Taylor Vortex Flow Research Articles

The Persistence of Vortex Structures Between Rotating Cylinders in the 106 Taylor Number Range

The flow in the annular gap d = Ro - Ri between a stationary outer cylinder of radius Ro and a co-axial rotating inner cylinder of radius Ri is characterised at large gap, over the radius ratio (η) range 0.44 ≤ η ≤ 0.53 and aspect ratio (Γ) range 7.81 ≤ Γ ≤ 11.36. These configurations are more representative of turbomachinery bearing chambers and large rotating machinery than the journal bearing geometries of narrow gap commonly reported in the literature. Particle Image Velocimetry measurements are taken across the full meridional plane over the Taylor number (Ta) range 258 × 10 3 ≤ Ta ≤ 10.93 × 10 6 , which is 1000 times higher than the critical Taylor number for the onset of the first axisymmetric Taylor instability. Well-defined azimuthal vortex structures persist over this high Taylor number range, characterised by a constant number of vortices at a given aspect ratio, vortex core axial and radial motion over time, and mixing between neighbour vortices. This regime, with wavy Taylor vortex flow like features, is defined over the range 1.18 × 10 6 ≤ Ta ≤ 6.47 × 10 6 . These results form a body of experimental evidence from which further progress in the understanding of the wavy Taylor vortex dynamics can be sought, through advanced flow dynamic models that reproduce the persistence of the observed flow features.

테일러 반응기의 유동특성과 입자 체류시간에 관한 수치적 연구

Using a computational fluid dynamics technique, the flow characteristics and particle residence time in a Taylor reactor were studied. Since flow characteristics in a Taylor reactor are dependent on the operating conditions, effects of the inlet flow velocity and reactor rotational speed were investigated. In addition, the particle residence time of LiNiMnCoO2 (NMC), which is a cathode material in lithium-ion battery, is estimated in the Taylor vortex flow (TVF) region. Without considering the complex chemical reaction at the inlet, the effect of Taylor flow was studied. The results show that the particle residence time increases as the rotating speed increased and the flow rate decreased.

Numerical stability of explicit off-lattice Boltzmann schemes: A comparative study

The off-lattice Boltzmann (OLB) method consists of numerical schemes which are used to solve the discrete Boltzmann equation. Unlike the commonly used lattice Boltzmann method, the spatial and time steps are uncoupled in the OLB method. In the currently proposed schemes, which can be broadly classified into Runge–Kutta-based and characteristics-based, the size of the time-step is limited due to numerical stability constraints. In this work, we systematically compare the numerical stability of the proposed schemes in terms of the maximum stable time-step. In line with the overall LB method, we investigate the available schemes where the advection approximation is explicit, and the collision approximation is either explicit or implicit. The comparison is done by implementing these schemes on benchmark incompressible flow problems such as Taylor vortex flow, Poiseuille flow, and lid-driven cavity flow. It is found that the characteristics-based OLB schemes are numerically more stable than the Runge–Kutta-based schemes. Additionally, we have observed that, with respect to time-step size, the scheme proposed by Bardow et al. (2006) [1] is the most numerically stable and computationally efficient scheme compared to similar schemes, for the flow problems tested here.

An extension of the SIMPLE based discontinuous Galerkin solver to unsteady incompressible flows

SummaryIn this paper, we present a SIMPLE based algorithm in the context of the discontinuous Galerkin method for unsteady incompressible flows. Time discretization is done fully implicit using backward differentiation formulae (BDF) of varying order from 1 to 4. We show that the original equation for the pressure correction can be modified by using an equivalent operator stemming from the symmetric interior penalty (SIP) method leading to a reduced stencil size.To assess the accuracy as well as the stability and the performance of the scheme, three different test cases are carried out: the Taylor vortex flow, the Orr‐Sommerfeld stability problem for plane Poiseuille flow and the flow past a square cylinder. (1) Simulating the Taylor vortex flow, we verify the temporal accuracy for the different BDF schemes. Using the mixed‐order formulation, a spatial convergence study yields convergence rates of k + 1 and k in the L2‐norm for velocity and pressure, respectively. For the equal‐order formulation, we obtain approximately the same convergence rates, while the absolute error is smaller. (2) The stability of our method is examined by simulating the Orr–Sommerfeld stability problem. Using the mixed‐order formulation and adjusting the penalty parameter of the symmetric interior penalty method for the discretization of the viscous part, we can demonstrate the long‐term stability of the algorithm. Using pressure stabilization the equal‐order formulation is stable without changing the penalty parameter. (3) Finally, the results for the flow past a square cylinder show excellent agreement with numerical reference solutions as well as experiments. Copyright © 2015 John Wiley & Sons, Ltd.

