Investigation of Characteristic of Flow Induced Vibration Caused by Turbulence Relating to Acoustically Induced Vibration

2014 ◽  
Author(s):  
Masato Nishiguchi ◽  
Hisao Izuchi ◽  
Gaku Minorikawa
Keyword(s):  
Pressure Drop ◽  
Fluid Velocity ◽  
Low Frequency ◽  
Piping System ◽  
Flow Induced Vibration ◽  
Pipe Wall Thickness ◽  
Large Pressure ◽  
Study Results ◽  
High Fluid ◽  
The Difference

In the flare piping system, it is known that piping vibrations occur caused by Acoustically Induced Vibration (AIV) and Flow Induced Vibration (FIV) corresponding to high flow rate, high pressure drop and relatively thin pipe wall thickness. For FIV, turbulence generated at combining tee with high fluid velocity results in low frequency piping vibration. For AIV, large noise produced through a component with large pressure drop results in high frequency piping vibration. Carucci and Mueller shows the several cases with piping failure due to AIV and most of these cases the piping failure occurred at the combining tee. In these piping failure cases, the velocity at the combining tee would be quite high close or equal to sound speed and this means piping vibrations could occur due to FIV in addition to AIV. This paper shows the investigation results of FIV at combining tee with 90 degrees using experimental data. The results are compared to the previous study results for 45 degrees combining tee and the difference between 90 and 45 degrees tees are discussed in the view points of pressure fluctuation and piping vibration. This paper also shows that the vibration index proposed by authors is quite effective to evaluate the vibration level caused by FIV for both of 90 and 45 degrees tees. This proposed vibration index is applied to failure and no failure cases presented in Carucci and Mueller paper with some assumptions and it is suggested that the vibration indexes for failure case is relatively higher than those of no failure cases. And this suggests that not only AIV but also FIV could affect the piping failure reported in Carucci and Mueller paper.

scholarly journals ANALISA PRESSURE DROP DENGAN PENAMBAHAN ZAT ADITIF CAIRAN COOLANT PADA PIPA SILINDER MENGGUNAKAN METODE EMPIRIS DAN METODE EKSPERIMEN

2018 ◽  
Vol 4 (1) ◽  
pp. 1
Author(s):  
Irwan Setiawan ◽  
Nurrohman . ◽  
Hablinur Al Kindi
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Data Retrieval ◽  
Piping System ◽  
Problem Analysis ◽  
Calibration Data ◽  
Literature Study ◽  
Pipe Length

The flow of fluid through the pipe creates fluid friction with pipe walls causing pressure drop and fluid flow velocity affecting the use of energy to drain it. Pressure drop can be affected by several factors such as friction or friction factor, pipe length, pipe diameter and fluid velocity. In this research, it will analyze pressure drop on piping system based on friction, fluid flow characteristics, and fluid velocity. The analysis was done by using two methods, namely experimental method and empirical calculation method. The stages of this study consist of problem analysis, literature study, calibration, data retrieval, empirical data processing and experiments, validation, analysis of results and conclusions. Based on the results of empirical and experimental research, the lowest pressure drop in the experiment and empirical was the 12 LPM discharge copper pipe and the water coolant ratio is 0: 100. This means that the best material pipes used were copper pipes rather than steel and galvanized pipes. The results of the tests and experiments have been tested for validation. The validation value of empirical and experimental data measurement is 91%.

Numerical Simulations on Throttle Characteristic With Large Pressure Drop and Optimal Design of the Orifice Plate

2018 ◽  
Author(s):  
Hu Chen ◽  
Wang Jue ◽  
Wang Cong ◽  
Gong Zili ◽  
Jia Zhen ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Velocity ◽  
Eddy Current ◽  
Low Frequency ◽  
Orifice Plate ◽  
Optimized Design ◽  
Multi Stage ◽  
Low Frequency Vibration ◽  
Large Pressure ◽  
Large Flow

