Spiral Flow Pattern Research Articles

Uterine blood flow assessment by colour Doppler for prediction of malignant endometrial pathologies in women with abnormal uterine bleeding

Introduction: Colour Doppler has emerged as useful adjunct to transvaginal sonography in evaluation of women with AUB. This study was carried out to evaluate the role of measurement of the Resistance index (RI) and Pulsatility index (PI) of the uterine arteries by Colour Doppler sonography to discriminate between benign and malignant endometrial condition in women with abnormal bleeding.Material and Methods: This prospective analytical study was performed to evaluate 70 women (30-60 years) with AUB. Spiral arterioles flow patterns, Resistance index (with 0.81 as cut off) and Pulsatility index (with 1.83 as cut off) of uterine arteries were analysed by colour Doppler after detailed TVS. They were compared with Histopathological report of Endometrial Aspiration biopsy. Results: 10 patients (14.3%) had RI in malignancy range (> 0.81) and 9 patients (12.9%) had PI in malignancy range (< 1.83). Out of these 8 had both RI and PI in malignancy range. Thus 11 cases (15.7%) having either RI/PI or RI and PI both, in malignancy range were considered to be suspected of malignancy. Out of these 11 cases, 5 patients were diagnosed to have Hyperplasia/Malignancy on histopathology. There were no False Negative cases, making the sensitivity 100% and specificity 90.7% of TVS with colour Doppler. For the vascular patterns, both cases of hyperplasia had scattered vessel pattern and all 3 cases of carcinoma had multiple vessel pattern, making the association of vascular pattern with AUB diagnosis significant (p<0.001).Conclusion: Colour Doppler of the uterine artery and endometrial spiral arteries, improves the diagnostic accuracy of TVS for the prediction of endometrial pathologies and facilitates in screening for malignant and premalignant lesions. Therefore, it is recommended that CDTU with TVS should be used as screening modality in all AUB patient.

Separation efficiency analysis of multiphase flow inside hydrocyclone using CFD

The study of the separation phenomena inside hydrocyclone often encounters an issue related to particles being misplaced at the outputs since there is a large variety of particle densities. This research presents a numerical study of multiphase flow inside hydrocyclone to analyse the relationship between the separation efficiency of particles and the diameter of the cylindrical section to complete the separation process which greatly affect the overall performance of hydrocyclone. The performance of the hydrocyclone were evaluated using (CFD) method to simulate multiphase flow inside the hydrocyclone. In this study, the Reynolds Stress Model (RMS) is used in the model to simulate the swirling turbulent flow of gas and liquid, and the Volume of Fluid (VoF) Multiphase Model is used to simulate the interface between the liquid and the air core. The solid particle motion is then tracked using the outcomes from the simulation of particle in the The Discrete Element method (DEM) model. Pressure and velocity play important roles in the separation of particles. A centrifugal force that separates particles according to their mass is produced when the hydrocyclone's input is subjected to higher pressure. The fluid's velocity increases as it moves towards the device’s centre, causing the hydrocyclone to rotates and produces a spiral flow pattern. Higher diameter of the cylindrical section, provide higher tangential velocity of particles and their centrifugal forces, resulting in great collection efficiency. In this paper, it has been demonstrated numerically that the performance of hydrocyclone is significantly influenced by the different diameter of the cylindrical section. As of the simulation analysis, increasing the diameter of the cylindrical section has increased the separation efficiency from 34.4% to 44.3% for particle size of 5 μm respectively. Based on the pressure, velocity and streamlines distribution profiles obtained, the results revealed that the tangential velocity contributes largely to the centrifugal forces, resulting in a substantial collection. The increase in diameter increases the residence time of particles inside the hydrocyclone making the swirl rotation of particles more frequent. Thus, it increases the effect of clarity separation and boosts separation accuracy and efficiency.

