scholarly journals The feasibility of generating low-frequency volcano seismicity by flow through a deformable channel

2008 ◽  
Vol 307 (1) ◽  
pp. 45-56 ◽  
Author(s):  
A. C. Rust ◽  
N. J. Balmforth ◽  
S. Mandre
Keyword(s):  
Low Frequency ◽  
Volcano Seismicity ◽  
Flow Through ◽  
Deformable Channel

scholarly journals Electrically stimulated acupuncture increases renal blood flow through exosome-carried miR-181

2018 ◽  
Vol 315 (6) ◽  
pp. F1542-F1549 ◽  
Author(s):  
Janet D. Klein ◽  
Xiaonan H. Wang
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Culture Medium ◽  
Gastrocnemius Muscle ◽  
Muscle Wasting ◽  
Muscle Protein ◽  
Low Frequency ◽  
Luciferase Reporter ◽  
Mouse Serum ◽  
Flow Through

Acupuncture with low-frequency electrical stimulation (Acu/LFES) can prevent muscle atrophy by increasing muscle protein anabolism in mouse models of chronic kidney disease. During the treatment of muscle wasting, we found that Acu/LFES on the gastrocnemius muscle of the leg enhances renal blood flow. We also found that Acu/LFES increases exosome abundance and alters exosome-associated microRNA expression in the circulation. When exosome secretion was blocked using GW4869, the Acu/LFES-induced increase in renal blood flow was limited. This provided evidence that the increased renal blood flow is exosome mediated. To identify how exosomes regulate renal blood flow, we performed microRNA deep sequencing in exosomes isolated from treated and untreated mouse serum and found that the 34 microRNAs are altered by Acu/LFES. In particular, miR-181d-5p is increased in the serum exosome of Acu/LFES-treated mice. In silico searching suggested that miR-181d-5p could target angiotensinogen. Using a luciferase reporter assay, we demonstrated that miR-181 directly inhibits angiotensinogen. When Acu/LFES-treated muscle was excised and incubated in culture medium, we found that the amount of exosomes and miR-181d-5p was increased in the medium providing evidence that Acu/LFES can increase miR-181 secretion. We conclude that Acu/LFES on leg hindlimb increases miR-181 in serum exosome leading to increased renal blood flow. This study provides important new insights about the mechanism(s) by which acupuncture may regulation of muscle-organ cross talk through exosome-derived microRNA.

Cavitating Orifice: Flow Regime Transitions and Low Frequency Sound Production

2005 ◽  
Author(s):  
Philippe Testud ◽  
Avraham Hirschberg ◽  
Pierre Moussou ◽  
Yves Aure´gan
Keyword(s):  
Sound Production ◽  
Low Frequency ◽  
Broadband Noise ◽  
Detailed Data ◽  
Hydraulic Conditions ◽  
Circular Orifice ◽  
Vapor Cloud ◽  
Orifice Flow ◽  
Flow Through ◽  
Regime Transitions

Detailed data are provided for the broadband noise in a cavitating pipe flow through a circular orifice in water. Experiments are performed under industrial conditions, i.e., with a pressure drop varying from 3 to 30 bars and a cavitation number in the range 0.10 ≤ σ ≤ 0.77. The speed of sound downstream of the orifice happens to vary spontaneously for a given set of hydraulic conditions. In the intermediate ‘developed cavitation’ regime, whistling associated with periodic vortex shedding is observed. In the ‘super cavitation’ regime, a vapor cloud develops itself and the whistling disappears. The broadband noise in each regime is presented and its dimensionless representation is discussed.

