Background of Multi-Dimensional Ultrasonic Doppler Velocimetry

Ultrasonic Doppler Velocity bi-Dimensional (UDV-2D) measuring technique is a method that enables the measurement of two velocity components (Vx and Vz) simultaneously along a line.

Ultrasonic Doppler Velocity tri-Dimensional (UDV-3D) measuring technique is a method that enables the measurement of three velocity components (Vx, Vy and Vz) simultaneously along a line.

To summarize
UDV-2D: Vx=f(z) and Vz=f(z)
UDV-3D: Vx=f(z), Vy=f(z) and Vz=f(z)

UDV-2D and UDV-3D have all the advantages of classical ultrasonic Doppler velocimetry, such as the capacity to realize measurements in non translucid liquids. One of the most interesting property of these techniques compared to other techniques that can measure simultaneously more than one velocity component is their real time feature. Only few tens of milliseconds are necessary to compute and display all three velocity components along a line.

Measurement principle

UDV-2D is based on a 3 transducers system, whether UDV-3D is based on a 4 transducers system. Only one transducer is used as an emitter. The two or three others are used as receivers.

For UDV-2D measurements the three transducers are arranged as displayed in the figure below. The two receivers are placed on each side of the emitter and at the same distance from it. All ultrasonic beam axis cross at the same point and are contained in the same plane. The piezo surface of these three transducers are aligned along the X-axis. This arrangement allows to measure velocities along the ultrasonic beam of the emitter in many points. The depths over which measurements are available depend on the geometry of the ultrasonic beam of the transducers, on their distance and on the receiver angle (the angle between the emitter's beam and one of the receiver's beam).

Each set of emitter-receiver gives one velocity component. These components are processed by the software of the instrument in order to give the velocity components in the Cartesian coordinates system of the figure below

UDV-2D transducers arrangement

For UDV-3D measurements, the same kind of arrangement is used, as one can see in figure 2. A central transducer is used to emit ultrasonic bursts and three lateral transducers, placed uniformly around the emitting transducer, are used to receive the echoes scattered by the liquid. The piezo surface of these four transducers are within the same XY-plane.

Each set of emitter-receiver gives one velocity component. These components are processed by the software of the instrument in order to give the velocity components in the Cartesian coordinates system of the figure below

Applying UDV-2D / 3D

UDV-2D and UDV-3D use a special external control unit which is connected to the DOP2000. The WDOP software allows to adapt the measurement parameters to the flow conditions and to the attached probe. Typical UDV-2D and UDV-3D displays of the screen of the instrument are illustrated below.

Typical UDV-2D displays

Typical UDV-3D displays