Heat transfer enhancement of water-cooled triply periodic minimal surface heat exchangers

Whether triply periodic minimal surface (TPMS) heat exchangers are applicable to cooling or cold storage systems as a cooler for supercritical carbon dioxide (SCO2) is undocumented. Here the conjugated heat transfer of SCO2 in TPMS Schoen-G heat exchanger and printed circuit heat exchanger (PCHE) was predicted based on three-dimensional steady turbulent Reynolds-averaged Navier-Stokes equations, energy equation and shear stress transport model using computational fluid dynamics software ANSYS CFX when SCO2 inlet temperature and pressure vary in 65–30 ℃ and (8–9)MPa. SCO2 in two heat exchangers is cooled under counter-flow conditions by a stream of cold water with given inlet temperature and mass flow rate. It was shown that the mean heat transfer coefficient of SCO2 in TPMS Schoen-G heat exchanger is larger than PCHE. As the inlet pressure rises, the friction factor increases and Nusselt number decreases in the heat exchangers due to decreased Reynolds number and Prandtl number, respectively. The friction factor ratio, Nusselt number ratio and performance evaluation criterion vary in the range of 0.38–0.50, 1.07–1.49, and 1.45–2.04 with Reynolds number and inlet temperature when the PCHE serves as a reference heat exchanger. The streamlines in TPMS Schoen-G heat exchanger are quite smooth even though the areas with a higher velocity appear. The streamlines in PCHE exhibit a spiral flow pattern to result in extra hydraulic loss. The heat transfer enhancement of TPMS Schoen-G heat exchanger is much better TPMS Schwarz-D heat exchanger at a Reynolds number higher than 16,000. The enhancement is attributed to a larger heat transfer surface area and more topological tortuosity without flow separation than PCHE.

Numerical Simulation of the Flow Pattern of Spiral Annular Flow with a Guide Strip by Spiral On-Way.

To study the gas–liquid two-phase spiral annular flow pattern and its conversion law in a horizontal tube with twist tape by spiral on-way, a numerical simulation is carried out using the RNG k-ε model, and the DPM model is adopted as the particle motion model. The research results show that three main flow patterns are obtained, which are spiraling churn flow, spiraling annular flow, and spiraling annular twine flow. The ratio of the liquid-phase to gas-phase velocity VL/VG is the main factor that affects the existence of the gas phase. When VL/VG > 1/2, the flow pattern is a spiral cluster flow; when 1/5 < VL/VG< 1/2, the flow pattern is a spiral annular flow; and when VL/VG < 1/5, the flow pattern is a spiral annular flow. Compared with the flow pattern of the local spiral flow pattern of the short twisted band, it was found that the occurrence conditions of annular flow were postponed and a new flow pattern appeared. The research results of this paper have guiding significance for the pipeline risk management of natural gas hydrates and the engineering application of the full rotation of guide strips.

Distributed encoding of curvilinear self-motion across spiral optic flow patterns

Self-motion along linear paths without eye movements creates optic flow that radiates from the direction of travel (heading). Optic flow-sensitive neurons in primate brain area MSTd have been linked to linear heading perception, but the neural basis of more general curvilinear self-motion perception is unknown. The optic flow in this case is more complex and depends on the gaze direction and curvature of the path. We investigated the extent to which signals decoded from a neural model of MSTd predict the observer’s curvilinear self-motion. Specifically, we considered the contributions of MSTd-like units that were tuned to radial, spiral, and concentric optic flow patterns in “spiral space”. Self-motion estimates decoded from units tuned to the full set of spiral space patterns were substantially more accurate and precise than those decoded from units tuned to radial expansion. Decoding only from units tuned to spiral subtypes closely approximated the performance of the full model. Only the full decoding model could account for human judgments when path curvature and gaze covaried in self-motion stimuli. The most predictive units exhibited bias in center-of-motion tuning toward the periphery, consistent with neurophysiology and prior modeling. Together, findings support a distributed encoding of curvilinear self-motion across spiral space.

Estimating curvilinear self-motion from optic flow with a biologically inspired neural system* *This work was supported by The Office of Naval Research ONR N00014-18-1-2283.

