A little help needed!!
 

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.

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.

@ ghorrock
 

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????

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.

CCL Attached!!
 

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.

output file attached!!
 

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.

Isn't the error obvious? It has not connected to your fortran routines. There is some problem with compilation or connection to the fortran.

hi
 

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.

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.

hi
 

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).

updtaed projectCCL
 

Hi Ghorrocks!! please look into this CCL ,i have removed all routines but "nickle viscosity "is still there.:confused:

thx for ur time bro!!

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:

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.

hi
 

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.

hey
 

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

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.

hi ghorrocks
 

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

Your definition of the material nickel says it is a solid, and the properties you define are suitable for solids only.

Hi GHorrocks
 

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.

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?

hi
 

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

This sounds like you need a good thermal model as well, and this will require the latent heat correctly modelled, this will be a challenge. Also you will need to develop some model for solid material, presumably this will be a high viscosity fluid. You will need to make the viscosity high enough that the solid material does not move significantly but low enough that the simulation converges. This is not always possible.

Hi
 

yeah it is true that this problem is quite tricky and needs some special treatment and concentration along with skills. I have value for latent heat but i dint get your point about solid and its viscosity. because solid is going to be defined as separate domain here ,if you are talking about the solid which is substrate (steel) also. Becuase its viscosity is no where mentioned in the code i am following or trying to redevelop.it is tretaed as separate entity or domain on material properties given in ANSYS library.THe heat transfer model for solid domain is used" thermal energy".
If you are talking about the solid which will be treated as droplet in molten form and solid ( after cooling/solidification process) then it is treated as two components (liquid Ni and Solid Ni) along with Air in Fluid pair system, and then modelled.
i hope if i understood your point right, otherwise please mention it.
My point is >>should i consider it as moving mesh?? and how should i define the interface so that i could develop a relation b/w contact angle and time?
Thanks

I did not understand your last post, but that is not important now. I recommend you do tutorials about conjugate heat transfer (CHT), multiphase flow and moving mesh so you understand these models before going any further.

Hi
 

Thanks for ur recommendations, i will go through them again. My last point was about the interface which is developed b/w Ni (when it is solidified) and substrate.As theoretically there exist an interface which should be mentioned in simulation after hitting and solidification. The previous student mentioned it by adding domian interface and then modelled it. What is ur thought abt moving mesh, if this problem lies in this category??

I asked about this many posts ago. You can model the solid with an interface at the solidification front but this is very tricky to actually implement and even harder to get to run. Modelling the solid as a fluid with a very high viscosity is easier if it works - if you can get the large range of viscosities to converge that is.

HI
 

so , u think defining a domain interface b/w substrate (steel) and molten droplet (Ni) is gonna be a tricky approcah to the problem. Yes convergence has been a big deal earlier. But i ave to follow it as i have to prepare a replica first, for the later work.
" Modelling the solid as a fluid with a very high viscosity is easier if it works - if you can get the large range of viscosities to converge that is".which solid r u talkin abt here?? its steel if i am right but i dont think it would would work for me.thanks

The steel plate (which I assume does not move, just gets hot) should be modelled as a solid, this is straight forward. It is the solid region in the Nickel which is tricky.

HI
 

Yea got it. ofc substrate is not moving ,its only nickle. i need suggestion about another point that is " another approach used was about using one of steel boundary ( on which Ni hits, infcat top of steel) can be defined as interface b/w Ni and Steel? rather defining the domain interface separately.
And one more thing about fluid and particle definition part, should i define splat (Ni); as liquid Ni and Solid Ni separately as components, by adding them as new materials in library. Or i should only use library material Ni and there is some other option available later in setup to use them as component? i am confused abt it bcz i did'nt find anything about defining them as components later .
Thanks a lot

The way you set it up depends on the approach you are going to use. If you are going to use the moving mesh interface tracking approach then you have one domain with air and liquid Ni, and another domain with solid Ni. If you are going to use the high viscosity approach you have a domain with air, liquid Ni and solid Ni (modelled as a liquid with high viscosity).

hey glen!!
 

can u plz explain this error;

"In Analysis 'Flow Analysis 1' - Domain 'splat' - Fluid 'user Ni': Equilibrium phase change in one phase in an MPF run is not supported by the solver".

What is the MPF ERROR?

Not sure, maybe multi-phase flow. You would have to ask support.