Acoustic Flowmeter

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

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:

\(\large{ l = \frac {2 \; v_a \cos \theta} { \left( \frac {1} {t_d} \;-\; \frac {1} {t_u} \right) } }\)

\(\large{ t_d = \frac {1} { \frac {2 \; v_a \; \cos \; \theta} {l} \;+\; \frac {1} {t_u} } }\)

\(\large{ t_u = \frac {1} { \frac {1} {t_d} \;-\; \frac {2 \; v_a \; \cos \; \theta} {l} } }\)

\(\large{ \theta = \arccos \; \left( \frac {l} {2 \; v_a} \left( \frac {1} {t_d} - \frac {1} {t_u} \right) \right) }\)

 

 

Tags: Equations for Flow Equations for Open Channel