Flow resistivity

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Hello everyone, I have a technical question. I have a rectangular geometry and inside it I have several small spheres to simulate a false porous medium. My study is acoustic (Acoustic pressure in the frequency domain). Is there a way to account for the flow resistivity in this medium using formulas in COMSOL?


4 Replies Last Post Jun 13, 2024, 12:41 a.m. EDT
Mark Cops COMSOL Employee

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Posted: 5 months ago Jun 6, 2024, 11:20 a.m. EDT

For modeling the acoustics of porous materials, there are a few different approaches:

  • Use a Poroacoustic Material model in Pressure acoustics. This is a fluid-equivalent homogenized model, so the geometry will only be the macro scale and not include any microstructure. The material model gets assigned to the entire domain. The flow resistivity is a common input to some Poroacoustic material models. https://doc.comsol.com/6.2/docserver/#!/com.comsol.help.aco/aco_ug_pressure.05.005.html

  • Use Poroelastic Waves interfaces to model the porous material based on Biot Theory

  • Use Thermoviscous Acoustics to model the detailed viscous and thermal losses that occur in boundary layers surrounding the fluid-microstructure interface. In this case, the geometry includes the detailed microstructure. This is usually only feasible for a unit cell due to the scale.

The first approach is the easiest and most lightweight approach.

-Mark

For modeling the acoustics of porous materials, there are a few different approaches: - Use a Poroacoustic Material model in Pressure acoustics. This is a fluid-equivalent homogenized model, so the geometry will only be the macro scale and not include any microstructure. The material model gets assigned to the entire domain. The flow resistivity is a common input to some Poroacoustic material models. https://doc.comsol.com/6.2/docserver/#!/com.comsol.help.aco/aco_ug_pressure.05.005.html - Use Poroelastic Waves interfaces to model the porous material based on Biot Theory - Use Thermoviscous Acoustics to model the detailed viscous and thermal losses that occur in boundary layers surrounding the fluid-microstructure interface. In this case, the geometry includes the detailed microstructure. This is usually only feasible for a unit cell due to the scale. The first approach is the easiest and most lightweight approach. -Mark

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Posted: 5 months ago Jun 6, 2024, 8:01 p.m. EDT

Thanks Mark, my case is that I need to obtain (for scientific purposes) the acoustic parameters of the porous medium such as absorption, reflection, transmission loss, tortuosity and flow resistivity (Sigma). I studied the first three and managed to plot them in COMSOL, now the flow resistivity and tortuosity, although they are formulas, I cannot implement them analytically in COMSOL (in the variables tab!).

Thanks Mark, my case is that I need to obtain (for scientific purposes) the acoustic parameters of the porous medium such as absorption, reflection, transmission loss, tortuosity and flow resistivity (Sigma). I studied the first three and managed to plot them in COMSOL, now the flow resistivity and tortuosity, although they are formulas, I cannot implement them analytically in COMSOL (in the variables tab!).

Acculution ApS Certified Consultant

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Posted: 5 months ago Jun 7, 2024, 2:31 a.m. EDT

There should no issue in implementing a formula under variables. Which error message do you get? Also, have a look at the JCA models under Poroacoustics. You can enter user defined expressions here as desired.

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René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com
There should no issue in implementing a formula under variables. Which error message do you get? Also, have a look at the JCA models under Poroacoustics. You can enter user defined expressions here as desired.

Raja Kumar Acoustics & Vibration

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Posted: 5 months ago Jun 13, 2024, 12:41 a.m. EDT

You need to learn 1) AFR testing standard 2) CFD module will be needed to find the AFR

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iamrajakumar@iitkgp.ac.in
iamrajakr@gmail.com
You need to learn 1) AFR testing standard 2) CFD module will be needed to find the AFR

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