Spinning Behaviour of Diametral Acoustic Modes in Deep Axisymmetric Cavities With Chamfered Edges

2014 ◽  
Author(s):  
Oleksandr Barannyk ◽  
Peter Oshkai
Keyword(s):  
Pressure Fluctuations ◽  
High Amplitude ◽  
Pronounced Change ◽  
Axisymmetric Cavity ◽  
Acoustic Modes ◽  
Splitter Plates ◽  
Flow Oscillations ◽  
Axisymmetric Cavities ◽  
Spinning Behaviour ◽  
Stationary Behaviour

Spinning behaviour of diametral acoustic modes associated with self-sustained flow oscillations in a deep, axisymmetric cavity located in a long pipeline was investigated experimentally. High-amplitude pressure fluctuations resulted from the excitation of the diametral acoustic modes by the fully-turbulent flow in the pipeline. The unsteady pressure was measured at three equally spaced azimuthal locations at the bottom of the cavity. This arrangement allowed calculation of the azimuthal orientation of the acoustic modes, which were classified as stationary, partially spinning or spinning. Introduction of shallow chamfers to the upstream and the downstream edges of the cavity resulted in changes of azimuthal orientation and spinning behaviour of the acoustic modes. In addition, introduction of splitter plates in the cavity led to pronounced change in the spatial orientation and the spinning behaviour of the acoustic modes. The short splitter plates changed the behaviour of the dominant acoustic modes from partially spinning to stationary, while the long splitter plates enforced the stationary behaviour across all resonant acoustic modes.

scholarly journals Forecasting rational working modes of long-operated gas-transport systems under conditions of their incomplete loading

2021 ◽  
Vol 4 (8(112)) ◽  
pp. 6-15
Author(s):  
Volodymyr Grudz ◽  
Yaroslav Grudz ◽  
Myroslav Iakymiv ◽  
Mykola Iakymiv ◽  
Pavlo Iagoda
Keyword(s):  
Mathematical Modeling ◽  
Energy Consumption ◽  
Transport System ◽  
Gas Transport ◽  
Pressure Fluctuations ◽  
Initial Pressure ◽  
High Amplitude ◽  
Nonstationary Process ◽  
Optimality Criteria ◽  
Transport Systems

Prolonged operation of the gas-transport system in conditions of partial loading involves frequent changes in the volume of gas transportation, which necessitates prompt forecasting of system operation. When forecasting the modes of operation of the gas transport system, the main criterion of optimality implies the maximum volume of gas pumping. After all, in this case, the largest profit of the gas-transport company is achieved under the condition of full provision of consumers with energy. In conditions of incomplete loading of the gas-transport system caused by a shortage of gas supply, optimality criteria change significantly. First, the equipment is operated in ranges far from nominal ones which leads to growth of energy consumption. Secondly, changes in performance cause high-amplitude pressure fluctuations at the outlet of compressor stations. Based on mathematical modeling of nonstationary processes, amplitude and frequency of pressure fluctuations at the outlet of compressor stations which can cause the pipeline overload have been established. To prevent this, it was proposed to reduce initial pressure relative to the maximum one. Calculated dependence was obtained which connects the amplitude of pressure fluctuations with the characteristics of the gas pipeline and the nonstationary process. Reduction in energy consumption for transportation is due to the shutdown of individual compressor stations (CS). Mathematical modeling has made it possible to establish regularities of reduction of productivity of the gas-transport system and duration of the nonstationary process depending on the location of the compressor station on the route. With an increase in the number of shutdown compression stations, the degree of productivity decrease and duration of nonstationarity reduces The established patterns and proposed solutions will improve the reliability of a gas-transport system by preventing pipeline overload and reduce the cost of gas transportation by selecting running numbers of shutdown stations with a known decrease in productivity.

scholarly journals Mathematical Modeling of Unsteady Gas Transmission System Operating Conditions under Insufficient Loading

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1325 ◽  
Author(s):  
Vasyl Zapukhliak ◽  
Lyubomyr Poberezhny ◽  
Pavlo Maruschak ◽  
Volodymyr Grudz ◽  
Roman Stasiuk ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Transmission System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Amplitude Fluctuations ◽  
Pipeline Route ◽  
Main Gas Pipeline ◽  
System Operating

Under insufficient loading of a main gas transmission system, high-amplitude fluctuations of pressure may occur in it. A mathematical model is proposed to estimate the amplitude of pressure fluctuations in a gas pipeline along its length. It has been revealed that the shutdown of compressor stations along the gas pipeline route has a significant impact on the parameters of the unsteady transient operating conditions. The possibility of minimizing oscillation processes by disconnecting compressor stations is substantiated for the “Soyuz” main gas pipeline.

scholarly journals Experimental and numerical studies of sound generated by cavities

2019 ◽  
Vol 137 ◽  
pp. 01011
Author(s):  
Sebastian Rulik ◽  
Włodzimierz Wrόblewski ◽  
Mirosław Majkut ◽  
Michał Strozik ◽  
Krzysztof Rusin
Keyword(s):  
High Frequency ◽  
Measurement Techniques ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
High Amplitude ◽  
Noise Generation ◽  
Flow Conditions ◽  
Numerical Studies ◽  
Wide Range ◽  
Specific Frequency

