Multiphase simulation of droplets in gas medium using Eulerian-Eulerian approach

- February 12, 2024 at 5:09 pm
  
  ENeo178
  Subscriber
  
  Hi, hope you is doing well and able to assist resolve this issue.
  A multiphase simulation of water droplets with higher density is added to a two-phase system of continuous stream of gas with lower density (no injection) in a 2D horizontal pipe, dimensions height 0.2m and length 15m, with defined inlet and outlet and adiabatic walls. The boundary conditions were 4m/s inlet velocity, 0.9 volume fraction (vf) gas and 0.1 water vf, all introduced at the inlet, with no slip walls. The simulation was initialised using the phase-scheme pressure coupling, having set the momentum, k-epsilon and vf to second-order, second-order and first-order (upwind) respectively. However, during simulation run, the continuity residual never converges but always give rise to a residual value of e-2 at the end of the iterations value. My query is which technique or approach is recommended in order for the continuity residual to converge ?, mind you I have a well refined mesh occupying an orthogonality value above 0.1 and skewness less than 0.9. Kindly assist me with this case of mine.
  Thanks,
  Edward
- February 13, 2024 at 8:51 am
  
  SRP
  Ansys Employee
  
  Hi,
  You mentioned that you have a well-refined mesh with orthogonality above 0.1 and skewness less than 0.9, which is a good start. However, you may want to further refine the mesh in critical areas, such as near walls or areas with high velocity gradients, to ensure that the flow physics are accurately captured.
  The way you initialize your simulation can have a significant impact on convergence. Try different initialization schemes.
  Ensure that your time step size is appropriate for the physics of the problem. A too-large time step can lead to numerical instability and difficulty in convergence.
  Hope this helps.
- February 13, 2024 at 9:05 pm
  
  ENeo178
  Subscriber
  
  Hi,
  Many thanks for your assistance. I was able to resolve the convergence instabilities through further mesh refinement and boundary condition update. Also, I want to confirm what you meant where you mentioned ''time step size'', do you regard the transient solver ?, just curious becasue the system is set to steady-state.
  Thanks again,
  Edward
- February 15, 2024 at 4:34 am
  
  SRP
  Ansys Employee
  
  Hi,
  It was just a one of possibility I mentioned. Its good that you get a converge solution on refinement.
  Thank you