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Topic: using solution of previous time step for DAE dde23 applicable
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Moritz

Posts: 8
Registered: 5/24/13
using solution of previous time step for DAE dde23 applicable
Posted: Sep 24, 2013 10:59 AM
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Dear all,

i do have a PDE which describes sedimentation. I do discretize it in space and end up with a system of ode´s. Fairly simple.

Now i use the same PDE (settling of particles) inside a syringe (no particles leave the syringe) and move the piston (pressure filtration). Therefore i do have a moving boundary at the piston. So i have to solve for the piston height too. One boundary is in fact an algebraic equation.

The system looks like
solving for the piston height:

dh/dt=(height(n+1)-height(n))/dt = someODE

i=1 (Algebraic equation for boundary)
y(i) =h(n)/h(n+1)*(something)
i=2:N
dy/dt= dh/dt*(something discretized) + h(n)/h(n+1)*(something discretized)

My question is if i can use dde23 here or not ? I do have a published method with euler timestepping and i would like to use the comfort of a variable time stepping routine. ode23 works well for the simple cases with MOL.

Sincerly

Moritz



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