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back flow and Recoverable error in residual,

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Hi all,
I am doing some simulation on Peristaltic pump by using comsol model from the model gallery.But when I am trying to change viscosity to very high,i am getting some error message like"
Recoverable error in residual, but solver could not recover.
Time : 0.3443258342877595
Last time step is not converged.
- Feature: Time-Dependent Solver 1 (sol1/t1)"

Also,I am getting back-flow when increasing the viscosity. why?
Can anyone help me to fix them?

In addition,I tried to change viscosity at the pressured part of the tube(when rotor is engaged and applies maximum pressure) as function of time by using the following smoothed unit step function:for water,
vis=.001+x*flc2hs(ts-0.5,0.0001)-.001*flc2hs(ts-0.5001,.9999) and then in material viscosity table call the function by vis(t/dt).
it worked for higher viscosity in pressured part of the tube where changing viscosity x.
As I am very new in comsol,can someone confirm me that the function is OK?
In this case I am getting some back flow as well.why?


Thanks in advance.

0 Replies Last Post 2014年11月6日 GMT-5 11:34
COMSOL Moderator

Hello Md Fayaz Ahamed

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