Extra Vortex Research Articles

Vortex flow reactor assessment for the purification of monoclonal antibodies from unclarified broths

The vortex flow reactor (VFR) can be used in many chemical engineering applications. This paper assesses its novel use in the purification of monoclonal antibodies from cell broth. To this end, the IgG2a antibody was purified from the unclarified fermentation broth of transgenic mouse 55/6 hybridoma cells. Visual experiments showed that the VFR worked in the laminar vortices flow regime and the vortices displaced slightly faster than the axial flow. The VFR has the advantage of creating two sorts of flows: axial flow to produce the expanded bed and an extra vortex flow to avoid channeling and stabilize the expanded bed, the hydrodynamic behavior of which is plug flow with an experimental Pèclet number higher than 20. The pH was adjusted in the untreated fermentation broth, which was directly introduced into the reactor thus reducing the number of stages. The IgG2a purification was carried out in a single device via two steps: antibody adsorption in the expanded bed and antibody elution in the settled bed using Streamline rProtein A. A thirty-fold increase in the high-purity antibody concentration was achieved at the top of the pH5 elution peak with a total recovery of 93.1% (w/w) between elution peaks pH 5 and 3.

Peregrine Falcon’s Dive: Pullout Maneuver and Flight Control Through Wing Morphing

During the pullout maneuver, peregrine falcons were observed to adopt a succession of specific flight configurations that are thought to offer an aerodynamic advantage over aerial prey. Analysis of the flight trajectory of a falcon in a controlled environment shows it experiencing load factors up to , and further predictions suggest this could be increased up to almost during high-speed pullout. This can be attributed to the high maneuverability promoted by lift-generating vortical structures over the wing. Wind-tunnel experiments on life-sized models in the different configurations together with high-fidelity computational fluid dynamics simulations (large-eddy simulations) show that deploying the hand wing in a pullout creates extra vortex lift, which is similar to that of combat aircraft with delta wings. The aerodynamic forces and the position of the aerodynamic center were calculated from the simulations of the flow around the different configurations. This allowed for an analysis of the longitudinal static stability in the early pullout phase, confirming that the falcon is flying unstably in pitch with a positive slope in the pitching moment and a trim angle of attack of about 5 deg, which is possibly to maximize responsiveness. The hand wings/primaries were seen to contribute to the augmented stability, acting as “elevons” would on a tailless blended-wing/body aircraft.

Interaction of tip vortex and laminar separation bubble over wings with different aspect ratios under low Reynolds numbers

In present study, aerodynamics of a NACA4412 wings with aspect ratio of 1 and 3 was considered experimentally at Reynolds numbers of 2.5 × 104, 5 × 104 and 7.5 × 104. Studies for AR = 1 wing showed that stall was delayed and extra (vortex) lift was obtained, because separation bubble got smaller in both chordwise and spanwise axes with effect of wing-tip vortices. Oil-flow experiments at higher angles of attack clarified the reason for vortex lift obtained from AR = 1 wing. However, there was an increase in drag coefficient as well as vortex lift, and stall delayed due to tip vortex. Turbulence intensity distributions pointed out location of the transition to turbulence; Reynolds stress and turbulence kinetic energy distributions indicated shear layer. Furthermore, in experiments of AR = 3 wing, the viscous forces and leading edge vortices were effective at Re = 2.5 × 104 and Re = 5 × 104, but flow over the wing at Re = 7.5 × 104 acted as a 2D flow. After α = 12°, bubble burst and stall consisted abruptly because effectiveness of 3D flow decreased over wing. Strouhal (St) numbers of vortex shedding frequencies in wake of AR = 3 wing had a certain difference from St = 0.17/sinα curve at lower angle of attack (α = 0° − 10°) due to separation bubble, but AR = 1 wings showed that St numbers were near St = 0.17/sinα curve.

Effects of blade rotation on axial turbine tip leakage vortex breakdown and loss

The tip leakage vortex breakdown occurs under a few conditions in modern turbines, which leads to extra vortex breakdown losses, but the mechanisms of vortex breakdown and its influencing factors still remain unclear. This paper is a continuation of the previous effort and focuses on the effect of blade rotation on the leakage vortex dynamics in an unshrouded turbine. The analyses on leakage vortex breakdown characteristics are first shown, and then the isolating effects of relative casing motion and Coriolis and centrifugal forces on leakage vortex breakdown and loss are investigated. Based on these, the overall effects of blade rotation on leakage vortex breakdown characteristics are examined. Results indicate that the scraping effects of the casing endwall have a great influence on the blade tip leakage vortex breakdown and loss. However, the effect of Coriolis and centrifugal forces is relatively small. Although the mismatch of both velocity components of the leakage flow and the main flow becomes slightly small with the casing motion, the blade tip mixing loss per unit leakage flow increases due to the fact that the leakage vortex breaks down in advance.

