VOF model for slurry deposition trough an extruder

Dear,
I, as a completely new guy to Ansys, started building up a model in fluent to simulate the slurry (fluid) deposition through an extruder. First I started to get to know the software via the tutorials in VOF modelling and some overall tutorials. Then I started with a 2D-model to try it out in a simplified model. After this gave me some decent results, I started rebuilding this model in 3d with the same parameters. But when I run this, the calculated VOF surface doesn't look realistic at all with a slurry being so vicious. Especially compared to the 2D-model. And next to that it gives the floating-point error after around 40 iterations. In the attachments of this topic, I uploaded one file containing the two summary files of the model. First, the 2D model summary is given, behind that the 3D model summary

Would be pleased to have someone that could look at it and give me some tips on what to do next to get some valid results.

Sincerely,

Guus

Comments

  • DrAmineDrAmine GermanyForum Coordinator
    edited April 20
    as an Ansys employee I do not download attachments. Slow settling or no settling slurries can be modeled as non Newtonian fluid. If you require sir as surrounding then simple two phase flow with the slurry with adjusted properties and non Newtonian viscosity
  • DrAmineDrAmine GermanyForum Coordinator
    edited April 20
    that was general hint without looking into your particular case. Add some more information regarding your 3d problem
  • GuusWezelGuusWezel Member
    edited April 21

    Dear Amine,

    Thanks for your hint.

    The 3D model now consists of a nozzle at a fixed distance above a substrate. The substrate is moving in one direction to model the slurry deposition during printing. To test the model, the slurry now just has a fixed viscosity of 1 pas/s, this will later be changed to a non Newtonian viscosity.

    As a time step I use a function that changes the time step per iteration: IF(iter<=600, 1 [s] *10**-(10-iter*0.01), 0.0001 [s]) with a total of 1700 iterations.

    Down here I put the text I wrote the settings of the 3d model (the same as in the attachments).

    Fluent
    Version: 3d, dp, pbns, vof, lam, transient (3d, double precision, pressure-based, VOF, laminar, transient)
    Release: 20.1.0
    Title:

    Models
    ------

       Model                        Settings                      
       ---------------------------------------------------------
       Space                        3D                            
       Time                         Unsteady, 1st-Order Implicit  
       Viscous                      Laminar                       
       Heat Transfer                Disabled                      
       Solidification and Melting   Disabled                      
       Species                      Disabled                      
       Coupled Dispersed Phase      Disabled                      
       NOx Pollutants               Disabled                      
       SOx Pollutants               Disabled                      
       Soot                         Disabled                      
       Mercury Pollutants           Disabled                      
       Structure                    Disabled                      

    Material Properties
    -------------------

       Material: slurry (fluid)

          Property                        Units     Method     Value(s)  
          -------------------------------------------------------------
          Density                         kg/m3     constant   7260      
          Cp (Specific Heat)              j/kg-k    constant   1006.43   
          Thermal Conductivity            w/m-k     constant   0.0242    
          Viscosity                       kg/m-s    constant   1         
          Molecular Weight                kg/kmol   constant   28.966    
          Thermal Expansion Coefficient   1/k       constant   0         
          Speed of Sound                  m/s       none       #f        

       Material: air (fluid)

          Property                        Units     Method     Value(s)    
          ---------------------------------------------------------------
          Density                         kg/m3     constant   1.225       
          Cp (Specific Heat)              j/kg-k    constant   1006.43     
          Thermal Conductivity            w/m-k     constant   0.0242      
          Viscosity                       kg/m-s    constant   1.7894e-05  
          Molecular Weight                kg/kmol   constant   28.966      
          Thermal Expansion Coefficient   1/k       constant   0           
          Speed of Sound                  m/s       none       #f          

       Material: aluminium (solid)

          Property               Units    Method     Value(s)  
          ---------------------------------------------------
          Density                kg/m3    constant   2719      
          Cp (Specific Heat)     j/kg-k   constant   871       
          Thermal Conductivity   w/m-k    constant   202.4     

