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Detlef Lohse - One of the best experts on this subject based on the ideXlab platform.
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turbulent taylor couette flow with stationary inner Cylinder
Journal of Fluid Mechanics, 2016Co-Authors: Rodolfo Ostillamonico, Roberto Verzicco, Detlef LohseAbstract:A series of direct numerical simulations were performed of Taylor–Couette (TC) flow, the flow between two coaxial Cylinders, with the outer Cylinder rotating and the inner one fixed. Three cases were considered, where the Reynolds number of the outer Cylinder was $Re_{o}=5.5\times 10^{4}$Reo=5.5×104, $Re_{o}=1.1\times 10^{5}$Reo=1.1×105 and $Re_{o}=2.2\times 10^{5}$Reo=2.2×105. The ratio of radii ${\it\eta}=r_{i}/r_{o}$η=ri/ro was fixed to ${\it\eta}=0.909$η=0.909 to mitigate the effects of curvature. Axially periodic boundary conditions were used, with the aspect ratio of vertical periodicity ${\it\Gamma}$Γ fixed to ${\it\Gamma}=2.09$Γ=2.09. Being linearly stable, TC flow with outer Cylinder Rotation is known to have very different behaviour than TC flow with pure inner Cylinder Rotation. Here, we find that the flow nonetheless becomes turbulent, but the torque required to drive the Cylinders and level of velocity fluctuations was found to be smaller than those for pure inner Cylinder Rotation at comparable Reynolds numbers. The mean angular momentum profiles showed a large gradient in the bulk, instead of the constant angular momentum profiles of pure inner Cylinder Rotation. The near-wall mean and fluctuation velocity profiles were found to coincide only very close to the wall, showing large deviations from both pure inner Cylinder Rotation profiles and the classic von Karman law of the wall elsewhere. Finally, transport of angular velocity was found to occur mainly through intermittent bursts, and not through wall-attached large-scale structures as is the case for pure inner Cylinder Rotation.
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turbulent taylor couette flow with stationary inner Cylinder
arXiv: Fluid Dynamics, 2016Co-Authors: Rodolfo Ostillamonico, Roberto Verzicco, Detlef LohseAbstract:A series of direct numerical simulations of Taylor-Couette (TC) flow, the flow between two coaxial Cylinders, with the outer Cylinder rotating and the inner one fixed, were performed. Three cases, with outer Cylinder Reynolds numbers $Re_o$ of $Re_o=5.5\cdot10^4$, $Re_o=1.1\cdot10^5$ and $Re_o=2.2\cdot10^5$ were considered. The radius ratio $\eta=r_i/r_o$ was fixed to $\eta=0.909$ to mitigate the effects of curvature. The vertical aspect ratio $\Gamma$ was fixed to $\Gamma=2.09$. Being linearly stable, outer Cylinder Rotation TC flow is known to have very different behavior than pure inner Cylinder Rotation TC flow. Here, we find that the flow nonetheless becomes turbulent, but the torque required to drive the Cylinders and level of velocity fluctuations was found to be smaller than those for pure inner Cylinder Rotation at comparable Reynolds numbers. The mean angular momentum profiles showed a large gradient in the bulk, instead of the constant angular momentum profiles of pure inner Cylinder Rotation. The near-wall mean and fluctuation velocity profiles were found to coincide only very close to the wall, showing large deviations from both pure inner Cylinder Rotation profiles and the classic von Karman law of the wall elsewhere. Finally, transport of angular velocity was found to occur mainly through intermittent bursts, and not through wall-attached large-scale structures as is the case for pure inner Cylinder Rotation.
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azimuthal velocity profiles in rayleigh stable taylor couette flow and implied axial angular momentum transport
Journal of Fluid Mechanics, 2015Co-Authors: Freja Nordsiek, Detlef Lohse, Sander G Huisman, Chao Sun, Roeland C A Van Der Veen, Daniel P LathropAbstract: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 ${\it\eta}=0.716$η=0.716, an aspect ratio of ${\it\Gamma}=11.74$Γ=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 $\mathit{Re}_{S}\sim O(10^{5})$ReS∼O(105), for both ${\it\Omega}_{i}>{\it\Omega}_{o}>0$Ωi>Ωo>0 (quasi-Keplerian regime) and ${\it\Omega}_{o}>{\it\Omega}_{i}>0$Ωo>Ωi>0 (sub-rotating regime), where ${\it\Omega}_{i,o}$Ωi,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 $\mathit{Re}_{S}$ReS. 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.
