Learning Forum

[jarmouni]

Hello everyone,

 

When linking Ansys Fluent and Rocky (2-way coupling unresolved), I received this error message. After the first time step this appears and then nothing happens during the simulation.

 

For information: I use a UDF to describe the viscosity of the non-Newtonian fluid.

 

 

Thank you very much for your support.

 

Kind regards,

 

Noureddien Jarmouni

****************************************************************************************************************************************************************************************************************

 

**UDF**
*************

#include "udf.h"

#include "math.h"

 

DEFINE_PROPERTY(Bingham_viscosity, c, t)

{

    real gamma_dot;             /* Scherrate */

    real tau_y;                 /* Yield Stress */

    real mu_p;                  /* Plastische Viskosität */

    real B;                     /* Magnetfeldstärke */

    real apparent_visc;         /* Scheinbare Viskosität */

    real k1 = 111252.7;         /* Materialkonstante 1 */

    real k2 = 43413.6;          /* Materialkonstante 2 */

 

    /* Benutzerspezifische Parameter */

    mu_p = 0.320;           /* Plastische Viskosität in Pa.s */

    B = 0.5;              /* Magnetfeldstärke in Tesla */

 

    /* Funktion für Yield Stress in Abhängigkeit vom Magnetfeld */

    tau_y = k1 * pow(B, 2) + k2 * B;

 

    /* Berechnung der effektiven Scherrate */

    gamma_dot = C_STRAIN_RATE_MAG(c,t);

 

    /* Vermeidung von Division durch Null */

    if (gamma_dot > 1e-6)

    {

        apparent_visc = (tau_y / gamma_dot) + mu_p;

    }

    else

    {

        apparent_visc = 0.320;  /* Hohe Viskosit t bei sehr niedrigen Scherraten */

    }

    

    //Message("B= %f , tau_y= %f , gamma_dot= %f , apparent_visc= %f \n", B, tau_y, gamma_dot, apparent_visc);

 

    return apparent_visc;

****************************************************************************************************************************************************************************************************************

**rocky-simulation.rocky20.log**
************************************

***************************************************************************************************

*                                      Ansys Rocky DEM Solver                                     *

*                           3D Discrete Element Modeling (DEM) Simulator                          *

*                                        Version 2024.0612                                        *

*                                          Release 24.2.0                                         *

 

*                            (c) 2024 Ansys, Inc. - All Rights Reserved                           *

***************************************************************************************************

 

Command line: 

    C:\Program Files\ANSYS Inc\v242\rocky\bin\RockySolver.exe

    --rcy-file=C:\Users\noureddine.jarmouni\Desktop\Rocky 20250125\Ansys-Rocky Kopplung_20250125_v01_JaN.rocky.files\simulation/rocky_simulation.rocky20

    --ncpus=10

OS info:

Windows 10 ServerStandard                

Release version 10.0.17763

License setup: 

Path: 

Vendor: Ansys

Heartbeat: 300

N. Retries: 5

Parameters:

Input filename: C:\Users\noureddine.jarmouni\Desktop\Rocky 20250125\Ansys-Rocky Kopplung_20250125_v01_JaN.rocky.files\simulation/rocky_simulation.rocky20

Number of processors to use: 10

Resume previous simulation: 0

Use GPU: 0

HDF library version: 1.12.1

CPU info:

CPU brand:       Intel(R) Xeon(R) CPU E5-2620 v2 @ 2.10GHz

Core count: 12

Checkout Ansys solver license: rocky_solver

Checkout 6 Rocky HPC unit licenses granted.

Dynamically allocated arrays growth rate set to: 1.1

Found an advanced parameters file, overwriting configuration.

Setting breakage_overlap_factor to 0.25

Setting reset_only_physical_contacts_data to 0

Setting refine_concave_search to 1

Setting use_non_round_torque_correction to 1

Setting linear_hyst_damp to 0

Setting monitor frequency to 1

Setting radl_update_distance_multiplier to 1

Setting radl_neighbor_distance_multiplier to 3

Using grid search: false

Using sparse grid: false

 

Particles:

Name: Diamantpartikel

Shape: ptSpherical

Material Index: 0

Smallest sieve size: 0.001

Meshing type: pmtNone

--------------------

 

Materials:

Index: 0

Name: Default Particles

Stiffness: 1e+07

--------------------

Index: 1

Name: Default Belt

Stiffness: 1e+10

--------------------

Index: 2

Name: Default Boundary

Stiffness: 1e+10

--------------------

Index: 3

Name: Diamant

Stiffness: 1.05e+11

--------------------

Index: 4

Name: HSS

Stiffness: 2.24e+10

--------------------

 

Loading addins configuration: C:\Users\noureddine.jarmouni\Desktop\Rocky 20250125\Ansys-Rocky Kopplung_20250125_v01_JaN.rocky.files\simulation\addins.config

Simulation setup done!

