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I have a quick question: if i decide to model two reactants (for example kerosene+oxygene) and they have their own NS equations separately (own velocity, density, temperature). For this case, should the reactions source be included on the continuity equation?

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  • $\begingroup$ There is not a separate NS equation for each species. The combination of the various species satisfies one overall NS equation. Movement of species relative to the mass average velocity is described by the diffusion equation. $\endgroup$ – Chet Miller Feb 16 '18 at 4:30
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For each reactant, you will have to include terms (in the continuity equations) that describe the non-conservation of each reactant. Further, you will probably need additional NS equation(s) for the reaction product(s).

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  • $\begingroup$ Thank @freecharly for the clarifications. Also, do I need to take into account the diffusion/convections terms when using single-equations set for each Fluid (Reactants/Products)? $\endgroup$ – Abdoulaye ndiongue Feb 15 '18 at 22:20
  • $\begingroup$ @Abdoulayendiongue - Why do you think that such terms can be neglected? I don't know about what version of the NS equations you are talking, you would have to show the equations. When you have equations for different reactants and reaction products, you will definitely have to include in each of them source and sink terms in the conservation of mass , momentum and energy. $\endgroup$ – freecharly Feb 15 '18 at 22:54
  • $\begingroup$ Sorry for the confusions.So, my concern is about to model reacting flows which will have their own momentum (velocity) and energy equations (Temperature) like when you model Multi-Phase flows. For this case, I read some books where the continuity equations are expressed in terms of density change (Time), Convection and Source Terms (Production/Destruction of species concentration during the chemical reactions). However, the diffusion term does not exist (Unlikely when using the Species Transport Equations) and my question was if it is right not to have this diffusity features. $\endgroup$ – Abdoulaye ndiongue Feb 16 '18 at 3:23
  • $\begingroup$ So, if i understand, the diffusion terms should be taken into account when you consider to have common velocity/Temperature for the whole fluid system (like Species Transport Equation)? $\endgroup$ – Abdoulaye ndiongue Feb 16 '18 at 3:37
  • $\begingroup$ @I would suspect that you have to include these terms. But I cannot be sure because I have not seen your equations and I do no know the exact conditions of the problem you want to solve. $\endgroup$ – freecharly Feb 16 '18 at 3:50

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