Optic flow provides rich information about world-relative self-motion and is used by many animals to guide movement. For example, self-motion along linear, straight paths without eye movements, generates optic flow that radiates from a singularity that specifies the direction of travel (heading). Many neural models of optic flow processing contain heading detectors that are tuned to the position of the singularity, the design of which is informed by brain area MSTd of primate visual cortex that has been linked to heading perception. Such biologically inspired models could be useful for efficient self-motion estimation in robots, but existing systems are tailored to the limited scenario of linear self-motion and neglect sensitivity to self-motion along more natural curvilinear paths. The observer in this case experiences more complex motion patterns, the appearance of which depends on the radius of the curved path (path curvature) and the direction of gaze. Indeed, MSTd neurons have been shown to exhibit tuning to optic flow patterns other than radial expansion, a property that is rarely captured in neural models. We investigated in a computational model whether a population of MSTd-like sensors tuned to radial, spiral, ground, and other optic flow patterns could support the accurate estimation of parameters describing both linear and curvilinear self-motion. We used deep learning to decode self-motion parameters from the signals produced by the diverse population of MSTd-like units. We demonstrate that this system is capable of accurately estimating curvilinear path curvature, clockwise/counterclockwise sign, and gaze direction relative to the path tangent in both synthetic and naturalistic videos of simulated self-motion. Estimates remained stable over time while rapidly adapting to dynamic changes in the observer’s curvilinear self-motion. Our results show that coupled biologically inspired and artificial neural network systems hold promise as a solution for robust vision-based self-motion estimation in robots.

Effect of Anastomosis Angles on Retrograde Perfusion and Hemodynamics of Hybrid Treatment for Thoracoabdominal Aortic Aneurysm

Hemodynamic effects on the retrograde visceral reconstruction (RVR) for thoracoabdominal aortic aneurysms treatment by anastomotic angle remains unclear. This study aims to qualitatively and quantitatively investigate the effects of different anastomotic angles on hemodynamics and patency. Three RVR models with 45°, 60° and 90° anastomotic angles were reconstructed respectively by manipulating apostoperative patient-specific model. The manipulated models of the RVRs were numerically simulated and analyzed in terms of hemodynamics including theinstant and cumulative patency, flow pattern and indicators based on wall shear stress (WSS). Although a smaller anastomotic angle may decrease the patency rate of common iliac arteries, it can improve the visceral perfusion during a cardiac cycle. More importantly, RVR with the smallest anastomotic angle experienced a minimal low time-averaged wall shear stress, high oscillatory shear index and relative residence time in the anastomosis region, whereas the largest anastomotic angle can introduce more unfavorable WSS in the graft trunk. Furthermore, a spiral flow pattern was observed in the proximal graft trunk of all three models, where no high-risk shear distribution was detected in this region. A smaller anastomotic angle may have more benefits of hemodynamic environment in RVR, especially the WSS distribution and flow pattern in the graft trunk. We may also suggest that additional stents or an extended cuff for the graft can be used to induce spiral flow intentionally, which can further improve local hemodynamic environment and long-term prognosis.

Design and Ductile Behavior of Torsion Configurations in Material Extrusion to Enhance Plasticizing and Melting.

In the present work, the ductile formation mechanism of a newly proposed torsion configuration has been investigated. One of the unique attributes of this paper is the first-time disclosure of the design and fabrication of a novel prototype screw with torsional flow character validating the orthogonal test model experimentally. The torsional spiral flow patterns that occurred in the torsion channel cause a ductile deformation of polymer in the form of a spiral, which in turn enhances the radial convection, achieving an effective mass transfer of material from the top region to the bottom region and vice versa. Furthermore, the characteristic parameters of torsion configuration have a significant influence on the plasticizing and melting capability of polymer. By range analysis and weight matrix analysis, the best factor and level combination was obtained. Results indicated that the aspect ratio of the torsion channel is almost equal to 1, and the plasticizing and melting capability of polymer is optimal. This novel design innovation offers a paradigm shift in the energy-efficient plasticization of polymer compounds.

