Abstract: A device for determining a flow characteristic, in particular flow velocity, of a fluid in a conduit, comprises a conduit body (110), at least four pairs of ultrasonic transducers (116, 118; 122, 124; 128, 130; 132, 1340 defining swirl sensitive acoustic paths (128, 130; 132, 134). The ultrasonic transducers are arranged such that they define paired acoustic paths. The device also comprises means (142, 144) for measuring the transit times of transmitted ultrasonic waves and for determining a flow characteristic from the measured transit times.

Abstract: A steerable acoustic waveguide apparatus includes plural plates arranged in one or more linear arrays. Steering of an acoustic beam radiated from the waveguide apparatus may be achieved through differential delays of acoustic signals resulting from differences in timing, frequency, or mode or resulting from differences in physical attributes of the plates. In one aspect, where the apparatus is used with a target that is confined by a conduit such as a pipe, a longitudinal plane for the conduit intersects the linear array, an array plane for the linear array has a conduit orientation relative to the longitudinal plane, and the conduit orientation is substantially perpendicular or substantially parallel. The waveguide apparatus may serve as a thermal buffer and may simplify access to an acoustic path in a device such as an ultrasonic flowmeter.

Abstract: A device for determining a flow characteristic, in particular flow velocity, of a fluid in a conduit, comprises a conduit body (110), at least four pairs of ultrasonic transducers (116, 118; 122, 124; 128, 130; 132, 1340 defining swirl sensitive acoustic paths (128, 130; 132, 134). The ultrasonic transducers are arranged such that they define paired acoustic paths. The device also comprises means (142, 144) for measuring the transit times of transmitted ultrasonic waves and for determining a flow characteristic from the measured transit times.

Abstract: A device for determining a flow characteristic of a fluid in a conduit comprises a conduit body (10), a first pair of first ultrasonic transducers (16, 18) defining a first swirl sensitive acoustic path (20) and a second pair of second ultrasonic transducers (24, 26) defining a second swirl sensitive acoustic path (28), a third pair of third ultrasonic transducers (30, 32) and a fourth pair of fourth ultrasonic transducers (36, 38) the transducers (30, 32) of the third pair being positioned diametrically opposite to each other at the wall (14) of the conduit body (10) such that the third transducers (30, 32) define a third acoustic path (34) having a single reflection against the inner (12) wall of the conduit body (10) and the transducers (36, 38) of the fourth pair being positioned diametrically opposite to each other such that the fourth transducers (36, 38) define a fourth acoustic path (40), wherein the transducers (16, 18; 24, 26; 30, 32; 36, 38) are capable of acting individually as a transmitter and r