Agglomeration of Ni-rich hydroxide crystals in Taylor vortex flow

The agglomeration of Ni-rich hydroxide crystals (Ni0.9Co0.05Mn0.05)(OH)2 was studied in a continuous Couette-Taylor (CT) crystallizer. Due to the excellent mixing and periodic fluid motion of the Taylor vortex flow in the CT crystallizer, the formation of spherical and uniform agglomerate particles of Ni-rich crystals was promoted as the rotation speed and the mean residence time increased. Thus, for a rotation speed of 1500rpm and mean residence time of 60min, with a high feed concentration of 3.0mol/L produced a high tap-density of agglomerate particles of 2.13g/cm3, which is higher than any previously reported values. These results were due to the excellent micromixing effects of Taylor vortex in the CT crystallizer. In addition, the long mean residence time contributed to the formation of spherical particles due to the extended exposure of the agglomerates to the fluid shear. Furthermore, the formation of spherical particles was optimized at a pH of 12.0 and required a high concentration of ammonia due to the high composition of Ni ions in the Ni-rich hydroxide crystals and the short mean residence time in the continuous CT crystallizer. Moreover, when comparing the crystallization in a continuous MSMPR crystallizer, which required a long mean residence time of 12h for a high tap-density of above 2.0g/cm3, the continuous CT crystallizer was clearly much more effective for the formation of uniform spherical particles due to the more efficient hydrodynamic fluid motion of the Taylor vortex in the CT crystallizer in contrast to the random turbulent eddy motion in the MSMPR crystallizer.

G1700101 Taylor渦バイオリアクターを用いた光合成微生物の増殖と藻体破壊

G1700101 Taylor渦バイオリアクターを用いた光合成微生物の増殖と藻体破壊

Effect of Gap Flow on the Torque for Blades in a Rim Driven Thruster without Axial Pressure Gradient

This paper applied RANS solver and angular momentum current analyzing method to study the effect of gap flow in a rim driven thruster on the torque of the blades when the propeller was replaced by a rotating disk. The rim's torque was divided into two parts, outer surface and end faces. The torque of outer surface was resulted by turbulent Taylor vortex flow in the radial gap between inner and outer cylinder. The torque of end faces was resulted by radial outflow and inflow in the axial gap. Based on N-S equations angular momentum current was conserved in radial gap by neglecting of influence of end faces. We employed RANS solver to investigate the effect of the ratio between inner and outer cylinder radius on the torque of the outer surface by keeping the axial gap ratio. As such the effect of axial gap ratio on the torque of end faces was explored by holding radial gap ratio. Whereafter angular momentum current conservation was applied to obtain a predicted formula to calculate the torque of the outer surface. A new predicted method of calculating the torque of end faces was obtained by fitting the CFD calculated results. Finally the developed method was validated by experiments in the large cavitation tunnel of CSSRC. It showed that the torque calculated by the new predicted method agreed well with experiments comparing with the empirical formulas from Bilgen and Boulos, Daily and Nece.

S1740104 超音波計測を用いた低アスペクト比Taylor渦流れの流動解析

S1740104 超音波計測を用いた低アスペクト比Taylor渦流れの流動解析

Numerical study of MHD Taylor vortex flow with low magnetic Reynolds number in finite-length annulus under uniform magnetic field

The effects of axial uniform magnetic field on Taylor vortex flow with low magnetic Reynolds number in a concentric finite-length annulus are investigated numerically. The inner cylinder is rotating and the outer one is held at rest. As the endwall effects play a significant role in determining the vortical structure, three endwall conditions are taken into account in present study: all are fixed, all are rotating with the inner cylinder, one is fixed but the other is rotating with the inner cylinder. All the boundaries are assumed to be insulating, and the chosen aspect ratio, the height of the cylinder to the gap width, is moderate Γ=10, hence the endwall effects and the Taylor vortex can be both considered. The governing equations are solved using collocation spectral method and projection method which allows pressure–velocity decoupling. The flow patterns and developments of vortical structure with different endwall conditions are presented at various strength of axial magnetic field. The effects of axial magnetic field on magnetohydrodynamics flow are discussed.

