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Species transport convergence issue


      Hello everyone 

      I am simulating a discrete phase model for a gas-liquid complex geometry with species transport (relative humidity through the geometry by adjusting the inlet and outlet boundary conditions), and droplet injection (a drug very similar to water properties in which the evaporation species will be water). When I use the simulation without species transport (only inert particle injection), the solution converges. But when I use the species transport, the continuity and drug are not converging which affects energy and water vapor residuals. However, I have refined the mesh ( near 2 million polyhedral or tetra) and adjusted the URFs, but couldn't get convergence still. the quality of the mesh has been checked and it is fine.

      The DPM update interval is every 10 iterations and after each update, it takes 2 more iterations for the increase of momentum, energy, drug and water vapor residuals. 

      I kept the density of injected drug with evaporated component (water) constant or slightly different, however, there were no changes regarding better convergence.

      I also tried using different methods (SIMPLE, SIMPLEC, PISO and Coupled) and it didn't change the convergence issue. 

      Thanks and regards

    • SRP
      Ansys Employee


      What message you got when solution diverges while simulating species transport?

      I recommend you to check previous forum discussion on species transport: Species Transport Convergence Issue (ansys.com)

      Thank you.


      Hi SRP and thank you for your response. I have already checked the previous discussion and could not solve the issue yet. The solution never diverges and fluctuates at each DPM update interval. I think the problem lies in the material section and the physical properties that I have. I am not sure if I have defined correct materials.

      I have velocity inlet ( I convert L/min to m/s based on the inlet area) and pressure outlet and have defined H2o (water vapor) based on the 50% relative humidity at both inlet and outlet species. The list of materials I used is attached. I have water in my drugsmi which evaporats so I defined water vapor at both fluid and species. I also have air in both. The drug you see in the list has water vapor physical properties and has mass fraction of 0 in the species. 

      Please let me know if you need more information.




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