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exploring the phase diagram of fully turbulent taylor couette flow
Journal of Fluid Mechanics, 2014Co-Authors: Rodolfo Ostilla Monico, Erwin P Van Der Poel, Roberto Verzicco, Siegfried Grossmann, Detlef LohseAbstract:Direct numerical simulations of Taylor–Couette flow, i.e. the flow between two coaxial and independently rotating Cylinders, were performed. Shear Reynolds numbers of up to 3×10 5 , corresponding to Taylor numbers of Ta=4.6×10 10 , were reached. Effective scaling laws for the torque are presented. The transition to the ultimate regime, in which asymptotic scaling laws (with logarithmic corrections) for the torque are expected to hold up to arbitrarily high driving, is analysed for different radius ratios, different aspect ratios and different Rotation ratios. It is shown that the transition is approximately independent of the aspect and Rotation ratios, but depends significantly on the radius ratio. We furthermore calculate the local angular velocity profiles and visualize different flow regimes that depend both on the shearing of the flow, and the Coriolis force originating from the outer Cylinder Rotation. Two main regimes are distinguished, based on the magnitude of the Coriolis force, namely the co-rotating and weakly counter-rotating regime dominated by Rayleigh-unstable regions, and the strongly counter-rotating regime where a mixture of Rayleigh-stable and Rayleigh-unstable regions exist. Furthermore, an analogy between radius ratio and outer-Cylinder Rotation is revealed, namely that smaller gaps behave like a wider gap with co-rotating Cylinders, and that wider gaps behave like smaller gaps with weakly counter-rotating Cylinders. Finally, the effect of the aspect ratio on the effective torque versus Taylor number scaling is analysed and it is shown that different branches of the torque-versus-Taylor relationships associated to different aspect ratios are found to cross within 15 % of the Reynolds number associated to the transition to the ultimate regime. The paper culminates in phase diagram in the inner versus outer Reynolds number parameter space and in the Taylor versus inverse Rossby number parameter space, which can be seen as the extension of the Andereck et al. (J. Fluid Mech., vol. 164, 1986, pp. 155–183) phase diagram towards the ultimate regime.
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exploring the phase diagram of fully turbulent taylor couette flow
arXiv: Fluid Dynamics, 2014Co-Authors: Rodolfo Ostilla Monico, Erwin P Van Der Poel, Roberto Verzicco, Siegfried Grossmann, Detlef LohseAbstract:Direct numerical simulations of Taylor-Couette flow (TC). Shear Reynolds numbers of up to $3\cdot10^5$, corresponding to Taylor numbers of $Ta=4.6\cdot10^{10}$, were reached. Effective scaling laws for the torque are presented. The transition to the ultimate regime, in which asymptotic scaling laws (with logarithmic corrections) for the torque are expected to hold up to arbitrarily high driving, is analysed for different radius ratios $\eta$, different aspect ratios $\Gamma$ and different Rotation ratios $Ro$. It is shown that the transition is approximately independent of $Ro$ and $\Gamma$, but depends significantly on $\eta$. We furthermore calculate the local angular velocity profiles and visualize different flow regimes that depend both on the shearing of the flow, and the Coriolis force originating from the outer Cylinder Rotation. Two main regimes are distinguished, based on the magnitude of the Coriolis force, namely the co-rotating and weakly counter-rotating regime dominated by Rayleigh-unstable regions, and the strongly counter-rotating regime where a mixture of stable and unstable regions exist. Furthermore, an analogy between $\eta$ and outer-Cylinder Rotation is revealed, namely that smaller gaps behave like a wider gap with co-rotating Cylinders, and that wider gaps behave like smaller gaps with weakly counter-rotating Cylinders. Finally, the effect of $\Gamma$ on the effective torque versus $Ta$ scaling is analysed and it is shown that different branches of the torque-versus-$Ta$ relationships associated to different aspect ratios are found to cross within $15%$ of the $Re$ associated to the transition to the ultimate regime. The paper culminates in phase diagram in the inner vs outer $Re$ number parameter space and in the $Ta$ vs $Ro$ parameter space, which can be seen as the extension of the Andereck \emph{et al.} phase diagram towards the ultimate regime.
