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Volume Integration in COMSOL using different limit
Posted 08.01.2018, 07:48 GMT-5 Optimization, Parameters, Variables, & Functions, Results & Visualization Version 5.2 3 Replies
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Dear COMSOL Users, I am integrating a geometrical model in COMSOL using volume integration in derived value tab. It integrate whole geometry at once through total height (h) but I want to take ratio of integration of total height to integration of 1/3rd of the height. Now I don't know How I can select 1/3 limit in COMSOL. Can anyone give me an idea about integration this single geomtry in limit from 0 to h/3 and 0 to h ? It should not consist of two domains as doing so will affect my simulation result.
Thank you
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Hi,
You can define an Integration coupling operator under Component>Definitions>Component Couplings (say, intop1), valid in all domains, and then evaluate it using a Global Evaluation node.
If you want to integrate the entire volume, then use
intop1(1)
If you want to integrate to another limit (in the z direction), then use
intop1(1*(z < zlim))
where zlim is the limit in the z direction, and the geometry starts at z = 0.
With 1 as the integrand, the intop1 operator computes the volume. You can use any other quantity to integrate instead, if desired.
You can also insert an "artificial boundary" at z = zlim so that you get separate domains for the top and bottom parts of the geometry. It should not affect your simulation results (other than enforcing the mesh to respect the boundary between the domains).
Best regards, Magnus Ringh, COMSOL
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Dear Magnus Ringh, Thank you for your response. I am integrating a composite column. I did create the intop1, but in global evolution it is giving error. If you could help me here. I am using Solid Mechanics, Eigenfrequency module and want to find elestic strian energy density (solid.Ws) through total height of composite column and different height value like(H/2,H/3,H/4 etc) so that I can take the ratio of these two integrated strain energy density values which I calculated. If you could comment on this. I did have tried dividing my column in two domains but first it is very lengthy process and secondly result obtained is not accurate, it contains error due to interface b/w two domains. COMSOL may take that interface as weak zone. Which affect my results.
Thank you
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Hi,
If you have defined the integration coupling operator so that it is active in the geometry, an expression such as intop1(solid.Ws) should work to integrate the elastic strain energy using a Global Evaluation node. For a ratio of integrated values, for example, you can evaluate an expression such as
intop1(solid.Ws*(z < H/2))/intop1(solid.Ws*(z < H/3))
if that is what you are interested in. To investigate why an added interior boundary would affect your simulation, we would need access to the model file. If this does not help you, I suggest that you contact COMSOL Multiphysics Support: COMSOL Multiphysics Support Center.
Best regards, Magnus Ringh, COMSOL