scholarly journals FENOMENA ALIRAN TAYLOR COUETTE POISEUILLE DENGAN ALIRAN AKSIAL-RADIAL DI DALAM SILINDER KONSENTRIS

2021 ◽  
Vol 5 (1) ◽  
pp. 145
Author(s):  
Sarip Sarip
Keyword(s):  
Couette Flow ◽  
Poiseuille Flow ◽  
Radial Flow ◽  
Outer Cylinder ◽  
Taylor Vortex ◽  
Digital Cameras ◽  
Concentric Cylinders ◽  
Flow Phenomena ◽  
Taylor Couette ◽  
Taylor Couette Flow

The filtering process using membrane technology is a modification of Taylor-Couette flow, which is a flow between two concentric cylinders that rotates with axial and radial flow and utilizes the vortex that occurs in Taylor-Couette flow which can increase membrane efficiency. The purpose this study was to determine the phenomenon of the Taylor Couette Poiseuille flow with axial-radial flow in concentric cylinders. The study was usesd a test section in the form of two concentric cylinders, in which the inner cylinder rotates as a membrane while the outer cylinder is stationary with a height of 500 mm, a radius ratio of 0.72; aspect ratio 40 and cylinder gap 12.5 mm. The inner cylinder rotation is set using an inverter to get the expected rotation. The phenomenon of observing flow patterns is done by using digital cameras on different inner cylinder turns. The results showed that changes in the inner cylinder rotations affect the flow pattern of Taylor-Couette that is formed in stages, namely laminar Couette, Taylor-vortex which is characterized by the appearance of paired vortexes, opposite directions that occur along the flow, wavy vortex and turbulant vortex. Changes in membrane porousity also show the effect of Taylor Couette Poiseuille flow phenomena with axial-radial flow which is higher, the transition to vortex occurs at higher Taylor numbers also means that Couette-Poiseuille flow stability increased. Keywords: axial-radial flow; Concentris cylinders; Taylor-Couette flow phenomenon. AbstrakProses penyaringan yang menggunakan teknologi membran merupakan modifikasi dari aliran Taylor-Couette, yaitu aliran diantara dua buah silinder konsentris yang berputar dengan aliran aksial dan radial serta memanfaatkan vortex yang terjadi pada aliran Taylor-Couette yang dapat meningkatkan efisiensi membran. Tujuan penelitian dilakukan untuk mengetahui fenomena aliran Taylor Couette Poiseuille dengan aliran aksial-radial di dalam silinder konsentris. Penelitian menggunakan seksi uji berupa dua silinder konsentris, yang mana silinder bagian dalam berputar sebagai membran sedangkan silinder luar diam dengan tinggi 500 mm, perbandingan radius 0,72; perbandingan aspek 40 dan celah silinder 12,5 mm. Putaran silinder bagian dalam diatur menggunakan inverter untuk mendapatkan putaran yang diharapkan. Fenomena pengamatan pola aliran dilakukan dengan menggunakan camera digital pada putaran silinder bagian dalam yang berbeda-beda. Hasil penelitian menunjukkan bahwa perubahan putaran silinder bagian dalam mempengaruhi pola aliran Taylor-Couette yang terbentuk secara berjenjang yaitu Couette laminar, Taylor-vortex yang ditandai dengan munculnya vortex yang saling berpasangan, berlawanan arah yang terjadi di sepanjang aliran, wavy vortex dan vortex turbulant. Perubahan porousitas membran juga menunjukkan pengaruh fenomena aliran Taylor Couette Poiseuille dengan aliran aksial-radial yang semakin tinggi maka transisi terjadinya  vortex terjadi pada bilangan Taylor yang lebih tinggi pula berarti stabilitas aliran Couette-Poiseuille meningkat.

