Acoustical analysis of pipes with flow using invariant field functions (original) (raw)
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Acoustic flowmeter for the measurement of the mean flow velocity in pipes
The Journal of the Acoustical Society of America, 2001
This paper proposes a new technique for measuring the gas flow velocity averaged along the finite length of a pipe as well as over its cross-sectional area. Unlike the conventional gas flowmeters, the proposed technique exploits the one-dimensional plane waves that propagate uniformly across the pipe cross-sectional area. When a fluid flows along the pipe, the plane waves are superposed with the flow field such that the positive-going and negative-going plane wave components undergo the change of their wave numbers. Such wave number variation due to the mean flow velocity has provided a major motivation for developing a new way of measuring the mean flow velocity in the pipe, which is referred to as the acoustic flowmeter. To examine the feasibility of the developed flow velocity measurement method, including its theoretical backgrounds, experimental setups are illustrated in this paper. Detailed experimental data for the flow velocity range of 2-27 m/s reveal the linearity of the proposed acoustic flowmeter and its salient environmental robustness for the different acoustic pressure patterns in the pipe and, furthermore, for different velocity profiles over the pipe cross-section area.
Multi-point Acoustic Sensing (MAS) technology makes use of hydrophone sensors placed at discrete distances along pipelines in order to detect third party interference (TPI) and leaks. In fact, any interaction with the pipe generates pressure waves that are guided within the fluid for long distances, carrying information on the source event. Pressure propagation is mainly governed by the absorption coefficient and the sound speed. These parameters are in turn complicated functions of the frequency, the geometrical and elastic parameters of the pipe shell, the elastic parameters of the surrounding medium, and the acoustic and thermodynamic properties of the transported fluid. We have designed several experimental campaigns on oil and gas transportation pipelines, instrumented with a proprietary MAS system. We have defined and simulated an exhaustive set of TPI and leak tests, taking care of the quantitative characterization of the dynamic parameters, especially at the source point. In...
Proceedings of IEEE Ultrasonics Symposium ULTSYM-94, 1994
In this paper, a non intrusive flowmeter based on non linear acoustical interactions, has been developed. This tool measures simultaneously the pressure and velocity fluctuations of fluids flowing in pipes. A transmitter produces a CW ultrasonic beam which crosses the tube wall, propagates through the opposite side, and is collected by a receiving transducer. Both transducers are just put against the tube wall so that it is not necessary to drill holes in order to install the probes. The ultrasonic propagation across the tube is modelized using a exact matrix numerical method. It allows to specify the geometry of the device. The high frequency beam and the low frequency flow fluctuation interact non linearly so that the ultrasonic signal is phase modulated. The amplitude of the modulation (about a hundredth radian) is a linear combination of the pressure and velocity fluctuations. A specific electronics, based on a PLL technique, has been developed for demodulating the signal. We present measurements obtained after generating flow fluctuations in cavity excited over a broad spectrum.
Identification of fluid excitation in pipes
2016
Flow-induced vibrations and noise are of importance in several engineering applications. Piping systems are used to carry fluids from one area to another in any plant whether it is a chemical plant, a storage terminal, or an oil refinery. High levels of radiating noise from piping systems occur when internal turbulent flow resulting from a pipe fitting for example, elbow, tee, valve, etc., separates from the pipe wall. The disturbed flow generates an intense internal sound field, comprising of plane waves and higher order acoustic modes which propagate throughout the piping system. These acoustic modes excite the pipe wall vibrations, which in turn generate external sound. Vibrations of pipe wall at any point in a system can be associated with the wall pressure fluctuations due to one, some, or all of the excitation as given below [2]: 1. Non-propagating local fluid dynamic and acoustic wall pressure fluctuations associated with the internal flow disturbances. 2. Fully developed tur...