The orifice throttle pipelines with large pressure drop suffer damages from two aspects: high frequency vibration caused by cavitation and low frequency vibration caused by high flow velocity. In order to solve the vibration phenomenon of typical throttling pipe with large pressure drop in the system of nuclear power plant, the key hydraulic characteristics such as pressure drop, flow velocity, streamline and eddy current were simulated and analyzed for single-stage orifice throttling pipe. The negative pressure area was found in the downstream of the orifice, where cavitation occurred. Eddy current was formed due to the large local velocity caused by the orifice plate jet. Then, the throttle performance of multi-stage concentric orifice plates was evaluated by means of blockage pressure drop method. The cavitation damage was relieved greatly. But it was not eliminated, especially in the last stage orifice. The expanding type five-stage orifice plate was designed according to pressure drop stage-decreasing principle, with which the possibility of cavitation was eliminated but large pressure drop resulted in large flow velocity at the downstream of the first orifice plate. Multi-stage eccentric orifice plate was designed with the consideration both in cavitation characteristics and velocity distribution, which could eliminate the harm of cavitation and reduce the low frequency vibration caused by large flow velocity to a maximum extent. As a result, multistage eccentric orifice plates could be recommended as an optimized design scheme for the vibration control of the orifice piping with large pressure drop.

scholarly journals Flow Induced Vibration (FIV) Research of Oil and Gas Process Piping System

2019 ◽  
Vol 8 (2S8) ◽  
pp. 1387-1390
Keyword(s):  
Wall Thickness ◽  
Low Frequency ◽  
Oil Production ◽  
Process Conditions ◽  
Piping System ◽  
Outer Diameter ◽  
Flow Induced Vibration ◽  
Flowing Fluid ◽  
Piping Systems ◽  
Production Facilities

Piping systems in crude oil production facilities tend to handle high pressure and high velocity flowing fluid at certain flow rate limit resulted in generation of turbulence flow. This turbulence can generate high levels of broad band kinetic energy which can propagate through the system. Even though the energy is distributed across a wide frequency range, most of the excitation is concentrated at low frequency (typically below 100 Hz); the lower the frequency, the higher the level of excitation from turbulence. This leads to excitation of the low frequency vibration modes of the pipe work, in many cases causing visible motion of the pipe and, in some cases, the pipe supports, and this phenomenon is called Flow induced vibration (FIV) and if excessive can result in fatigue failure. This objective of the paper is to identify potential sources of FIV on piping by predicting the Likelihood of failure (LOF) and advising on the necessity for system modifications to minimize or eliminate any FIV induced piping or line failure from Flow Induced Turbulence. These are done by conducting a FIV assessment for piping systems in oil production facilities which are potentially affected by vibration due to both process conditions and mechanically induced pipework vibration. Another scope of this paper is to apply the recommendation action required in order to reduce the likelihood of failure by changing pipe diameter and/or wall thickness by looking at the fluid structure interaction (FSI). By changing the outer diameter and the wall thickness of the pipe, the formation of the excitation in flow regime and the presence of the critical flow disturbance will decrease. These changes are able to reduce the formation of FIV thus increasing the lifespan of the piping system

Vibration Design of Amine Regenerator Tower and its Piping System

2019 ◽  
Author(s):  
Jae-Yeol Park ◽  
Minsung Chae
Keyword(s):  
Fluid Dynamics ◽  
Analytical Study ◽  
Fluid Velocity ◽  
Low Frequency ◽  
High Elevation ◽  
Normal Operation ◽  
Piping System ◽  
Dynamic Force ◽  
Capacity Measurement ◽  
Dominant Peak

Abstract Fluid induced vibration in high-elevation tower and its piping system is examined with on-site measurement, numerical simulation, and analytical model. In this article, Amine regeneration tower in gas separation plant is subjected to investigation since significant vibration in both tower and its piping system prevents the normal operation especially with increased loading capacity. Measurement in frequency domain for inlet piping system shows single dominant peak as well as small peaks in low frequency range. In search of solution, analytical study with computational fluid dynamics model is conducted to reduce fluid velocity which results in decreased dynamic force in both piping system and regeneration tower and reduces the fluid-induced vibration associated with slug flow. Based on the fluid dynamics study, piping modification is designed and applied to the piping system and tower and vibration improvement is achieved as expected.

scholarly journals Analysis of Low-Frequency Mutations Associated with Drug Resistance to Raltegravir before Antiretroviral Treatment