Inlet conditions effect on tip leakage vortex breakdown in unshrouded axial turbines

The TLV (tip leakage vortex) breakdown occurs under some conditions in modern turbines, which leads to extra vortex breakdown losses, but the mechanisms of vortex breakdown and its influencing factors remain unclear. This paper computationally investigates the effects of inlet conditions on the TLV dynamics in an unshrouded turbine. The TLV dynamics analysis is first shown, and then the effects of inlet CBL (casing boundary layer) parameters and flow incidence on the TLV breakdown and loss are investigated respectively. Based on these, a comparison of effects of different inlet conditions on tip leakage mixing loss is examined. Results indicate that the increased CBL thickness and turbulence intensity increases the adverse-pressure gradient in the rear part of the blade tip in varying degrees, but has a minor effect on TLV breakdown location. An increased incidence leads both to the reduction of the initial streamwise velocity on the vortex core and the adverse-pressure gradient in the rear part of the blade tip. Overall, as the incidence increases, the TLV breakdown location moves first upstream and then downstream. All these mean that the TLV initial state is another influencing factor on its breakdown.

Impact of phase on collision between vortex solitons in three-dimensional cubic-quintic complex Ginzburg-Landau equation.

We present a systematic analysis for three generic collisional outcomes between stable dissipative vortices with intrinsic vorticity S = 0, 1, or 2 upon variation of relative phase in the three-dimensional (3D) cubic-quintic complex Ginzburg-Landau equation. The first type outcome is merger of the vortices into a single one, of which velocity can be effectively controlled by relative phase. With the increase of the collision momentum, the following is creation of an extra vortex, and its velocity also increases with growth of relative phase. However, at largest collision momentum, the variety of relative phase cannot change the third type collisional outcomes, quasielastic interaction. In addition, the dynamic range of the outcome of creating an extra vortex decreases with the reduction of cubic-gain. The above features have potential applications in optical switching and logic gates based on interaction of optical solitons.

On the Study of Magneto-Hydrodynamic Non-Newtonian Fluid Flow throughout Curvilinear Channel with Corrugated Walls

This article aims to numerically investigate the flow pattern for Newtonian and power law non-Newtonian fluid in a semi-half circular channel with corrugated walls under the influence of a magnetic field. The results indicate that, presence of a magnetic field affects the flow field in several aspects, especially in the vortex creation and dissipation. In addition, the analysis is carried out for different Reynolds numbers to ascertain the influence of magnetic field on each flow regime. Eventually, the analysis is carried out for a range of power indices including pseudo plastic (shear-thinning) to dilatants (shear-thickening) fluids. The results show that by increasing the power-index, the vortices begin to form and grow gradually so that in the shear-thickening fluid an extra vortex is formed and created nearby the corrugated part of the channel.

MIPAS-STR measurements in the Arctic UTLS in winter/spring 2010: instrument characterization, retrieval and validation

Abstract. The mid-infrared FTIR-limb-sounder Michelson Interferometer for Passive Atmospheric Sounding–STRatospheric aircraft (MIPAS-STR) was deployed onboard the research aircraft M55 Geophysica during the RECONCILE campaign (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) in the Arctic winter/spring 2010. From the MIPAS-STR measurements, vertical profiles and 2-dimensional vertical cross-sections of temperature and trace gases are retrieved. Detailed mesoscale structures of polar vortex air, extra vortex air and vortex filaments are identified in the results at typical vertical resolutions of 1 to 2 km and typical horizontal sampling densities of 45 or 25 km, depending on the sampling programme. Results are shown for the RECONCILE flight 11 on 2 March 2010 and are validated with collocated in-situ measurements of temperature, O3, CFC-11, CFC-12 and H2O. Exceptional agreement is found for the in-situ comparisons of temperature and O3, with mean differences (vertical profile/along flight track) of 0.2/−0.2 K for temperature and −0.01/0.05 ppmv for O3 and corresponding sample standard deviations of the mean differences of 0.7/0.6 K and 0.1/0.3 ppmv. The comparison of the retrieved vertical cross-sections of HNO3 from MIPAS-STR and the infrared limb-sounder Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere–New Frontiers (CRISTA–NF) indicates a high degree of agreement. We discuss MIPAS-STR in its current configuration, the spectral and radiometric calibration of the measurements and the retrieval of atmospheric parameters from the spectra. The MIPAS-STR measurements are significantly affected by continuum-like contributions, which are attributed to background aerosol and broad spectral signatures from interfering trace gases, and are important for mid-infrared limb-sounding in the Upper Troposphere/Lower Stratosphere (UTLS) region. Taking into consideration continuum-like effects, we present a scheme suitable for accurate retrievals of temperature and an extended set of trace gases, including the correction of a systematic line-of-sight offset.