Performance investigation of transparent photovoltaic‐thermal collector with horizontal oscillating and rectangular spiral flow patterns

Performance investigation of transparent photovoltaic‐thermal collector with horizontal oscillating and rectangular spiral flow patterns

Electrostatic charging behaviour of polypropylene particles during pulse pneumatic conveying with spiral gas flow pattern

The electrostatic charging behaviour of 5-µm and 1500-µm polypropylene particles were studied during pulse pneumatic conveying with a spiral air flow. The conveying line was made of stainless steel with a total length of 1.3 m and inner diameter of 0.035 m. Effects of conveying gas velocity as well as particles mass loading were studied on particles charge-to-mass (Q/m) ratio. A high-speed camera set at 5000 frames per second (fps) capturing speed was used to record the particles movement pattern within the conveying line. Results clearly indicated a relationship between the particles motion pattern and their electrostatic charging behaviour. A direct relationship was observed between the conveying gas velocity and particles Q/m, whereas in general, particles Q/m magnitude was found to be inversely related with the mass loading. The Q/m of larger particles was found to be greater than that for the smaller particles. Additionally, charge measurements were performed and compared between a cyclone-type Faraday cage and a through-type Faraday cage with a filter bag inside. It was observed that the charge measured by these Faraday cages could differ drastically depending on particles size. The back pressure created inside the filter bag was suspected to be a significant contributor for such as observation.

Numerical and experimental investigation of dough kneading in a three-dimensional spiral kneader

This work reports on the first three-dimensional viscoelastic dough kneading simulation performed in a spiral kneader. Unstructured tetrahedral grids were generated using ICEM CFD 17.1. Viscoelastic volume-of-fluid simulations were performed using OpenFOAM v.4.0 in combination with the RheoTool package v.2.0. The White-Metzner model with a Bird-Carreau type of shear-rate dependency of the viscosity and relaxation time was utilized to describe the rheology of the dough matrix. We validated our numerical method by simulating the viscoelastic rod climbing benchmark problem in a cylindrical bowl. The temporal evolution of the dough surface was compared with screenshots obtained with a high-speed video camera during laboratory kneading. We found that the curvature of the free surface matches the experimental data well. With our numerical approach, we were able to predict the formation, extension, and breakup of dough pockets. The dough is convected around the inner stationary rod by the rotation of the outer cylindrical bowl, whereas the spiral arm located in between these two parts produces spiral flow patterns. Vertical mixing is not as good as radial mixing and may be enhanced by utilizing two spiral arms similar to hand kneading. Industrial kneading geometries and processes may be further optimized by performing such types of simulations.

Onset of three-dimensionality in supersonic flow over a slender double wedge

An investigation shows that laminar supersonic flow on a 2D compression corner can destabilize to become 3D beyond a critical turn angle. This compressible instability resides in the recirculating flow, producing spiral wall flow patterns postseparation and wall temperature streaks downstream.

Performance simulation on unilateral ladder type helical baffle heat exchanger in half cylindrical space

A unilateral ladder type helical baffle heat exchanger (ULHBHX) which is a novel countercurrent U-tube heat exchanger was proposed and investigated for better characteristics of high heat transfer coefficient, low resistance, anti-vibration and anti-fouling with a spiral flow pattern than those of the conventional segment one. The numerical model of ULHBHX was established and simulated by CFD software with 38 heat transfer tubes and 2 rod and spacing tube assemblies in the lower half cylindrical space under the parameters of subcooling of a high pressure feedwater heater in power plants. Different views such as on baffle-parallel slices and polygonal slices were presented to show the flow patterns of the main helical flow, secondary vortex flow and the leakage flow. The influences of geometrical parameters of baffle pitch and projection length of the inclined section on heat transfer and pressure drop were discussed quantitatively. The results show that the shell-side heat transfer coefficient ho of the ULHBHXs is 13.2%–18.2%, with an average of 16.0%, higher than those of the corresponding segment schemes, and the comprehensive index hoΔpo−1/3 is 15.7%–46.4%, with an average of 28.3%, higher than those of the corresponding segment schemes with identical baffle pitches in the discussed range.