SPH Density Monitor: the module is being disabled because the simulation has no SPH elements.

Triangle scalars

Edge Length [m] data type size: 24bytes

Particle Scalars

Time Of Release [s] data type size: 8bytes

Contact Info Starting Index [-] data type size: 4bytes

CFD Index [-] data type size: 4bytes

SolidExplicitForce [N/m3] data type size: 24bytes

SolidImplicitForce [N.s/m4] data type size: 8bytes

Particle Contact scalars

Normal [m] data type size: 12bytes

Scale [-] data type size: 4bytes

Near Global Index [-] data type size: 4bytes

Normal Force [N] data type size: 8bytes

Contact Point Coordinate [m] data type size: 24bytes

Overlap [m] data type size: 8bytes

Previous Overlap [m] data type size: 8bytes

Home Index [-] data type size: 4bytes

Near Index [-] data type size: 4bytes

State [-] data type size: 2bytes

Tangential Force [N] data type size: 24bytes

Is Sliding [-] data type size: 1bytes

Previous Normal Vector [-] data type size: 12bytes

Triangle Contact scalars

Normal [m] data type size: 12bytes

Scale [-] data type size: 4bytes

Near Global Index [-] data type size: 4bytes

Normal Force [N] data type size: 8bytes

Contact Point Coordinate [m] data type size: 24bytes

Overlap [m] data type size: 8bytes

Previous Overlap [m] data type size: 8bytes

Home Index [-] data type size: 4bytes

Near Index [-] data type size: 4bytes

Near Location [-] data type size: 4bytes

State [-] data type size: 2bytes

Tangential Force [N] data type size: 24bytes

Is Sliding [-] data type size: 1bytes

Previous Normal Vector [-] data type size: 12bytes

Fluid scalars

Fluid Density [kg/m3] data type size: 8bytes

Fluid Viscosity [Pa.s] data type size: 8bytes

Solid Volume Fraction [-] data type size: 8bytes

Fluid Velocity [m/s] data type size: 24bytes

Fluid Pressure Gradient [Pa/m] data type size: 24bytes

Solid Explicit Force [N/m3] data type size: 24bytes

Solid Implicit Force [N.s/m4] data type size: 8bytes

Fluid Velocity U Gradient [1/s] data type size: 24bytes

Fluid Velocity V Gradient [1/s] data type size: 24bytes

Fluid Velocity W Gradient [1/s] data type size: 24bytes

Static Pressure [Pa] data type size: 8bytes

 

N. Total Particles: 35808

enabled: 35808

released: 35808

Particle scalars not dimensionalized: 

Contact Info Starting Index

CFD Index

Contact scalars not dimensionalized: 

Normal

Scale

Near Global Index

Home Index

Near Index

State

Is Sliding

Previous Normal Vector

Contact scalars not dimensionalized: 

Normal

Scale

Near Global Index

Home Index

Near Index

Near Location

State

Is Sliding

Previous Normal Vector

Rocky CFD coupling mode = Two Way By IPC

Rocky Fluent TwoWay Initialize Coupling: connection id = 11984

Waiting for fluent message

Fluent write data message received.

Sent Fluent Data Read Message.

CFD travel distance updated: 0.00025

minimum_cell_length: 7.94834e-05

minimum_spherical_particle_diameter: 0.001

overwrite_cfd_update_distance: 0

user_cfd_update_distance: 0

Fluent neighbor averaging:

Averaging method: cfd_avrg_method_VolumetricDiffusion

Min iterations (averaging_parameters.min_iterations): 1

Max iterations (averaging_parameters.max_iterations): 500

Solid fraction target (averaging_parameters.sfract_target): 0.65

Number of elements: 5918350

Number of sides: 11967060

 

Output time set to: 0.001s

N. CFD iterations per output: 1

Fluent time-step: 0.001s

N. Rocky iterations per output: 808.142

CFDCoupling: Target DT = 0.001

Simulation initialization done!

