Axial Stream Research Articles

A new approach to live reaction monitoring using active flow technology in ultra-high-speed HPLC with mass spectral detection.

A new type of chromatography column referred to as a parallel segmented flow (PSF) column enables ultra-high-speed high-performance liquid chromatography-MS to be undertaken. This occurs because the separation efficiency obtained on PSF columns has been shown in prior studies to be superior to conventional columns, and the flow stream is split radially inside the outlet end fitting of the column, rather than in an axial post-column flow stream split. As a result, the flow through the column can be five times higher than the flow through the MS. In this work, the degradation of amino acids in dilute nitric acid was used to illustrate the process. Separations were obtained in less than 12 s, although the reinjection process was initiated 6 s after the previous injection. The degradation rate constant of tryptophan, in the presence of tyrosine and phenylalanine, was determined.

A two-dimensional model of He/O2 atmospheric pressure plasma needle discharge**Project supported by the National Natural Science Foundation of China (Grant No. 11465013), the International Science and Technology Cooperation Program of China (Grant No. 2015DFA61800), and the Natural Science Foundation of Jiangxi Province, China (Grant No. 20151BAB212012).

In this paper, a computational modeling study of stream propagation in the atmospheric-pressure helium plasma in ambient atmosphere (oxygen) is presented. A coupled fluid model between time-dependent plasma dynamics and steady state neutral gas flow is employed to provide a fundamental insight into the evolution of the streamers. The obtained simulation results showing that the sheath forms near the dielectric surface and shields the axial stream propagation. The stream front propagates with axial velocity in a range of 104 m/s–105 m/s. And, the increasing accumulated surface charge should be responsible for reducing the propagation velocity of the streamer front in the axial direction. Besides, when the gas flow rate is 1.1 standard liter per minute (SLM), we find that the concentration of oxygen drastically increases at a larger radial position near a treated surface. Therefore, Penning ionization by helium metastables and oxygen peaks at an off-axis position, corresponding to the ring-shaped emission profile in cylindrical coordinates. In this case, the simulated results show the ring-shaped ground atomic oxygen density profile near the treated surface (z = 0.5 mm) at a large gas flow rate of 1.1 SLM, which is consistent with the observation in a similar experiment.

Convective boundary conditions effect on peristaltic flow of a MHD Jeffery nanofluid

This work is aimed at describing the influences of MHD, chemical reaction, thermal radiation and heat source/sink parameter on peristaltic flow of Jeffery nanofluids in a tapered asymmetric channel along with slip and convective boundary conditions. The governing equations of a nanofluid are first formulated and then simplified under long-wavelength and low-Reynolds number approaches. The equation of nanoparticles temperature and concentration is coupled; hence, homotopy perturbation method has been used to obtain the solutions of temperature and concentration of nanoparticles. Analytical solutions for axial velocity, stream function and pressure gradient have also constructed. Effects of various influential flow parameters have been pointed out through with help of the graphs. Analysis indicates that the temperature of nanofluids decreases for a given increase in heat transfer Biot number and chemical reaction parameter, but it possesses converse behavior in respect of mass transfer Biot number and heat source/sink parameter.

Geology of Unaweep Canyon and its role in the drainage evolution of the northern Colorado Plateau

