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• # Problem in Multiphase

Posted by on September 7, 2023 at 7:19 pm

Good evening,

Hope you are doing well. I have got an issue with a problem for multiphase tutorial. I am not able to solve the problem as the error depicting on the console bar is floating point exceeds. However, I was able to determine the coefficient of discharge for the delta p .5 and 1 bar. Delta p above 1 bar depicting same issues for all case even using optimise relaxation and advanced stabilisation.

The input for our problem is mentioned below,

Solution

Pressure at Inlet: 3.5 Bar

Operating temperature: 288.16 K

Turbulent viscosity ratio: 5

Algorithm used: Coupled

Pressure: PRESTO

Momentum: Second order up wind

Volume Fraction: Compressive

Modified Turbulent Viscosity: Second order up wind

Turbulence models: Spalart â€“ Allmaras

Fluid density: 998.2 kg/m^3

Outlet: Varying

Pseudo transient: On/Off, as elementary while using pseudo transient high fluctuations are seen for problematic cases.

Multiphase

Homogenous Model: Volume of fluid

Formulation: Implicit

Interfacing modelling: Sharp

Volume fraction cutoff: 1e-5

Remarks, the case taken here in 2D as to formulate a structural mesh. Mesh data is given below.

Orthogonal quality: 0.99991 (Avg.)

Skewness: 5.9019e-003 (Avg.)

No. of elements: 112512

Please go through the attached images for mesh reference. Hope you will understand.

Thanking you,

With regards,

Pratham Chauhan.

replied 7 months, 1 week ago 2 Members · 5 Replies
• 5 Replies
• ### Pratham

Member
September 7, 2023 at 7:23 pm

More reference at delta 1.5 bar

• ### Pratham

Member
September 7, 2023 at 7:24 pm

Fluctuations countered, at 1.5 bar

• ### Sandeep

September 7, 2023 at 8:34 pm

Please use k-omega SST model and Pseudo transient approach with a time scale factor of 0.1. That should help to stabilize it

• ### Pratham

Member
September 8, 2023 at 3:27 pm

Good evening,

Professor,

Thank you for your earlier response. I will definitely do that. But I have a doubt regarding Â (Coefficient of discharge). For example, for delta p at .5 bar my mass flow rate at outlet is around 80.943439 kg/s. Whereas ideal mass flow rate is 1000 kg/s approximately.

If I apply the given values to the formula. My Â is coming around 0.08, which is wrong in my opinion. Remarks area of outlet is 0.1 m^2.

Hope you will understand.

Thanking you,

With regards,

Pratham Chauhan.