Numerical Simulation of Air-Core Vortex at Intake

In order to study the features of vortex at horizontal intakes, numerical investigations have been performed. The tangential, radial, and axial distributions, and water surface profile were simulated to evaluate the flow behaviour and existence of an air-core vortex. The numerical results agree with existing experimental data. The correlation of vortex characteristics between numerical and experimental results was good. Regarding formed funnel profile of flow in the basin towards horizontal intake, its limits at the existence of an air-core vortex were analysed. The spiral flow pattern from surface towards intake was identified around the air-core vortex. This numerical simulation may help to get a deeper understanding in determining the submergence required to avoid air-entraining vortices in a reservoir.

Experimental Study on the Characteristics of a Miniature Laminar Plasma Torch with Different Gas Flow Patterns

As laminar plasma jet has long stable plasma jet, low temperature gradient, negligible noise emission, good processing reproducibility and controllability, it is suitable for industrial applications with high precision requirement. However, the conventional laminar plasma torches are large in size and thus can hardly be applied in processing occasions with space limitation. In this paper, a miniature DC non-transferred arc laminar plasma torch with an external size of about 57 × 56 × 42 mm is proposed to meet the processing requirements in these occasions. It can generate long laminar plasma jet with a maximum jet length of about 300 mm at atmospheric pressure with pure nitrogen. Experimental study on the proposed plasma torch has been carried out to obtain its arc voltage characteristics and the jet length characteristics. It has been founded that the plasma torch with spiral gas flow pattern generally has higher arc voltage and longer jet length than that with axial gas flow pattern. In addition, a special jumping arc voltage characteristic and the variation appearances of the plasma jet were founded, which may be used to design miniature laminar plasma torch with high arc voltage and thus low arc current for the same output power as the conventional ones.

Side-Channel Flow: Physical Model Studies

AbstractHydraulic investigations of three hydraulic model studies on side channels are presented. These include the side channels of the Trangslet Dam, Sweden, the Karahnjukar Dam, Iceland, and the Lyssbach diversion tunnel, Switzerland, of which the former two have a trapezoidal cross section and the latter has a rectangular cross section. The observed flow patterns are described, with particular attention on the single- and two-vortex spiral flow patterns, the formation of a tornado vortex, and air entrainment. The measured streamwise free-surface profiles are compared with one-dimensional computations on the basis of the standard spatially varied flow equation. Although a good agreement results in general, deviations are primarily explained by local perturbations. The measured cross-sectional free-surface profiles indicate an increase in the flow depth along the side walls compared with the computed flow depth at the impact point of lateral inflow. For the side-channel design, safety provisions should ...

Cycle-to-cycle variation analysis of early flame propagation in engine cylinder using proper orthogonal decomposition

Experimental investigations on the cycle-to-cycle variations of early flame propagation were conducted at two intake air swirl ratio of 0.55 and 5.68 in a single-cylinder spark-ignition direct-injection (SIDI) optical engine. Both the crank-angle resolved flame images through the quartz insert in the piston and the in-cylinder pressure were simultaneously recorded for 250 consecutive cycles. An algorithm based on the cross-correlation of flame pattern was implemented to compute the two-dimensional velocity fields representing an early flame propagation. Afterwards, the proper orthogonal decomposition (POD) was performed to access the cycle-to-cycle variations of flame propagation. During early flame formation, the uncertainty of velocity was evaluated to be less than 5%. The velocity fields of early flame propagation were significantly affected by in-cylinder air flow. Increasing the swirl ratio from 0.55 to 5.68 augmented the average early flame propagation speed from 2.1m/s to 3.2m/s, and the COV of flame speed was reduced from 49.7% to 25.1%. Good correlations were identified between early flame speed and the pressure-derived results. Similar magnitude of reduction in COV (coefficient of variation) of IMEP (indicated mean efficient pressure) & PP was also found. The coefficients of POD mode 1 were found to represent the flame speed, and the remaining higher POD modes were related to the fluctuation in kinetic energy. The POD coefficients showed good correlations with the pressure-derived results such as CA05 (5% of total heat release) & PP (peak pressure). The weak spiral flow pattern, observed within the flame, was only found in higher POD modes. In summary, using the coefficients and modes of POD, the average and fluctuating parts of early flame propagation can be resolved, thereby providing more quantitative information of the cycle-to-cycle variation during the early combustion process in an engine cylinder.