Dennis R Vigil - One of the best experts on this subject based on the ideXlab platform.
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droplet size distributions in liquid liquid semi batch taylor vortex flow
AIP Advances, 2020Co-Authors: Charlton Campbell, Michael G Olsen, Dennis R VigilAbstract:Optical methods were used to measure droplet size distributions in a liquid–liquid Taylor vortex reactor oriented vertically along its main axis and operated in a semi-batch fashion with continuous feed of the dispersed phase and no feed or removal of the continuous liquid. The effects of two operational parameters on droplet size distributions were considered, including the inner Cylinder angular velocity and the dispersed phase inlet flow rate. Both the mean droplet diameter and the droplet size distribution were found to depend upon the jet Reynolds number and were independent of Cylinder Rotation speed up to the largest azimuthal Reynolds number investigated (60 000). The droplet size distribution underwent a transition from a unimodal distribution at low Cylinder Rotation speeds to a bimodal distribution at intermediate speeds. At the largest Rotation speeds considered, the bimodal distribution became right-skewed. These observations provide support for the hypothesis that the mean droplet size and size distribution are determined primarily by jet breakage dynamics at the tips of inlet nozzles. Furthermore, the mean droplet size data collected from two geometrically distinct reactors can be collapsed onto a universal curve by plotting the Weber number against the jet Reynolds number.
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comprehensive computational model for combining fluid hydrodynamics light transport and biomass growth in a taylor vortex algal photobioreactor lagrangian approach
Bioresource Technology, 2017Co-Authors: Xi Gao, Bo Kong, Dennis R VigilAbstract:A comprehensive quantitative model incorporating the effects of fluid flow patterns, light distribution, and algal growth kinetics on biomass growth rate is developed in order to predict the performance of a Taylor vortex algal photobioreactor for culturing Chlorella vulgaris. A commonly used Lagrangian strategy for coupling the various factors influencing algal growth was employed whereby results from computational fluid dynamics and radiation transport simulations were used to compute numerous microorganism light exposure histories, and this information in turn was used to estimate the global biomass specific growth rate. The simulations provide good quantitative agreement with experimental data and correctly predict the trend in reactor performance as a key reactor operating parameter is varied (inner Cylinder Rotation speed). However, biomass growth curves are consistently over-predicted and potential causes for these over-predictions and drawbacks of the Lagrangian approach are addressed.
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light limited continuous culture of chlorella vulgaris in a taylor vortex reactor
Environmental Progress, 2013Co-Authors: Bo Kong, Dennis R VigilAbstract: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
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axial dispersion during low reynolds number taylor couette flow intra vortex mixing effects
Chemical Engineering Science, 1997Co-Authors: Richard John Campero, Dennis R VigilAbstract:Abstract Tracer experiments were employed to study axial mass transport in a Taylor-Couette device with a radius ratio of 0.875. The inner Cylinder was rotated (with the outer Cylinder fixed) at circumferential Reynolds numbers ranging from 1.05 to 7.50 times the critical value for the onset of laminar Taylor vortex flow. Apparent axial dispersion coefficients were found by fitting a three parameter model to tracer-response data. The model consisted of a network of CSTRs (each with an associated exchange volume) connected in series. The CSTRs corresponded to the well mixed outer layers of the Taylor vortices; the exchange volumes represented poorly mixed vortex cores. For 1.05 ≤ Re Re c , the apparent axial dispersion coefficient increased nonmonotonically with increasing Reynolds numbers. At inner Cylinder Rotation rates Re Re c > 5.0 , the model recovered the commonly used discrete approximation of the one-dimensional diffusion equation.
