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Fluid interaction failing to evaluate variable and expression

Posted Jan 22, 2011, 8:36 p.m. EST MEMS & Nanotechnology, Fluid & Heat, MEMS & Piezoelectric Devices, Bioengineering, Geometry, Studies & Solvers Version 4.0 3 Replies

Juanita Trevino
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I am trying to model an obstacle in a fluid by using solid mechanics, moving mesh, and laminar flow. The obstacle is a simplified version of a trileaflet heart valve with the linear elastic material module and moving mesh module applied to it. The errors I am getting are
Failed to evaluate variable
-Variable: p
-Geometry:1
-boundary:12 18 23

Failed to evaluate expression
-expression: p
-plot surf1 (surface)

Where the boundaries 12,18, and 23 are the edges of the heart valve that touch each other. I have tried to match COMSOLs obstacle in fluid model as closely as possible.

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3 Replies Last Post Jan 30, 2011, 4:29 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 23, 2011, 3:02 a.m. EST
Hi

you have one difficulty there with your model. It is the topology, when the valve opens you change the topology of your geoemtry, new boundaries appear and the domains are linked differently. This will not work as COMSOL have to renumber the entities.

You must start with your vavle just slightly open to allow a small flow through it, then it would probably work better

--
Good luck
Ivar
Hi you have one difficulty there with your model. It is the topology, when the valve opens you change the topology of your geoemtry, new boundaries appear and the domains are linked differently. This will not work as COMSOL have to renumber the entities. You must start with your vavle just slightly open to allow a small flow through it, then it would probably work better -- Good luck Ivar
Juanita Trevino
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Posted: 1 decade ago Jan 29, 2011, 1:27 p.m. EST
Hi Ivar,
Thank you for the reply. I have attempted to set the initial conditions of the valve slightly open by applying an initial velocity of 2 m/s. Unfortunately, I am still getting the same errors. Is there a better way to have set the valve initially open?
-Juantia T
Hi Ivar, Thank you for the reply. I have attempted to set the initial conditions of the valve slightly open by applying an initial velocity of 2 m/s. Unfortunately, I am still getting the same errors. Is there a better way to have set the valve initially open? -Juantia T

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 30, 2011, 4:29 a.m. EST
Hi

yes but your model has "continuity" between the valve border, these cannot "open" because this means a topology change that no geoemtrical FEM can handle, like that, not even COMSOL.

You must "cut open" a small rim in between the three valve borders, with the fluid, then find out how to handle the different cvolumes w.r.t the ALE to avoid fully mesh collaps, a delicate but possible operation

--
Good luck
Ivar
Hi yes but your model has "continuity" between the valve border, these cannot "open" because this means a topology change that no geoemtrical FEM can handle, like that, not even COMSOL. You must "cut open" a small rim in between the three valve borders, with the fluid, then find out how to handle the different cvolumes w.r.t the ALE to avoid fully mesh collaps, a delicate but possible operation -- Good luck Ivar

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