# Alternative transient eddy-current flowmetering methods for liquid metals

## TL;DR

This paper analyzes alternative methods for transient eddy-current flowmetering in liquid metals, focusing on tracking emf features to measure flow velocity, and discusses the impact of system symmetry on measurement accuracy.

## Contribution

It introduces and evaluates new measurement schemes for transient eddy-current flowmeters using a simple model and analyzes the effects of system asymmetry on performance.

## Key findings

- Zero crossing points and spatial extrema of emf travel with the medium.
- Temporal extrema of emf experience a delay depending on conductivity and velocity.
- Flowmeter reliability depends on system symmetry, with asymmetry affecting accuracy at low velocities.

## Abstract

We present a comprehensive numerical analysis of alternative transient eddy-current flowmetering methods for liquid metals. This type of flowmeter operates by tracking eddy-current markers excited by the magnetic field pulses in the flow of a conducting liquid. Using a simple mathematical model, where the fluid flow is replaced by a translating cylinder, a number possible alternative measurement schemes are considered. The velocity of the medium can be measured by tracking zero crossing points and spatial or temporal extrema of the electromotive force (emf) induced by transient eddy currents in the surrounding space. Zero crossing points and spatial extrema of the emf travel synchronously with the medium whereas temporal extrema experience an initial time delay which depends on the conductivity and velocity of the medium. Performance of transient eddy-current flowmetering depends crucially on the symmetry of system. Eddy current asymmetry of a few per cent makes the detection point drift with a velocity corresponding to a magnetic Reynolds number $Rm\sim 0.1.$ With this level of asymmetry transient eddy-current flowmetering can be reliably applicable only to flows with $Rm\gtrsim 0.1.$ A more accurate symmetry adjustment or calibration of flowmeters may be necessary at lower velocities.