Fluids

Fluids

Explicit and Implicit formulation schemes

    • i.tamunodienye2
      Subscriber

      Hi All,

      I am modeling multiphase flow (water-liquid and ideal gas). Is it appropriate to leave spartial discretization (density, momentum, TKE, SDR, energy and transient formulation) in first order when explicit scheme is selected. Surface tension and pressure forces acting on the bends of the structure are important.

      Also,  in the same multiphase flow modelling, is it appropriate to leave spartial discretization (density, momentum, TKE, SDR, transient formulation and energy) as second order when implicit formulation scheme is selected.  Like above, surface tension and pressure forces are important.

      Your help is much appreciated.

       

      Regards

    • Rob
      Ansys Employee

      Ideally you want second order, what are the defaults? However, spatial (mesh) and temporal (time) resolution may be more critical: do NOT just rely on y+ to show the mesh is adequate. 

      Which model, and what are you actually simulating? The correct choice of multiphase model will far out weigh discretisation schemes. 

    • i.tamunodienye2
      Subscriber

      Hi Rob,

      Thanks for your response.

      I am simulating multiphase flow (ideal and water-liquid) in a pipe to analyse the forces at the bends as a result of flow induced vibration generated by the momentum of the two-phase flow. So pressure forces at the bends are important information i need. It is multiphase flow.

       

      Thanks

    • Rob
      Ansys Employee

      Which flow regime? Which multiphase model? 

    • i.tamunodienye2
      Subscriber

      Predominantly slug flow regime

      VOF multiphase model.

    • DrAmine
      Ansys Employee

      Explicit formulation has nothing to do with the spatial discreization of other transportaed variables as the latter do not use any multi-time steps when advecting the equation. So try as much as possible to use Secon Order Accuracy Schemes.

    • Rob
      Ansys Employee

      So, as Amine says, ideally second order. Also read up on turbulence damping for VOF. You're going to need a small time step, well resolved mesh and patience for this. 

    • i.tamunodienye2
      Subscriber

      Thank you Rob and Dr Amine.

    • DrAmine
      Ansys Employee

      Good Luck!

Viewing 8 reply threads
  • You must be logged in to reply to this topic.