Different Acoustic Interfaces
Depending on the basic dependent variable used to model the acoustic field, the acoustical interfaces can be divided into the following main categories.
•
Pressure acoustics — The dependent variable is the acoustic pressure p.
•
Acoustic-solid interaction — The dependent variables are the pressure p and the displacement field u in the solid. This type of problem requires the addition of the Acoustics Module.
•
Poroelastic waves — The dependent variables are the pressure p inside the saturating fluid and the total displacement u of the porous matrix. This type of problem requires the addition of the Acoustics Module.
•
Aeroacoustics — The dependent variables are the acoustic perturbations to the background mean flow fields. In the Linearized Potential Flow interface, it is the potential ϕ for the acoustic particle-velocity field v = ∇ϕ. In the Linearized Euler interface, the dependent variables are the acoustic variations in pressure p, density ρ, and velocity field u. In the linearized Navier–Stokes, they are the pressure p, velocity field u, and temperature T. In the typical situation, the background fluid is in motion with, for example, a total velocity utot = u0 + u, split into a stationary background-flow velocity u0 and the particle velocity u associated with the acoustic waves. This type of problem requires the addition of the Acoustics Module.
•
Thermoviscous acoustics — The dependent variables are the acoustic pressure p, the particle-velocity field v, and the acoustic temperature variation T. This is a detailed acoustic model solving the full set of linearized equations for a compressible flow: Navier–Stokes (momentum conservation), continuity (mass conservation), and energy conservation equations. This type of problem requires the addition of the Acoustics Module.
•
Geometrical acoustics — At high frequencies when the typical wavelength becomes comparable with the geometrical features, standard finite element methods are no longer appropriate. Instead the acoustic field can be solved using ray tracing methods or energy methods. The Ray Acoustics and Acoustic Diffusion Equation interfaces apply here. This type of problem requires the addition of the Acoustics Module.