Circular Flow Pattern Research Articles

Control of light-induced torque in quantum well waveguides through electron spin coherence

We explore the mechanical effects of light interacting with a quantum well waveguide, specifically focusing on the emergence of quantized torque. We investigate the response of the waveguide to the influence of two intense coupling fields in conjunction with two weaker fields. We find that the electron spin coherence plays a crucial role in amplifying the torque applied to the waveguide emitters. This heightened torque, in turn, triggers a distinctive circular current flow pattern within the waveguide. Furthermore, we explore different scenarios for modulating the torque by adjusting system parameters, thereby establishing a means to control current flow. The emergence of a light-induced quantized torque not only illuminates the interplay between quantum emitters and electromagnetic fields but also opens up exciting possibilities for innovative approaches to govern induced-torque behavior within quantum well waveguides.

Investigation of the unsteady pressure fluctuation mechanism in a regenerative flow pump based on proper orthogonal decomposition

The regenerative flow pump (RFP) derives its name from the circular flow pattern akin to a vortex. However, the presence of numerous vortices results in highly turbulent flow and pressure fluctuation. This study delves into the characteristics of the internal unsteady flow in two distinct RFP models featuring different blade shapes. Numerical simulations are employed to obtain the pressure field, which is subsequently scrutinized using the proper orthogonal decomposition (POD) method. The results show that the average pressure in the peripheral direction undergoes minimal variation during the flow developing stage, experiences a sharp increase in the fully developed stage, and finally exhibits substantial changes in the stripper. The transient pressure in the time domain fluctuates periodically, and the dominant blade passing frequency in the frequency domain demonstrates a similar trend along the circumferential direction as the average pressure. Moreover, the fluctuating intensity of pressure diminishes along the impeller's rotating direction but intensifies significantly in the stripper. Comparative analysis indicates that the exchange intensity is influenced by the flow at different developmental stages, and the exchange flow conditions could reflect the fluctuating intensity. Furthermore, the study reveals that the frequency amplitude of the time coefficient gradually decreases as the mode order increases. The first and second modes exhibit a gradually changing trend associated with pressure increase patterns, whereas the third and fourth modes highlight the emergence of localized modulation phenomena linked to exchange flow. Thus, the POD method offers a unique perspective for comprehending the flow mechanisms within RFPs.

Cooperative Roundabout Control Strategy for Connected and Autonomous Vehicles

Intersections in the urban network are potential sources of traffic flow inefficiency. Existing intersection control mostly adopts the “cross” flow pattern model, while the use of the roundabout circular flow pattern is rather sparse. Connected and autonomous vehicle (CAV) technologies can enable roundabouts to better compete with traditional intersection designs in terms of performance. This study proposes a roundabout control strategy for CAVs to enhance intersection performance while ensuring vehicle safety. A hierarchical framework is developed to decouple the flow-level performance objective and vehicle-level safety constraints to achieve computational tractability for real-time applications. It entails developing a roundabout flow control model to optimize merge-in flows, a merge-in decision model to generate vehicle passing sequence from the optimal flows, and a virtual platoon control model to achieve safe and stable vehicle operations in a circular roundabout platoon. The performance of the proposed roundabout control strategy is illustrated through numerical studies and compared to existing intersection control methods. Its stability and safety characteristics are also demonstrated.

