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