This research describes a method of using distributed acoustic sensing to noninvasively measure volumetric flow rate via multiple unique sensor styles. This work modifies previously used methods of flow detection via fiber optic acoustic sensors affixed onto the exterior body of a flow apparatus. Flow rate measurement methods for two unique sensor styles are described.
Weak trends are additionally observed as a function of flow temperature that may represent opportunity for future optimization.
A discussion of current noninvasive flow rate measurement methods is given as well as their limitations. A background of distributed acoustic sensing is presented along with a summary of its fundamentals as well as its functionality in noninvasive flow rate measurement. A description of previous techniques that utilized distributed acoustic sensing in conjunction with fiber optic acoustic sensing is shown.
The acoustic properties of the fluid-induced vibrations are measured as a function of flow rate and flow temperature utilizing a special type of fiber optic sensor. Numerically smoothed frequency domain acoustic peaks are evaluated by intensity, area, central frequency, and full width at half maximum as flow conditions vary. All tested sensors were found to yield a strong dependence between peak intensity and flow rate. A dependence between central frequency and flow temperature was observed in some cases. The sensor system developed was able to measure fluid-induced vibration intensity and vibrational central frequency and offers potential uses in a myriad of vibrational applications. / Master of Science / This research provides a method of measuring fluid-induced vibrations caused by internal pressure fluctuations stemming from a variety of flow conditions. In this case, a specially fabricated optical fiber is applied to the external surface of the pipe. As water flows at a known volumetric flow rate and temperature, the acoustic signal generated is detected by the optical sensor signal demodulation system. The fiber used is a silicate material designed to transmit optical signals over long distances with minimal loss. Modifications to the fiber can be made to differentiate the measured optical signal loss by frequency band, as well as to designate the spatial position on a fiber sensor to locate where loss is occurring. By measuring optical loss of distinct fiber spatial positions at high sampling frequencies, an abundance of sensing opportunities become available. In knowing optical signal travel time of select wavelengths to corresponding strain characteristics amongst a section of fiber, optoelectronic devices with strong computing power called interrogators can powerfully measure the intensity and rate of fiber strain at a significantly high sampling frequency.
Fiber optic sensors have been used in many areas where monitoring of changes in positional microstrain is desired. Such sensors are embedded in-ground for seismic monitoring, as well as on the ocean floor for submarine structural characterization with long singular fibers. Flow rate measurement is performed with fiber coils and various other geometries for active oil wells, fission reactors, and other areas. Improving the performance and applicational flexibility of these sensors allows for greater opportunity for scientific advancement in an array of fields.
This research was completed to offer a new method of flow rate measurement while also gauging if flow temperature was able to be measured via a single fiber optic sensor. Fiber strain was observed to be strongly dependent on flow rate, whereas the rate at which strain occurred suggests simultaneous flow and temperature measurement is possible in certain types of fiber arrangements. The work produced in this research is a step towards singular-fiber flow rate and temperature sensing.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113960 |
| Date | 24 February 2023 |
| Creators | Snider, Steven Michael |
| Contributors | Materials Science and Engineering, Pickrell, Gary R., Wang, Anbo, Homa, Daniel S. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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