Large-Eddy Simulation of Shallow Water Langmuir Turbulence Using Isogeometric Analysis and the Residual-Based Variational Multiscale Method

Abstract We develop a residual-based variational multiscale (RBVMS) method based on isogeometric analysis for large-eddy simulation (LES) of wind-driven shear flow with Langmuir circulation (LC). Isogeometric analysis refers to our use of NURBS (Non-Uniform Rational B-splines) basis functions which have been proven to be highly accurate in LES of turbulent flows (Bazilevs, Y., et al. 2007, Comput. Methods Appl. Mech. Eng., 197, pp. 173–201). LC consists of stream-wise vortices in the direction of the wind acting as a secondary flow structure to the primary, mean component of the flow driven by the wind. LC results from surface wave-current interaction and often occurs within the upper ocean mixed layer over deep water and in coastal shelf regions under wind speeds greater than 3 m s−1. Our LES of wind-driven shallow water flow with LC is representative of a coastal shelf flow where LC extends to the bottom and interacts with the sea bed boundary layer. The governing LES equations are the Craik-Leivobich equations (Tejada-Martínez, A. E., and Grosch, C. E., 2007, J. Fluid Mech., 576, pp. 63–108; Gargett, A. E., 2004, Science, 306, pp. 1925–1928), consisting of the time-filtered Navier-Stokes equations. These equations possess the same structure as the Navier-Stokes equations with an extra vortex force term accounting for wave-current interaction giving rise to LC. The RBVMS method with quadratic NURBS is shown to possess good convergence characteristics in wind-driven flow with LC. Furthermore, the method yields LC structures in good agreement with those computed with the spectral method in (Thorpe, S. A., 2004, Annu. Rev. Fluids Mech., 36, pp. 584 55–79) and measured during field observations in (D’Alessio, S. J., et al., 1998, J. Phys. Oceanogr., 28, pp. 1624–1641; Kantha, L., and Clayson, C. A., 2004, Ocean Modelling, 6, pp. 101–124).

Spatially-resolved heat transfer characteristics in channels with pin fin and pin fin-dimple arrays

A comparative study has been conducted to investigate the spatially-resolved heat transfer characteristics of air turbulent flow in rectangular channels with pin fin and pin fin-dimple arrays. A combined method of experiments and numerical computation was adopted to obtain the spatially-resolved Nusselt numbers on the endwall surface of the pin fin and pin fin-dimple channels. Compared with the pin fin channel, the pin fin-dimple channel shows distinctive local heat transfer characteristics on the endwall beneath the main flow and the wake flow region. Due to the presence of the dimples in the pin fin arrays, extra strong vortex flows are generated near the wall beneath the main flow region downstream the dimples, which distinctively increase the turbulent mixing there and enhance the heat transfer rates; however the turbulent mixing in the wake of the pin fins is reduced appreciably, which leads to decreased heat transfer rates in the wake especially at relatively low Reynolds number. Overall, the dimples in the pin fin arrays increase not only the averaged heat transfer coefficient, but also the heat transfer area on the endwall.

An efficient micromixer based on multidirectional vortices due to baffles and channel curvature.

An efficient planar micromixer based on multidirectional vortices in a curved channel with radial baffles is proposed and examined in this work. The curvature of the microchannel and the radial baffles induce vortices in different directions. The multidirectional vortices and the converging-diverging flow caused by the baffles contribute together to the enhancement of mixing. The micromixer is fabricated with polydimethylsiloxane by a single planar microlithography process and the mixing behaviors are observed by a confocal spectral microscope imaging system to validate the simulation obtained by a commercial code. The simulation and experimental results are in reasonable agreement. The concentration distributions and flow patterns obtained reveal the following trends. (i) The mixing efficiency of the basic C-shaped micromixer with the first baffle attached to the internal cylinder and the second attached to the external cylinder is better than that of the C-shaped micromixer with inverted arrangement of baffles. (ii) When the radius of the curved channel and the width of the passage between the baffle and the cylindrical wall are small enough and the Reynolds number (Re) is large enough, an extra separation vortex develops in the downstream of the second baffle. This phenomenon is one of the reasons of trend (i). (iii) A micromixer consisting of a few basic C-shaped micromixers connected by straight channels may generate a high degree of mixing for the case with a large Re.