Unaweep Canyon (Colorado, USA) is a large, Precambrian-cored gorge that bisects the Uncompahgre Plateau of the northeastern Colorado Plateau, but has no through-flowing axial stream; it is drained by two underfit creeks (East and West Creek) that head at a divide within the canyon. The history of the canyon and its role in drainage evolution of the Colorado River system remain controversial. New mapping of both bedrock and Quaternary units as well as analyses of Quaternary deposits in and near the canyon shed light on its late Cenozoic history, and call into question whether the canyon was incised by a Cenozoic river, or merely exhumed by one. Gravels near the western mouth of Unaweep Canyon (Gateway, Colorado) exhibit a distinctive intermediate volcanic provenance recording the presence of an ancestral Gunnison River; the youngest gravels are dated to 1.46 ± 0.33 Ma. Previously documented coring within the canyon reveals a thick (locally >330 m) fill that includes a lacustrine succession (∼140 m thick), dated to 1.4–1.3 Ma, overlain by stacked paleosols and a thick (∼160 m) conglomeratic unit emplaced between 1.3 Ma and the present, in addition to a basal unit of possible late Paleozoic age. Lake formation reflects catastrophic mass wasting in western Unaweep Canyon that blocked the ancestral Gunnison River, causing partial backfilling of the canyon, and forcing the river to seek a lower elevation exit eastward by breaching the Mesozoic rim at the northeast end of Cactus Park (Mesa County, Colorado). Ultimately, the ancestral Gunnison River joined the lower elevation Colorado River near Grand Junction by 1.3 Ma, incising the East Creek of Unaweep Canyon during the overspilling event. Thermochronological data from Precambrian basement within Unaweep Canyon and Permian strata at the western mouth of the canyon indicate onset of incision in latest Miocene time (ca. 6–5 Ma), at a time-averaged rate of ∼210–275 m/m.y. Onset of canyon occupation and rapid incision by the ancestral Gunnison River coincided with the timing of integration of the lower Colorado River system to the Gulf of California. The synchroneity of this incision across the Colorado Plateau supports the inference of an ultimate tectonic or epeirorogenic driver for this widespread incision and ultimate drainage integration. Several aspects of this data set support the previously published hypothesis that the ancestral Gunnison River exhumed a paleovalley. New mapping at the western mouth of the canyon documents a paleovalley filled with Permian strata that leads into the modern Precambrian-hosted gorge of Unaweep Canyon. In addition, the ancestral Gunnison River paralleled the Uncompahgre Plateau before making a 90° turn to bisect the structural axis in a manner that opposes both the northwestward plunge of the uplift and the northeastward dip of its northern flank. The rate of incision of Unaweep Canyon exceeds regional time-averaged incision rates, consistent with removal of sedimentary fill rather than incision of crystalline basement. This hypothesis implies that very ancient landforms can influence drainage evolution in even tectonically active landscapes.

ЧИСЕЛЬНЕ МОДЕЛЮВАННЯ РОЗПОДІЛУ ТЕМПЕРАТУРИ В ПОТОЦІ МЕТАНУ В ВИХРОВИЙ ТРУБІ РАНКА-ХІЛША

In present numerical research, the temperature separation in methane stream within a counter flow Ranque-Hilsch vortex tube was investigated. A complete three-dimensional geometry of the vortex tube was used to generate a high-density computational grid. A vortex tube with two tangential inlet nozzles, an axial cold stream outlet and a circumferential hot stream outlet was considered. Methane was used as a fluid along with Peng-Robinson cubic equation of state. Fluid properties like total temperature and total pressure were analyzed for a range of inlet mass flow rates and inlet total pressure values. Also the total pressure and total temperature distribution along the axial direction was investigated. The temperature separation effect is more significant for air then for methane at all investigated pressures. Created model can be used to design industrial vortex tubes for oil and gas industry where methane is a main product.

Peristaltic Creeping Flow of Power Law Physiological Fluids through a Nonuniform Channel with Slip Effect

A mathematical study on creeping flow of non-Newtonian fluids (power law model) through a nonuniform peristaltic channel, in which amplitude is varying across axial displacement, is presented, with slip effects included. The governing equations are simplified by employing the long wavelength and low Reynolds number approximations. The expressions for axial velocity, stream function, pressure gradient, and pressure difference are obtained. Computational and numerical results for velocity profile, pressure gradient, and trapping under the effects of slip parameter, fluid behavior index, angle between the walls, and wave number are discussed with the help of Mathematica graphs. The present model is applicable to study the behavior of intestinal flow (chyme movement from small intestine to large intestine). It is also relevant to simulations of biomimetic pumps conveying hazardous materials, polymers, and so forth.

Models of Invasion and Establishment for African Mustard (Brassica tournefortii)

AbstractIntroduced exotic plants can drive ecosystem change. We studied invasion and establishment ofBrassica tournefortii(African mustard), a noxious weed, in the Chemehuevi Valley, western Sonoran Desert, California. We used long-term data sets of photographs, transects for biomass of annual plants, and densities of African mustard collected at irregular intervals between 1979 and 2009. We suggest that African mustard may have been present in low numbers along the main route of travel, a highway, in the late 1970s; invaded the valley along a major axial valley ephemeral stream channel and the highway; and by 2009, colonized 22 km into the eastern part of the valley. We developed predictive models for invasibility and establishment of African mustard. Both during the initial invasion and after establishment, significant predictor variables of African mustard densities were surficial geology, proximity to the highway and axial valley ephemeral stream channel, and number of small ephemeral stream channels. The axial valley ephemeral stream channel was the most vulnerable of the variables to invasions. Overall, African mustard rapidly colonized and quickly became established in naturally disturbed areas, such as stream channels, where geological surfaces were young and soils were weakly developed. Older geological surfaces (e.g., desert pavements with soils 140,000 to 300,000 years old) were less vulnerable. Microhabitats also influenced densities of African mustard, with densities higher under shrubs than in the interspaces. As African mustard became established, the proportional biomass of native winter annual plants declined. Early control is important because African mustard can colonize and become well established across a valley in 20 yr.

