Ultrasonic Transducers

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:

• Orthogonal to the face of the transducer (parallel with the normal vector)
• In-line with the face (perpendicular to the normal vector)

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

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.

Radiation Patterns

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:

• Black dotted-dashed hemisphere: This represents the effective measurement surface over which the measurements would be taken.
• Red Radiation Pattern: Extract the magnitudes of the radiation pattern along the blue hemisphere and then deform (scale) the black hemisphere to get the red curve.

P-Wave Dominant

P-wave dominant transducers excite ultrasonic waves by injecting energy normal (perpendicular) to the surface on which the transducer is placed.

Figure: (left) Compressional (P-wave) component of the transducer. (right) Shear (S-wave) component of the transducer.

S-Wave Dominant

S-wave dominant transducers excite ultrasonic waves by injecting energy parallel to the surface on which the transducer is placed.

Figure: (left) Compressional (P-wave) component of the transducer. (right) Shear (S-wave) component of the transducer.