scholarly journals Pharmaceutical crystallization in Couette-Taylor crystallizer: A case study of polymorphism of amino acid L-glutamic acid

2016 ◽  
Vol 19 (3) ◽  
pp. 11-23 ◽  
Author(s):  
Quang Chau Khuu ◽  
Giang Truong Dang ◽  
Huyen Thi Thanh Trinh ◽  
Tuan Anh Nguyen
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Phase Transformation ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Vortex Flow ◽  
Fluid Motion ◽  
Taylor Vortex ◽  
Cooling Crystallization ◽  
Taylor Vortex Flow

The influence of intensity Taylor vortex flow in Couette-Taylor crystallizer on the crystallization of polymorphic amino acid L-glutamic acid was investigated in cooling crystallization. Here, the L-glutamic acid was chosen as the model crystal product, where it has two kinds of polymorphism including the unstable phase α-form and stable phase β-form crystal. In cooling crystallization, the α-form crystal transformed to the β-form crystal corresponding to the phase transformation of α-form to β-form crystal. The present study found that the selective polymorphism of α-form and β-form crystal as well as the phase transformation significantly depended on the intensity of turbulent Taylor vortex flow in Couette-Taylor crystallizer. Here, the selective β-form nucleation and phase transformation were remarkably promoted as increasing the rotation speed of inner cylinder in Couette-Taylor crystallizer. By comparison with the conventional stirred tank (ST) crystallizer, the Couette-Taylor (CT) crystallizer was at least 2.0 times more effective as regards the selective β-form polymorphism and phase transformation time. The advantage of CT crystallizer over the conventional ST crystallizer was explained in terms of the high shear stress and mass transfer of turbulent Taylor vortex flow in CT crystallizer. Here, the shear stress of Taylor vortex flow in CT crystallizer was at least 23.0 times higher than that of fluid motion in conventional ST crystallizer, whereas the mass transfer of Taylor vortex flow in CT crystallizer was at least 1.2 times higher than that of fluid motion in conventional ST crystallizer. As such, the high turbulent shear stress of Taylor vortex flow was expected to promote the β-form nucleation via the effective molecules alignment, whereas the high mass transfer of Taylor vortex flow facilitated the dissolution rate of α-form and growth rate of β-form crystal, resulting in an acceleration of phase transformation rate.

Experimental Study on Oscillatory Couette-Taylor Flows Behaviour

2013 ◽  
Author(s):  
Emna Berrich ◽  
Fethi Aloui ◽  
Jack Legrand
Keyword(s):  
Mass Transfer ◽  
Angular Velocity ◽  
Time Evolution ◽  
Vortex Flow ◽  
Outer Cylinder ◽  
Taylor Vortex ◽  
Shear Rates ◽  
Taylor Vortices ◽  
Taylor Vortex Flow ◽  
Wall Shear

In the simplest and original case of study of the Taylor–Couette TC problems, the fluid is contained between a fixed outer cylinder and a concentric inner cylinder which rotates at constant angular velocity. Much of the works done has been concerned on steady rotating cylinder(s) i.e. rotating cylinders with constant velocity and the various transitions that take place as the cylinder(s) velocity (ies) is (are) steadily increased. On this work, we concentrated our attention in the case in which the inner cylinder velocity is not constant, but oscillates harmonically (in time) clockwise and counter-clockwise while the outer cylinder is maintained fixed. Our aim is to attempt to answer the question if the modulation makes the flow more or less stable with respect to the vortices apparition than in the steady case. If the modulation amplitude is large enough to destabilise the circular Couette flow, two classes of axisymmetric Taylor vortex flow are possible: reversing Taylor Vortex Flow (RTVF) and Non-Reversing Taylor Vortex Flow (NRTVF) (Youd et al., 2003; Lopez and Marques, 2002). Our work presents an experimental investigation of the effect of oscillatory Couette-Taylor flow, i.e. both the oscillation frequency and amplitude on the apparition of RTVF and NRTVF by analysing the instantaneous and local mass transfer and wall shear rates evolutions, i.e. the impact of vortices at wall. The vortices may manifest themselves by the presence of time-oscillations of mass transfer and wall shear rates, this generally corresponds to an instability apparition even for steady rotating cylinder. On laminar CT flow, the time-evolution of wall shear rate is linear. It may be presented as a linear function of the angular velocity, i.e. the evolution is steady even if the angular velocity is not steady. At a “critical” frequency and amplitude, the laminar CT flow is disturbed and Taylor vortices appear. Comparing to a steady velocity case, oscillatory flow accelerate the instability apparition, i.e. the critical Taylor number corresponds to the transition is smaller than that of the steady case. For high oscillation amplitudes of the inner cylinder rotation, the mass transfer time-evolution has a sinusoidal evolution with non equal oscillation amplitudes. If the oscillation amplitude is large enough, it can destabilize the laminar Couette flow, Taylor vortices appears. The vortices direction can be deduced from the sign of the instantaneous wall shear rate time evolution.