Roberto Verzicco - One of the best experts on this subject based on the ideXlab platform.
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turbulent taylor couette flow with stationary inner Cylinder
Journal of Fluid Mechanics, 2016Co-Authors: Rodolfo Ostillamonico, Roberto Verzicco, Detlef LohseAbstract:A series of direct numerical simulations were performed of Taylor–Couette (TC) flow, the flow between two coaxial Cylinders, with the outer Cylinder rotating and the inner one fixed. Three cases were considered, where the Reynolds number of the outer Cylinder was $Re_{o}=5.5\times 10^{4}$Reo=5.5×104, $Re_{o}=1.1\times 10^{5}$Reo=1.1×105 and $Re_{o}=2.2\times 10^{5}$Reo=2.2×105. The ratio of radii ${\it\eta}=r_{i}/r_{o}$η=ri/ro was fixed to ${\it\eta}=0.909$η=0.909 to mitigate the effects of curvature. Axially periodic boundary conditions were used, with the aspect ratio of vertical periodicity ${\it\Gamma}$Γ fixed to ${\it\Gamma}=2.09$Γ=2.09. Being linearly stable, TC flow with outer Cylinder Rotation is known to have very different behaviour than TC flow with pure inner Cylinder Rotation. Here, we find that the flow nonetheless becomes turbulent, but the torque required to drive the Cylinders and level of velocity fluctuations was found to be smaller than those for pure inner Cylinder Rotation at comparable Reynolds numbers. The mean angular momentum profiles showed a large gradient in the bulk, instead of the constant angular momentum profiles of pure inner Cylinder Rotation. The near-wall mean and fluctuation velocity profiles were found to coincide only very close to the wall, showing large deviations from both pure inner Cylinder Rotation profiles and the classic von Karman law of the wall elsewhere. Finally, transport of angular velocity was found to occur mainly through intermittent bursts, and not through wall-attached large-scale structures as is the case for pure inner Cylinder Rotation.
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turbulent taylor couette flow with stationary inner Cylinder
arXiv: Fluid Dynamics, 2016Co-Authors: Rodolfo Ostillamonico, Roberto Verzicco, Detlef LohseAbstract:A series of direct numerical simulations of Taylor-Couette (TC) flow, the flow between two coaxial Cylinders, with the outer Cylinder rotating and the inner one fixed, were performed. Three cases, with outer Cylinder Reynolds numbers $Re_o$ of $Re_o=5.5\cdot10^4$, $Re_o=1.1\cdot10^5$ and $Re_o=2.2\cdot10^5$ were considered. The radius ratio $\eta=r_i/r_o$ was fixed to $\eta=0.909$ to mitigate the effects of curvature. The vertical aspect ratio $\Gamma$ was fixed to $\Gamma=2.09$. Being linearly stable, outer Cylinder Rotation TC flow is known to have very different behavior than pure inner Cylinder Rotation TC flow. Here, we find that the flow nonetheless becomes turbulent, but the torque required to drive the Cylinders and level of velocity fluctuations was found to be smaller than those for pure inner Cylinder Rotation at comparable Reynolds numbers. The mean angular momentum profiles showed a large gradient in the bulk, instead of the constant angular momentum profiles of pure inner Cylinder Rotation. The near-wall mean and fluctuation velocity profiles were found to coincide only very close to the wall, showing large deviations from both pure inner Cylinder Rotation profiles and the classic von Karman law of the wall elsewhere. Finally, transport of angular velocity was found to occur mainly through intermittent bursts, and not through wall-attached large-scale structures as is the case for pure inner Cylinder Rotation.
