esys-escript

Using PDEs for Coupled problem

Asked by ArashM

Hi,
I have two sets of equations:
1- K(du)+L(dp)=R using PDEs in Escript K=Aijkl and L=Xij
2- LT(du)-Hp=G

The second eqaution is abit tricky.I changed the second like this (p is replaced with a term from previous time step):

LT(du)-H(p_old+dpdt)=G

Thus:

LT(du)-Hdpdt=G+Hp_old or Hdp=-LT(du)/dt+Hp_old/dt+G/dt

Now I define this equation in Escript like this:

H=Aijkl ,Y==-LT(du)/dt+Hp_old/dt

Is this correct?tnx.

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Lutz Gross
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Best Lutz Gross (l-gross) said : 		#1

Looks good! You may want to solve for Dp=dt*dp then the dt business becomes easier.
You will probably set

X=A_ijkl * grad(p_old/dt) Y=LT(du)/dt

assuming that LT=div.

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ArashM (arash-mohajeri) said : 		#2

Can I ask how you actually obtained 'X' as 'A_ijkl * grad(p_old/dt) '?why grad(p_old/dt)?Do you mean that in Escript,I should write:

H=Aijkl
Y=div(du)/dt
X=A_ijkl * grad(p_old/dt)=H*grad(p_old/dt)

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ArashM (arash-mohajeri) said : 		#3

Thanks Lutz Gross, that solved my question.