Q366 : Resolving Time Delays in HIFREQ-FFTSES

Question
When I look at time-domain results for the scalar potential on a conductor energized some distance away, I do not see the expected time-delay before the potential starts to rise. What could be the problem?

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Answer
This is probably due to an insufficient number of computation frequencies being used in the run.

In a software that uses a time-domain synthesis of frequency results through a Fourier transform (as does the HIFREQ-FFTSES software) the intervals where the results are expected to be zero are quite difficult to get right: the contributions from a large number of individual frequency results must add up to zero. These intervals often require a larger number of frequencies than FFTSES recommends in order to get a very small response (you will never get precisely zero, but it will get closer to zero as the number of computation frequencies increase).

The solution is therefore to run more computation frequencies, evenly distributed across the entire spectrum. This should improve the situation.

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