Finally, two special borehole sources are modeled analytically and numerically. For the Downhole Orbital Vibrator, actual rotation of a radial force is incorporated into a mathematical expression for the source. By using this source and the Green's functions, the three displacement components in isotropic and TI media are provided. Their numerical evaluation shows that the source may be useful in detecting shear wave anisotropy. For a drill-bit source, the BEM technique of Chapter 4 is extended to model its radiation pattern.
Results suggest that the borehole has little effect on drill-bit radiation.