Fluids

Fluids

Relationship between particle diameter and mesh cell size

    • nselvara
      Ansys Employee

      In a dispersed multiphase flow, once the particle fluid interaction in DPM, DDPM and Eulerian Models are defined as empirical models for sub-grid particles (e.g.: Schiller Naumann Drag Model), the particle diameter must be much smaller than cell size to account the interaction between phases accurately. If the particle diameter are larger than cell size, you must adopt the Macroscopic Particle Model, in which the interactions between phases are determined as part of the solution. In this case, particles span many fluid cells.

    • nselvara
      Ansys Employee

      What is the relationship between particle diameter and mesh cell size?

    • George
      Subscriber

      That is true. Do you have a reference for your words? I mean why cell size must be bigger than particle size and what is the cell size range for particular particle size?. I appreciate if you introduce some references for this allegation. Thanks.

    • DrAmine
      Ansys Employee

      Grid can be smaller than particles and that is the idea behind the Eulerian Framework. For Euler Granular you recommend using a grid not larger than 10 time the particle size otherwise you require filtered drag models. For DDPM the mesh should be larger to avoid granular volume fraction larger than 1.


      That is debate and pure academic. I would say we should always have enough particles: basic of continuum. A reference is the bool of Loth, 2010: Particles, drops and bubbles: Fluid Dynamics and Numerical Methods


       

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