Simulation Flags:

has_round_particles: 1

has_non_round_particles: 0

has_only_round_particles: 1

has_particles_instantaneous_breakage: 0

has_particles_discrete_breakage: 0

has_custom_particles: 0

has_fiber_particles: 0

has_shell_particles: 0

has_concave_particles: 0

has_meshed_particles: 0

has_boundaries_wear: 0

has_adhesion: 0

 

Physics models:

Rolling resistance model: rrmNone

Normal force model: nfmLinearHysteresis

Adhesion model: amConstant

Tangential force model: tfmElasticTangential

Impact energy model: iemRocky

Restitution model: rmConstant

Stiffness correction factor: 0.1

Thermal modeling: 0

Thermal conduction correction model: tcmNone

Coarse Grain Modeling (Bierwisch): 0

Coarse Grain Modeling - Intra Parcel Dissipation (Radl): 0

 

Domain settings:

Coordinate limits at boundary limits:

Boundary limits min: (-0.04, -0.02, 0)

Boundary limits max: (0.04, 0.02, 0.0645)

No Periodic boundaries

 

Solver settings:

Timestep: 1.23741e-06

Timestep model: tmConstant

Simulation duration: 0.005

Current time: 0

Output frequency: 0.001

Total number of outputs to generate: 5

Wear start: 9.998

Energy Spectra start: 10

Breakage start: 9.998

Energy Spectra release time delay: 2

Breakage release time delay: 2

Wear geometry update frequency: 0.005

Loading n-steps: 15

Release particles without overlap check: 0

Overlap particles delay: 0.025 [s]

Push active particles period: 0.0249993 [s]

Particles sorting distance: 0.0025 [m]

Neighboring Distance (particle-particle): 0.000375 [m]

Neighboring Distance (particle-triangle): 0.000375 [m]

Use GPU Sorting: 0

 

Motion frames:

Number of frames: 6

Periodic motion: 0

Has free body motion: 0

 

CFD settings:

Coupling mode: cfdcTwoWay

Particle Group: Diamantpartikel

Drag law: cfd_drag_law_HuilinGidaspow2003

Lift law: cfd_lift_law_none

Torque law: cfd_torque_law_none

Virtual mass law: cfd_virtual_mass_law_none

Heat convection law: cfd_convection_law_none

 

Solver progress summary frequency set to: 0.001

Particles sorting distance changed from: 0.0025  to: 0.00843811 current simulation time is: 1.23609e-06

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Volumetric diffusion averaging may be taking too long.

501 iterations were required.

Sending fluent message

First Fluent data send.

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Send Rocky Data Write Message.

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

1 particle(s) reentered the cfd domain

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

CFDCoupling: Send CFD data

Rocky current time = 0.001 iteration: 809 last output time: 0.001

CFD flow time: 0.001 iteration: 0

Sending fluent message

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Send Rocky Data Write Message.

Issues found since last output!

 - 11 particles reentered the cfd domain during 7 events (average of 1.57143 particles per event)

 - Contacts overlap, an average of:

    0.502% of contacts reached more than 2.5% overlap.

    0.103% of contacts reached more than 10% overlap.

    0.0588% of contacts reached more than 20% overlap.

      collected in 809 timesteps totaling 47284047 contact overlaps

 

Issues found since last output!

 - An average of 501 iterations during 14 events produced the following output volume fraction statistics: minimum = 0.67, maximum = 0.68, average = 0.67

Issues found since last output!

 - Sorting distance has changed within: 0.00843811 to: 0.00844657 in 2 events

 

Waiting for fluent message

Fluent write data message received.

Sent Fluent Data Read Message.