COMPARISON OF SUB-GRID-SCALE MODELS BASED ON PREDICTION OF COHERENT STRUCTURES IN PLANE TURBULENT JETS

A compressible plane jet at Mach 0.9 is numerically studied by large-eddy simulation. The governing equations are discretized by fourth-order spatial and third-order temporal schemes. Five sub-grid-scale (SGS) models, namely, the standard Smagorinsky model (SM), the coherent structure kinetic model (CKM) and the selective mixed-scale model (SMSM), the localized dynamic Smagorinsky model (LDSM), and the coherent-structure Smagorinsky model (CSM), are employed for closure of the sub-grid scale (SGS) terms, respectively, and compared. Proper orthogonal decomposition (POD) method is applied to extract the leading modes of the fluctuating velocity components, i.e., \begin{document}$u'$\end{document} in the streamwise, \begin{document}$v'$\end{document} in the lateral and \begin{document}$w'$\end{document} in the spanwise. The averaged flow fields, dissipation, the instantaneous vortical structures and the coherent structures represented by the leading POD modes, are compared. The leading POD modes of \begin{document}$u'$\end{document} are two longitudinal stripes with fracted contours in the turbulent region, representing the multi-scaled flow and the decay of fluctuation strength. The leading modes of \begin{document}$v'$\end{document} are a row of ribs with the lateral size growing along the streamwise, while the modes of \begin{document}$\left( {u', v'} \right)$\end{document} are in a circular flow pattern around the ends of the ribs. The circular pattern penetrates both the jet flow and the peripheral flow, representing the flow entrainment. The leading modes of \begin{document}$w'$\end{document} are a train of ridges along streamwise. Their positive and negative values represent the spanwise stretching pattern of the coherent structures. In comparison of these five SGS models, the instantaneous multi-scale vortical flow is not effectively predicted by the SM and the CKM, as the small vortical scale is smeared. The POD modes are found to be sensitive to the sub-grid dissipation, since the valley regions of the mode of \begin{document}$u'$\end{document} coincide with the peak dissipation regions predicted by the CKM. The circular flow pattern is also not clearly predicted by the CKM. Neither the ridge pattern of the mode of \begin{document}$w'$\end{document} is predicted by the SM. On the other hand, the multi-scales turbulent flow and the flow patterns of POD modes are well predicted by the CSM, the SMSM, and the LDSM, in which the CSM is computationally more efficient.

A Novel Method to Gently Mix and Uniformly Suspend Particulates for Automated Assays.

The SpinVessel system provides a methodology using pulsed radial flow to gently mix and uniformly suspend particulates (cells, magnetic beads, silica beads, and microcarrier beads) for automated assays. SpinVessels are well suited for aliquoting on robotic liquid handlers and with robotic reagent dispensers, as well as manually. The SpinVessel system combines two critical features: (1) special internal side fins and projections in the bottom of the vessels and (2) an instrument that quickly spins the vessels and repeatedly reverses the spin direction. This rapid reversing motion sends multiple pulses of fluid up the side walls of the SpinVessel, creating a circular radial flow pattern. We tested five different particulates and six different SpinVessels with volume capacities varying from 50 mL to 1200 mL. SpinVessels are compatible with either single-, 8-, 12-, 96-, or 384-channel pipettors or with siphon tubing on robotic reagent dispensers. Experiments have demonstrated high viability of cells and undamaged morphology of microcarrier beads even after hours of constant agitation. The uniformity of aliquots collected at various vertical depths and horizontally across the SpinVessels demonstrated that cells, magnetic beads, and silica beads were uniformly suspended throughout the height and breadth of the SpinVessels, and uniformity of samples was consistent from the beginning to the end of the aliquoting procedure. Only 5 min of mixing is required to resuspend settled particulates. This novel mixing methodology has many applications in laboratory automation where particulate aliquot uniformity and/or particulate integrity are important to automating assays.

Peristaltic flows: A quantitative measure for the size of a bolus

In this paper, we give an exact definition for the size of a bolus sb (a circular flow pattern developed in peristaltic flows) based on the area of the outermost closed streamline around an equilibrium (or stagnation) point. The detailed analytical and numerical working of the proposed definition is given with the aid of some examples. It is shown that there is little difference between the analytical and numerical results, however, the analytical implementation involves much more effort than is required in the numerical implementation. We also show that the proposed definition works better than the conventional approaches where the size of a bolus is usually inferred by visually inspecting the contour plots of a stream function. The proposed definition can serve as a basis for the development of mathematical framework which can be used to investigate the quantitative effects of various flow parameters on the size of a bolus.

