Plane Wave Outside of Model Extents

pmcardle

  It is my understanding that results/planewaves exist outside of the model extents and that only the model needs to adhere to the model extents. This is from correspondence I had with an applications engineer at Altair. My question is then how far outside of the model extents does the plane wave extend? 

 

Cheers,

Patrick

Johan_Huysamen

Hi Patrick

 

Theoretically a plane wave comes from infinity and is incident onto the geometry. The plane wave is applied as an excitation onto the geometry (mesh) in Feko. As such, it is applied to, and interacts with, the mesh where-ever there is a mesh element in the model. Similarly, when a (near) field result is requested, the plane wave will be considered in the calculation of that near field point where-ever required.

 

Consider a Perfectly Electrically Conductive (PEC) sphere with radius r meshed into surface mesh triangles and solved with the default Method of Moments (MoM) in Feko. If we have an incident plane wave as excitation and we sample near fields say on a spherical surface at a radius of 2*r, the plane wave is applied as follows:

1. Mathematically the plane wave excitation is evaluated at the positions of the mesh triangles and applied to the MoM solution matrix as an excitation (known as the right-hand side vector)
2. The MoM is solved to compute the induced surface currents on the mesh triangles.
3. The near fields are calculated by considering two contributions at each required near field request point:
   • the (re)radiation of the induced surface currants and
   • the contribution of the incident plane wave

In effect then the plane wave does not have a physical extent. It is applied and evaluated by Feko where-ever it is required based on the mesh and requested results.

 

Kind regards,

Johan H