Simultaneous Measurement of the Flow Velocities of Liquids and Gases

Abstract

This contribution presents a measuring system for the simultaneous measurement of the flow velocity and direction of air and water in a partially filled pipe. A possible application for the presented system are drainage pipes in railway tunnels. A train passing a tunnel causes a strong pressure wave, depending on its speed. Under disadvantageous conditions, this can adversely affect the atmospheric environment of the tunnel drainage. Since railway tunnels usually have a very low gradient, the effect of the pressure wave can cause a critical reversal of the air flow direction, which can also reverse the flow direction of the water.

The presented measuring system is based on the ultrasonic transit time difference method and has a measuring uncertainty of less than $1\,\mathrm{cm}/\mathrm{s}$ in air as well as in water. The setup of the measuring system and the applied signal processing are presented. The performance of the measuring system is evaluated using results obtained under laboratory conditions. Furthermore, the systems suitability for the use in drainage pipes of a railway tunnel is confirmed by results of a first test in a tunnel.

The authors gratefully acknowledge the financial support of this work by the Austrian Research Promotion Agency (FFG) under grant 864515.