Ultrasonic measurement method for transversal component of water flow velocity

The conventional method for the water flow speed measurement uses two-way transmission of ultrasound wave through the water. One transmission is toward downstream and the other is toward the upstream direction. The delay time difference between the two wave transmissions provides the flow velocity component along the sound propagation direction. Therefore, when the flow direction is unknown, this method will not measure the flow rate directly. A method that uses one-way ultrasound transmission and two receivers is proposed. This method measures the flow velocity component perpendicular to the sound propagation path. Therefore, this method gives the flow rate of the current directly without any prior knowledge about the flow direction. This paper shows detailed procedures of the method and a result obtained from an experiment in a river.