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Cacluate power exchanged between solid/fluid and solid/solid
Posted 04.11.2012, 16:51 GMT-5 Acoustics & Vibrations, Structural Mechanics Version 4.3 1 Reply
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Dear all,
I've solved a coupled linear elasto-acoustic model using COMSOL's Acoustic-Solid Interaction module. During the post-processing I would like to calculate energy balances to better analyze the implemented system. I have 2 questions.
Firstly, so far I've managed to calculate the power exchanged between a solid and a fluid domain using the surface integration function. However, I noticed that using the local velocity components (spatial) "acsl.vx, acsl.vy, acsl.vz" of the fluid domain provides a correct result whereas using the the velocity components of the solid domain (Material) "acsl.u_tX, acsl.u_tY, acsl.u_tZ" results in a deviation. Usually these two velocities should provide the same results due to the continuity of stress vectors and displacements. How come the results are different?
Secondly, I have problems implementing the power exchanged between two solid domains. I would like to implement the "...surface_integral((sigma.n) * conj(...))". I have difficulties to chose the correct tensor of constraints from the list.
Thank you very much in advance.
Kind regards,
Martin
I've solved a coupled linear elasto-acoustic model using COMSOL's Acoustic-Solid Interaction module. During the post-processing I would like to calculate energy balances to better analyze the implemented system. I have 2 questions.
Firstly, so far I've managed to calculate the power exchanged between a solid and a fluid domain using the surface integration function. However, I noticed that using the local velocity components (spatial) "acsl.vx, acsl.vy, acsl.vz" of the fluid domain provides a correct result whereas using the the velocity components of the solid domain (Material) "acsl.u_tX, acsl.u_tY, acsl.u_tZ" results in a deviation. Usually these two velocities should provide the same results due to the continuity of stress vectors and displacements. How come the results are different?
Secondly, I have problems implementing the power exchanged between two solid domains. I would like to implement the "...surface_integral((sigma.n) * conj(...))". I have difficulties to chose the correct tensor of constraints from the list.
Thank you very much in advance.
Kind regards,
Martin
1 Reply Last Post 13.11.2012, 09:08 GMT-5
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Posted:
1 decade ago
Dear Martin
In Comsol there are already intensity variables defined that you can use for post processing or for analyzing energy balances. The intensity vector has the components (acsl.Ix, acsl.Iy, acsl.Iz). They are defined for frequency domain studies and acsl is the prefix if you use the acoustic-solid interaction interface.
In the acoustics documentation they are described under the section "Special Variables in the Acoustics Module".
If you wold rather use the displacement field to determine the intensity transmitted to the structure try and calculate it as (for the x-component): Ix=0.25*(p*conj(u*acsl.iomega)+conj(p)*u*acsl.iomega). Multiplication with iomega is a time differential in the frequency domain.
Best regards
Mads
In Comsol there are already intensity variables defined that you can use for post processing or for analyzing energy balances. The intensity vector has the components (acsl.Ix, acsl.Iy, acsl.Iz). They are defined for frequency domain studies and acsl is the prefix if you use the acoustic-solid interaction interface.
In the acoustics documentation they are described under the section "Special Variables in the Acoustics Module".
If you wold rather use the displacement field to determine the intensity transmitted to the structure try and calculate it as (for the x-component): Ix=0.25*(p*conj(u*acsl.iomega)+conj(p)*u*acsl.iomega). Multiplication with iomega is a time differential in the frequency domain.
Best regards
Mads