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exploring the phase diagram of fully turbulent taylor couette flow
Journal of Fluid Mechanics, 2014Co-Authors: Rodolfo Ostilla Monico, Erwin P Van Der Poel, Roberto Verzicco, Siegfried Grossmann, Detlef LohseAbstract:Direct numerical simulations of Taylor–Couette flow, i.e. the flow between two coaxial and independently rotating Cylinders, were performed. Shear Reynolds numbers of up to 3×10 5 , corresponding to Taylor numbers of Ta=4.6×10 10 , were reached. Effective scaling laws for the torque are presented. The transition to the ultimate regime, in which asymptotic scaling laws (with logarithmic corrections) for the torque are expected to hold up to arbitrarily high driving, is analysed for different radius ratios, different aspect ratios and different Rotation ratios. It is shown that the transition is approximately independent of the aspect and Rotation ratios, but depends significantly on the radius ratio. We furthermore calculate the local angular velocity profiles and visualize different flow regimes that depend both on the shearing of the flow, and the Coriolis force originating from the outer Cylinder Rotation. Two main regimes are distinguished, based on the magnitude of the Coriolis force, namely the co-rotating and weakly counter-rotating regime dominated by Rayleigh-unstable regions, and the strongly counter-rotating regime where a mixture of Rayleigh-stable and Rayleigh-unstable regions exist. Furthermore, an analogy between radius ratio and outer-Cylinder Rotation is revealed, namely that smaller gaps behave like a wider gap with co-rotating Cylinders, and that wider gaps behave like smaller gaps with weakly counter-rotating Cylinders. Finally, the effect of the aspect ratio on the effective torque versus Taylor number scaling is analysed and it is shown that different branches of the torque-versus-Taylor relationships associated to different aspect ratios are found to cross within 15 % of the Reynolds number associated to the transition to the ultimate regime. The paper culminates in phase diagram in the inner versus outer Reynolds number parameter space and in the Taylor versus inverse Rossby number parameter space, which can be seen as the extension of the Andereck et al. (J. Fluid Mech., vol. 164, 1986, pp. 155–183) phase diagram towards the ultimate regime.
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exploring the phase diagram of fully turbulent taylor couette flow
arXiv: Fluid Dynamics, 2014Co-Authors: Rodolfo Ostilla Monico, Erwin P Van Der Poel, Roberto Verzicco, Siegfried Grossmann, Detlef LohseAbstract:Direct numerical simulations of Taylor-Couette flow (TC). Shear Reynolds numbers of up to $3\cdot10^5$, corresponding to Taylor numbers of $Ta=4.6\cdot10^{10}$, were reached. Effective scaling laws for the torque are presented. The transition to the ultimate regime, in which asymptotic scaling laws (with logarithmic corrections) for the torque are expected to hold up to arbitrarily high driving, is analysed for different radius ratios $\eta$, different aspect ratios $\Gamma$ and different Rotation ratios $Ro$. It is shown that the transition is approximately independent of $Ro$ and $\Gamma$, but depends significantly on $\eta$. We furthermore calculate the local angular velocity profiles and visualize different flow regimes that depend both on the shearing of the flow, and the Coriolis force originating from the outer Cylinder Rotation. Two main regimes are distinguished, based on the magnitude of the Coriolis force, namely the co-rotating and weakly counter-rotating regime dominated by Rayleigh-unstable regions, and the strongly counter-rotating regime where a mixture of stable and unstable regions exist. Furthermore, an analogy between $\eta$ and outer-Cylinder Rotation is revealed, namely that smaller gaps behave like a wider gap with co-rotating Cylinders, and that wider gaps behave like smaller gaps with weakly counter-rotating Cylinders. Finally, the effect of $\Gamma$ on the effective torque versus $Ta$ scaling is analysed and it is shown that different branches of the torque-versus-$Ta$ relationships associated to different aspect ratios are found to cross within $15%$ of the $Re$ associated to the transition to the ultimate regime. The paper culminates in phase diagram in the inner vs outer $Re$ number parameter space and in the $Ta$ vs $Ro$ parameter space, which can be seen as the extension of the Andereck \emph{et al.} phase diagram towards the ultimate regime.
Bamin Khomami - One of the best experts on this subject based on the ideXlab platform.