Droplet behavior in a Taylor vortex

Here we present the study on the behavior of individual droplets in a Taylor vortex of immiscible working fluid. The droplets (water or ethanol with the volume of 15–30μL) were introduced into a Taylor–Couette device with an aspect ratio of 6 and a radius ratio of 0.67, in which a mineral oil (density of 0.86g/cm3 and viscosity of 0.066Pas) was used as the working fluid. This configuration ensures a laminar Taylor vortex flow with no occurrence of wavy vortex in the entire operating range. The behavior of the droplets was investigated with a high speed camera and a phase Doppler particle analysis (PDPA) system. The water droplet can be trapped in the vortex center at low Reynolds numbers, corresponding to a circular trajectory, which gradually develops into a three-dimensional toroidal motion with the increasing Reynolds number. Differently, the ethanol droplet exhibits the toroidal motion at low Reynolds numbers and follows the circular trajectory at high Reynolds numbers. Due to their deformability, both water and ethanol droplets are elongated as an ellipsoid shape when moving in the gap, although its length-to-diameter ratio varies along the annulus. Furthermore, the ethanol droplet subject to a sudden-start of the fluid can break into lots of small droplets with the size of microns, which later coalesce into a single droplet again after the Taylor vortex flow becomes stable. The study can help to better understand the droplet behaviors in a Taylor vortex and therefore benefit possible applications conducted in Taylor vortex devices.

Experimental investigation of mixing and axial dispersion in Taylor–Couette flow patterns

The flow and mixing in a Taylor–Couette device have been characterized by means of simultaneous particle image velocimetry and planar laser-induced fluorescence (PLIF) measurements. Concentration of a passive tracer measurements was used to investigate mixing efficiency for different flow patterns (from steady Taylor vortex flow to modulated wavy vortex flow, MWVF). Taylor–Couette flow is known to evolve toward turbulence through a sequence of flow instabilities. Macroscopic quantities, such as axial dispersion and mixing index, are extremely sensitive to internal flow structures. PLIF measurements show clear evidences of different transport mechanisms including intravortex mixing and tracer fluxes through neighboring vortices. Under WVF and MWVF regimes, intravortex mixing is controlled by chaotic advection, due to the 3D nature of the flow, while intervortex transport occurs due to the presence of waves between neighboring vortices. The combination of these two mechanisms results in enhanced axial dispersion. We show that hysteresis may occur between consecutive regimes depending on flow history, and this may have a significant effect on mixing for a given Reynolds number

Effect of the number of vortices on the torque scaling in Taylor–Couette flow

AbstractTorque measurements in Taylor–Couette flow, with large radius ratio and large aspect ratio, over a range of velocities up to a Reynolds number of 24 000 are presented. Following a specific procedure, nine states with distinct numbers of vortices along the axis were found and the aspect ratios of the vortices were measured. The relationship between the speed and the torque for a given number of vortices is reported. In the turbulent Taylor vortex flow regime, at relatively high Reynolds number, a change in behaviour is observed corresponding to intersections of the torque–speed curves for different states. Before each intersection, the torque for a state with a larger number of vortices is higher. After each intersection, the torque for a state with a larger number of vortices is lower. The exponent, from the scaling laws of the torque, always depends on the aspect ratio of the vortices. When the Reynolds number is rescaled using the mean aspect ratio of the vortices, only a partial collapse of the exponent data is found.

The Taylor-vortex dynamo

The generation of a magnetic field by dynamo action in a Taylor-vortex flow is investigated numerically. We first discuss how the Taylor vortices generate a spatially subharmonic dynamo, for which the axial wavelength of the magnetic field is twice the one of the flow pattern. Then, we investigate the influence of the Reynolds number and the turbulent fluctuations on the structure and the onset of the Taylor-Couette dynamo. Finally, based on the subharmonic nature of this dynamo, we propose new configurations which could be relevant for laboratory experiments.