CFDCoupling: Received CFD data. Target DT = 0.001

File: 1

Simulation time: 0.001

 

N. Total Particles: 35808

N. Enabled Particles: 35808

N. Released Particles: 35808

 

N. Enabled Elements: 0

N. Released Elements: 0

N. Particle Fragments: 0

 

N. Triangles: 24

N. Triangle Nodes: 16

 

N. Neighbors: 206285

N. Particle Neighbors: 200785, RR: 200785, RN: 0, NN: 0

N. Triangle Neighbors: 5500, TR: 5500, TN: 0

N. Surface Contacts: 64821, particles: 62677, triangles: 2144

N. Adhesion Contacts: 0, particles: 0, triangles: 0

Neighbor Contact Ratio: 3.182379

 

Estimated Limits of Surface Velocity:

     Total - min:      2e+01 max:      2e+01 average:      2e+01

Boundaries - min:      2e+01 max:      2e+01 average:      2e+01

Particles - min:          8 max:      1e+01 average:          9

 

CPU:

Memory Usage: 3949 MB of 65503 MB

Free Memory: 18522 MB

 

Execution Times:

Execution Times per Call:

 

                  Search - Cumulative:     0.02204[s] n_calls:    79, From last output:     0.02204[s] n_calls:    79

               Search PP - Cumulative:     0.05591[s] n_calls:    26, From last output:     0.05591[s] n_calls:    26

              -- Sorting - Cumulative:     0.01493[s] n_calls:     2, From last output:     0.01493[s] n_calls:     2

        -- BuildBVHTree, - Cumulative:     0.00222[s] n_calls:    26, From last output:     0.00222[s] n_calls:    26

            -- Neighbors - Cumulative:     0.03621[s] n_calls:    26, From last output:     0.03621[s] n_calls:    26

               Search PT - Cumulative:     0.00504[s] n_calls:    57, From last output:     0.00504[s] n_calls:    57

         -- CheckActives - Cumulative:     0.00001[s] n_calls:    57, From last output:     0.00001[s] n_calls:    57

          -- MarkActives - Cumulative:     0.00002[s] n_calls:     2, From last output:     0.00002[s] n_calls:     2

          -- PushActives - Cumulative:     0.00001[s] n_calls:    57, From last output:     0.00001[s] n_calls:    57

            -- UpdateBVH - Cumulative:     0.00006[s] n_calls:    57, From last output:     0.00006[s] n_calls:    57

            -- Neighbors - Cumulative:     0.00120[s] n_calls:    57, From last output:     0.00120[s] n_calls:    57

 

                 Overlap - Cumulative:    12.66359[s] n_calls:   809, From last output:    12.66359[s] n_calls:   809

                   Force - Cumulative:     0.75080[s] n_calls:   809, From last output:     0.75080[s] n_calls:   809

                    Move - Cumulative:     0.00211[s] n_calls:   809, From last output:     0.00211[s] n_calls:   809

                  Output - Cumulative:  1791.88875[s] n_calls:     1, From last output:  1791.88875[s] n_calls:     1

               Iteration - Cumulative:    16.11244[s] n_calls:   809, From last output:    16.11244[s] n_calls:   809

 

Total Execution Times: 13035[s], From last output: 13035[s]

 

                  Search - Total:        1.74[s] =   0.01 %, From last output:        1.74[s] =   0.01 %

             - Search PP - Total:        1.45[s] =  83.48 %, From last output:        1.45[s] =  83.48 %

             -- Sorting, - Total:        0.03[s] =   2.05 %, From last output:        0.03[s] =   2.05 %

        -- BuildBVHTree, - Total:        0.06[s] =   3.98 %, From last output:        0.06[s] =   3.98 %

           -- Neighbors, - Total:        0.94[s] =  64.78 %, From last output:        0.94[s] =  64.78 %

             - Search PT - Total:        0.29[s] =  16.51 %, From last output:        0.29[s] =  16.51 %

         -- CheckActives - Total:        0.00[s] =   0.11 %, From last output:        0.00[s] =   0.11 %

          -- MarkActives - Total:        0.00[s] =   0.02 %, From last output:        0.00[s] =   0.02 %

          -- PushActives - Total:        0.00[s] =   0.30 %, From last output:        0.00[s] =   0.30 %

            -- UpdateBVH - Total:        0.00[s] =   1.17 %, From last output:        0.00[s] =   1.17 %

            -- Neighbors - Total:        0.07[s] =  23.82 %, From last output:        0.07[s] =  23.82 %

 

                 Overlap - Total:    10244.85[s] =  78.60 %, From last output:    10244.85[s] =  78.60 %

                   Force - Total:      607.39[s] =   4.66 %, From last output:      607.39[s] =   4.66 %