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direct numerical simulation of taylor couette flow subjected to a radial temperature gradient
Physics of Fluids, 2015Co-Authors: Hao Teng, Xiyun Lu, Bamin KhomamiAbstract:Direct numerical simulations have been performed to study the Taylor-Couette (TC) flow between two rotating, coaxial Cylinders in the presence of a radial temperature gradient. Specifically, the influence of the buoyant force and the outer Cylinder Rotation on the turbulent TC flow system with the radius ratio η = 0.912 was examined. For the co-rotating TC flows with Rei (inner Cylinder) =1000 and Reo (outer Cylinder) =100, a transition pathway to highly turbulentflows is realized by increasing σ, a parameter signifying the ratio of buoyant to inertial force. This nonlinear flow transition involves four intriguing states that emerge in sequence as chaotic wavy vortexflow for σ = 0, wavy interpenetrating spiral flows for σ = 0.02 and 0.05, intermittent turbulent spirals for σ = 0.1 and 0.2, and turbulent spirals for σ = 0.4. Overall, the fluid motion changes from a centrifugally driven flow regime characterized by large-scale wavy Taylor vortices (TVs) to a buoyancy-dominated flow regime characterized by small-scale turbulentvortices. Commensurate changes in turbulence statistics and heat transfer are seen as a result of the weakening of large-scale TV circulations and enhancement of turbulentmotions. Additionally, the influence of variation of the outer Cylinder Rotation, −500 < Reo < 500 in presence of buoyancy (σ = 0.1) with Rei = 1000, has been considered. Specifically, it is demonstrated that this variation strongly influences the azimuthal and axial mean flows with a weaker influence on the fluctuating fluid motions. Of special interest, here are the turbulent dynamics near the outer wall where a marked decrease of turbulence intensity and a sign inversion of the Reynolds stressRrz are observed for the strongly counter-rotating regimes (Reo = − 300 and −500). To this end, it has been shown that the underlying flow physics for this drastic modification are associated with the modification of the correlation between the radial and axial fluctuating motions. In turn, the intriguing effects of this modification on the mean axial flow,turbulent statistics, force balance, and dynamic processes such as turbulence production and dissipation are discussed.
Shingjiang Jessie Lue - One of the best experts on this subject based on the ideXlab platform.
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using a couette taylor vortex flow reactor to prepare a uniform and highly stable li ni0 80co0 15al0 05 o2 cathode material
Journal of Alloys and Compounds, 2021Co-Authors: Manojkumar Seenivasan, Chunchen Yang, Wenchen Chien, Rajan Jose, Shingjiang Jessie LueAbstract:Abstract This study mainly focuses on the preparation technique of Ni-rich NCA hydroxide by a Couette–Taylor flow reactor (CTFR), by systematically optimizing the preparation parameters, including Cylinder Rotation speed and calcination temperature to study its electrochemical performance. Because of the uniform mixing and constant fluid motion of the Taylor vortex, we obtained spherical and uniform Ni0·80Co0·15Al0·05(OH)2 particles. The Rotation speed of the inner Cylinder determined the degrees of particle agglomeration and growth. X-ray diffraction and Rietveld refinement revealed that the sample prepared at 600 rpm had relatively large particles and a high degree of crystallinity; when calcined to 750 °C, it featured much smaller primary particles, a comparatively lower degree of cation mixing, and better layer structure ordering. The Ni-rich LiNi0·80Co0·15Al0·05O2 prepared under the optimal conditions delivered a high discharge capacity of 190.6 mAh g−1 at 0.1C, on par with that of commercially available NCA powders; it also exhibited a remarkable improvement in rate capability, with a discharge capacity of 138 mAh g−1 at 10C (101 mAh g−1 for a commercial sample). In long cycle life tests, the prepared NCA sample retained a high capacity (87.4%) after 100 cycles at 1C, compared with 70.0% for the commercial sample. Furthermore, cyclic voltammetry and electrochemical impedance spectroscopy demonstrated the importance of the calcination temperature on the electrochemical performance and structural stability of our Ni-rich cathodes. Our as-prepared NCA cathode materials, obtained using a CTFR, appear to have great potential for application in Li-ion batteries.
