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Since you were not familiar with transient/steady state problems, I suggest you to read Patankar's book (S.V. Patankar, Numerical Heat Transfer and Fluid Flow - you can find it online). You will get information about the time step you can use, and also the different transient methods you can apply. |
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The only reason I haven't been testing the physics using the steady solver is due to the porosity being a function of time. Is there a temporary workaround for this so that I can use the steady solver until I establish a viable model? |
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variable porosity
Hi all,
I am simulation porous media that at first there are water, methane and hydrate (solid phase), as the pressure decreases the solid phase(hydrate) will dissociate to water and methane. here i have to define a effective porosity that is a function of hydrate saturation using UDF. phi(eff)=phi(abs)*(1-Saturation(hydrate)) can any one help me how to do it? |
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There are many examples in this topic, have a look, try it and return questions if you have. |
hydrate dissociation
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i am new in fluent and i have some basic questions. i have defined two phases (water and methane) in porous media, now i have to define the third phase (hydrate as a solid phase ) that is stagnant and has no motion. 1)how can i define the initial saturation of this solid phase in porous media? does it need a UDF? 2) the hydrate will dissociate as the pressure fall bellow the hydrate stability pressure (p(equilibrium). ch4.6h2o----> ch4 + 6h2o should i define it as a reaction or just a multi phase flow with defining source and sink? 3) i have to define the kinetic of hydrate dissociation for fluent using UDF, mass generation rate of gas= K*phi*S(hydrate)*(p(equilibrium)-p) phi= porosity, K=dissociation rate constant, S= saturation of hydrate, p=pressure should i define this in source term of mass equation? your answer will be helpfull for me. thank you. |
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2) You can define the reactions in your UDF and use it as source/sink term for the mass/species equation. 3) If you have the generation or sink of species, both mass and species conservation equations must be considered for this source/sink term, otherwise there will be no conservation. |
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My questions is will either of these two methods do what I'm trying to do? And if so, which one is preferred? |
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Here is the code I'm currently using: Code:
#include "udf.h"
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porous media
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i want to simulate porous media just for one phase in two way 1) Check the “Porous Zone” to enable porous zone in cell zone condition 2) using a momentum source term i have done them and the pressure contours in both was the same. but the velocity contours was different. the code is: #include "udf.h" #define por_gdl 0.4 #define i_permeability 5.68e6 // Inverse Permeability (1/m^2) #define urf 0.1 // under relaxation factor for stability of momentum source term real s1=0., s2=0.; DEFINE_SOURCE(xmom_src,c,t,dS,eqn) { real source, mu, u; mu = C_MU_L(c,t); u = C_U(c,t); source = -(mu*u*i_permeability); dS[eqn] = -(mu*i_permeability); s1 = s1*(1-urf) + source*urf; return s1; } DEFINE_SOURCE(ymom_src,c,t,dS,eqn) { real source, mu, v; mu = C_MU_L(c,t); v = C_V(c,t); source = -(mu*v*i_permeability); dS[eqn] = -(mu*i_permeability); s2 = s2*(1-urf) + source*urf; return s2; } can u tell me what is the problem? |
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