Leaky Lamb Wave Flowmeter for Pipe Wall Acoustic Sensing
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Solution Overview
Problem
Ultrasonic clamp-on flowmeters face limitations in stability, linearity at low flow speeds, and inability to measure flow profiles, requiring complex alignment and setup parameters, which restricts their accuracy and applicability compared to in-line meters.
Innovation Solution
A novel clamp-on ultrasonic flow metering technique that selectively excites and receives Lamb waves in the pipe to measure flow rates, utilizing the frequency-dependent leak rates of these waves to estimate flow velocity and profile, with transducers designed for broad-band selective excitation and connected to analytical or machine learning algorithms for data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If clamp-on ultrasonic transducers are used for non-invasive flow measurement, then installation complexity is reduced and pipe shutdown is avoided, but measurement stability and accuracy deteriorate
Solution Approach 1:
The flow measurement function is segmented into multiple independent ultrasonic transducers (transmitters and receivers) that can be separately mounted on the pipe surface. Each transducer operates independently to transmit or receive acoustic signals, allowing the clamp-on device to achieve reliable measurements through distributed sensing while maintaining easy installation without pipe cutting or shutdown.
Solution Approach 2:
The pipe wall itself serves as an intermediary medium that transmits acoustic energy from the externally mounted transducers to the fluid flow. By utilizing guided acoustic waves that propagate through the pipe wall and couple into the fluid, the system achieves non-invasive measurement stability without requiring direct contact with the fluid or complex internal transducer mounting.
2Measurement precision
If traditional ultrasonic flow measurement methods are used, then basic flow rate measurement is achieved, but the ability to measure flow profiles and low flow speeds deteriorates
Solution Approach 1:
Different regions of the pipe circumference are probed by strategically positioning multiple receivers at different angular positions around the pipe. This allows the system to capture local velocity information at different locations, enabling flow profile reconstruction while maintaining accurate bulk flow rate measurement. The local quality of measurement is enhanced by distributing sensing points throughout the pipe perimeter.
Solution Approach 2:
The measurement capability is extended from one-dimensional bulk flow rate to two-dimensional flow profiles by adding angular positioning of receivers around the pipe circumference. This dimensional expansion allows the system to resolve velocity variations across the pipe cross-section, providing comprehensive flow characterization including both average velocity and profile shape.
3Measurement precision
If multi-path in-line meters are used to measure flow profiles, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
Instead of placing transducers inside the pipe with complex multi-path geometries, the measurement approach is inverted by mounting transducers externally on the pipe surface. Acoustic waves are transmitted through the pipe wall and fluid, with receivers detecting signals from multiple paths around the pipe circumference. This inversion simplifies the physical device while achieving flow profile measurement capability through clever acoustic path design.
Solution Approach 2:
The same external transducer array serves multiple functions: measuring bulk flow rate, resolving flow profiles, and detecting low flow speeds. By utilizing the pipe wall as a waveguide and positioning receivers at different angular positions, a single clamp-on device achieves capabilities previously requiring multiple specialized sensors, reducing overall system complexity.
4Speed
If transit-time ultrasonic measurement is used, then flow velocity measurement is achieved, but sensitivity at low flow speeds and linearity deteriorate
Solution Approach 1:
The system utilizes acoustic vibration waves transmitted through the pipe wall and fluid to detect flow velocity. By measuring the modulation of acoustic wave propagation caused by fluid motion, the system achieves enhanced sensitivity at low flow speeds through the resonant nature of acoustic vibrations, improving linearity in the low-velocity regime compared to traditional transit-time methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and repeatability of flow measurements, simplifies installation, and provides better sensitivity across a wide dynamic range, enabling the measurement of both laminar and turbulent flows, and expands the application space of clamp-on flowmeters.
Implementation Method 1
exciting one or more leaky Lamb waves in a wall of the pipe with one or more of the acoustic transducers
Implementation Method 2
Lamb waves in the pipe wall adjacent to a fluid medium can leak. The leak rate is approximately a few wavelengths.
Implementation Method 3
the leak rate changes as a function of the flow speed, flow direction and acoustic frequency
Data Source
AI summary
Propagation of leaky Lamb waves in pipe walls is used to provide a clamp-on acoustic flow meter for single-phase fluid flow in pipes. The received acoustic signals can be analyzed analytically, or by matching to numerical models, or with machine learning. In a preferred embodiment, variation of penetration depth of the leaky Lamb waves into the fluid flow with frequency provides an approach for measuring flow rate vs. radius with a clamp-on flow meter.