3D features in the calendering of thermoplastics: A computational investigation

We present results of a fully three‐dimensional computational study of the calendering process of thermoplastics using the fluid dynamics software OpenFOAM. Our aim is to elucidate unique 3D features of the process, such as spreading and melt flow. We assume that the material is fed in the form of a sheet of finite thickness and detaches from the cylinders at a prescribed thickness. The rotational motion of the cylinders, the consequent pressure build‐up (both in the machine and the transverse directions) and the presence of the free surfaces (sides) of the calendered sheet—both deformable and at ambient pressure—forces the thermoplastic melt to spread in the transverse direction. A decoupled iterative procedure is used to predict the shape of the spreading side surfaces under different conditions. A spiraling transverse flow pattern in the melt feeding section is shown to exist, which determines the actual flow path of the calendered material in a nonintuitive way. We show that insofar as the material redistribution (from the fed sheet to the produced film) during the process is concerned, the results of the present analysis predict a 3D spiral flow pattern and a redistribution of the fed material from the central region of the fed sheet to the sides of the calendered product. POLYM. ENG. SCI., 54:1712–1722, 2014. © 2013 Society of Plastics Engineers

Airlift column photobioreactors for Porphyridium sp. culturing: Part I. effects of hydrodynamics and reactor geometry

Photosynthetic microorganisms have been attracting world attention for their great potential as renewable energy sources in recent years. Cost effective production in large scale, however, remains a major challenge to overcome. It is known to the field that turbulence could help improving the performance of photobioreactors due to the so-called flashing light effects. Better understanding of the multiphase fluid dynamics and the irradiance distribution inside the reactor that cause the flashing light effects, as well as quantifying their impacts on the reactor performance, thus, are crucial for successful design and scale-up of photobioreactors. In this study, a species of red marine microalgae, Porphyridium sp., was grown in three airlift column photobioreactors (i.e., draft tube column, bubble column, and split column). The physical properties of the culture medium, the local fluid dynamics and the photobioreactor performances were investigated and are reported in this part of the manuscript. Results indicate that the presence of microalgae considerably affected the local multiphase flow dynamics in the studied draft tube column. Results also show that the split column reactor works slightly better than the draft tube and the bubble columns due to the spiral flow pattern inside the reactor.

Gas Phase Pressure Drop of a Water-Sparged Aerocyclone Reactor

Air stripping of ammonia is a widely used process for the pretreatment of wastewater. Scaling and fouling on the packing surface in packed towers and a lower stripping efficiency are the two major problems in this process. New patented equipment that is suitable for the air stripping of wastewater with suspended solids has been developed. Air stripping of ammonia from water with Ca(OH)2, was performed in the newly designed gas-liquid contactor, a water-sparged aerocyclone (WSA). The pressure drop of gas phase was investigated in order to know the momentum transfer characteristic of the WSA. It was found that the gas phase pressure drop exhibited a different change tendency compared with the traditional aerocyclone, and could be divided into three characteristic stages, including low pressure drop, pressure drop jump and high pressure drop phases. The three different pressure drop areas corresponds to steady jet, spiral and fogged flow patterns of the liquid phase. The critical value for the air flow rate which caused the mass transfer coefficient to increase rapidly took place at the point where the steady jet was transformed into the spiral flow pattern.