Intercellular mass transfer in wavy/turbulent Taylor vortex flow

1998 ◽  
Vol 19 (2) ◽  
pp. 159-166 ◽  
Author(s):  
Naoto Ohmura ◽  
Tsukasa Makino ◽  
Atsushi Motomura ◽  
Yuichiro Shibata ◽  
Kunio Kataoka
Keyword(s):  
Mass Transfer ◽  
Vortex Flow ◽  
Taylor Vortex ◽  
Taylor Vortex Flow

scholarly journals Hydrodynamic education with rheoscopic fluid

2019 ◽  
Vol 213 ◽  
pp. 02014
Author(s):  
Daniel Duda ◽  
Marek Klimko ◽  
Radek Škach ◽  
Jan Uher ◽  
Václav Uruba
Keyword(s):  
Vortex Flow ◽  
Maximum Stress ◽  
Fluid Motion ◽  
Shear Layers ◽  
Taylor Vortex ◽  
Taylor Vortices ◽  
Taylor Vortex Flow ◽  
Concentric Cylinders ◽  
The Subject

We present a educational poster supporting the subject „Mechanics of fluids I“, which the students evaluate to be difficult mainly due to abstractness. Our goal is to show in vivo the behavior, especially the non-linearity, of various flows transiting into turbulence. The fluid motion is visualized by using the rheoscopic fluid, which consist of water and the dust of mica, whose particles are longitudinal and shiny resulting into easily observable reflections, when the particles coherently orient along the maximum stress. This happens mainly in shear layers, e.g. at the boundary between vortex core and envelope. An example of flow transiting into turbulence is the Taylor-Couette flow between two concentric cylinders, which with increasing Taylor number passes through various regimes from fully laminar bearing flow through the Taylor vortex flow (TVF) and later Wavy vortex flow (WVF) up to Turbulent Taylor vortices regime (TTV) and, finally, the regime of featureless turbulence.

scholarly journals Crystallization in Couette-Taylor Crystallizer: Effect of Taylor Vortices Flow on the Nucleation and Reconstruction of L-Glutamic Acid in Cooling Crystallization

2016 ◽  
Vol 54 (5) ◽  
pp. 625 ◽  
Author(s):  
Huyen Thi Thanh Trinh ◽  
Tuan Anh Nguyen ◽  
Thao Thanh Phan ◽  
Quang Chau Khuu ◽  
Nhan Thi Hong Le ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Energy Dissipation ◽  
Glutamic Acid ◽  
Fluid Motion ◽  
High Energy ◽  
Taylor Vortices ◽  
Cooling Crystallization ◽  
Significant Difference ◽  
High Energy Dissipation

The effect of Taylor vortices flow of Couette-Taylor (CT) crystallizer on the nucleation and reconstruction of L-glutamic acid was firstly investigated in cooling crystallization. Generally, L-glutamic acid has two kinds of polymorphic crystal including metastable α-form and stable β-form, where the α-form is initially crystallized and then slowly transformed into the β-form, which is called the phase transformation. The present study explored that there was a significant difference between CT and the conventional ST crystallizer as regards the nucleation and reconstruction of L-glutamic acid. Here, the phase transformation determined by the nucleation and reconstruction was 40h in ST crystallizer, yet it was only 20h as using the CT crystallizer, implying that the nucleation and reconstruction of L-glutamic acid was facilitated 2.0 times as using the Taylor vortices flow. The advantage of Taylor vortices flow in CT crystallizer over the random fluid motion in ST crystallizer with regard to the nucleation and reconstruction was explained in terms of the high energy dissipation of Taylor vortices flow.

Development and Effects of Super-Critical Taylor-Vortex Flow in a Lightly Loaded Journal Bearing

1974 ◽  
Vol 96 (1) ◽  
pp. 28-35 ◽  
Author(s):  
R. C. DiPrima ◽  
J. T. Stuart
Keyword(s):  
Vortex Flow ◽  
Axial Direction ◽  
Basic Flow ◽  
Circular Cylinders ◽  
Taylor Vortex ◽  
Taylor Vortices ◽  
Taylor Vortex Flow ◽  
Secondary Motion ◽  
The Stability ◽  
Unified Description

At sufficiently high operating speeds in lightly loaded journal bearings the basic laminar flow will be unstable. The instability leads to a new steady secondary motion of ring vortices around the cylinders with a regular periodicity in the axial direction and a strength that depends on the azimuthial position (Taylor vortices). Very recently published work on the basic flow and the stability of the basic flow between eccentric circular cylinders with the inner cylinder rotating is summarized so as to provide a unified description. A procedure for calculating the Taylor-vortex flow is developed, a comparison with observed properties of the flow field is made, and formulas for the load and torque are given.

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