Rearing juvenile brown Salmo trutta (L.), and rainbow trout Oncorhynchus mykiss (Walbaum), in earthen ponds with and without an induced current

ABSTRACT Because moderate sustained exercise enhances growth in salmonids, we investigated whether paddle-wheel aerators (PWAs) used to provide juvenile brown and rainbow trout with conditions for sustained swimming can increase growth. On site a commercial farm, earthen ponds were provided with PWA and flow patterns recorded or ponds left without PWA. Growth was determined periodically and proximate body composition analyzed at 111 (rainbow trout) and 169 (brown trout) days. The PWA created circular flow patterns with a range of current speeds. First results show that brown trout reared with current had higher protein and lower fat. Rainbow trout reared with current had higher ash, lower fat, and lower energy. The current affected growth in weight of rainbow trout, while no effects on growth were observed in brown trout. PWA can also be used to create a circular flow pattern, allowing for volitional exercise at no or minor additional costs.

Unified Description of the Classical Hall Viscosity.

In the absence of time-reversal symmetry, viscous electron flow hosts a number of interesting phenomena, of which we focus here on the Hall viscosity. Taking a step beyond the hydrodynamic definition of the Hall viscosity, we derive a generalized relation between the Hall viscosity and the transverse electric field using a kinetic equation approach. We explore two different geometries where the Hall viscosity is accessible to measurement. For hydrodynamic flow of electrons in a narrow channel, we find that the viscosity may be measured by a local probe of the transverse electric field near the center of the channel. Ballistic flow, on the other hand, is dominated by boundary effects. In a Corbino geometry, viscous effects arise not from boundary friction but from the circular flow pattern of the Hall current. In this geometry, we introduce a viscous Hall angle that remains well defined throughout the crossover from ballistic to hydrodynamic flow and captures the bulk viscous response of the fluid.

Spatiotemporal organization of cilia drives multiscale mucus swirls in model human bronchial epithelium

Mucociliary clearance is a biomechanical mechanism of airway protection. It consists of the active transport along the bronchial tree of the mucus, a fluid propelled by the coordinated beating of a myriad of cilia on the epithelial surface of the respiratory tract. The physics of mucus transport is poorly understood because it involves complex phenomena such as long-range hydrodynamic interactions, active collective ciliary motion, and the complex rheology of mucus. We propose a quantitative physical analysis of the ciliary activity and mucus transport on a large panel of human bronchial cultures from control subjects, patients with asthma and chronic obstructive pulmonary disease obtained from endobronchial biopsies. Here we report on the existence of multiple ciliary domains with sizes ranging from the tens of a micron to the centimeter, where ciliary beats present a circular orientational order. These domains are associated with circular mucus flow patterns, whose size scales with the average cilia density. In these domains, we find that the radial increase of the ciliated cell density coupled with the increase in the orientational order of ciliary beats result in a net local force proportional to the mucus velocity. We propose a phenomenological physical model that supports our results.

On mass transport in porosity waves

Porosity waves arise naturally from the equations describing fluid migration in ductile rocks. Here, we show that higher-dimensional porosity waves can transport mass and therefore preserve geochemical signatures, at least partially. Fluid focusing into these high porosity waves leads to recirculation in their center. This recirculating fluid is separated from the background flow field by a circular dividing streamline and transported with the phase velocity of the porosity wave. Unlike models for one-dimensional chromatography in geological porous media, tracer transport in higher-dimensional porosity waves does not produce chromatographic separations between relatively incompatible elements due to the circular flow pattern. This may allow melt that originated from the partial melting of fertile heterogeneities or fluid produced during metamorphism to retain distinct geochemical signatures as they rise buoyantly towards the surface.

An Insight into the Temperature Field and Particle Flow Patterns in a Fluidized Bed Reactor for Nonpelletizing Polyethylene Process Using a 3D CFD-PBM Model

This work aims at exploring the temperature and polyethylene (PE) particle flow patterns in a pilot-plant fluidized bed reactor via 3D CFD modeling approach. A Eulerian–Eulerian model involving ethylene polymerization kinetics is integrated with population balance model to investigate the issues for both traditional pelletizing PE process (TPPP) and nonpelletizing PE process (NPPP). The results show that the regions with large temperature gradients have been observed in top area. The revealed particle flow patterns in two cases are analyzed using four typical flow patterns (patterns a–d) reported in literature. PE particles are vigorously contacted and mixed along the lateral and vertical planes of the reactor in TPPP (patterns b–d). Solid dispersion is intensely enhanced in the bed vertical direction (pattern d), and the flow patterns show larger circular flow (pattern a) in the radial direction under NPPP due to the larger particle size and gas velocity.

