Learning Forum

[wolterj]

Hey,

following Problem:
I try to simulate flow throught a nozzel.

 

Physics:

Transient, Pressurebased

VOF-simulations 2 phases(Water-liquid/Air) Implicit body force, level set, interfacial anti-diffusion. Viscous model is SAS.

With Sufcae Tension and Wall adhesion

Boundryconditons is a profil from Simulations of the inlet-pipe(50mm long with a diameter of 3mm)

Solving:

   PISO

      SC: 2

      NC: 1

      N/C coupling

Gradient  

   Least Cell....

Pressure:

   PRESTO!

Momentum:

   Bounded central Differencing

Volume-Fraction:

   Geo-Reconstruct

Turbulence Kinetic energy:

   Second Order

Rest: first order

Controls:

   Pressure: 0.8 

   Desity: 1

   Body Forces: 1

   Momentum: 0.7

   Turbulence Kinetic Energy: 0.8

   Specific Dissipation rate: 0.8

   Turbulent Viscousity 1

   Level set Funktion 0.3

 

This setup were copied from an earlier project. in which somebody simulatet sth similar (simpler geometry of the nozzel)

Initialization Hybrid:

1 1.000000e+00

2 1.483658e-03

3 2.464239e-04

4 7.808120e-05

5 1.954829e-05

6 2.758029e-05

7 7.300978e-06

8 1.637179e-05

9 3.304232e-06

10 5.462358e-06

11 1.297115e-06

12 2.780550e-06

13 5.708590e-07

14 1.221940e-06

15 2.387166e-07

 

Time step size:  5e-5s

 im using ANSYS 19.1

If any more data is needed dont mind to ask.

Thanks for ur help

 

 

 

[wolterj]

Mesh:

   Check:

    Domain Extents:

x-coordinate: min (m) = -2.298173e-02, max (m) = 7.017803e-03

y-coordinate: min (m) = -2.199953e-02, max (m) = 8.000000e-03

z-coordinate: min (m) = -1.910000e-01, max (m) = -1.510000e-01

Volume statistics:

minimum volume (m3): 6.296011e-14

maximum volume (m3): 8.751962e-11

total volume (m3): 2.268875e-05

Face area statistics:

minimum face area (m2): 1.152058e-09

maximum face area (m2): 4.271876e-07

 

 

[wolterj]

Mesh:

Quality:

   Minimum Orthogonal Quality = 7.22601e-02 cell 351028 on zone 2 (ID: 2859648 on partition: 7) at location (-5.55571e-03 -7.51119e-03 -1.56400e-01)

(To improve Orthogonal quality , use "Inverse Orthogonal Quality" in Fluent Meshing,

where Inverse Orthogonal Quality = 1 - Orthogonal Quality)

 

Maximum Aspect Ratio = 4.45425e+01 cell 354648 on zone 2 (ID: 2850200 on partition: 0) at location (-9.28973e-03 -8.64463e-03 -1.56400e-01)

[DrAmine]

Check if poor quality is related to some few cells but even some few cells with poor metrics might cause issues. Under solver expert (TUI) enable saving residuals and post-process them to see where they accumulate.

[wolterj]

got a better quality but still problems but not as bad as before. Its still converging to slow

 

Minimum Orthogonal Quality = 2.07948e-01 cell 167471 on zone 2 (ID: 5768309 on partition: 14) at location (-9.47030e-03 -7.19996e-03 -1.59992e-01)

(To improve Orthogonal quality , use "Inverse Orthogonal Quality" in Fluent Meshing,

where Inverse Orthogonal Quality = 1 - Orthogonal Quality)

 

Maximum Aspect Ratio = 1.60527e+01 cell 26041 on zone 2 (ID: 5959628 on partition: 14) at location (-6.47500e-03 -8.72246e-03 -1.59122e-01)

 

[DrAmine]

What kind of mesh do you have. CLSVOF and surface tension better with structured uniform grid.