One can model P-wave versus S-wave dominant transducers within an elastic medium by orienting the individual point sources within the transducer object to be either:
The disk in the above figure represents the transducer while the arrows pointing away from the transducer's center represent the orientations of the individual point sources that are required for achieving a P-wave or S-wave dominant transducer.
P- and S-wave separation involves isolating the respective compressional and shear components within the ultrasonic wavefield. Below is a simple example where such a wavefield separation approach is used to distinctly identify the parts of the wavefield that correspond to the P- and S-wave arrivals.
For a comprehensive overview of separating the P- and S-wave components from a wavefield, see here.
Transducer radiation patterns are a depiction of the maximum wave amplitude emitted by the transducer. These can be used to get an impression of the directivity characteristics of the individual ultrasound elements. Different ultrasound devices can often excite wave modes which are either P- or S-wave dominant. That is, they can either produce waves which are dominated by compressional (P-) or shear (S-) waves.
Being able to accurately produce digital twins of such ultrasound transducers is imperative for producing physically accurate wave simulations.
The radiation patterns are plotted with two overlays:
P-wave dominant transducers excite ultrasonic waves by injecting energy normal (perpendicular) to the surface on which the transducer is placed.
S-wave dominant transducers excite ultrasonic waves by injecting energy parallel to the surface on which the transducer is placed.