Hydrodynamic study of freely swimming shark fish propulsion for marine vehicles using 2D particle image velocimetry.

Two-dimensional velocity fields around a freely swimming freshwater black shark fish in longitudinal (XZ) plane and transverse (YZ) plane are measured using digital particle image velocimetry (DPIV). By transferring momentum to the fluid, fishes generate thrust. Thrust is generated not only by its caudal fin, but also using pectoral and anal fins, the contribution of which depends on the fish’s morphology and swimming movements. These fins also act as roll and pitch stabilizers for the swimming fish. In this paper, studies are performed on the flow induced by fins of freely swimming undulatory carangiform swimming fish (freshwater black shark, L = 26 cm) by an experimental hydrodynamic approach based on quantitative flow visualization technique. We used 2D PIV to visualize water flow pattern in the wake of the caudal, pectoral and anal fins of swimming fish at a speed of 0.5–1.5 times of body length per second. The kinematic analysis and pressure distribution of carangiform fish are presented here. The fish body and fin undulations create circular flow patterns (vortices) that travel along with the body waves and change the flow around its tail to increase the swimming efficiency. The wake of different fins of the swimming fish consists of two counter-rotating vortices about the mean path of fish motion. These wakes resemble like reverse von Karman vortex street which is nothing but a thrust-producing wake. The velocity vectors around a C-start (a straight swimming fish bends into C-shape) maneuvering fish are also discussed in this paper. Studying flows around flapping fins will contribute to design of bioinspired propulsors for marine vehicles.

The role of transvaginal power Doppler ultrasound in the differential diagnosis of benign intrauterine focal lesions

The purpose of this prospective study was to assess the role of power Doppler imaging in the differential diagnosis of benign intrauterine focal lesions such as endometrial polyps and submucous myomas using the characteristics of power Doppler flow mapping. A total of 480 premenopausal patients with abnormal uterine bleeding were evaluated by transvaginal ultrasonography (TVS) searching for intrauterine pathology. Sixty-four patients with a suspicious focal endometrial lesion received saline infusion sonography (SIS) after TVS. Fifty-eight patients with focal endometrial lesions underwent power Doppler ultrasound (PDUS). Three different vascular flow patterns were defined: Single vessel pattern, multiple vessel pattern, and circular flow pattern. Finally, hysteroscopic resection was performed in all cases, and Doppler flow characteristics were then compared with the final histopathological findings. Histopathological results were as follows: endometrial polyp: 40 (69 %), submucous myoma: 18 (31 %). Of the cases with endometrial polyps, 80 % demonstrated a single vessel pattern, 7.5 % a multiple vessel pattern, and 0 % a circular pattern. Vascularization was not observed in 12.5 % of patients with polyps. Of the cases with submucousal myomas, 72.2 % demonstrated a circular flow pattern, 27.8 % a multiple vessel pattern, and none of them showed a single vessel pattern. The sensitivity, specificity, and positive and negative predictive values of the single vessel pattern in diagnosing endometrial polyps were 80, 100, 100, and 69.2 %, respectively; and for the circular pattern in diagnosing submucous myoma, these were 72.2, 100, 100, and 88.9 %, respectively. Power Doppler blood flow mapping is a useful, practical, and noninvasive diagnostic method for the differential diagnosis of benign intrauterine focal lesions. Especially in cases of recurrent abnormal uterine bleeding, recurrent abortion, and infertility, PDUS can be preferred as a first-line diagnostic method.

