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Thermal expansion of a fluid or gas - how to model ?
Posted Jan 24, 2014, 12:45 p.m. EST Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Structural Mechanics Version 4.4 0 Replies
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Someone asked this years ago, but no answer was registered.
see www.comsol.com/community/forums/general/thread/10927/
I attach some small COMSOL-Files and screenshots of my trials with a very simple model
Generally the "thermal expansion" is calculated by the "solid mechanics" node.
But I assume water is not really a solid mechanics material and some parameters for water lack the available parameters like thermal expansion coefficient (2.07e-2), Youngs modulus (2.09e9) and poisson number (0.5). That is in the moment I add the "solid mechanics" node, materials claim the lack.
So probably a different module is intended to calculate thermal expansion of fluids or gases.
But which one was intended to be used ??
("Fluid-solid -Interaction" sounds good from its name, but is placed in the "Fluid flow" module and it does not seem to be suiable.)
Nevertheless I tried to calculate the fluid expansion by adding the lacking parameters manually and model its expansion.
Geometry: A cylinder
Material: Water
Physics: "Heat transfer in solids" with included "heat transfer in fluids" and "boundary heat source"
Physics: "Solid mechanics"
Multiphysics: "Temperature Coupling" and "Thermal Expansion"
Study: "Time dependend"
I get an error message:
Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
There are 1678 equations giving NaN/Inf in the matrix rows for the variable comp1.u.
at coordinates: (-0.0955014,-0.029656,0), (-0.0895277,-0.044551,0), (-0.0812485,-0.0582982,0), (-0.1,0,0), (-0.098869,-0.0149976,0), ...
There are 1678 equations giving NaN/Inf in the matrix rows for the variable comp1.v.
at coordinates: (-0.0955014,-0.029656,0), (-0.0895277,-0.044551,0), (-0.0812485,-0.0582982,0), (-0.1,0,0), (-0.098869,-0.0149976,0), ...
There are 1678 equations giving NaN/Inf in the matrix rows for the variable comp1.w.
at coordinates: (-0.0955014,-0.029656,0), (-0.0895277,-0.044551,0), (-0.0812485,-0.0582982,0), (-0.1,0,0), (-0.098869,-0.0149976,0), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns.
Attachments:
Hello Hans Gennerich
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