Bifurcations, stability, and dynamics of multiple matter-wave vortex states

In the present work, we offer a unifying perspective between the dark soliton stripe and the vortex multipole (dipole, tripole, aligned quadrupole, quintopole, etc.) states that emerge in the context of quasi-two-dimensional Bose-Einstein condensates. In particular, we illustrate that the multivortex states with the vortices aligned along the (former) dark soliton stripe sequentially bifurcate from the latter state in a supercritical pitchfork manner. Each additional bifurcation adds an extra mode to the dark soliton instability and an extra vortex to the configuration; moreover, the bifurcating states inherit the stability properties of the soliton prior to the bifurcation. The critical points of this bifurcation are computed analytically via a few-mode truncation of the system, which clearly showcases the symmetry-breaking nature of the corresponding bifurcation. We complement this small(-er) amplitude, few mode bifurcation picture, with a larger amplitude, particle-based description of the ensuing vortices. The latter enables us to characterize the equilibrium position of the vortices, as well as their intrinsic dynamics and anomalous modes, thus providing a qualitative description of the nonequilibrium multivortex dynamics.

Slow collisions of Bose–Einstein condensates in both ground and excited states

We study the dynamics of merging two initially independent Bose–Einstein condensates by adiabatically deforming the trap potential from a double well into a single well. The process of slowly decreasing the height of the central barrier of the double well is simulated by a full 3D calculation of the Gross–Pitaevskii equation. We investigate the dynamics by considering some factors relevant to experiments, e.g., the atom number, the initial state in each well, the initial relative phase between the two condensates. For a small number of 4400 atoms in each well and the same initial phase, we find for both condensates in the ground state or the p-wave soliton state that the final state is the ground state or the p-wave soliton state of the final trap potential. For cases in which both condensates are vortex states, we find much richer dynamics with the appearance of an extra vortex. We also discuss the cases for different initial relative phases. For comparison, we present results for 44 000 atoms corresponding to a larger nonlinear term in the Gross–Pitaevskii equation. In support of future experimental observations, we show both probability density and current maps.

Experimental Blowout Limits and Computational Flow Field of Axial Single and Multijet Flames

Measurements of the lean blowout equivalence ratio (Φoverall,b) along with the numerical simulations of flame structure and dynamics of the flow field for coaxial burner configurations are reported. The burner comprises central mixture (air+liquefied petroleum gas) issuing either through six holes distributed radially each of 2mm diameter or through a circular single port of area equal to the total areas of the six holes. A bluff-body stabilizer is attached to provide recirculation of the coaxial air surrounding the central flame. The study covers the effect of the central injection configuration with emphasis on the multijet on the overall lean equivalence ratio at which flame is extinguished. The dynamics of the flow field for the multiflame configurations were identified and compared with the single flame, using the generalized finite-rate chemistry model of FLUENT 6.2 with the detailed chemical reaction mechanism defined by GRI-MECH 3.0 and other mechanisms for the higher carbon species. The computed flow field of the multijet flame provides an extra intermediate vortex in addition to the two counter-rotating vortices observed for cases of the single central stream configuration. Such a vortex is believed to enhance the stability characteristics for all the test flames in the form of reduced experimental Φoverall,b-values.

Critical currents for vortex defect motion in superconducting arrays

We study numerically the motion of vortices in two-dimensional arrays of resistively shunted Josephson junctions. An extra vortex is created in the ground states by introducing novel boundary conditions and made mobile by applying external currents. We then measure critical currents and the corresponding pinning energy barriers to vortex motion, which in the unfrustrated case agree well with previous theoretical and experimental findings. In the fully frustrated case our results also give good agreement with experimental ones, in sharp contrast with the existing theoretical prediction. A physical explanation is provided in relation with the vortex motion observed in simulations.