Reflection of circumferential modes in a choked nozzle

2002 ◽  
Vol 467 ◽  
pp. 215-239 ◽  
Author(s):  
S. R. STOW ◽  
A. P. DOWLING ◽  
T. P. HYNES
Keyword(s):  
Acoustic Wave ◽  
Low Frequency ◽  
Effective Length ◽  
Mean Flow ◽  
Small Perturbations ◽  
Choked Flow ◽  
First Case ◽  
Propagating Waves ◽  
Flow Through ◽  
Good Agreement

Small perturbations of a choked flow through a thin annular nozzle are investigated. Two cases are considered, corresponding to a ‘choked outlet’ and a ‘choked inlet’ respectively. For the first case, either an acoustic or entropy or vorticity wave is assumed to be travelling downstream towards the nozzle contraction. An asymptotic analysis for low frequency is used to find the reflected acoustic wave that is created. The boundary condition found by Marble & Candel (1977) for a compact choked nozzle is shown to apply to first order, even for circumferentially varying waves. The next-order correction can be expressed as an ‘effective length’ dependent on the mean flow (and hence the particular geometry of the nozzle) in a quantifiable way.For the second case, an acoustic wave propagates upstream and is reflected from a convergent–divergent nozzle. A normal shock is assumed to be present. By considering the interaction of the shock's position and flow perturbations, the reflected propagating waves are found for a compact nozzle. It is shown that a significant entropy disturbance is produced even when the shock is weak, and that for circumferential modes a vorticity wave is also present. Numerical calculations are conducted using a sample geometry and good agreement with the analysis is found at low frequency in both cases, and the range of validity of the asymptotic theory is determined.

Prediction of Invsicid Flow in Axial Turbines in Comparison With Measurements

1993 ◽  
Author(s):  
N. Haspel ◽  
J. F. Mayer ◽  
H. Stetter
Keyword(s):  
Low Frequency ◽  
Transformation Procedure ◽  
Turbine Stator ◽  
Flow Fluctuations ◽  
Flow Phenomena ◽  
Time Marching ◽  
Flow Through ◽  
Last Stage ◽  
Axial Turbines ◽  
Marching Method

A CFD code for simulation of 3D inviscid throughflow in turbine stages will be presented in this paper. The discretization is realized by a finite difference method applying a transformation procedure. The time dependent Enter equations are solved by the explicit time marching method of Lax, Wendroff and Richtmyer. The coupling between stator and rotor flow is achieved by circumferentially averaged flow data, enabling the simulation of low frequency flow fluctuations. The flow through a gas turbine stator is simulated by the code. In this case secondary flow phenomena caused by a nonuniform inlet flow are of special interest. A throughflow calculation of the last stage of a LP steam turbine shows that the program is able to manage 3D complex transonic flows as well. The CFD results are compared in both cases with experimental data.

scholarly journals The Relationship Between Cerebral Blood Flow and the EEG in Normals

1980 ◽  
Vol 7 (3) ◽  
pp. 195-198 ◽  
Author(s):  
Devidas Menon ◽  
Zoltan Koles ◽  
Allen Dobbs
Keyword(s):  
Blood Flow ◽  
Low Frequency ◽  
Weight Percent ◽  
Initial Slope ◽  
Inhalation Technique ◽  
Frequency Components ◽  
Flow Through ◽  
Gamma Rhythms ◽  
The Subject ◽  
The Relationship

SUMMARY:Using the Xel33 inhalation technique, measurements of the blood flow to the left and right parietal and temporal regions of the cerebrum were obtained in 5 healthy individuals while simultaneously recording their EEGs. Up to 3 measurements were obtained from each of the subjects the first while they were mentally at rest and the others while they were engaged in prescribed forms of mental activity. Relationships between the measured blood flow through grey matter, initial slope index, relative grey weight, percent grey flow and power in the delta, delta-theta, alpha, beta and gamma rhythms of the EEG were examined. The results showed that for the subject group as a whole there was a strong correlation between the power present in the low frequency components of EEG and the grey flow and relative grey weight parameters of blood flow. On an individual basis, the observed relationships were highly variable particularly at high flow rates and at low relative grey weights, but became much more definitive at low flows and high weights. The results as they relate to previous work of this kind are discussed.

