EMAS Simulations in FC-43 for Uniform Shading

Model Source Waveform

Propagation curves. Upper trace is peak-positive pressure. Lower trace is the peak-negative pressure. The geometrical focus is at 47 mm. The large peak in p+ around 37 mm appears to be due to the spike from the back of the waveform. Here are the propagation curves from a higher resolution for comparison.

Axial Waveforms. The axial waveforms show far more nonlinear distortion and lengthening than the water waveforms, as one would expect. The large spike in the tail of the waveform at z=40 mm corresponds with the observed peak in the propagation curve for p+. Here are the axial waveforms from a higher resolution.

Idealised Source Waveform

Propagation curves. The curves show similar qualitative behaviour to the results using the model source waveform - infact the peakin p+ occurs even closer tothe source. This indicates that there is not something peculiar happening with the truncation of the model source waveform. The oscillations in p+ are Gibbs type phenomenon and can be suppressed by adding more points and waiting longer for the code to run.

Axial Waveforms. The spike in the waveform in this case occurs even earlier and is even more pronounced than in the case of the more realistic model waveform. This corroborates the fact that the it is not a peculiarity in the source waveform that is repsonsible for the spike. The presence of the spike is due to the stronger nonlinearity and diffraction present in the FC-43 scenario.

KZK Texas Time Domain page

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