Velocity‐Fields, Reynolds Stresses, and Swirl‐Induced Intermittency in Free and Enclosed Rotating Flows

2002 ◽  
pp. 135-155
Author(s):  
Frank Holzäpfel ◽  
Klaus Döbbeling ◽  
Bernhard Lenze
Keyword(s):  
Velocity Fields ◽  
Rotating Flows ◽  
Reynolds Stresses

scholarly journals Turbulence Measurements in Pipe Flow With Drag Reducing Polymer Additives

2016 ◽  
Author(s):  
L. Marylin Pumisacho ◽  
Luis Fernando A. Azevedo
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Velocity Fields ◽  
Instantaneous Velocity ◽  
Shear Stresses ◽  
Normal Velocity ◽  
Reynolds Stresses ◽  
Velocity Fluctuations ◽  
Turbulent Reynolds Number ◽  
Viscous Shear

Pressure drop and instantaneous velocity fields were measured for fully developed turbulent pipe flow of water and a solution of water and long chain polymer at low concentration. Two-dimensional Particle Image Velocimetry technique — PIV, coupled with a particle tracking technique was employed to yield velocity fields with high spatial resolution. Turbulence statistics were obtained from a series of approximately 2500 instantaneous velocity fields measured for each flow configuration characterized by the turbulent Reynolds number and the polymer concentration. Tests were conducted for a turbulent Reynolds number range from Reτ≈1764 to Reτ≈3154, and for 20 wppm of Superfloc A110 polymer in water. Time-averaged, rms velocity fluctuations and turbulent shear stresses profiles were measured. Drag reductions of the order of 50% were measured. Changes in the axial and wall-normal velocity fluctuations were measured and linked to the presence of the polymer. Reynolds stresses were also shown to decrease in the buffer layer of polymer solution flows as a result of a decrease in the correlation of axial and wall normal fluctuations. A deficit of the viscous shear stress and Reynolds stresses in relation to the total stress was measured close to the wall and attributed to the polymer stresses exerted on the fluid. All the results obtained were in agreement with the available literature, which serve to validate the procedures and test section employed in the experiments.

Comparison Between a Slot Jet and Round Jets Impinging a Curved Wall

2003 ◽  
Author(s):  
V. Gilard ◽  
L.-E. Brizzi
Keyword(s):  
Data Processing ◽  
Flow Structure ◽  
Statistical Data ◽  
Velocity Fields ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Statistical Data Processing ◽  
Round Jets ◽  
The Mean

Velocity measurements by PIV are realized in order to compare a slot jet and round jets impinging a curved surface. A statistical data processing allows us to obtain the mean velocity fields and the Reynolds stresses. For the two jet geometries, the flow structure is described. Some velocity distributions according to different axis are extracted of the mean velocity fields and are also described.

Slot Jet Impinging a Curved Wall

2002 ◽  
Author(s):  
V. Gilard ◽  
L.-E. Brizzi
Keyword(s):  
Data Processing ◽  
Statistical Data ◽  
Velocity Fields ◽  
Pressure Measurements ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Concave Wall ◽  
Wall Flow ◽  
The Mean

In order to study the aerodynamics of a slot jet impinging a concave wall, flow visualisations, velocity measurements by PIV and pressure measurements are carried out. A statistical data processing allows us to obtain the mean velocity fields and the Reynolds stresses. Among the studied parameters, the effect of the relative curvature of the wall is studied in particular because of a jet beating phenomenon observed for a low relative curvature. Three flow modes are then described.

scholarly journals Alpha-Quenched Alpha-Lambda Dynamos and the Excitation of Nonaxisymmetric Magnetic Fields

1993 ◽  
Vol 157 ◽  
pp. 147-151
Author(s):  
Dale M. Barker ◽  
David Moss
Keyword(s):  
Magnetic Fields ◽  
Differential Rotation ◽  
Large Scale ◽  
Meridional Circulation ◽  
Mean Field ◽  
Velocity Fields ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Navier Stokes Equation ◽  
Mean Field Dynamo

We present calculations showing how stable nonaxisymmetric magnetic fields may be excited in an alpha-quenched mean field dynamo in a deep spherical shell. The large scale velocity fields (differential rotation, meridional circulation) are determined by solving the axisymmetric Navier-Stokes equation, neglecting the Lorentz force but including a term parameterizing the turbulent Reynolds stresses.

scholarly journals Influence of pressure on the wake of a hydrophobic circular cylinder for a flow regime with Reynolds number of 2.2×105

2021 ◽  
Vol 2119 (1) ◽  
pp. 012011
Author(s):  
K G Dobroselsky
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Vortex Flow ◽  
Flow Region ◽  
Velocity Fields ◽  
Wake Flow ◽  
Flow Structures ◽  
Reynolds Stresses ◽  
Two Dimensional Image

Abstract Vortex flow structures in a turbulent wake behind a circular Teflon cylinder immersed in an incoming flow with a change in pressure for the Reynolds number Re = 2.2×105 have been experimentally studied using a two-dimensional image (2D-PIV) of particles in a closed-circuit water tunnel. The obtained results are presented in the form of time-averaged velocity fields, Reynolds stresses, and distributions of turbulent kinetic energy. The flow data showed that the size of the wake flow region, Reynolds stresses and turbulent kinetic energy change depending on the pressure in the flow. As a result of a 20% reduction in pressure, the size of the vortex zone in the wake increases by about 20%.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

Central kiloparsec of NGC 1326 observed with SINFONI

2020 ◽  
Vol 638 ◽  
pp. A53
Author(s):  
Nastaran Fazeli ◽  
Gerold Busch ◽  
Andreas Eckart ◽  
Françoise Combes ◽  
Persis Misquitta ◽  
...  
Keyword(s):  
Black Hole ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Stellar Content ◽  
Stellar Rotation ◽  
Supermassive Black Hole ◽  
Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

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