Duct Noise Control by Using Very Light Composite Plate

2011 ◽  
Vol 410 ◽  
pp. 361-365
Author(s):  
Y.S. Choy ◽  
Yang Liu ◽  
Kin Tak Lau
Keyword(s):  
Theoretical Study ◽  
Noise Control ◽  
Transmission Loss ◽  
Low Frequency ◽  
Composite Plates ◽  
Bending Stiffness ◽  
Composite Panel ◽  
Frequency Noise ◽  
Reinforced Composite ◽  
Flow Through

A compact flow-through plate silencer is constructed for low frequency noise control by using new reinforced composite plates. The concept comes from the previous theoretical study [1] that in a duct, a clamped supported plate covered with a rigid cavites. The structural property of the very light plate with high bending stiffness is very crucial element in such plate silencer. In this study, an approach to fabricate new reinforced composite panel with light weight and high bending stiffness is developed in order to realize the function of this plate silencer practically. The performance of two plate silencer with the stopband from 229 to 618Hz in which the transmission loss is higher than 10 dB over the whole frequency band can be achieved.

Unsteady Flow Simulation Through a Centrifugal Pump

2005 ◽  
Author(s):  
Yulin Wu ◽  
Naixiang Chen ◽  
Zhaohui Xu ◽  
Shuhong Liu
Keyword(s):  
Centrifugal Pump ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Flow Simulation ◽  
Boundary Layer Separation ◽  
Flow Instabilities ◽  
Structural Vibration ◽  
Flow Through ◽  
Vane Diffuser

Flow in a typical centrifugal pump is known to be unsteady due to flow instabilities and mutual interactions between the rotating part and the stationary parts. Flow instabilities are mostly viscous phenomena such as boundary layer separation and vortex shedding that produces relatively low frequency and small amplitude pressure fluctuations. Mutual interaction between the impeller blades and the guide vane diffuser produces relatively high frequency and large amplitude pressure fluctuations. This phenomenon is more closely related to compressibility than viscosity. It is important because it may cause structural vibration and noise. In this paper, the steady and unsteady turbulent flow through the whole flow passage of an entire centrifugal pump, has been computed to predict the pressure fluctuation of flow in the pump.

Structural and Acoustic Noise Sources Due to Turbulent Flow Through an Elbow: Formulation of Analysis Methods

2003 ◽  
Author(s):  
Stephen A. Hambric ◽  
L. Joel Peltier ◽  
John B. Fahnline ◽  
David A. Boger ◽  
John E. Poremba
Keyword(s):  
Power Transmission ◽  
Acoustic Noise ◽  
Low Frequency ◽  
Navier Stokes ◽  
Fe Model ◽  
Noise Sources ◽  
Turbulent Fluid Flow ◽  
Fluid Forces ◽  
Piping Systems ◽  
Flow Through

The low-frequency structure- and fluid-borne noise from elbows excited by fluctuating forces within turbulent fluid flow is investigated. Computational Fluid Dynamics (CFD) Reynolds Averaged Navier Stokes (RANS) analyses of the flow through a piping elbow with a radius to diameter ratio of 2.8 compare favorable to measurements made by previous investigators. The CFD RANS solutions are post-processed to estimate the spectra of the fluctuating wall pressures beneath the turbulent boundary layer (TBL) flow. The CFD RANS solutions are also used to identify regions within the core flow that might excite acoustic modes within the piping fluid. A finite element (FE) model of the piping walls is coupled with a boundary element (BE) model of the interior acoustic fluid and is excited by the fluctuating wall and fluid forces estimated from the CFD RANS solutions. The power transmission through the inlet and discharge ports of the elbow is computed and separated into its structure-borne and fluid-borne components. The influence of both structural and acoustic resonances on the power transmission is evident for both excitation mechanisms. The power transmission curves at the elbow ports may be used as source inputs to transfer matrix models of piping systems that contain elbows.

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