Effects of thermal radiation parameter and magnetic field on the peristaltic motion of Williamson nanofluids in a tapered asymmetric channel

Abstract This paper deals with a theoretical investigation of the peristaltic transport of a Williamson nanofluid in a tapered asymmetric channel under the action of a thermal radiation parameter. In general, the nanofluids are electrically conducting nature. A model of wall-induced fluid flow within an infinite tapered channel has been developed to simulate the transport phenomena due to asymmetric wall displacements. This problem has plentiful applications. Moreover, it may serve as a model for the intrauterine fluid motion in a sagittal cross-section of the uterus under cancer therapy and drug analysis. The analytical solution has been obtained for the temperature and concentration of the nanofluid. The expressions for the axial velocity, stream function and pressure gradient were also obtained by a regular perturbation technique. Numerical computations have been performed for the pressure rise and the effect of various emerging parameters on the flow characteristics are shown and discussed with the help of graphs. The numerical results shown that the trapped bolus was increased in size and more trapped bolus were also occurred near the right wall with increasing Weissenberg number and thermophoresis parameter but that got decreased for large values of local temperature Grashof number.

English

This paper focuses on the behavior of the boundary-layer laminar flow produced by a large radius no-thickness disc which rotates inside an axial stream. Some early solutions are only known for the upstream flow field, but the details of the flow behind the disc are still obscure. A better understanding of the mechanisms and the properties of the shear layer close to disc is sought through the development of an analytic theory and then is completed by CFD computations. This article also shows that the basic flow on the leeward side of disc is mostly rotational-inviscid and only on in the neighborhood of the disc surface there is a viscous layer which rotates drawn by disc. The viscous layer containing a thin Ekman sublayer and a thicker essentially inviscid superlayer, governed by Taylor-Proudman theorem, can carry three possible actions: centrifugal (pumping) mode, neutral mode and centripetal (suction) mode. The action type depends on the relative importance of effects given by translation of the fluid (W) and rotation of the disc (ΩR), defined by a rotating parameter (W/ΩR). The existence of such modes is connected to the amount of angular momentum transferred outside the Ekman sublayer. A CFD analysis was used to identify the vortex structure which is responsible for the angular momentum transfer from the rotating disc to an axial stream.

Hydromagnetic effect on inclined peristaltic flow of a couple stress fluid

In this paper, we have investigated the effect of channel inclination on the peristaltic transport of a couple stress fluid in the presence of externally applied magnetic field. The slip velocity at the channel wall has been taken into account. Under the long wave length and low-Reynolds number assumptions, the analytical solutions for axial velocity, stream function, pressure gradient and pressure rise are obtained. The computed results are presented graphically by taking valid numerical data for non-dimensional physical parameters available in the existing scientific literatures. The results revealed that the trapping fluid can be eliminated and the central line axial velocity can be reduced with a considerable extent by the application of magnetic field. The flow phenomena for the pumping characteristics, trapping and reflux are furthermore investigated. The study shows that the slip parameter and Froude number play an important role in controlling axial pressure gradient.

Exact Solution for Peristaltic Transport of a Micropolar Fluid in a Channel with Convective Boundary Conditions and Heat Source/Sink

This paper investigates the peristaltic transport of an incompressible micropolar fluid in an asymmetric channel with heat source/sink and convective boundary conditions. Mathematical formulation is completed in a wave frame of reference. Long wavelength and low Reynolds number approach is adopted. The solutions for velocity, microrotation component, axial pressure gradient, temperature, stream function, and pressure rise over a wavelength are obtained. Velocity and temperature distributions are analyzed for different parameters of interest

Experimental investigation of acoustic streaming in a cylindrical wave guide up to high streaming Reynolds numbers

Measurements of streaming velocity are performed by means of Laser Doppler Velocimetry and Particle Image Velociimetry in an experimental apparatus consisting of a cylindrical waveguide having one loudspeaker at each end for high intensity sound levels. The case of high nonlinear Reynolds number ReNL is particularly investigated. The variation of axial streaming velocity with respect to the axial and to the transverse coordinates are compared to available Rayleigh streaming theory. As expected, the measured streaming velocity agrees well with the Rayleigh streaming theory for small ReNL but deviates significantly from such predictions for high ReNL. When the nonlinear Reynolds number is increased, the outer centerline axial streaming velocity gets distorted towards the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes. This kind of behavior is followed by outer streaming cells only and measurements in the near wall region show that inner streaming vortices are less affected by this substantial evolution of fast streaming pattern. Measurements of the transient evolution of streaming velocity provide an additional insight into the evolution of fast streaming.