Kinematic alignment of non-interacting CALIFA galaxies

We present 80 stellar and ionised gas velocity maps from the Calar Alto Legacy Integral Field Area (CALIFA) survey in order to characterize the kinematic orientation of non-interacting galaxies. The study of galaxies in isolation is a key step towards understanding how fast-external processes, such as major mergers, affect kinematic properties in galaxies. We derived the global and individual (projected approaching and receding sides) kinematic position angles (PAs) for both the stellar and ionised gas line-of-sight velocity distributions. When compared to the photometric PA, we find that morpho-kinematic differences are smaller than 22 degrees in 90% of the sample for both components; internal kinematic misalignments are generally smaller than 16 degrees. We find a tight relation between the global stellar and ionised gas kinematic PA consistent with circular-flow pattern motions in both components. This relation also holds generally in barred galaxies across the bar and galaxy disk scales. Our findings suggest that even in the presence of strong bars, both the stellar and the gaseous components tend to follow the gravitational potential of the disk. As a result, kinematic orientation can be used to assess the degree of external distortions in interacting galaxies.

Specific aerobic granules can be developed in a completely mixed tank reactor by bioaugmentation using micro-mycelial pellets of Phanerochaete chrysosporium

Aerobic granules were firstly developed in a completely mixed tank reactor (CMTR) by seeding micro-mycelial pellets (MMPs) of Phanerochaete chrysosporium. During phenol wastewater treatment, sludge granulation rate reached 67 % after 15-day operation. The granules in CMTR are different from aerobic granules described in literature in morphology, and a majority of them are rod-shaped or rodlike sludge besides spherical granules. The polymorphic granules, having no essential difference with aerobic granules previously reported, achieve advantages over conventional activated sludge in settling ability, biomass concentration, density, integrity coefficient and removal ability to phenol wastewater. The optimized parameters for sludge granulation in CMTR including temperature, inoculum quantity, rotary speed and superficial air upflow velocity are 30 °C, 5–7 g/l, 150 rpm, and 0.5 cm/s, respectively. Analysis on sludge granulation mechanism indicates that MMPs not only result in the formation of aerobic granules containing MMPs as nuclei, but also induce the formation of biogranules which do not have MMP at their cores. The work challenges the general belief that the homogenous circular flow pattern of microbial aggregates is necessary for aerobic sludge granulation.

Role of endometrial power Doppler ultrasound using the international endometrial tumor analysis group classification in predicting intrauterine pathology

To assess the contribution of the terms and definitions recently described by international endometrial tumor analysis (IETA) group when evaluating endometrial lesions on power Doppler imaging. Patients requiring endometrial sampling were examined prospectively by transvaginal B-mode and power Doppler sonography (PDS) the day before scheduled diagnostic procedure. Sonographic features were classified using IETA group classification. These were compared with the final histopathological diagnosis. Ninety-seven patients were included in the study. The histopathological diagnoses were as follows: endometrial polyp: 39 cases (40.2 %), endometrial hyperplasia: 9 cases (9.3 %), submucous myoma: 10 cases (10.3 %), endometrium cancer: 7 cases (7.2 %), non-specific findings: 32 cases (33 %). The sensitivity, specificity and positive and negative predictive values for single dominant or branching single dominant vessel pattern in diagnosing endometrial polyps were 66.67, 98.28, 96.3 and 81.43 %; for multiple vessels with focal origin pattern in diagnosing endometrial cancer, they were 42.86, 91.11, 27.27 and 95.35 %; for multifocal origin at the myometrial-endometrial junction in diagnosing other non-specific endometria, they were 81.25, 89.23, 78.79 and 90.62 %; for scattered vessel pattern in diagnosing endometrial hyperplasia, they were 88.89, 88.64, 44.4 and 98.73 % and for circular flow pattern in diagnosing submucosal fibroids, they were 80, 100, 100 and 97.75 %, respectively. The color score of the endometrium was not statistically different among different endometrial pathologies (P value >0.05). The nomenclature described by IETA group for power Doppler assessment of the endometrium is clinically valuable and reasonable. Using this terminology, it will be easier to compare results of different studies on endometrial Doppler sonography in the future.