Application of Taylor Vortex to Crystallization

This study summarizes crystallization technology when using a Taylor vortex flow. A Taylor vortex is created in the gap between two co-axially positioned cylinders based on the rotation of the inner cylinder. Due to its unique periodic flow motion, a Taylor vortex has a significant influence on the processes of nucleation, growth, and agglomeration breakage in various crystallizations, including reaction recrystallization, drowning-out crystallization, and cooling crystallization. In the gas–liquid reaction crystallization of calcium carbonate, the mass transfer at the gas–liquid interface is greatly facilitated by a Taylor vortex, resulting in small crystals with a uniform size and morphology. Further, due to molecular alignment by the periodic Taylor vortex motion, the polymorphic nucleation of stable crystals is also promoted. This effect of molecular alignment by a Taylor vortex is demonstrated by the phase transformation of sulfamerazine. Furthermore, the Taylor vortex flow in a Taylor crystallizer improves the productivity of crystallization when compared with the random turbulent eddy flow in an MSMPR crystallizer. Consequently, the high performance of a Taylor crystallizer using a Taylor vortex has strong potential for application to various crystallizations.

GS05 低アスペクト比Taylor渦による撹拌混合のための超音波流速分布計測法について

Taylor vortex flow with a small aspect ratio has characteristics such as the different vortex structure, because of the Ekman effect in the top and bottom boundary layers and the acceleration of the inner cylinder. This feature is expected to develop a new typed mixing bioreactor system, but this vortex flow mechanism like a chaotic flow has not been investigated much. Furthermore, the multiphase flow such as the solid-liquid flow is important to be analyzed with a measurement system. An ultrasound measurement method is a useful device for observation of the flows. In this report we mainly analyzed the vortex structure in higher Reynolds number with using the ultrasound measurement system, and compare the result with Direct Numerical Simulation.

244 Taylor渦を用いた固液分離濾過装置に関する検討(流体工学II)

244 Taylor渦を用いた固液分離濾過装置に関する検討(流体工学II)

Effect of Slit Number on the Stability of Taylor Vortex Flow

Effect of Slit Number on the Stability of Taylor Vortex Flow

245 Taylor渦バイオリアクターを用いた光合成微生物の増殖と藻体破壊(流体工学II)

245 Taylor渦バイオリアクターを用いた光合成微生物の増殖と藻体破壊(流体工学II)

Experiments on two immiscible fluids in spherical Couette flow

This paper deals with the experimental instabilities analysis of spherical Couette flow. We consider the flow of two immiscible fluids superimposed between concentric spheres when the outer sphere is fixed and the inner one rotates. The working fluids have rather different viscosities and thus different Reynolds numbers. The obtained results are compared with a reference case of filled gap using one fluid (Γmax = 20). Experiments are performed for different aspect ratio values, and Laser photometric technique is used for visualization. Our analysis is mainly focused on the type of instabilities and their relationship with the laminar-turbulent transition regime. We intend to explore the combined effects of the aspect ratio and the interaction between the two superposed fluids on the appearance of different instability evolutions. The evolution of the phase velocity for different aspect ratio of heavy fluid ΓHF = HHF/d is presented. The immiscible fluids are separated by a liquid–liquid interface (water–oil). In order to control instability occurrence, Taylor number variation is presented versus aspect ratio. Instability phenomena are found to be the same as for the nominal case for large heavy fluid aspect ratios. The first equatorial symmetry breaking of the flow is observed for a critical value Γc = 13 where the Taylor vortex flow is introduced with three stationary cells. For the same aspect ratio, the interaction of the immiscible fluids leads to the appearance of gravitational waves near the equatorial zone. A surface cell, starting before the appearance of Taylor vortices, is detected in the light fluid for low aspect ratios. This cell of Ekman type has not been observed before, to our best knowledge, in spherical Couette flow.

Light‐limited continuous culture of Chlorella vulgaris in a Taylor vortex reactor

Recently, it has been demonstrated that Taylor vortices—hydrodynamic structures that arise in the annular region between two concentric cylinders when the inner cylinder rotates—can substantially improve the growth rate of algal biomass in a batch photobioreactor by inducing the flashing light effect. In order to assess the potential for using Taylor vortex flow to continuously culture algae, experiments were carried out in a continuous flow Taylor vortex algal photobioreactor using Chlorella vulgaris. Specifically, two important operating parameters were varied: the dilution rate and the inner cylinder rotation speed. For a fixed inner cylinder rotation speed, biomass productivity was independent of dilution rate. In contrast, biomass productivity was found to increase with increasing inner cylinder rotation speed for a fixed dilution rate, but this effect became less pronounced at higher rotation speeds. Overall, it is demonstrated that a continuous flow Taylor vortex algal photobioreactor can be used to produce and sustain high biomass production and carbon dioxide capture rates when operated in continuous flow mode. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 884–890, 2013