Fast acoustic streaming in standing waves: Generation of an additional outer streaming cell

Rayleigh streaming in a cylindrical acoustic standing waveguide is studied both experimentally and numerically for nonlinear Reynolds numbers from 1 to 30 [Re(NL)=(U0/c0)(2)(R/δν)(2), with U0 the acoustic velocity amplitude at the velocity antinode, c0 the speed of sound, R the tube radius, and δν the acoustic boundary layer thickness]. Streaming velocity is measured by means of laser Doppler velocimetry in a cylindrical resonator filled with air at atmospheric pressure at high intensity sound levels. The compressible Navier-Stokes equations are solved numerically with high resolution finite difference schemes. The resonator is excited by shaking it along the axis at imposed frequency. Results of measurements and of numerical calculation are compared with results given in the literature and with each other. As expected, the axial streaming velocity measured and calculated agrees reasonably well with the slow streaming theory for small ReNL but deviates significantly from such predictions for fast streaming (ReNL>1). Both experimental and numerical results show that when ReNL is increased, the center of the outer streaming cells are pushed toward the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes.

Thermocapillary flow regimes and instability caused by a gas stream along the interface

AbstractWe present the results of a numerical study of the thermocapillary (Marangoni) convection in a liquid bridge of $\mathit{Pr}= 12$ ($n$-decane) and $\mathit{Pr}= 68$ (5 cSt silicone oil) when the interface is subjected to an axial gas stream. The gas flow is co- or counter-directed with respect to the Marangoni flow. In the case when the gas stream comes from the cold side, it cools down the interface to a temperature lower than that of the liquid beneath and in a certain region of the parameter space that cooling causes an instability due to a temperature difference in the direction perpendicular to the interface. The disturbances are swept by the thermocapillary flow to the cold side, which leads to the appearance of axisymmetric waves propagating in the axial direction from the hot to cold side. The mechanism of this new two-dimensional oscillatory instability is similar to that of the Pearson’s instability of the rest state in a thin layer heated from below (Pearson, J. Fluid Mech., vol. 4, 1958, p. 489), and it appears at the value of the transverse Marangoni number ${ \mathit{Ma}}_{\perp }^{cr} \approx 39\text{{\ndash}} 44$ lower than that of the Pearson’s instability in a horizontal layer ($48\lt { \mathit{Ma}}_{\perp }^{cr} \lt 80$, depending on the Biot number). The generality of the instability mechanism indicates that it is not limited to cylindrical geometry and might be observed in a liquid layer with cold gas stream.

Convective Heat Transfer Analysis on Prandtl Fluid Model with Peristalsis

The effects of magnetohydrodynamic (MHD) on peristaltic transport of Prandtl fluid in a symmetric channel have been studied under the assumptions of long wave length and low-Reynolds number. Channel walls are considered compliant in nature. Series solutions of axial velocity, stream function and temperature are given by using regular perturbation technique for small values of Prandtl fluid parameter. The effects of physical parameters on the velocity, streamlines and temperature are examined by plotting graphs.

Convective heat transfer analysis on Prandtl fluid model with peristalsis

The effects of magnetohydrodynamic MHD on peristaltic transport of Prandtl fluid in a symmetric channel have been studied under the assumptions of long wave length and low-Reynolds number. Channel walls are considered compliant in nature. Series solutions of axial velocity, stream function and temperature are given by using regular perturbation technique for small values of Prandtl fluid parameter. The effects of physical parameters on the velocity, streamlines and temperature are examined by plotting graphs.

Flow analysis of acoustic streaming pattern produced by ultrasonic transducer using stereoscopic PIV

Quantitative flow fields from the acoustic streaming were measured experimentally using the stereoscopic PIV. The acoustic streaming pattern between the ultrasonic transducer and stationary plate, maximum acoustic streaming velocity, velocity variation at resonance and non-resonance, variation of flow pattern and velocity with gap variation were experimentally verified. The maximum acoustic velocity between the gap in the open channel at resonance and non-resonance was located at the ultrasonic transducer center at radial direction and at the neighborhood of the ultrasonic transducer at axial direction. In the vicinity of the ultrasonic transducer surface, larger average acoustic velocity occurred at the edge of the transducer than at the transducer center at the resonant gap. At non-resonant gap, the maximum acoustic velocity exists toward the edge of the transducer. The turbulent intensity varied with gap size and maximum value existed at the transducer center with radial direction and at surface of the stationary plate or transducer with axial direction. At resonant gaps, there was almost zero radial acoustic streaming velocity at the ultrasonic transducer center and there existed only axial streaming velocity. For axial directions, maximum acoustic streaming velocity was located at z position of − 16 mm.

