Fluids

Fluids

LES with DPM injection

    • jjlee
      Subscriber

      Hi.

      I want to perform LES combined with DPM, spray evaporation on to chamber

      Just so you know, there is no other inlet condition (inlet velocity, mass flow inlet) except DPM injection.

      (2 dimensional rectangular geometry)

      I know that LES requires precursor RANS simulation steps for inlet profile, but in my case, I don't have any inlet condition except DPM injection

      Plus, I’ve read also RANS steps should not be used for reacting flows from [ANSYS quick guide to setting up LES-type simulations].

      So, I’ve tried several LES with DPM, without precursor RANS simulation.

      But it resulted in high continuity residual.( close to 1e+02)

       

      The conditions used in my simulations are as follows

      Mesh element size: 0.01mm (near injector) with high mesh orthogonal quality

      Transient simulation with time step size 1e-6 [s]

      Method: SIMPLEC, Bounded central differencing, and Transient Formulation: Bounded Second Order Implicit

      Models

      -       Species transport

      -       DPM with single injection, 500m/s (X-velocity), ethyl-alcohol-liquid, Particle type: Droplet(Evaporating of droplet applied)

       

      I want to know whether LES with DPM is possible without RANS pre-simulations.

      (I tried several LES with DPM, turning off ‘species transport’ but still it resulted in high continuity residual.)

      I thought that mesh size and time step were small enough compared to conventional RANS simulations, but the results were frustrating.

      the geometry and residuals are as below.

      I really appreciate if you let me know what the problem is :)

       

       

       

    • Rob
      Ansys Employee

      Plot the flow field and use some monitors to see what's going on. Also, carefully read what the residual plot is, and explain why it might not be as useful as we'd like in this case. 

    • DrAmine
      Ansys Employee

      LES and 2D?

      I recommend using a precursor ran to assess mesh resolution and time step and based on that you can setup your LES or SBES run make velo field instatneoues and run.

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