Experimental Study of Axial Slit Wall Effect on Taylor-Couette Flow

2007 ◽  
Author(s):  
Sang-Hyuk Lee ◽  
Hyoung-Bum Kim
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Vortex Flow ◽  
Outer Cylinder ◽  
Velocity Fields ◽  
Taylor Vortex ◽  
Stable Mode ◽  
Taylor Vortex Flow ◽  
Taylor Couette ◽  
Taylor Couette Flow

Taylor-Couette flow has been studied extensively and lots of variables which affect the flow instability are being reported. The wall geometry effect of Taylor-Couette flow, however, has been less studied. In this study, we investigated the effect of axial slit of outer cylinder. This kind of configuration can be easily seen in rotating machinery. Particle image velocimetry method was used to measure the velocity fields in longitudinal and latitudinal planes. The index matching method was used to avoid light refraction. The velocity fields between the slit and plain model which has the smooth wall were compared. From the experiments, both models have the same flow mode below Re = 143. The transition from circular Couette flow to plain Taylor vortex flow began at Re = 103, and the next transition to wavy vortex flow occurred at 124. The effect of slit wall appeared when the Reynolds number is larger than Re = 143. Above this Reynolds number, there was no stable mode and plain and wavy Taylor vortex flow randomly appeared.

Experiments on the Stability of Taylor-Couette Flow With Different Radial Temperature Gradient

2010 ◽  
Author(s):  
Dong Liu ◽  
Hyoung-Bum Kim
Keyword(s):  
Reynolds Number ◽  
Temperature Gradient ◽  
Couette Flow ◽  
Outer Cylinder ◽  
Transition Process ◽  
Taylor Vortex ◽  
Radial Temperature ◽  
Buoyant Force ◽  
Taylor Couette ◽  
Taylor Couette Flow

The effect of the temperature gradient and the presence of slits in the outer cylinders involved in creating a Taylor-Couette flow was investigated by measuring the velocity field inside the gap simultaneously. The slits were azimuthally located along the inner wall of outer cylinder and the number of slits was 18. The results showed that the buoyant force due to the temperature gradient clearly generated the helical flow when the rotating Reynolds number is small. For the plain model, the transition to turbulent Taylor vortex flow is not affected by the temperature gradient considered in this study. In addition, the transition process of 18-slit model was accelerated due to the slit wall. As the temperature gradient became larger, the critical Reynolds number of the transition process decreased.

Spatio-temporal character of non-wavy and wavy Taylor–Couette flow

1998 ◽  
Vol 364 ◽  
pp. 59-80 ◽  
Author(s):  
STEVEN T. WERELEY ◽  
RICHARD M. LUEPTOW
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Vortex Flow ◽  
Outer Cylinder ◽  
Taylor Vortex ◽  
Meridional Plane ◽  
Azimuthal Wave ◽  
Moderate Reynolds Number ◽  
Taylor Couette ◽  
Taylor Couette Flow

The stability of supercritical Couette flow has been studied extensively, but few measurements of the velocity field of flow have been made. Particle image velocimetry (PIV) was used to measure the axial and radial velocities in a meridional plane for non-wavy and wavy Taylor–Couette flow in the annulus between a rotating inner cylinder and a fixed outer cylinder with fixed end conditions. The experimental results for the Taylor vortex flow indicate that as the inner cylinder Reynolds number increases, the vortices become stronger and the outflow between pairs of vortices becomes increasingly jet-like. Wavy vortex flow is characterized by azimuthally wavy deformation of the vortices both axially and radially. The axial motion of the vortex centres decreases monotonically with increasing Reynolds number, but the radial motion of the vortex centres has a maximum at a moderate Reynolds number above that required for transition. Significant transfer of fluid between neighbouring vortices occurs in a cyclic fashion at certain points along an azimuthal wave, so that while one vortex grows in size, the two adjacent vortices become smaller, and vice versa. At other points in the azimuthal wave, there is an azimuthally local net axial flow in which fluid winds around the vortices with a sense corresponding to the axial deformation of the wavy vortex tube. These measurements also confirm that the shift-and-reflect symmetry used in computational studies of wavy vortex flow is a valid approach.

scholarly journals Multiplicity of states in Taylor-Couette flow of a dense granular gas

2021 ◽  
Vol 249 ◽  
pp. 03015
Author(s):  
Nandu Gopan ◽  
Meheboob Alam
Keyword(s):  
Couette Flow ◽  
Outer Cylinder ◽  
Taylor Vortex ◽  
Damping Force ◽  
Granular Gas ◽  
Taylor Vortex Flow ◽  
Wide Range ◽  
Taylor Couette ◽  
Dynamics Simulations ◽  
Taylor Couette Flow