Non-steady peristaltic propulsion with exponential variable viscosity: a study of transport through the digestive system

A theoretical study is presented for transient peristaltic flow of an incompressible fluid with variable viscosity in a finite length cylindrical tube as a simulation of transport in physiological vessels and biomimetic peristaltic pumps. The current axisymmetric analysis is qualitatively similar to two-dimensional analysis but exhibits quantitative variations. The current analysis is motivated towards further elucidating the physiological migration of gastric suspensions (food bolus) in the human digestive system. It also applies to variable viscosity industrial fluid (waste) peristaltic pumping systems. First, an axisymmetric model is analysed in the limit of large wavelength () and low Reynolds number () for axial velocity, radial velocity, pressure, hydromechanical efficiency and stream function in terms of radial vibration of the wall (), amplitude of the wave (), averaged flow rate () and variable viscosity (). Subsequently, the peristaltic flow of a fluid with an exponential viscosity model is examined, which is based on the analytical solutions for pressure, wall shear stress, hydromechanical efficiency and streamline patterns in the finite length tube. The results are found to correlate well with earlier studies using a constant viscosity formulation. This study reveals some important features in the flow characteristics including the observation that pressure as well as both number and size of lower trapped bolus increases. Furthermore, the study indicates that hydromechanical efficiency reduces with increasing magnitude of viscosity parameter.

Stratigraphic Architecture of An Experimental Basin With Interacting Drainages

Abstract The stratigraphic architecture of intracontinental rift basins is defined by a dynamic relationship between depositional processes associated with the basin floor and flanking tributary streams. The resulting depositional belts are sensitive to a variety of factors, including basin geometry, subsidence rate, and sediment discharge. The Experimental EarthScape run in 2006 (XES06) examined the development of fluvial morphology and alluvial architecture as a function of subsidence and sediment flux in an experimental basin based on the form of a simple half graben. Sediments from tributary drainages were introduced into the axial stream through toe cutting and realignment of transverse drainage courses to parallel the prevailing axial-flow direction. Transverse sediment contributions to the axial stream were almost equally apportioned over a wide range of sediment discharges tested in the experiments. Sediment tracers showed a larger contribution of footwall-derived sediment into the axial belt, probably due to more frequent and aggressive toe cutting by axial streams. Changes in the axial–transverse deposit boundary to external forcing (by subsidence and sediment discharge), and relatively rapid intrastage stabilization of the depositional belts, resembles the large-scale self-organization observed in moving boundaries that define the morphology of fluviodeltaic systems. Basin sedimentation was matched to subsidence in order to maintain a constant base level, which made the location and width of the axial belt sensitive to the relative sediment fluxes from the transverse systems, rather than the axis of maximum subsidence. The asymmetrical subsidence pattern and the transverse-fan morphology influenced the preservation of sedimentary sequences. Stage-bounding stratigraphic lacunae were well preserved in the hanging-wall succession, providing a reliable record of basin development.

Fluvial Morphology and Sediment-Flux Steering of Axial-Transverse Boundaries In An Experimental Basin

Abstract The distinction between depositional belts associated with the basin axis and flanking piedmont streams is a fundamental attribute of the stratigraphic architecture of intracontinental rift basins. Spatiotemporal distributions of these lithofacies associations are sensitive to a combination of factors, including basin geometry, subsidence rate, and sediment discharge; however, most studies have focused on one or two controls and one depositional component (axial or tributary) of the basin-fill succession. A new perspective on how these depositional belts develop under simple but precisely controlled boundary conditions of steady subsidence, sediment flux, and water discharge is achieved through the creation of an experimental stratigraphic succession. The Experimental EarthScape run in 2006 (XES06) focused on the geomorphic evolution of sedimentary successions within an asymmetrically subsiding basin, analogous to a simple half graben, containing four interacting supply points of sediment and water. Under the imposed conditions, the experimental system self-organized into an axial stream flanked by transverse fans. Imposition of various combinations of longitudinal and lateral sediment flux showed that the locations and widths of the axial and transverse systems were strongly controlled by relative sediment fluxes (“flux steering”), and less influenced by the location of the subsidence maximum and subsidence rate. The axial drainage was dominated by transversely sourced sediment through toe cutting of the transverse fans, except during the highest axial-sediment discharges. Footwall fans persisted even under conditions of very large axial-sediment discharge, aided by topographic inheritance of the steeper transverse depositional slopes.