Hi Dr. Treeby and Dr. Cox,
I understand that in kWave, the wave equations are discretised in time by Δt and in space through wavenumbers by Δξ; spatial gradient calculations are calculated (“sampled”) at every Δt time interval and Δξ spatial interval.
It is straightforward to see that, with such discretisation, the supported frequency is limited to f_max = c_min/2Δξ.
My question is, is there a lower limit of the frequency that is supported by a particular grid? In other words, let's say, the smallest non-zero wavenumber supported by the grid is Δk_ξ = 2π/(Δξ×N_ξ); would this defines the lower limit of the computational grid to f_min = c_max/(Δξ×N_ξ), considering that f = (c×k_ξ)/2π?
I am asking this question because I am using pstdElastic2D code to simulate wave propagation problems in stratified media and start to observe some strange behaviours when the excitation frequency decreases under a certain limit.
Regards,
Dat