Experimental Acoustic Determination of the Void Fraction in Two-Phase Flow in Horizontal Pipelines
Journal of Mechanics Engineering and Automation, 2014
In multi-phase flows, the phases can flow and arranged in different spatial configurations in the pipe, which called flow patterns. This type of flow is found in the oil, chemical and nuclear industries. For example, in the production and transport of oil and gas, the identification of the flow patterns are essential for answering those questions which are related to the economic return of the field, such as, measuring the volumetric flow, determining the pressure drop along the flow lines, production management and supervision. In offshore production, these factors are very important. This paper presents a new method for measuring the void fraction in horizontal pipelines, taking the air as gas in water-air two-phase flow. Through acoustic analysis of the frequency response of the pipe, the method gets the parameters to changes in runoff regime, in an experimental arrangement constructed on a small scale. The main advantages are the non-intrusive characteristic and easy to implement. The paper is composed of a qualitative experimental evaluation and transducers (microphone) which are used to analyze variations in the response accompanying variations in void and flow pattern changes. Changes are imposed and controlled by a two-phase flow experimental simulation rig, including a measurement cell constituted of an external casing that can isolate the measurement from the environmental background noise fitted with acoustic pressure transducers radially arranged, and the impact of a monitored excitation mechanism. The signals which captured by the microphones are processed and analyzed by checking their frequency contents changes according to the amount of air in the mixture.
Characterization of In-Pipe Acoustic Wave for Water Leak Detection
Volume 8: Mechanics of Solids, Structures and Fluids; Vibration, Acoustics and Wave Propagation, 2011
This paper presents experimental observations on the characteristics of the acoustic signal propagation and attenuation inside water-filled pipes. An acoustic source (exciter) is mounted on the internal pipe wall, at a fixed location, and produces a tonal sound to simulate a leak noise with controlled frequency and amplitude, under different flow conditions. A hydrophone is aligned with the pipe centerline and can be re-positioned to capture the acoustic signal at different locations. Results showed that the wave attenuation depends on the source frequency and the line pressure. High frequency signals get attenuated more with increasing distance from the source. The optimum location to place the hydrophone for capturing the acoustic signal is not at the vicinity of source location. The optimum location also depends on the frequency and line pressure. It was also observed that the attenuation of the acoustic waves is higher in more flexible pipes like PVC ones.
Experiments were carried out to study the effectiveness of using inside-pipe measurements for leak detection in plastic pipes. Acoustic and pressure signals due to simulated leaks, opened to air, are measured and studied for designing a detection system to be deployed inside water networks of 100 mm (4 inch) pipe size. Results showed that leaks as small as 2 l/min can be detected using both hydrophone and dynamic pressure transducer under low pipe flow rates. The ratio between pipe flow rate and leak flow rate seems to be more important than the absolute value of leak flow. Increasing this ratio resulted in diminishing and low frequency leak signals. Sensor location and directionality, with respect to the leak, are important in acquiring clean signal.
Wavenumber-Frequency Analysis of Internal Aerodynamic Noise in Constriction-Expansion Pipe
Applied Sciences, 2017
High-pressure gas is produced during the oil production process at offshore plants, and pressure relief devices, such as valves, are widely used to protect related systems from it. The high-pressure gas in the pipes connected to the flare head is burned at the flare stack, or, if it is nontoxic, is vented to the atmosphere. During this process, excessive noise is generated by the pressure relief valves that are used to quickly discharge the high-pressure gas to the atmosphere. This noise sometimes causes severe acoustic-induced vibration in the pipe wall. This study estimated the internal aerodynamic noise due to valve flow in a simple constriction-expansion pipe, by combining the large eddy simulation technique with a wavenumber-frequency analysis, which made it possible to decompose the fluctuating pressure into the incompressible hydrodynamic pressure and compressible acoustic pressure. First, the steady-state flow was numerically simulated, and the result was compared with a quasi-one-dimensional theoretical solution, which confirmed the validity of the current numerical method. Then, an unsteady simulation analysis was performed to predict the fluctuating pressure inside a pipe. Finally, the acoustic pressure modes in a pipe were extracted by applying the wavenumber-frequency transform to the total pressure field. The results showed that the acoustic pressure fluctuations in a pipe could be separated from the incompressible ones. This made it possible to obtain accurate information about the acoustic power, which could be used to assess the likelihood of a piping system failure due to acoustic-induced vibration, along with information about the acoustic power spectrum of each acoustic mode, which could be used to facilitate the systematic mitigation of the potential acoustic-induced vibration in piping systems.