Non-Invasive Flow Measurement Via Distributed Acoustic Sensing Utilizing Frequency Spectra Analysis of Wall Pressure Fluctuations

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.