If you are doing it using a restart simulation, then you need to reset the boundary condition too.

Does it make sense?
Hi,
yes simulation is running after filling is complete but with some restrictions. Probably when i was uenabling air entrainment model along with filling and segregation model then i suppose it wasnt possible for me to run simulation after filling is complete. But when i left the air entrainement model and used only filling and segergation, it worked.
Though it took lot of time for the simulation to complete.
I have got two queries actually.
1. During filling in HPDC, the flow is in turbulent regime and i am using turbulent modelling. But when filling of mould is completed and then during solidification i dont thing that the flow will be turbulent (at the later stages of solidification). So should i switch off the turbulent model during solidification (while restarting the prepin file) or i should use turbulent model even during solidification.

2. I am putting symmetry boundary condition at the inlet once filling completes along with using laminar during solidification.

3. My solute concentration is going beyond the eutectic concentration while should not happen. I m putting values and i have seen the phase diagram it is coming out to be correct. But i dont khnow why the solute concentartion is going beyond CEUT.

Any comments regrading this..??

Thanks and Regards..

NP
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Old   April 14, 2009, 13:51
Default concentration above eutectic
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Hi~
Where are the locations of concentration going above the eutectic? Do they appear in droplets of fluid or in the overall simulation? If the concentration going above the eutectic are located in droplets then I think you can plot the results in 3-D and limit the contour without any loss to the actually results. To this go to anlayze>3-D panel> Under contour limits select User defined radio buttons then type the limits.
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Old   April 16, 2009, 18:16
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Hi Pathak,

I sent you an email this morning. There is a problem using the segregation model during filling caused by an instability in the advection algorithm. I am working on a fix. For now you will have to activate the model after the cavity is full.

If you don't get the email, let me know.

Michael
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