The problem of how to accurately measure the flowrate of oil–gas–water mixtures in a pipeline remains one of the key challenges in the petroleum industry. This paper discusses why three-phase flow measurement is still important and why it remains a difficult problem to solve. The measurement strategies and principal base technologies currently used by commercial manufacturers are described, and research developments that could influence future flowmeter design are considered. Finally, future issues, which will need to be addressed by manufacturers and users of three-phase flowmeters, are discussed.

https://iopscience.iop.org/article/10.1088/0957-0233/24/1/012003/pdf

Three-phase flow measurement in the petroleum industry

Robotic applications often require robust tactile sensing capabilities on curved surfaces, such as artificial fingertips. Flexible tactile sensors could be conformally wrapped around curved digits and could enhance grip by cushioning impacts and increasing the effective contact area during grasp. Flexible microfabricated devices that use thin film or solid electrical components are susceptible to failure due to cracking and fatigue. Conductive fluids have been used as transduction media, electrical connections, and in resistance-based pressure and bend sensors. In this work, a flexible and multilayer capacitive microfluidic normal force sensor is developed with a 5 × 5 taxel array. The sensor uses liquid metal-filled microfluidic channels as the capacitive plates and conductive interconnects. The sensor is microfabricated using soft lithography microfabrication techniques and consists of multiple layers of PDMS microchannels filled with the liquid metal alloy Galinstan and air pockets that modify the mechanical and electrical properties of the sensor. A single taxel is calibrated for normal forces ranging from 0 to 2.5 N, is shown to provide repeatable measurements of static uniaxial loads, and follows the loading and unloading phases of low-frequency dynamic loads (0.4–4 Hz). The sensor prototype has a spatial resolution on the order of 0.5 mm, performs reliably when wrapped around a surface having a curvature similar to that of a human finger (1.575 cm−1), and has been shown to tolerate curvatures as high as 6.289 cm−1. The deformable liquid capacitive plates and heterogeneous PDMS-air dielectric medium can be designed to tune the sensor's sensitivity and range. The sensor prototype provides greater sensitivity at low loads, a feature which can be exploited for robotic applications in which light touch is important.

Flexible microfluidic normal force sensor skin for tactile feedback

Tomographic absorption spectroscopy for the study of gas dynamics and reactive flows

High-resolution gas–oil two-phase flow visualization with a capacitance wire-mesh sensor

Uncovering complex oil-water flow structure represents a challenge in diverse scientific disciplines. This challenge stimulates us to develop a new distributed conductance sensor for measuring local flow signals at different positions and then propose a novel approach based on multi-frequency complex network to uncover the flow structures from experimental multivariate measurements. In particular, based on the Fast Fourier transform, we demonstrate how to derive multi-frequency complex network from multivariate time series. We construct complex networks at different frequencies and then detect community structures. Our results indicate that the community structures faithfully represent the structural features of oil-water flow patterns. Furthermore, we investigate the network statistic at different frequencies for each derived network and find that the frequency clustering coefficient enables to uncover the evolution of flow patterns and yield deep insights into the formation of flow structures. Current results present a first step towards a network visualization of complex flow patterns from a community structure perspective.

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Multi-frequency complex network from time series for uncovering oil-water flow structure

We introduce a new wire-mesh sensor based on capacitance (permittivity) measurements. The sensor can be used to measure transient phase fraction distributions in a flow cross-section, such as in a pipe or other vessel, and is able to discriminate fluids having different relative permittivity (dielectric constant) values in a multiphase flow. We designed and manufactured a prototype sensor which comprises two planes of 16 wires each. The wires are evenly distributed across the measuring cross-section, and measurement is performed at the wire crossings. Time resolution of the prototype sensor is 625 frames per second. Sensor and measuring electronics were evaluated showing good stability and accuracy in the capacitance measurement. The wire-mesh sensor was tested in a silicone oil/water two-phase bubbly flow.

http://iopscience.iop.org/article/10.1088/0957-0233/18/7/059/pdf

Capacitance wire-mesh sensor for fast measurement of phase fraction distributions

Comparative study of gas–oil and gas–water two-phase flow in a vertical pipe

Image processing techniques for high-speed videometry in horizontal two-phase slug flows

We describe a fast optical tomography sensor which has been designed for the investigation of single- and two-phase flows in smaller flow cross-sections, such as pipes and bubble columns. It enables image acquisition at frame rates of up to 4.5 kHz at roughly 2 mm image resolution. The sensor works similar to a conventional CT of the fourth generation with 256 light emitters and 32 light receivers arranged about the object's cross-section. The light emitters are sequentially flashed while the light receiver intensities are recorded synchronously. A primary area of application is single-phase flows with dye tracers. Another potential application is the investigation of bubbly two-phase flows at low gas fractions. Principle tests have been made for both problems.

http://iopscience.iop.org/article/10.1088/0957-0233/19/9/094006/pdf

M. J. da Silva

Papers

Capacitance wire-mesh sensor for fast measurement of phase fraction distributions

High-resolution gas–oil two-phase flow visualization with a capacitance wire-mesh sensor

Comparative study of gas–oil and gas–water two-phase flow in a vertical pipe

Image processing techniques for high-speed videometry in horizontal two-phase slug flows

Design of an optical tomograph for the investigation of single- and two-phase pipe flows