The extraordinary events of the major, sudden stratospheric warming, the diminutive antarctic ozone hole, and its split in 2002

Great interest in the unprecedented events of the major, sudden stratospheric warming and the ozone hole split over Antarctica in September 25, 2002 motivates a necessity to analyze the current understanding on the dynamics, chemistry and climate impacts that are associated with both events. Significant progress in the analysis of the observational data obtained, as well as successful development and application of dynamical modeling, which have been achieved very recently, create a basis for the first survey on the role of the major, sudden stratospheric warming observed in the southern hemisphere and its relationship to the diminutive Antarctic ozone hole and its break up into two parts. Special attention has been paid to assessments of the causes of the major warming event and the future expectations concerning the stratospheric ozone depletion effect. Among the principal results is the fact that, as the polar vortex elongated, it became hydrodynamically unstable, and this insta-, bility affected the upper troposphere and stratosphere. During the major, sudden stratospheric warming, the middle stratospheric vortex split into two pieces; one piece rapidly mixed with extra vortex air, while the other returned to the pole as a much weaker and smaller vortex. The polar night jet was considerably weaker than normal, and was displaced more poleward than has been observed in previous winters, resulting from a series of wave events (propagated from the troposphere) that took place over the course of the winter. Finally, the relative ozone decrease (increase) in the eastern Antarctic is tightly associated with westerly (easterly) zonal wind anomalies near the southern tip of South America, and the unusual behavior of the ozone hole in 2002 therefore appears to be caused by great easterlies in this region. The main conclusion is that the southern polar vortex and the diminutive ozone hole split into two parts in September 2002, due to the prevalence of very strong planetary waves, led to the appearance of a major, sudden stratospheric warming. Although there is evidence that sea surface temperature anomalies contributed to the excitation of the quite strong planetary waves over Antarctica in 2002, there is not yet a widely approved mechanism supporting that. The appearance of the near-record size of the 2003 ozone hole confirmed that the 'no-ozone-hole' episode observed in the year 2002 does not denote a recovery of the ozone layer. Despite the current successful attempts to get a sufficient understanding for the genesis of both extraordinary events, more observations and further modeling efforts are necessary to more reliably assess the contribution of various dynamic mechanisms to the recently observed tropo-stratospheric surprises.

Simulation of Planar Entrance Flow Using Strain-Rate-Dependent Shear and Elongational Viscosities

A finite element simulation of the flow in a planar channel with an abrupt contraction is presented. The effect of the elongational viscosity of a polymer on the entrance flow is analyzed employing a truncated power-law model. The power-law index and the strain rate characterizing the transition from Newtonian to power-law behavior for the elongational viscosity are treated as being independent of the values of these two parameters for the shear viscosity. The effect of flow rate on planar entrance flow is also analyzed. It is confirmed that Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow. Extra pressure loss and vortex length predicted by a finite element simulation of a planar entrance loss are compared with the corresponding predictions from Binding’s approximate analysis.

Simulation of Planar Entrance Flow Using Strain-Rate-Dependent Shear and Elongational Viscosities

A finite element simulation of the flow in a planar channel with an abrupt contraction is presented. The effect of the elongational viscosity of a polymer on the entrance flow is analyzed employing a truncated power-law model. The power-law index and the strain rate characterizing the transition from Newtonian to power-law behavior for the elongational viscosity are treated as being independent of the values of these two parameters for the shear viscosity. The effect of flow rate on planar entrance flow is also analyzed. It is confirmed that Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow. Extra pressure loss and vortex length predicted by a finite element simulation of a planar entrance loss are compared with the corresponding predictions from Binding’s approximate analysis.

Effect of elongational viscosity on axisymmetric entrance flow of polymers

AbstractA finite element simulation of the flow in a channel with an abrupt contraction is presented. The effects of the shear and elongational viscosities of a polymer on the entrance flow are analyzed employing a truncated power‐law model. The power‐law index and the strain rate characterizing the transition from Newtonian to power‐law behavior for the elongational viscosity are treated as being independent of the values of these two parameters for the shear viscosity. The effect of flow rate on entrance flow is also analyzed. It is confirmed that the Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow. Extra pressure loss and vortex length predicted by a finite element simulation of entrance loss are compared with the corresponding predictions from Binding's approximate analysis.

Existence of extra vortex and twin vortex of anomalous mode in Taylor vortex flow with a small aspect ratio

This experimental work on Taylor vortex flow in a gap with a small aspect ratio is concerned with two extra vortices and a twin vortex system, each of which depends on an anomalous cell of the anomalous mode. Extra vortices are smaller than other vortices such as defined cells. At any Reynolds number and aspect ratio extra vortices can be found at the corner of the end plate and inner rotating cylinder and at the corner of the end plate and outer stationary cylinder. For a one-cell flow (anomalous one-cell mode) in a symmetric system, an outer extra vortex develops and grows to the same size as the main cell, only in an aspect ratio of less than one. A twin vortex is observed to form when two vortices are aligned in the direction of the radius. There are three flow fields on the end plate; two are extra vortex flows and the other is the main cell flow. The flow direction of the anomalous cell is from the inner cylinder to the outer one, at the end plate opposite of the flow direction of the normal cell.