Molecular dynamics simulations with a purely repulsive Lennard-Jones potential and a normal damping force is used to simulate the granular flow in the annular region between two differentially-rotating cylinders, called the Taylor-Couette flow. The flow transition from the azimuthally-invariant Circular Couette flow (CCF) to the Taylor-vortex flow (TVF) is studied by increasing the rotation rate (ωi) of the inner cylinder, with the outer cylinder being kept stationary. Multiplicity of states, highlighting the hysteretic nature of the “CCF ↔ TVF” transition, is observed over a wide range of rotation rates. The onset of Taylor vortices is quantified in terms of the maximum radial velocity and the net circulation per vortex.

scholarly journals Taylor-Couette flow with mixed convection heat transfer and variable properties in a horizontal annular pipe

2021 ◽  
pp. 271-271
Author(s):  
Ismahane Chaieb ◽  
Toufik Boufendi ◽  
Xavier Nicolas
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Couette Flow ◽  
Outer Cylinder ◽  
Convection Heat Transfer ◽  
Numerical Code ◽  
Taylor Vortex ◽  
Aspect Ratios ◽  
Taylor Couette ◽  
Taylor Couette Flow

Taylor-Couette flows in a horizontal annular gap between finite coaxial cylinders in rotor-stator configuration are numerically investigated. The inner cylinder (rotor) rotates at a constant angular velocity while the outer cylinder (stator) is at rest. They are limited at their extremities by two fixed walls that prevent axial fluid flow. In addition, a heat transfer is generated by an imposed temperature difference, with the rotor hotter than the stator while the end-walls are adiabatic. The fluid physical properties are temperature dependent. This non-linear physics problem, with a strong coupling of the conservation equations and boundary conditions, is solved by a finite volume method with numerical schemes of second order space and time accuracies. The radius and aspect ratios and the Taylor, Grashof and Prandt numbers are the control parameters. The developed numerical code has been tested for different meshes and perfectly validated. Extensive calculations have been made in large ranges of the Taylor and Grashof numbers to analyze the Taylor-Couette flow in convection modes. The results highlight the dynamic and thermal instabilities generated in the Taylor Couette flow from the appearance of Ekman cells to the Taylor vortex propagation in the entire annulus. The combined effect of these vortices with the secondary flow improves the heat transfer. Furthermore, the influence of the physical properties in the radial direction is more marked in the vicinity of the walls. Finally, we propose an empirical correlation of the Nusselt number in the studied parameter ranges.

Experimental Study of Taylor-Couette Flow With Constant Radial Temperature Gradient

2009 ◽  
Author(s):  
Dong Liu ◽  
Seok-Hwan Choi ◽  
Sang-Hyuk Lee ◽  
Jung-Ho Lee ◽  
Hyoung-Bum Kim
Keyword(s):  
Temperature Gradient ◽  
Couette Flow ◽  
Flow Instability ◽  
Outer Cylinder ◽  
Taylor Vortex ◽  
Radial Temperature Gradient ◽  
Obvious Effect ◽  
Radial Temperature ◽  
Taylor Couette ◽  
Taylor Couette Flow

The flow between two concentric cylinders with the inner one rotating and with an imposed radial temperature gradient is studied using digital particle image velocimetry (DPIV) method. Four models of the outer cylinder without and with different numbers of slits (6, 9 and 18) are considered, and the radius ratio and aspect ratio of each models were 0.825 and 48, respectively. The flow regime in the Taylor-Couette flow was studied by increasing the Reynolds number. The results showed that smaller number of slits has no obvious effect on the transition process, which only change the shape of the vortex, and the transition to turbulent Taylor vortex is accelerated as the number of slit increases in both isothermal and non-isothermal conditions. It is also shown that the presence of temperature gradient increased the flow instability obviously as the Froude number larger than 0.0045.

scholarly journals Azimuthal velocity profiles in Rayleigh-stable Taylor–Couette flow and implied axial angular momentum transport

2015 ◽  
Vol 774 ◽  
pp. 342-362 ◽  
Author(s):  
Freja Nordsiek ◽  
Sander G. Huisman ◽  
Roeland C. A. van der Veen ◽  
Chao Sun ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Couette Flow ◽  
Outer Cylinder ◽  
Azimuthal Velocity ◽  
Velocity Profiles ◽  
Body Rotation ◽  
Solid Body Rotation ◽  
Angular Momentum Transport ◽  
Taylor Couette ◽  
Taylor Couette Flow