2010 ◽  
Vol 55 (3) ◽  
pp. 1114-1119 ◽  
Author(s):  
Jia Liu ◽  
Michael D. Miller ◽  
Robert M. Danovich ◽  
Nathan Vandergrift ◽  
Fangping Cai ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Treatment Failure ◽  
Low Frequency ◽  
Hiv Treatment ◽  
Viral Population ◽  
Virologic Suppression ◽  
Resistance Mutations ◽  
The Difference ◽  
Allele Specific Sequencing ◽  
Hiv 1

ABSTRACTRaltegravir is highly efficacious in the treatment of HIV-1 infection. The prevalence and impact on virologic outcome of low-frequency resistant mutations among HIV-1-infected patients not previously treated with raltegravir have not been fully established. Samples from HIV treatment-experienced patients entering a clinical trial of raltegravir treatment were analyzed using a parallel allele-specific sequencing (PASS) assay that assessed six primary and six secondary integrase mutations. Patients who achieved and sustained virologic suppression (success patients,n= 36) and those who experienced virologic rebound (failure patients,n= 35) were compared. Patients who experienced treatment failure had twice as many raltegravir-associated resistance mutations prior to initiating treatment as those who achieved sustained virologic success, but the difference was not statistically significant. The frequency of nearly all detected resistance mutations was less than 1% of viral population, and the frequencies of mutations between the success and failure groups were similar. Expansion of pre-existing mutations (one primary and five secondary) was observed in 16 treatment failure patients in whom minority resistant mutations were detected at baseline, suggesting that they might play a role in the development of drug resistance. Two or more mutations were found in 13 patients (18.3%), but multiple mutations were not present in any single viral genome by linkage analysis. Our study demonstrates that low-frequency primary RAL-resistant mutations were uncommon, while minority secondary RAL-resistant mutations were more frequently detected in patients naïve to raltegravir. Additional studies in larger populations are warranted to fully understand the clinical implications of these mutations.

scholarly journals Meteorological conditions over Antarctic blue-ice areas and their influence on the local surface mass balance

2001 ◽  
Vol 47 (156) ◽  
pp. 37-50 ◽  
Author(s):  
Richard Bintanja ◽  
Carleen H. Reijmer
Keyword(s):  
Mass Balance ◽  
Low Frequency ◽  
Meteorological Conditions ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Wind Speeds ◽  
Dry Conditions ◽  
The Difference ◽  
Sublimation Rates ◽  
Different Characteristics

AbstractThis paper addresses the causes of the prevailing meteorological conditions observed over an Antarctic blue-ice area and their effect on the surface mass balance. Over blue-ice areas, net accumulation is zero and ablation occurs mainly through sublimation. Sublimation rates are much higher than over adjacent snowfields. The meteorological conditions favourable for high sublimation rates (warm, dry and gusty) are due to the specific orographic setting of this blue-ice area, with usually a steep upwind mountainous slope causing strong adiabatic heating. Diabatic warming due to radiation, and entrainment of warm air from aloft into the boundary layer augment the warming. The prevailing warm, dry conditions explain roughly 50% of the difference in sublimation, and the different characteristics of blue ice (mainly its lower albedo) the other 50%. Most of the annual sublimation (∼70%) takes place during the short summer (mainly in daytime), with winter ablation being restricted to occasional warm, dry föhn-like events. The additional moisture is effectively removed by entrainment and horizontal advection, which are maximum over the blue-ice area. Low-frequency turbulent motions induced by the upwind mountains enhance the vertical turbulent transports. Strong gusts and high peak wind speeds over blue-ice areas cause high potential snowdrift transports, which can easily remove the total precipitation, thereby maintaining zero accumulation.

Dynamics of Ferroelectric and Nematic Liquid Crystals Confined in Porous Matrices

1994 ◽  
Vol 366 ◽  
Author(s):  
Fouad M. Aliev
Keyword(s):  
Liquid Crystals ◽  
Heterogeneous Media ◽  
Volume Fraction ◽  
Low Frequency ◽  
Pore Wall ◽  
Polar Molecules ◽  
Average Pore ◽  
Surface Polarization ◽  
The Difference ◽  
Frequency Relaxation