    Cell Zone Conditions
    --------------------

       Zones

          name    id   type   
          ------------------
          fluid   3    fluid  

       Setup Conditions

          fluid

             Condition       Value  
             ---------------------
             Frame Motion?   no     
             Mesh Motion?    no     

    Boundary Conditions
    -------------------

       Zones

          name              id   type             
          --------------------------------------
          wall-fluid        1    wall             
          symmetry-plane    6    symmetry         
          pressure-outlet   7    pressure-outlet  
          moving-wall       8    wall             
          velocity-inlet    9    velocity-inlet   

       Setup Conditions

          wall-fluid

             Condition                  Value                                   
             -----------------------------------------------------------------
             Wall Motion                0                                       
             Shear Boundary Condition   0                                       
             Contact Angles             (((constant . 2.0943948) (profile  )))  

          symmetry-plane

             Condition   Value  
             -----------------

          pressure-outlet

             Condition   Value  
             -----------------

          moving-wall

             Condition                                            Value                                   
             -------------------------------------------------------------------------------------------
             Wall Motion                                          1                                       
             Shear Boundary Condition                             0                                       
             Define wall motion relative to adjacent cell zone?   yes                                     
             Velocity Magnitude (m/s)                             0.01                                    
             Contact Angles                                       (((constant . 1.5707963) (profile  )))  

          velocity-inlet

             Condition                  Value  
             --------------------------------
             Velocity Magnitude (m/s)   0.01   

    Solver Settings
    ---------------

       Equations

          Equation          Solved  
          ------------------------
          Flow              yes     
          Volume Fraction   yes     

       Numerics

          Numeric                         Enabled  
          ---------------------------------------
          Absolute Velocity Formulation   yes      

       Unsteady Calculation Parameters

                                                         
          ---------------------------------------------
          Time Step (s)                   2.5118864e-09  
          Max. Iterations Per Time Step   20             

       Non-Iterative Solver Factors

          Variable          Max. Corrections   Correction Tolerance   Residual Tolerance   Relaxation Factor  
          --------------------------------------------------------------------------------------------------
          Pressure          10                 0.25                   0.0001               1                  
          Momentum          5                  0.05                   0.0001               1                  
          Volume Fraction   5                  0.05                   0.0001               1                  

       Linear Solver

          Variable          Solver Type   Termination Criterion   Residual Reduction Tolerance  
          ------------------------------------------------------------------------------------
          Pressure          F-Cycle       0.1                                                   
          X-Momentum        Flexible      0.1                     0.7                           
          Y-Momentum        Flexible      0.1                     0.7                           
          Z-Momentum        Flexible      0.1                     0.7                           
          Volume Fraction   Flexible      0.1                     0.7                           

       Pressure-Velocity Coupling

          Parameter   Value            
          ---------------------------
          Type        Fractional Step  

       Discretization Scheme

          Variable          Scheme       
          -----------------------------
          Pressure          PRESTO!      
          Momentum          QUICK        
          Volume Fraction   Compressive  

       Solution Limits

          Quantity                    Limit  
          ---------------------------------
          Minimum Absolute Pressure   1      
          Maximum Absolute Pressure   5e+10  
          Minimum Temperature         1      
          Maximum Temperature         5000   

     

    I hope you now have a general idea of the problem and that you can help me further.

    Sincerely,

    Guus van Wezel

     

  • DrAmineDrAmine GermanyForum Coordinator
    edited April 21

    What is now the problem?

  • GuusWezelGuusWezel Member
    edited April 21

    Dear Amine,

    The problem is that the results of the 2D and 3D models are very different. Where the 2D model gives a realistic flow of the slurry, the 3D model does not give a realistic flow at all. This is shown in the figure below.

    Model results of the 2D model (on top) and the 3D model (below)

     

    Since the input parameters for both models are the same, I can't locate the problem within the model.

     

    Sincerely,

     

    Guus

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