We present azimuthal velocity profiles measured in a Taylor–Couette apparatus, which has been used as a model of stellar and planetary accretion disks. The apparatus has a cylinder radius ratio of ${\it\eta}=0.716$, an aspect ratio of ${\it\Gamma}=11.74$, and the plates closing the cylinders in the axial direction are attached to the outer cylinder. We investigate angular momentum transport and Ekman pumping in the Rayleigh-stable regime. This regime is linearly stable and is characterized by radially increasing specific angular momentum. We present several Rayleigh-stable profiles for shear Reynolds numbers $\mathit{Re}_{S}\sim O(10^{5})$, for both ${\it\Omega}_{i}>{\it\Omega}_{o}>0$ (quasi-Keplerian regime) and ${\it\Omega}_{o}>{\it\Omega}_{i}>0$ (sub-rotating regime), where ${\it\Omega}_{i,o}$ is the inner/outer cylinder rotation rate. None of the velocity profiles match the non-vortical laminar Taylor–Couette profile. The deviation from that profile increases as solid-body rotation is approached at fixed $\mathit{Re}_{S}$. Flow super-rotation, an angular velocity greater than those of both cylinders, is observed in the sub-rotating regime. The velocity profiles give lower bounds for the torques required to rotate the inner cylinder that are larger than the torques for the case of laminar Taylor–Couette flow. The quasi-Keplerian profiles are composed of a well-mixed inner region, having approximately constant angular momentum, connected to an outer region in solid-body rotation with the outer cylinder and attached axial boundaries. These regions suggest that the angular momentum is transported axially to the axial boundaries. Therefore, Taylor–Couette flow with closing plates attached to the outer cylinder is an imperfect model for accretion disk flows, especially with regard to their stability.

scholarly journals Taylor–Couette–Poiseuille flow with a weakly permeable inner cylinder: absolute instabilities and selection of global modes

2018 ◽  
Vol 849 ◽  
pp. 741-776
Author(s):  
Nils Tilton ◽  
Denis Martinand
Keyword(s):  
Numerical Simulations ◽  
Poiseuille Flow ◽  
Radial Flow ◽  
Temporal Frequency ◽  
Outer Cylinder ◽  
Global Mode ◽  
Permeable Membrane ◽  
Global Modes ◽  
Taylor Couette ◽  
Base Flows

Variations in the local stability of the flow in a Taylor–Couette cell can be imposed by adding an axial Poiseuille flow and a radial flow associated with one or both of the cylinders being permeable. At a given rotation rate of the inner cylinder, this results in adjacent regions of the flow that can be simultaneously stable, convectively unstable, and absolutely unstable, making this system fit for studying global modes of instability. To this end, building on the existing stability analysis in absolute modes developing over axially invariant base flows, we consider the case of axially varying base flows in systems for which the outer cylinder is impermeable, and the inner cylinder is a weakly permeable membrane through which the radial flow is governed by Darcy’s law. The frameworks of linear and nonlinear global modes are used to describe the instabilities and assess the results of direct numerical simulations using a dedicated pseudospectral method. Three different axially evolving set-ups are considered. In the first, fluid injection occurs along the full inner cylinder. In the second, fluid extraction occurs along the full inner cylinder. Besides its fundamental interest, this set-up is relevant to filtration devices. In the third, fluid flux through the inner cylinder evolves from extraction to injection as cross-flow reversal occurs. In agreement with the global mode analyses, the numerical simulations develop centrifugal instabilities above the predicted critical rotation rates and downstream of the predicted axial locations. The global mode analyses do not fully explain, however, that the instabilities observed in the numerical simulations take the form of axial stacks of wavepackets characterized by jumps of the temporal frequency.

