238 R. Schultz and T. Walsh Fig. 22.8 (a) Mean SPL, averaged over frequency, for nodes on the wetted surface for simulations using target node sets of 18 to 1000. (b)Mean SPL of a subset of nodes on the wetted surface for simulations using target node sets of 18 to 1000 Fig. 22.9 (a) Mean percent difference from the truth simulation of frequency-averaged real and imaginary parts of pressure. (b) Mean percent difference from the truth simulation of node-averaged real and imaginary parts of pressure 22.6.4 Comparing MAC of the Pressure Shape on the Wetted Surface A MAC allows comparison of the shapes represented by two vectors. Here, the shape of interest is the pressure spectrum on the wetted surface. The baseline shape vector is the pressure field from the original forward run, here called the truth data. The comparison vectors are the pressure fields from the various target set runs. MACs are computed using pressure shapes based on the magnitude, the phase, real and imaginary parts to see if the results depend on the chosen representation. In each case, the pressure MAC diagonal values are plotted against frequency. It can be seen in Fig. 22.10 that there is frequency dependence to the various comparison metrics presented. Generally, at lower frequencies the agreement to the truth field is good even for low target node counts. As frequency increases, however,
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