Ultrasonic flow-rate measurement device and ultrasonic flow-rate measurement method

An ultrasonic flow-rate measurement method with an ultrasonic flow-rate measurement device, the ultrasonic flow-rate measurement device including:

• a transmitter that is installed in a pipe through which a fluid to be measured flows and emits an ultrasonic pulse;
• and
• at least three receivers that are installed in the pipe to face the transmitter and on which the ultrasonic pulse is incident,
• the ultrasonic flow-rate measurement method comprising:
• a reference-sound-pressure distribution waveform holding step of holding a reference sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the at least three receivers in a state where a flow velocity of the fluid to be measured in the pipe is zero;
• a variable-sound-pressure distribution waveform acquisition step of acquiring a variable sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the at least three receivers in a state where the flow velocity of the fluid to be measured in the pipe is not zero;
• and
• a flow-rate calculation step of obtaining a shift amount, which is a difference between the reference sound pressure distribution waveform and the variable sound pressure distribution waveform, and integrating the shift amount, thereby calculating a flow rate of the fluid to be measured in the pipe.