Cavities and gaps are an important element in the construction of many devices and machines, including energy sector applications. This type of flow is usually coupled with strong pressure fluctuations inside the cavity, which are emitted into the far field in the form of a sound wave responsible for the noise generation. This applies to both subsonic and supersonic flows. Pressure fluctuations often have the character of single tones of a specific frequency and high amplitude and their generation is associated with a vortex shedding formed directly above the inlet and its interaction with the walls of the cavity. The presented work include description of developed test stand and applied measurement techniques dedicated to the analysis of high frequency phenomena. In addition, the adopted numerical model will be described, including conducted two-dimensional and three-dimensional analysis. The developed models will be validated based on experimental measurements concerning wide range of flow conditions.

Multiphase Flow Induced Vibrations at High Pressure: CFD Analysis of Multiphase Forces

2021 ◽  
Author(s):  
Paul Emmerson ◽  
Mike Lewis ◽  
Neil Barton ◽  
Steinar Orre ◽  
Knud Lunde ◽  
...  
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
Gas Flow ◽  
Production Systems ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Operating Pressure ◽  
Cfd Analysis ◽  
Cfd Modelling ◽  
Test Loop

Abstract CFD analysis of a high pressure 2” pipe test loop with water-gas flow was undertaken using three different solvers. Multiphase flow induced forces were predicted on the bends at a range of operating pressures between 10 and 80 barg and compared with forces reconstructed from vibration measurements. Overall the three different CFD solvers predicted consistent results. The fluid forces predicted on the bends of the double U-loop test rig have a good range of values compared to the test reconstructed forces. The forces predicted at low pressure were in line with the experimental reconstructed values, whilst at high pressure all three CFD solvers predicted higher forces. The trend of the forces reducing with increased operating pressure, evident in test, was matched by one of the CFD methods, but less well by the other two. At low operating pressure the forces are dominated by the momentum of the liquid in the multiphase flow, whilst at high pressure the pressure fluctuations and turbulent effects will be more important. All three CFD solvers use VOF methods and above about 40 barg it is possible that they struggle to fully resolve the flow behaviour, which will be more influenced by bubble and droplet entrainment and turbulence. Multiphase flow can induce high amplitude vibrations in piping systems, potentially leading to fatigue failures. CFD modelling offers a potentially powerful tool to provide the flow induced forces required for assessing and diagnosing multiphase flow induced pipework vibration problems in hydrocarbon production systems.

Study on Flow Characteristics Downstream of Annular Inlet Guide Vanes

2013 ◽  
Author(s):  
Masanori Kudo ◽  
Koichi Nishibe ◽  
Masayuki Takahashi ◽  
Kotaro Sato ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Unsteady Flow ◽  
Flow Instability ◽  
Velocity Ratio ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Flow Instabilities ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Flow Oscillations ◽  
Measured Pressure

The main objectives of the present study are to identify the dominant parameters responsible for the generation of unsteady flow, determine the conditions under which flow oscillations are produced and the relation between the flow characteristics and the number of vanes with identical solidity. The flow instabilities downstream of inlet guide vanes (IGV) are clarified experimentally and by numerical simulation. The conditions for the onset of flow instability, including the number of cells and the oscillation characteristics of the unsteady flow, are discussed based on measured pressure fluctuations and the propagating angular velocity ratio of the instability for various radius ratios (r3/r2). The effectiveness of adjusting the number of vanes to control the flow instabilities is also discussed.

Experimental Investigation of Flow-Acoustic Coupling in a Deep Axisymmetric Cavity

2013 ◽  
Author(s):  
Peter Oshkai ◽  
Oleksandr Barannyk
Keyword(s):  
Noise Suppression ◽  
Quantitative Imaging ◽  
Pressure Fluctuations ◽  
Internal Flow ◽  
Acoustic Mode ◽  
Mode Shapes ◽  
Internal Cavity ◽  
Reference Case ◽  
Axisymmetric Cavity ◽  
Acoustic Coupling

In this paper, the phenomenon of self-sustained pressure oscillations due to the flow past a deep, circular, axisymmetric cavity is investigated. In many engineering applications, such as flows through open gate valves, there exists potential for coupling between the vortex shedding from the upstream edge of the cavity and a diametral mode of the acoustic pressure fluctuations. In the present study, the unsteady pressure was measured at several azimuthal locations at the bottom of the cavity walls, and the associated acoustic mode shapes were calculated numerically for the four representative cases of the internal cavity geometry, which involved a reference case with sharp, 90°edges as well as several modifications that involved chamfers of various length of the upstream and the downstream edges of the cavity. In addition, the flow velocity in the vicinity of the cavity opening in selected cases was measured using digital particle image velocimetry (PIV). The optical access to the highly confined internal flow was provided by implementing an endoscope attached to the camera. This global, quantitative imaging approach yielded patterns of velocity, streamlines and out-of-plane vorticity component. Instantaneous and time-averaged flow patterns provided insight into the mechanism of the flow tone generation. Among the considered cavity geometries, the configuration that corresponded to the most efficient noise suppression was identified.

