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contribution of convective source in total source? 

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July 27, 2008, 20:31 
contribution of convective source in total source?

#1 
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Hi all, I just read a Phoenics document concerning source. I can't grasp the understanding of convective source of a conserved variable (PHI) as a result of setting COVAL(Patch_Name,PHI,C,Vphi) : S_phi = T*C*(V_phi  Phi_p) + max(0,Sp)*(V_phi  Phi_p) where Sp is mass source imposed to the same patch.
Suppose I already set a positive mass source Sp in a patch X. Now I want to set the total source of a conserved variable (Phi) in the patch X as S_phi = 20*(10  Phi_p). I thought this was simply done by setting COVAL(X,Phi,20,10). But having read a Phoenics document about convective source, I am confused. Given the mass source Sp, does it mean I need to set COVAL (X,Phi,20Sp/T,10) so that in total I will have : S_phi = T*(20 Sp/T)*(10  phi_p) + Sp*(10  phi_p) = T*20*(10  phi_P) ? My understanding prior to this was that, after defining a mass source S, we also need to set the value (let's name it VS_Phi) of Phi transported by the source S, thus giving the total source : S_phi = T*20(10  phi_p) + S*VS_Phi Now I don't understand the importance of setting this VS_phi if the total source is defined by T*C*(V_phi  Phi_p) + max(0,Sp)(V_phi  Phi_p) I also tried to work out this source with the Phoenics Mathematical Basis, but still cannot catch how this convective source T*C*(V_phi  Phi_p) + max(0,Sp)*(V_phi  Phi_p) come about in the equation. Can somebody release my deep confusion ? Regards, Antony 

July 29, 2008, 08:01 
Re: contribution of convective source in total sou

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The source of Phi associated with a mass source patch is given by:
S_phi = [ C_phi*T + max(0,Sp)]*(V_phi  Phi_p) where Sp = C_p*T*(V_p  P_p) and T is a geometric multiplier, such as area. As an example, the PATCH settings would be: PATCH(X,WEST,1,1,1,NY,1,NZ,1,LSTEP) COVAL(X,P1,FIXFLU,mf_in) COVAL(X,U1,ONLYMS,u1_in) COVAL(X,C1,ONLYMS,c1_in) so that T=Aw (west area), C_phi=ONLYMS=0.0, and Sp = mf_in*Aw with mf_in>0.0 Thus,with V_c1=c1_in and V_u1=u1_in, we have S_C1 = mf_in*Aw*(c1_in  c1_p) and S_u1 = mf_in*Aw*(u1_in  u1_p) The coeffcient C_phi would be greater than zero if one wished to account for the diffusive inflow of material. 

July 29, 2008, 23:26 
Re: contribution of convective source in total sou

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Thank's a lot, Mike. A nice example. Your first sentence makes me doubt my understanding.
With the source defined by : S_phi = [ C_phi*T + max(0,Sp)]*(V_phi  Phi_p) Which one is true in the following ? 1. S_phi is the total source of Phi in a cell designated by the patch 2. S_phi is a source of Phi associated with a mass source patch only (not the total source of Phi) ? If I have the following setting (with mf_in > 0) : PATCH(X,WEST,1,1,1,NY,1,NZ,1,LSTEP) COVAL(X,P1,FIXFLU,mf_in) COVAL(X,C1,ONLYMS,c1_in) PATCH(Y,CELL,1,1,1,NY,1,NZ,1,LSTEP) COVAL(Y,C1,Cov,c2_in) which one is true in the following ? 1. S_C1 = mf_in*Aw*(c1_in  c1_p) + [Cov + mf_in*Aw]*(c2_in  c1_p) 2. S_C1 = mf_in*Aw*(c1_in  c1_p) + Cov*(c2_in  c1_p) Regards, Antony 

July 29, 2008, 23:35 
Re: contribution of convective source in total sou

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Sorry, this is the correct post. I forgot to preview the previous message.
 Thank's a lot, Mike. A nice example. Your first sentence makes me doubt my understanding. With the source defined by : S_phi = [ C_phi*T + max(0,Sp)]*(V_phi  Phi_p) Which one is true in the following ? 1. S_phi is the total source of Phi in a cell designated by the patch 2. S_phi is a source of Phi associated with a mass source patch only (not the total source of Phi) ? Likewise, if I have the following setting (with mf_in > 0) : PATCH(X,WEST,1,1,1,NY,1,NZ,1,LSTEP) COVAL(X,P1,FIXFLU,mf_in) COVAL(X,C1,ONLYMS,c1_in) PATCH(Y,CELL,1,1,1,NY,1,NZ,1,LSTEP) COVAL(Y,C1,Cov,c2_in) which one is true in the following ? 1. S_C1 = mf_in*Aw*(c1_in  c1_p) + [Cov + mf_in*Aw]*(c2_in  c1_p) 2. S_C1 = mf_in*Aw*(c1_in  c1_p) + Cov*(c2_in  c1_p) Regards, Antony 

July 30, 2008, 05:15 
Re: contribution of convective source in total sou

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S_phi is a source of Phi associated with a mass source patch only.
If you have the following settings (with mf_in > 0) : PATCH(X,WEST,1,1,1,NY,1,NZ,1,LSTEP) COVAL(X,P1,FIXFLU,mf_in);COVAL(X,C1,ONLYMS,c1_in) and PATCH(Y,CELL,1,1,1,NY,1,NZ,1,LSTEP) COVAL(Y,C1,Cov,c2_in) Then PATCH X creates a "massflow" source for C1 givcen by: S_C1_X = mf_in*Aw*(c1_in  c1_p) and PATCH Y creates a C1 source given by: S_C1_Y = Cov*(c2_in  c1_p) Consequently, the total source of C1 is given by (2) at the bottom of your posting, ie: S_C1_TOT = S_C1_X + S_C1_Y = mf_in*Aw*(c1_in  c1_p) + Cov*(c2_in  c1_p) S_phi defines total source for phi 

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