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Problem in assigning boundary and initial conditions

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Hello,

I am new to comsol & i want to simulate a very simple system; water in a pipe with a spherical ball kept as a disturbance.

I am using comsol multiphysics 4.0a. I opened comsol, clicked on 2D> fluid flow> single phase> laminar flow, then I chose stationary study and finished the initial settings by clicking on the checkered flag.

In geometry, i created a rectangle and a circle inside it. Under laminar flow, i clicked on wall properties to assign boundary conditions.

Here is the problem. By default, comsol has selected all lines & curves as boundary and the 'Selection:' has been disabled, so I cannot change it manually. I face same problem while assigning initial value conditions. I cannot give 'Initial Values' to my model. The problem remains same even when I switch between 'Form an assembly' to 'Form a union' under Geometry.

The problem remains same even when I try to simulate structural problems or any other physics.

I am sure this problem has a very simple answer but as a biginner I am unaware of the features and it'll take me life long to explore each feature all by myself. I appreciate anyone who would like to help me.

Thank you in advance.

1 Reply Last Post 2012年9月28日 GMT-4 16:31
COMSOL Moderator

Hello Raju Purohit

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Posted: 1 decade ago 2012年9月28日 GMT-4 16:31
Hello, I think you are talking about the predefined border conditions that any physics add when started, being true that the borders of the model can be des-selected, when you add the border condition that you require the initial border conditions will be owerwritten, I personaly think that this feature was implemented to try to protect the softwarer of ill posed problems, anyway if you eliminate the non.canonical border conditions the by-defect border conditions will return.
Hello, I think you are talking about the predefined border conditions that any physics add when started, being true that the borders of the model can be des-selected, when you add the border condition that you require the initial border conditions will be owerwritten, I personaly think that this feature was implemented to try to protect the softwarer of ill posed problems, anyway if you eliminate the non.canonical border conditions the by-defect border conditions will return.

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