Investigation on Complex Pressure Fluctuations in a Gas-Solids Circulating Fluidized Bed Rieser

2012 ◽  
Vol 538-541 ◽  
pp. 610-615
Author(s):  
Jun Xu ◽  
Xing Xing Chen ◽  
Gui Lei Wang ◽  
Yao Dong Wei
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Axial Direction ◽  
High Amplitude ◽  
Solid Mass ◽  
Two Phase ◽  
Mass Fluxes

The experiment is carried out in a 13-meter-high circulating fluidized bed(CFB) to investigate gas-solid two-phase flow by pressure sensor. The axial pressure and pressure fluctuation are measured in different solid mass fluxes. With the solid mass flux increasing, pressure gradually increases, and pressure gradually decreases along the riser upwards. The characteristic of pressure fluctuation in the riser is analyzed, which indicates that pressure fluctuation in the riser originates from the inlet. The intensity of the pressure fluctuation decreases along the riser upwards. This pressure fluctuation is composed of two types: one is of low frequency and high amplitude, which is resulted from unstable feeding to the riser and keeps coherent along the axial direction. And the other is of high frequency and low amplitude, which is the result of a variety of factors, such as cluster movement, gas-solid interaction and gas velocity fluctuation.

Boiling Flow Pressure Drop Modeling in a Minichannel

2003 ◽  
Author(s):  
D. Brutin ◽  
L. Tadrist
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Phase Flow ◽  
Homogeneous Fluid ◽  
Phase Zone ◽  
Two Phase ◽  
Mean Pressure ◽  
Flow Pressure

The present paper deals with two-phase flow pressure drop modeling. This is based on solving the mass, momentum and energy balance equations in steady state conditions. In the two-phase zone, the liquid-vapor is assumed to be a homogeneous fluid. The calculated pressure drop variation is found to be similar to the experimental one when the two–phase flow is steady. In the unsteady state conditions characterized by high amplitude of the pressure fluctuations, the computed pressure drop is found to be different from the experimental mean pressure drop. This difference is all the higher as the pressure fluctuation is high.

Resonance of Trapped Acoustic Modes of a Ducted Rectangular Cavity

2015 ◽  
Author(s):  
Michael Bolduc ◽  
Samir Ziada ◽  
Philippe Lafon
Keyword(s):  
Shear Layer ◽  
Particle Velocity ◽  
Acoustic Mode ◽  
Velocity Fields ◽  
Mode Shapes ◽  
Test Results ◽  
Trapped Modes ◽  
Cross Sectional ◽  
Acoustic Modes ◽  
Axisymmetric Cavities

Flow over ducted cavities can lead to strong resonances of the trapped acoustic modes due to the presence of the cavity within the duct. Aly & Ziada [1–3] investigated the excitation mechanism of acoustic trapped modes in axisymmetric cavities. These trapped modes in axisymmetric cavities tend to spin because they do not have preferred orientation. The present paper investigates rectangular cross-sectional cavities as this cavity geometry introduces an orientation preference to the excited acoustic mode. Three cavities are investigated, one of which is square while the other two are rectangular. In each case, numerical simulations are performed to characterize the acoustic mode shapes and the associated acoustic particle velocity fields. The test results show the existence of stationary modes, being excited either consecutively or simultaneously, and a particular spinning mode for the cavity with square cross-section. The computed acoustic pressure and particle velocity fields of the excited modes suggest complex oscillation patterns of the cavity shear layer because it is excited, at the upstream corner, by periodic distributions of the particle velocity along the shear layer circumference.

Forced Oscillations in Combustors With Spray Atomizers

1999 ◽  
Vol 124 (1) ◽  
pp. 20-30 ◽  
Author(s):  
M. Zhu ◽  
A. P. Dowling ◽  
K. N. C. Bray
Keyword(s):  
Liquid Fuel ◽  
Pressure Fluctuations ◽  
Droplet Size Distribution ◽  
Forced Oscillations ◽  
Combustion Instabilities ◽  
Unsteady Combustion ◽  
Fuel Droplets ◽  
Rate Of Combustion ◽  
Flow Oscillations ◽  
Insight Into

Most types of combustion-driven devices experience combustion instabilities. For aeroengine combustors, the frequency of this oscillation is typically in the range 60–120 Hz and is commonly called “rumble.” The rumble oscillations involve coupling between the air and fuel supplies and unsteady flow in the combustor. Essentially pressure fluctuations alter the inlet fuel and air, thereby changing the rate of combustion, which at certain frequencies further enhances the pressure perturbation and so leads to self-excited oscillations. The large residence time of the liquid fuel droplets, at idle and subidle conditions, means that liquid and gaseous phases must both be considered. In the present work, we use a numerical model to investigate the forced unsteady combustion due to specified time-dependent variations in the fuel and air supplies. Harmonic variations in inlet air and fuel flows have been considered and the resulting unsteady combustion calculated. The influence of droplet size distribution has also been investigated. The calculations provide insight into the interaction between atomization, unsteady combustion, and flow oscillations.

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