EMP Analysis of a Building
Behaviour and propagation of electromagnetic fields in indoor environments are relevant to a range of technologies including through-wall radar devices, shielding of critical equipment in hospitals and the analysis of lightning strikes or electromagnetic pulses (EMP) incident on buildings.
In this white paper we will investigate the behaviour a high power EM source typical of an EMP incident on a two storey building. Various simulation approaches are discussed such that the building structure can be analysed accurately and efficiently. Results are presented in frequency and time domain to give insight into how the pulse propagates through the structure and identifies areas in the building which may be susceptible to higher fields.
- a single FDTD simulation is sufficient for the time domain pulse analysis
- the voxel mesh is more suitable to capture the geometric details of the building especially when including the rebars
- applying GPU acceleration enables the structure to be simulated in several minutes
The E- and H-field are calculated at different planes within the building (a spatial resolution of 0.5 m is used for the near-field requests).
E-, H-Field and Poynting Vector distributions at different frequencies
The tendency is that at lower frequencies the fields are reflected, but as the frequency increases there are more creeping and propagating waves around and through the building. Above 100 MHz, higher fields are seen inside the building.
After the simulations are run, the time analysis is performed in POSTFEKO using the defined pulse. The advantage of this approach is that it is possible to change the pulse waveform definition without needing to rerun the simulation. The following two movies show the animations of the pulsed E- and H-fields respectively, illustrating how the field propagates through the building.
Probed E-, H-Fields
An efficient approach was illustrated how a building tens of wavelengths in size can be simulated, capturing frequency and time domain aspects of how a typical EMP signal will propagate through the structure.