k-Wave

1. qiangbo
   

   Member
   Joined: Jul '13
   Posts: 15

   I am wondering what is the definition k-wave used to calculate acoustic intensity. Some papers define acoustic intensity as I = p^2/(rho*c), which is a scalar. But the acoustic intensity from k-wave is a vector. Thanks!

   Posted 10 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi qiangbo,

   Acoustic intensity characterises the flow of acoustic energy in a particular direction in units of W/m^2. The instantaneous acoustic intensity is defined as the product of the acoustic pressure and particle velocity, i.e., I = p * u. As the particle velocity is a vector, so too is the intensity.

   As an example, consider a plane wave passing through an imaginary surface. The energy that passes through the surface will depend on its orientation relative to the plane wave. Thus, intensity must be a vector quantity.

   In the special case of a plane wave, the acoustic pressure and particle velocity in the direction of the wave are related by p = c0 * rho0 * u, where c0 and rho0 are the sound speed and mass density of the fluid. Substituting this into I = p * u gives your expression. This is the component of the intensity in the direction of the plane wave.

   In k-Wave, the intensity is calculated using the more general expression I = p * u. Note that in the current version (v1.0), there are a few issues related to calculating intensity close to the Nyquist limit of 2 grid points per wavelength (see this discussion). This has been improved for the next release.

   Hope that helps,

   Brad.

   Posted 10 years ago #

3. qiangbo
   

   Member
   Joined: Jul '13
   Posts: 15

   Thanks. It is a great explanation!

   Posted 10 years ago #

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