Computation of sound absorption coefficient with and without creating a boundary layer mesh

The sound absorption coefficient is a measure of the ability of a material to absorb sound waves. It is typically determined experimentally, but it can also be calculated using numerical methods such as the finite element method (FEM). When using FEM to calculate the sound absorption coefficient, the accuracy of the results can depend on whether or not a boundary layer mesh is created. Here's a general overview of how the sound absorption coefficient can be computed with and without creating a boundary layer mesh:

Without creating a boundary layer mesh:

1. Define the geometry of the material and the surrounding air space in a finite element analysis software.

2. Assign material properties to the geometry, including the sound absorption coefficient of the material.

3. Define the acoustic boundary conditions, such as the sound pressure at the boundaries of the simulation domain.

4. Solve the finite element equations to obtain the sound pressure distribution in the simulation domain.

5. Calculate the sound absorption coefficient from the sound pressure distribution using the following formula:

alpha = 1 - (P_r / P_i)^2

where alpha is the sound absorption coefficient, P_r is the reflected sound pressure, and P_i is the incident sound pressure.

Creating a boundary layer mesh:

1. Create a boundary layer mesh around the surface of the material. The boundary layer mesh should have a thickness of at least one-tenth of the wavelength of the sound waves being studied.

2. Define the geometry, material properties, and acoustic boundary conditions as in the non-boundary layer mesh case.

3. Solve the finite element equations to obtain the sound pressure distribution in the simulation domain.

4. Calculate the sound absorption coefficient as in the non-boundary layer mesh case.

The main advantage of using a boundary layer mesh is that it can improve the accuracy of the results, especially for high-frequency sound waves. The boundary layer mesh can capture the boundary layer effects near the surface of the material, which can significantly affect the sound absorption coefficient. However, creating a boundary layer mesh can also increase the computational cost and complexity of the simulation.

It's important to note that the specific details of the computational method used for sound absorption coefficient calculations can vary depending on the software and numerical method used. Also, the accuracy of the results will depend on the quality of the input data and the assumptions made in the simulation.

Hope it helps!!

Credit: Mainly to AI tools

Mohammad Imam Thanks for your detailed answer. Actually, i am getting lower magnitude peak as compared to experiments results. Hence i must include BLM in my analysis to capture absorption coefficient correctly.