Fluids

Fluids

Species fraction in a DPM spray analysis

    • inouzil
      Subscriber

      Hi,

      I want to simulate a minimum quantity lubrication process and am using the DPM model in fluent. I want to include the affect of vaporization of the oil droplet and therefore have used the species transport model. below image shows the species dialogue inputs:

      The injection input for the base oil is as shown below:

      My question is, since I have specified the mass flow rate for the oil through the DPM dialogue, what input do I give for the species mass fraction at the inlet? Should I just keep it as zero? 

      Kindly assist. 

      Nouzil

    • DrAmine
      Ansys Employee

      You should provide the mass fractions corresponding to your inflow gas. I assume you have Air coming in: then provide the air mass fraction composition. Aslo you defined 5 components but you did only show 4: what is the fifth one?

    • inouzil
      Subscriber

      Hi,

      Thank you for the support. Really appreciate the quick answer. Air was the fifth one. Since I have its component species already defined in the template, I removed air. That is the correct way to go? The outlet species fractions I kept same as the inlet. 

      Ibrahim

    • DrAmine
      Ansys Employee

      How many species do you have now? What is the abundant specie? At your inlet you are prompted to provide 4 Components Mass Fractions which is wrong if you have only 4 components.

      If you do not know what is outside then just the outlet species which might correspond to most realistic composition whenever a "theoretical" or "phyiscal" reversal flow can occur.

    • inouzil
      Subscriber

      Hi,

      Following are the species now defined: h20, N2, O2, baseoil (liquid oil). I selected nitrogen as the abundant specie (last specie). At the inlet I am prompted to enter mass fraction for all components except nitrogen. I chose nitrogen as the abundant specie since air has very high mass flow rate compared to oil. Below is an image of the inlet boundary condition:

       

      Since there are no reactions at the inlet (or no gaseous phase of oil at inlet), I keep the mass fractions as zero. Is that right? 

      And at outlet if I input mass fractions as zero, it would mean no reverse flow at the outlet? 

      Thank you for the assistance. 

      Ibrahim

    • DrAmine
      Ansys Employee

      If you are assuming that only N2 is entering at inlet then it is correct. If you are not expecting that only N2 will flow in then you need to provide the right mass/mole fraction of the composition.

       

      At the outlet if you input the same as now at your inlet this will mean that in case of reversal flow  only N2 will enter from the outlet. Default Pressure Outlet in Ansys Fluent is acting as an Opening: it allows inflow and outflow.

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