A fixed-volume microfluidic mixer realized using multilayer PDMS technology

We present leakage-free valves and an efficient fixed-volume mixer fabricated using a four-layer soft lithography technique in polydimethylsiloxane (PDMS). Mixing is achieved with a 95% efficiency in a few seconds by creating circular flow patterns inside a simple rectangular chamber. Pressurized air is used to actuate control chambers for active valving and mixing. In our device, neither the mold nor the microfluidic channel requires complex designs.

Impact of turbulence on riverine zooplankton: a mesocosm experiment

Summary1. With increases in river discharge over time and space, zooplankton generally encounter increased turbulence, turbidity, hydraulic forces, downstream advection and food limitations, all of which should affect species diversity and densities. Of these factors, the role of turbulence on the distribution of zooplankton is least known along longitudinal and lateral dimensions in river networks.2. We tested the factorial effects of turbulence and grazing level on Ohio River potamoplankton in spring and summer using twelve 1600‐L, outdoor mesocosms. Turbulence was calculated using the Froude number for equal depths but with current velocities of 0.064 and 0.32 m s−1. Grazing levels corresponded to a high density treatment (=ambient river densities of rotifers, copepods and cladocerans) and a low density treatment (initially no zooplankton >64 μm). All tanks had the same water residence time, and hydraulic stress was minimized by circular flow patterns.3. Zooplankton densities and population growth rates were significantly affected by turbulence level and season. In general, rotifer populations grew faster in high turbulence tanks (though Keratella and Brachionus populations flourished in both treatments in summer) and microcrustaceans thrived better in low turbulence environments. The larger, calanoid copepods handled more turbulent conditions much better than cyclopoids or nauplii. Zooplankton had no detectable effects on particulate organic carbon concentrations in either month (values were higher in spring), but rotifers reduced chlorophyll concentrations in both months.4. The relative importance of turbulence in controlling potamoplankton is probably to vary not only on a longitudinal basis in river networks but also with both the hydrogeomorphic complexity of river reaches and the type and amount of river regulation. Plans for river rehabilitation and management should incorporate non‐turbulent habitats in large rivers as a means of enhancing zooplankton populations and providing an important food web component for planktivores.

Simulation of Parallel SOL Flows with UEDGE

AbstractNear‐sonic parallel plasma flows in the tokamak scrape‐off layer (SOL) are modeled with two‐dimensional multi‐fluid edge plasma transport code UEDGE. As shown, the dominant mechanism driving such flows is fast non‐diffusive intermittent cross‐field transport (due to blobs) which has strong ballooning‐like poloidal asymmetry. The properties of asymmetric‐transport‐driven flows, recycling, and divertor detachment are studied. The conditions for zonal and circular flow patterns in the SOL are analyzed. The impact of plasma drifts on non‐diffusive transport driven flows is modeled and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Echocardiographic diagnosis of subepicardial aneurysm ruptured into the right ventricle after inferior myocardial infarction

A subepicardial aneurysm is a rare complication of myocardial infarction that sometimes causes a left to right shunt at the ventricular level. We report on echocardiographic observations in two recent cases of inferior myocardial infarction complicated by rupture of a subepicardial aneurysm into the right ventricle (RV). Two-dimensional and color flow Doppler images in several planes offered diagnostic characteristics of the lesion, including discontinuity of the myocardium at the neck of the aneurysm, a narrow neck relative to the diameter of the aneurysm, and a back and forth flow at the neck of the aneurysm. These techniques also provided new findings, such as a two-chambered structure of the aneurysm and a circular flow pattern within the inner aneurysmal cavity. In addition, color flow Doppler imaging showed multiple shunt flows from the aneurysm to the RV. Echocardiographically diagnosed abnormalities were verified by and successfully treated with surgery in both cases. In conclusion, echocardiography with color flow Doppler imaging may have the potential to diagnose the anatomic and hemodynamic condition of a subepicardial aneurysm. (J Am Soc Echocardiogr 1997;10:192-96.)