ABSTRACTWe performed dielectric spectroscopy measurements to study dynamics of collective modes of ferroelectric (FLC) and molecular motion of nematic (NLC) liquid crystals with polar molecules confined in silica macroporous and microporous glasses with average pore sizes of 1000 Å (volume fraction of pores 40%) and 100 Å (27%) respectively. For FLC the Goldstone and the soft modes are found in macropores. The rotational viscosity associated with the soft mode is about 10 times higher in pores than in the bulk. These modes are not detected in micropores although low frequency relaxation is present. The last one probably is not connected with the nature of liquid crystal but is associated with surface polarization effects typical for two component heterogeneous media. The difference between the dynamics of orientational motion of the polar molecules of NLC in confined geometries and in the bulk is qualitatively determined by the total energy Fs of the interaction between molecules and the surface of the pore wall, which is found Fs ≈ 102erg/cm2.

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

Comparative analysis of codon usage patterns in SARS-CoV-2, its mutants and other respiratory viruses

2021 ◽  
Author(s):  
Neetu Tyagi ◽  
Rahila Sardar ◽  
Dinesh Gupta
Keyword(s):  
Codon Usage ◽  
Codon Usage Bias ◽  
Gc Content ◽  
Respiratory Illness ◽  
Respiratory Viruses ◽  
Nucleotide Composition ◽  
Health Crisis ◽  
Study Results ◽  
Usage Patterns ◽  
The Difference

AbstractThe Coronavirus disease 2019 (COVID-19) outbreak caused by Severe Acute Respiratory Syndrome Coronavirus 2 virus (SARS-CoV-2) poses a worldwide human health crisis, causing respiratory illness with a high mortality rate. To investigate the factors governing codon usage bias in all the respiratory viruses, including SARS-CoV-2 isolates from different geographical locations (~62K), including two recently emerging strains from the United Kingdom (UK), i.e., VUI202012/01 and South Africa (SA), i.e., 501.Y.V2 codon usage bias (CUBs) analysis was performed. The analysis includes RSCU analysis, GC content calculation, ENC analysis, dinucleotide frequency and neutrality plot analysis. We were motivated to conduct the study to fulfil two primary aims: first, to identify the difference in codon usage bias amongst all SARS-CoV-2 genomes and, secondly, to compare their CUBs properties with other respiratory viruses. A biased nucleotide composition was found as most of the highly preferred codons were A/U-ending in all the respiratory viruses studied here. Compared with the human host, the RSCU analysis led to the identification of 11 over-represented codons and 9 under-represented codons in SARS-CoV-2 genomes. Correlation analysis of ENC and GC3s revealed that mutational pressure is the leading force determining the CUBs. The present study results yield a better understanding of codon usage preferences for SARS-CoV-2 genomes and discover the possible evolutionary determinants responsible for the biases found among the respiratory viruses, thus unveils a unique feature of the SARS-CoV-2 evolution and adaptation. To the best of our knowledge, this is the first attempt at comparative CUBs analysis on the worldwide genomes of SARS-CoV-2, including novel emerged strains and other respiratory viruses.

A Simplified Approach to Estimate Flow-Induced Vibrations on an Elbowed Piping System

2018 ◽  
Author(s):  
André Baramili ◽  
Ludovic Chatellier ◽  
Laurent David ◽  
Loïc Ancian
Keyword(s):  
Element Model ◽  
Numerical Approach ◽  
Piping System ◽  
Least Squares Regression ◽  
Flow Induced Vibration ◽  
Simplified Approach ◽  
Eddy Simulation ◽  
Spatially Distributed ◽  
Closed Water ◽  
Modeling Strategy

A mixed experimental and numerical approach was undertaken in order to develop a data-based model of the flow-induced vibration levels attained in a piping system containing a 90° elbow. A closed water loop was used to provide unsteady flow data as well as wall pressure and vibration measurements. In parallel, the unsteady water flow through the elbow was computed using an incompressible Large-Eddy Simulation (LES). Proper Orthogonal Decomposition (POD) and Partial Least Squares Regression (PLSR) were used in order to build a relationship between the flow properties and the resulting excitation. This relationship was then used to estimate the evolution of the spatially distributed loadings, which were finally applied to a finite element model of the piping structure. The results consisted of an estimation of the vibration levels. The estimated vibrations were then compared to measurements in order to validate the proposed modeling strategy.

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