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Old   January 24, 2012, 00:52
Default A little help needed!!
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Danial
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Hi guyz,
i am beginner and working on some simulation of molten nickle on steel e.g solidification case. i am getting the same error;

""In Analysis 'Flow Analysis 1' - Domain 'splat': The following materials require Viscosity to be defined: 'Nickel'""

and i have spent a lot more time on this issue but still unbale to remove it. While i have generated an expression for nickle viscosity too which is not working. Could you please suggest any possible remedy??

Please suggest a book regarding ansys CFX tutorials.
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Old   January 24, 2012, 06:08
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CFX has no built in solidification model, so you will have to develop the details of this model yourself. And the reason it is not in CFX by default is it is fiendishly complicated. This does not sound like the sort of model a beginner should be taking on.
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Old   January 24, 2012, 16:35
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thanks for the suggestion. I have done some tutorials already. But its my Phd work part and someone has already done some work on it in ANSYS. As it is done earlier so i can't say that its not possible in ansys. i have mentioned the details of nickle material already but don't know what's wrong with its viscosity. For your convenience i am posting details of the problem.
"" a molten nickle droplet (high temp) is hit on steel piece (ambient temp) with gun. it hits the steel surface and cools down as circular disk. this is the first step of whole problem.""
hey ! it would be fine if you can give me some advice about animation of this single drop" do you think there is something to do with time steps or initial time details as it completes in micros seconds. i have made geometry for the problem as two recatngular boxes on each other but they are in different planes. i am not sure if i can join them in a single plane.,,any suggestions please????
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Old   January 24, 2012, 17:38
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I did not say it could not be done, I said it was fiendishly complicated. And if you have an example of somebody who has done it before then why not just copy their method?

There are many approaches to do solidification modelling depending on what you want to do. How are you modelling the solidification at the moment? If you could attach the CCL that would be good.
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Old   January 26, 2012, 23:04
Default CCL Attached!!
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hi ghorrocks!!
i have tried to attach CCL but failed but i have uploaded the "output file" . please mention if you find anything strange or suspected.
it would be nice of you.
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Old   January 26, 2012, 23:06
Default output file attached!!
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hi ghorrocks!!

i have tried to attach CCL but failed but i have uploaded the "output file" . please mention if you find anything strange or suspected.

it would be nice of you.
Attached Files
File Type: txt output.txt (25.7 KB, 35 views)
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Old   January 26, 2012, 23:55
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Isn't the error obvious? It has not connected to your fortran routines. There is some problem with compilation or connection to the fortran.
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Old   January 27, 2012, 00:31
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i have removed those routines, they were to measure some property(contact resistance) which i m nt interested in nw. so it does'nt matter.the only error it shows is the one i mentioned earlier.
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Old   January 27, 2012, 00:43
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No, all the errors in your output file are associated with the fortran files. They are not warnings, they are fatal errors so it is not skipping it. If you have removed the fortran files then you have to remove the link to them in CFX-Pre as well.
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Old   January 27, 2012, 01:06
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thx ghorrocks, i will chk it again and generate a new output file. But why in cfx pre it gives global error about nickle viscosity while i have mentioned it in both states (liquid and solid stae viscosities).
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Old   January 27, 2012, 01:21
Default updtaed projectCCL
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Hi Ghorrocks!! please look into this CCL ,i have removed all routines but "nickle viscosity "is still there.

thx for ur time bro!!
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File Type: zip updatedproject.zip (4.3 KB, 17 views)
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Old   January 27, 2012, 01:47
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You seem to be doing a 2 phase free surface simulation, like as you would for water and air except you have nickel as the liquid phase. You even say in the CCL:

Quote:
FLUID DEFINITION: air at 25C
Material = Air at 25 C
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID DEFINITION: splat
Material = Nickel
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
So splat is the liquid phase and you have defined that as nickel. But nickel is defined as a solid and therefore you have not defined a viscosity. The two phase approach you are using requires both phases to be fluids and to have a viscosity. You cannot have one phase a solid.

