# Acoustic Flowmeter

This type of flowmeter (ultrasonic) can give a continuous measurement of the flow rates of both open channel or pipe. It is nonintrusive, nonmechanical and can give a reading in either flow direction.

There are two types used:

- Ultrasonic Doppler Meter
- Ultrasonic Transit-time Meter

## Acoustic Flowmeter FORMULA\(\large{ v_a = \frac {l} {2 \; \cos \; \theta} \left( \frac {1} {t_d} - \frac {1} {t_u} \right) }\) Where: \(\large{ v_a }\) = average axial velocity of water flow \(\large{ l }\) = acoustic path length between transducer faces \(\large{ t_d }\) = acoustic signal downstream travel time \(\large{ t_u }\) = acoustic signal upstream travel time \(\large{ \theta }\) = angle between acoustic path and the pipe's longitudinal axis Solve for: \(\large{ l = \frac {2\; v_a \cos \theta} { \left( \frac {1} {t_d} \;-\; \frac {1} {t_u} \right) } }\) \(\large{ t_d = \frac {1} { \frac {2 \;v_a \; \cos \; \theta} {l} \;+\; \frac {1} {t_u} } }\) \(\large{ t_u = \frac {1} { \frac {1} {t_d} \;-\; \frac {2\; v_a \; \cos \; \theta} {l} } }\) \(\large{ \theta = \arccos \; \left( \frac {l} {2\; v_a} \left( \frac {1} {t_d} - \frac {1} {t_u} \right) \right) }\) |