add missing volume member to dft_energy class and Scheme example for computing group velocity #753
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stevengj
reviewed
Mar 6, 2019
| @@ -1082,6 +1082,7 @@ class dft_energy { | |||
| double freq_min, dfreq; | |||
| int Nfreq; | |||
| dft_chunk *E, *H, *D, *B; | |||
| volume where; | |||
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This needed only if you add an fields::output_dft method for dft_energy.
stevengj
reviewed
Mar 6, 2019
| E = add_dft(direction_component(Ex, d), where->v, freq_min, freq_max, Nfreq, true, 1.0, E); | ||
| D = add_dft(direction_component(Dx, d), where->v, freq_min, freq_max, Nfreq, false, 1.0, D); | ||
| H = add_dft(direction_component(Hx, d), where->v, freq_min, freq_max, Nfreq, true, 1.0, H); | ||
| B = add_dft(direction_component(Bx, d), where->v, freq_min, freq_max, Nfreq, false, 1.0, B); |
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The change to pass false for two of the fields is what is fixing your dV factor. Adding the where field to dft_energy is unrelated (and is actually unused in this PR).
bencbartlett
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to bencbartlett/meep
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Sep 9, 2021
…computing group velocity (NanoComp#753) * add volume to dft_energy * add example demonstrating equivalence of computing group velocity using two methods
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Fixes a bug in the
dft_energyclass from #744 where thevolumeof thedftobject was not being stored as a class member and therefore not used to normalize the energy density values as part of the quadrature.Also adds a Scheme example demonstrating the equivalence of computing the group velocity of a waveguide mode (from the
EigenModeSourcetutorial) using two different methods: (1) as the ratio of the Poynting flux to energy density and (2) directly viaget-eigenmode-coefficientsinvolving mode decomposition. This example can be ported to Python as part of #747. The test would verify that the relative error in the two values converges monotonically to 0 as theresolutionis increased (e..g., 10, 20, and 40).