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How do I edit equation in COMSOL Multiphysics?

Posted Apr 16, 2019, 9:35 p.m. EDT Acoustics & Vibrations, Parameters, Variables, & Functions, Equation-Based Modeling Version 5.3a 6 Replies

Koushik Paul
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I am using COMSOL Multiphysics 4.3a. I want to simplify the Helmholtz equation in "Pressure acoustics". How can I make some variable (Monopole and Dipole source item etc) value zero to simplify it? I am attaching a picture here of the equation which I want to simplify. Thanks in advance.

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6 Replies Last Post Sep 3, 2019, 7:39 a.m. EDT
Magnus Ringh COMSOL Employee

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Posted: 6 years ago Apr 17, 2019, 3:53 a.m. EDT

Hi,

The monopole and dipole sources are part of the equation because they are available and can be included if desired (by adding a Monopole Domain Source node or a Dipole Doman Source Node). By default, those terms are zero.

Best regards,

Magnus Ringh, COMSOL

Hi, The monopole and dipole sources are part of the equation because they are available and can be included if desired (by adding a Monopole Domain Source node or a Dipole Doman Source Node). By default, those terms are zero. Best regards, Magnus Ringh, COMSOL
Koushik Paul
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Posted: 6 years ago Apr 17, 2019, 12:40 p.m. EDT

Hi,

Thank you for the explaination. So when I am seeing an equation in "Equation" option of a particular "Physics", how would I know that which variable values are by default zero and which variables are activeely taking part in my simulation? Thank you.

Regards, Koushik paul

Hi, Thank you for the explaination. So when I am seeing an equation in "Equation" option of a particular "Physics", how would I know that which variable values are by default zero and which variables are activeely taking part in my simulation? Thank you. Regards, Koushik paul
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Apr 17, 2019, 1:32 p.m. EDT

Hi,

The equations shown in the Equation section are in general conceptual, rather than an accurate mathematical statement.

But with that said, here is a rule: The contribution from a certain node in the Model Builder tree is underlined in its equation.

So if you look at a Pressure Acoustics node, you will find the left hand side of the equation underlined. If you add various sources like Monopole Point Source, Dipole Point Source etc., you will see various right hand sides underlined.

To see the exact mathematical formulation you can either turn to a theory section in the documentation or, even more detailed, switch on Equation View and examine the exact variables and weak expression used to form the numerical model.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, The equations shown in the **Equation** section are in general conceptual, rather than an accurate mathematical statement. But with that said, here is a rule: The contribution from a certain node in the Model Builder tree is underlined in its equation. So if you look at a **Pressure Acoustics** node, you will find the left hand side of the equation underlined. If you add various sources like **Monopole Point Source**, **Dipole Point Source** etc., you will see various right hand sides underlined. To see the exact mathematical formulation you can either turn to a theory section in the documentation or, even more detailed, switch on **Equation View** and examine the exact variables and weak expression used to form the numerical model. Regards, Henrik
Koushik Paul
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Posted: 6 years ago Apr 17, 2019, 3:25 p.m. EDT

Hi,

So I have started my simulation by coupling Acoustics and Solid mechanics physics in COMSOL Multiphysics 5.3a. But when I tried to run the simulation error is showing up. I have attached a scrrenshot of that particular error. Can you please exlain why this error is showing up? Thank you.

Regards, Koushik Paul

Hi, So I have started my simulation by coupling **Acoustics** and **Solid mechanics** physics in COMSOL Multiphysics 5.3a. But when I tried to run the simulation error is showing up. I have attached a scrrenshot of that particular error. Can you please exlain why this error is showing up? Thank you. Regards, Koushik Paul

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Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Apr 18, 2019, 8:34 a.m. EDT
Updated: 6 years ago Apr 18, 2019, 9:25 a.m. EDT

Hi,

This is a licensing error. To see available licenses, look under File->Licensed and Used Products or Options->Licensed and Used Products depending on which version you are using.

This type of error can for example occur if all applicable licences are occupied, or if you have received a model created on an installation wich has another set of licensed modules than your site.

You probably need to check with your system administrator or support.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, This is a licensing error. To see available licenses, look under **File->Licensed and Used Products** or **Options->Licensed and Used Products** depending on which version you are using. This type of error can for example occur if all applicable licences are occupied, or if you have received a model created on an installation wich has another set of licensed modules than your site. You probably need to check with your system administrator or support. Regards, Henrik
Shweta Raturi
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Posted: 5 years ago Sep 3, 2019, 7:39 a.m. EDT

Hi,

I want to use non-dimensional equations. How to proceed? and the equations are coupled.

Hi, I want to use non-dimensional equations. How to proceed? and the equations are coupled.

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