I am not sure you have thought out how you are approaching this. Have you considered what approach you should use for solidification modelling? There is nothing built in so you are going to have to develop it? Are you going to model the solid as a fluid but with a very high viscosity? Or as a true solid and use a deforming mesh to track the solidification interface? What are you going to do with the latent heat? How are you modelling the heat transfer to the thing it hits? How are you modelling the initial conditions? Does the nickel have any further phase transformations at these rates of cooling (just to make it even more diabolical)? As I said this is a very tricky model and your current CCL contains no answers to these issues.
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Old   January 27, 2012, 02:13
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Thx bro. i guess i should explain it how i am going to do it. the problem statement is like "" we are hitting a nickle droplet 1700C approx. (molten) with the gun on some steel substrate (25C). here nickle is in fluid (molten) form ,it hits and solidifies in micro seconds. i have mentioned the value of thermal contact resistance and also have chosen some heat transfer models as u can see in output file. as i am beginner , i might be missing something really tricky but as far as viscosity of nickel error is concerned, that's right that it changes from fluid to solid during solidification in the whole process. i think i have selested it fluid as u can see, or may be i am not getting ur point when u say i have defined it solid.
FLUID DEFINITION: splat
Material = Nickel
as far as approach to problem is concerned, i have to develop a model showing solidification of nickel on steel along with its phase change from molten to solid shape ( we say disk) on steel. all other heat relevant data is added as expressions.( latent heat, liquid viscosity, solid viscosity,heat capacity e.g.).
molten nickle (fluid) >>>>> solidified nickel (solid) ; heat transfers from nickel to steel, heat trasfer coeficient is defined at interface also.conduction is only source assumed.
initial conditions are a real mess, i am worried about. i need some clues about it what it contains. if its about initial time ,time step and total time then it contins say 10 steps, for total time of 1 microsecond starting from i nano second. am i clear otherwise just mention some other necessary things required to define initial conditions.

thax a lot for ur help bro.
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Old   January 27, 2012, 03:15
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what i have found that;
" inhomogeneous interphase heat transfer model" will be used and regarding that i hv provided enough data in expressions list like flux, heat transfer coefficient etc. i guess u r gonna agree with me on that.the reason is the heat transfer is taking place b/w molten phase of nickel to solid phase of steel, while both are having different temps and enthalpies.
thx
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Old   January 27, 2012, 07:28
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You should read up about multiphase modelling. Read the theory chapter in the documentation about the models you are using. I do not think the approach you are using is going to work from what you have described. Quite simply it cannot model a solid, both phases must be fluid.
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Old   January 27, 2012, 18:19
Default hi ghorrocks
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Ok got it. i will go through them again but i cant understand teh point u raised that i have defined nickel as solid while it is quite obvious that its defined as fluid domain (continuous fluid). Can you please give me some hint about your suspecion of nickel being soild???how did u evaluate it??on what basis?

thx plz
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Old   January 29, 2012, 05:51
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Your definition of the material nickel says it is a solid, and the properties you define are suitable for solids only.

Quote:
MATERIAL: Nickel
Material Group = CHT Solids,Particle Solids
Option = Pure Substance
Thermodynamic State = Solid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 8903 [kg m^-3]
Molar Mass = 58.69 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 4.44E+02 [J kg^-1 K^-1]
END
REFERENCE STATE:
Option = Specified Point
Reference Specific Enthalpy = 0 [J/kg]
Reference Specific Entropy = 0 [J/kg/K]
Reference Temperature = 25 [C]
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 90.7 [W m^-1 K^-1]
END
END
END
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Old   January 30, 2012, 01:20
Default Hi GHorrocks
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Thanks a lot bro. dT was so nice of you. i found it. Later i tried to define material properties and add them in material library but oculd not yet ,may be administrator doe'nt allow it nad i will have to aks IT department.

As far as, model selection is concerned , i have bennn through the documentation and i have concluded that Eulerian -Eulerian multiphase homogeneous model would be the best option considering it as free surface flow problem. does it look alright??

BUt i have some questions like why are we CALCULATING the interface b/w air/droplet while i have to model the parameters which belongs to
droplet(Ni) and solid substrate( steel) because these two make real interface on contact and i have to measure something here at contact time. dont you think that air and molten droplet contact time is in just few microseconds and it does'nt even plays significant transfer (mass,heat etc). Would you please help me if i am taking this problem completely wrong? any suggestions plz.
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Old   January 30, 2012, 01:28
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Have you done the free surface tutorial? Free surface flow over a bump. It shows the way to setup and run a normal air/water free sirface simulation.

What physics are you trying to model? What is the simulation going to tell you? The choice of physical model to use depends on what you want out of the simulation.

What is important out of this list:
* the latent heat of the phase change
* phase changes in the solid cooling process
* any mushy states during liquid/solid phase change
* heat transfer to the plate
* cooling time of the nickel
* shape of the final nickel solid blob
* Anything else?
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Old   January 30, 2012, 01:44
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My purpose of simulation is to get following results;
  • contact angle (angle of droplet with substrate after hitting) vs time
  • to study the affect of that thermal contcat resistance b/w droplet and substrate as a thin layer is supposed to be formed after contact of droplet and substrate and this layer has theoretically affect on droplet final shape after hitiing.
  • Final shape of droplet (probably disk like usually depends on thermal contact resistance)
I would first try to get droplet shape on the basis of thermal contact resistance and ANSYS 13 is offering this thermal contact resisiatnce so getting shape is my my first aim. yEah i have done that free surface problem.thx
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