Velocity profiles, flow structures and scalings in a wide-gap turbulent Taylor–Couette flow

2017 ◽  
Vol 831 ◽  
pp. 330-357 ◽  
Author(s):  
A. Froitzheim ◽  
S. Merbold ◽  
C. Egbers
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Couette Flow ◽  
Outer Cylinder ◽  
Azimuthal Velocity ◽  
Cylinder Wall ◽  
Taylor Vortices ◽  
Wide Gap ◽  
Taylor Couette ◽  
Taylor Couette Flow

Fully turbulent Taylor–Couette flow between independently rotating cylinders is investigated experimentally in a wide-gap configuration ($\unicode[STIX]{x1D702}=0.5$) around the maximum transport of angular momentum. In that regime turbulent Taylor vortices are present inside the gap, leading to a pronounced axial dependence of the flow. To account for this dependence, we measure the radial and azimuthal velocity components in horizontal planes at different cylinder heights using particle image velocimetry. The ratio of angular velocities of the cylinder walls $\unicode[STIX]{x1D707}$, where the torque maximum appears, is located in the low counter-rotating regime ($\unicode[STIX]{x1D707}_{max}(\unicode[STIX]{x1D702}=0.5)=-0.2$). This point coincides with the smallest radial gradient of angular velocity in the bulk and the detachment of the neutral surface from the outer cylinder wall, where the azimuthal velocity component vanishes. The structure of the flow is further revealed by decomposing the flow field into its large-scale and turbulent contributions. Applying this decomposition to the kinetic energy, we can analyse the formation process of the turbulent Taylor vortices in more detail. Starting at pure inner cylinder rotation, the vortices are formed and strengthened until $\unicode[STIX]{x1D707}=-0.2$ quite continuously, while they break down rapidly for higher counter-rotation. The same picture is shown by the decomposed Nusselt number, and the range of rotation ratios, where turbulent Taylor vortices can exist, shrinks strongly in comparison to investigations at much lower shear Reynolds numbers. Moreover, we analyse the scaling of the Nusselt number and the wind Reynolds number with the shear Reynolds number, finding a communal transition at approximately $Re_{S}\approx 10^{5}$ from classical to ultimate turbulence with a transitional regime lasting at least up to $Re_{S}\geqslant 2\times 10^{5}$. Including the axial dispersion of the flow into the calculation of the wind amplitude, we can also investigate the wind Reynolds number as a function of the rotation ratio $\unicode[STIX]{x1D707}$, finding a maximum in the low counter-rotating regime slightly larger than $\unicode[STIX]{x1D707}_{max}$. Based on our study it becomes clear that the investigation of counter-rotating Taylor–Couette flows strongly requires an axial exploration of the flow.

scholarly journals Optimal Taylor–Couette flow: direct numerical simulations

2013 ◽  
Vol 719 ◽  
pp. 14-46 ◽  
Author(s):  
Rodolfo Ostilla ◽  
Richard J. A. M. Stevens ◽  
Siegfried Grossmann ◽  
Roberto Verzicco ◽  
Detlef Lohse
Keyword(s):  
Angular Velocity ◽  
Couette Flow ◽  
Scaling Laws ◽  
Outer Cylinder ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Experimental Result ◽  
Counter Rotation ◽  
Taylor Couette ◽  
Taylor Couette Flow

AbstractWe numerically simulate turbulent Taylor–Couette flow for independently rotating inner and outer cylinders, focusing on the analogy with turbulent Rayleigh–Bénard flow. Reynolds numbers of $R{e}_{i} = 8\times 1{0}^{3} $ and $R{e}_{o} = \pm 4\times 1{0}^{3} $ of the inner and outer cylinders, respectively, are reached, corresponding to Taylor numbers $Ta$ up to $1{0}^{8} $. Effective scaling laws for the torque and other system responses are found. Recent experiments with the Twente Turbulent Taylor–Couette (${T}^{3} C$) setup and with a similar facility in Maryland at very high Reynolds numbers have revealed an optimum transport at a certain non-zero rotation rate ratio $a= - {\omega }_{o} / {\omega }_{i} $ of about ${a}_{\mathit{opt}} = 0. 33$. For large enough $Ta$ in the numerically accessible range we also find such an optimum transport at non-zero counter-rotation. The position of this maximum is found to shift with the driving, reaching a maximum of ${a}_{\mathit{opt}} = 0. 15$ for $Ta= 2. 5\times 1{0}^{7} $. An explanation for this shift is elucidated, consistent with the experimental result that ${a}_{\mathit{opt}} $ becomes approximately independent of the driving strength for large enough Reynolds numbers. We furthermore numerically calculate the angular velocity profiles and visualize the different flow structures for the various regimes. By writing the equations in a frame co-rotating with the outer cylinder a link is found between the local angular velocity profiles and the global transport quantities.

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