US Patent 7823463 Ultrasonic flow sensor using two streamlined probes

A time-of-flight ultrasonic flow meter uses transducers placed on streamlined heads of probes that are spaced out along a pipe. The placement of the transducers and probes is selected so that an acoustic signal can propagate between the transducers on the two probes along a path that involves at least one reflection from an internal surface of the pipe.