                    Move - Total:        1.71[s] =   0.01 %, From last output:        1.71[s] =   0.01 %

                  Output - Total:     1791.89[s] =  13.75 %, From last output:     1791.89[s] =  13.75 %

 

Module Execution Times:

    CFD Coupling

             - Averaging - Cumulative:   207.44257[s] n_calls:     2, From last output:   207.44257[s] n_calls:     2

             - Send Data - Cumulative:   375.11285[s] n_calls:     2, From last output:   375.11285[s] n_calls:     2

          - Receive Data - Cumulative:  1767.81645[s] n_calls:     1, From last output:  1767.81645[s] n_calls:     1

         - Update Domain - Cumulative:   818.95781[s] n_calls:    12, From last output:   818.95781[s] n_calls:    12

            - Find Cells - Cumulative:     0.01242[s] n_calls:    13, From last output:     0.01242[s] n_calls:    13

       - Volume Fraction - Cumulative:    54.72847[s] n_calls:    11, From last output:    54.72847[s] n_calls:    11

        - Exchange Terms - Cumulative:     0.00294[s] n_calls:   809, From last output:     0.00294[s] n_calls:   809

 

Total Module Execution Times: 13365[s], From last output: 13365[s]

            CFD Coupling - Total:    13364.98[s] = 102.53 %, From last output:    13364.98[s] = 102.53 %

              - Averaging - Total:      414.89[s] =   3.10 %, From last output:      414.89[s] =   3.10 %

              - Send Data - Total:      750.23[s] =   5.61 %, From last output:      750.23[s] =   5.61 %

           - Receive Data - Total:     1767.82[s] =  13.23 %, From last output:     1767.82[s] =  13.23 %

          - Update Domain - Total:     9827.49[s] =  73.53 %, From last output:     9827.49[s] =  73.53 %

             - Find Cells - Total:        0.16[s] =   0.00 %, From last output:        0.16[s] =   0.00 %

        - Volume Fraction - Total:      602.01[s] =   4.50 %, From last output:      602.01[s] =   4.50 %

         - Exchange Terms - Total:        2.38[s] =   0.02 %, From last output:        2.38[s] =   0.02 %

 

Total Execution Times (All listed above):     12647.58[s] =  97.03 %

Total Execution Times (Unlisted):               387.39[s] =   2.97 %

 

8 particle(s) reentered the cfd domain

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Volumetric diffusion averaging may be taking too long.

501 iterations were required.

DEM-CFD critical explicit time step:

    78.2% of the particles exceeded 50% the CFD critical explicit time step.

    78.1% of the particles exceeded 75% the CFD critical explicit time step.

    78% of the particles exceeded 100% the CFD critical explicit time step.

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

Particles sorting distance changed from: 0.00844657  to: 0.00879211 current simulation time is: 0.00100494

Averaging warning: target volume fraction of 0.65 not reached after 500 iterations limit

[Rob]

If you run without Rocky what does the viscosity contour look like? How are you adding particles in Rocky? Ie what separation is there between them on the release?

[jarmouni]

Hi Rob,

 

Thank you for your reply.

 

I add the particles in Rocky normally, i.e. I define a “Volummetric Inlet” via the “Inets and Outlets” menu, then I enter the mass of the particles I want to have in the tank. This gives me the number of particles in my tank via “Info” in this menu.

 

This is what the viscosity contour looks like.

[Rob]

Do you think a viscosity of 2.95e7 kg/m/s is sensible?

[jarmouni]

In my simulation, I am dealing with a magnetorheological fluid whose viscosity is strongly influenced by an external magnetic field. I had concerns about the viscosity values as they appeared to be very high. For this reason, I performed analytical calculations that support the viscosity results from ANSYS.

[Rob]

And is that fluid moving? As the viscosity becomes (very) high particles will move with the fluid, and if injected may not clear the inlet region before the next one arrives. 

[jarmouni]

Unfortunately I don't know, because after the first time step of the simulation I didn't receive any further updates. In this time step you can see that the particles are moving.In addition, the inlet is defined as a volume as can be seen in the picture.

Thank you for your support.

 

[Rob]

Can you try limiting the viscosity to around 0.01 Pa.s and see how it behaves. Once the model is working you can ramp it up.