Swirling Flow Pattern Research Articles

Experimental study on flow patterns and pressure gradient of decaying swirling gas-liquid flow in a horizontal pipe

The utilization of swirling flow in multiphase flow devices is prevalent for purposes such as mixing, separation, stabilization, and heat transfer enhancement, primarily owing to its characteristic of inducing low-pressure drop. In the nuclear industry, for example, two-phase swirling flow is applied in the nuclear gas generator to improve gas quality. In this study, an experimental investigation was conducted on the decaying swirling flow of gas-liquid in a horizontal pipe equipped with a vane-type swirler. The flow patterns were visually examined, and the pressure gradients along the test pipe and across the swirler were measured. The findings suggest the presence of four distinct swirling flow patterns at the swirler outlet (z/D = 0), namely chain flow, swirling gas column flow, swirling intermittent flow, and swirling annular flow. Because of swirl decay, these swirling flows recover their original pattern approximately 70D downstream from the swirler, with the exception of the swirling gas column flow. The flow regime maps at z/D = 10, 40, 70 and 100 are proposed and the pattern-based pressure gradient characteristics are analyzed. It is shown that the pressure gradient rises as both gas superficial velocity (jg) and liquid superficial velocity (jl) increase. The largest pressure gradient occurs within the swirler section, while the lowest is found upstream of the swirler. Near the swirler outlet (z/D = 0–33), the pressure gradient is approximately 1.5–2.3 times higher than at z/D = 33–67. Further downstream, at z/D = 67–100, it is 2.2–3.5 times greater, depending on the flow patterns.

Experimental study of swirling flow pattern at the swirler outlet using a Wire-Mesh sensor

Entrained droplets and flow pattern change adversely affects separation performance of swirl-vane separators. Investigating gas–liquid distribution at swirler outlet, an experiment was conducted using a wire-mesh sensor positioned. Air and liquid superficial velocities ranged from 8.3 to 25.6 m/s and 0.1 to 1.4 m/s, respectively, covering swirling annular and swirling churn flow at swirler outlet. In swirling annular flow, liquid phase primarily exists as a stable thin film which facilitates efficient separation. In swirling churn flow, wall liquid film has unstable large amplitude disturbance waves. Disrupting liquid film leads to entrained droplets forming in gas center, increasing separation distance and hindering gas–liquid separation. The transition boundary from swirling churn to swirling annular is crucial. Increasing swirler angle shifts the transition boundary towards higher gas velocity at the same liquid velocity. A theoretical model based on interfacial shear stress and gas core blockage predicts the flow pattern transition at swirler outlet.

Analysis of vortex mixing in passive micromixers with misaligned inlet and rectangular winglets

In the present study, a three-dimensional design of a passive micromixer is proposed which induces the swirling flow pattern by employing the misaligned inlets and winglets. The concepts of fluid stretching and twisting are utilized to improve the mixing efficiency. Stretching is quantified in terms of the modified flow tortuosity parameter. The dependence of various geometrical parameters on flow tortuosity is examined to increase the diffusive mixing by increasing the lateral Peclet number. A detailed analysis is carried out to understand the impact of geometrical features on the vortex formation, propagation, and intensification. Lambda 2 and the helicity approach are used to identify the vortex core region and quantified using a modified swirl number & vortex index. For vortex T misalignment, the aspect ratio 1 along with the staggered common flow-down configuration of winglets is highly effective. For misaligned Y inlet, both interfacial diffusive mixing along with longitudinal vortices at winglets generate highly effective mixing even at a low Reynolds number. For Reynolds number 1 to 70 and channel length 3.5 mm, mixing efficiency above 82% is achieved, and the mixing energy cost is subsequently reduced. A detailed comparative study is done to establish the effectiveness of the present design.

Study on cavitating vortex rope characteristics of reversible pump-turbine under part load turbine condition

Pressure fluctuations in the draft tube mainly arise from the rotational motion of the vortex rope. The formation and development of the vortex rope are significantly influenced by cavitation. However, the precise mechanism underlying the progression of cavitation from its initial weak state to a more severe level remains unclear. The objective of this study is to investigate cavitation in a pump-turbine operating under part load turbine conditions. Numerical simulations were conducted to analyze the impact of the cavitation coefficient on various parameters, including vapor volume, efficiency, and head. With increasing degree of cavitation, the vortex rope's pattern in the draft tube undergoes a transition from a helical type to a torch-like type. This transition consequently leads to a shift in the dominant frequency of pressure fluctuations within the draft tube. Furthermore, the helical vortex rope exhibits a higher rotational speed compared to the torch-like vortex rope, thereby causing a more pronounced effect on the pressure field. The factors contributing to the morphological transition of the vortex rope were explored, with particular emphasis on the accelerating reverse axial flow and the reduction in the draft tube's circumferential velocity. Additionally, this study examined the effect of the cavitation coefficient on the swirl number and flow pattern, while also assessing its impact on entropy production. These findings provide valuable insight into the control of cavitation flow in pump-turbines operating under part load conditions. Moreover, they carry significant implications for the design and optimization of pump-turbine systems.

Transient Analysis of Fluid Flow, Solidification, and Inclusion Behavior in Electromagnetically Stirred Bloom Caster Mold Using Bifurcated Submerged Entry Nozzle

Herein, the effect of bifurcated submerged entry nozzle (SEN) port angles on transient flow, solidification, and inclusion behavior in a bloom caster mold with electromagnetic stirring (EMS) is investigated. A 3D numerical model is developed to simulate the process, including time‐varying electromagnetic field and Lagrangian inclusion tracking approach, by varying inclusion density and size. The inclusion is modeled to be entrapped in the solidified shell when primary dendrite arm spacing (PDAS) is greater than inclusion size. As compared to the case without use of EMS, the percentage of shell thickness at the strand outlet is seen to increase by 22.18%, 9.45%, 8.03%, 9.31%, and 13.40% for different port angle values of 0°, 15°, 20°, 25°, and 30°, respectively, with EMS. The results show that EMS significantly influences the flow behavior by generating the swirl flow pattern that hinders the movement of inclusion downward in the domain. The bifurcated SEN with 30° port angle (without EMS) is seen to reduce inclusion entrapment and hence enhance inclusion removal. The outcome of present research may provide useful insights for optimizing the parameters of bloom caster mold to improve product quality, reduce production costs, and increase overall efficiency.

Mass transfer enhancement for CO2 chemical absorption in a spiral baffle embedded microchannel

This paper presents an experimental study on CO2 chemical absorption by Monoethanolamine (MEA) solution in microchannel. In particular, a novel spirally distributed baffle structure is proposed to be embedded into the microchannel so as to generate the swirling flow pattern and to enhance the mass transfer. The effect of spiral baffle structure on the two phase flow pattern transition, the CO2 gas void fraction, the pressure drop, and the mass transfer performance are characterized and discussed, under varied gas and liquid flow rates, and MEA concentrations. Results demonstrate that the spiral baffle structure could significantly enhance the gas–liquid mass transfer, with overall liquid side volumetric mass transfer rate (kLa) up to 2.35 s−1 and enhancement number E up to 1.387 at small gas and liquid Reynolds numbers (ReG < 5.5; ReL < 14). New predictive correlations have also been proposed by considering both the structure enhancement factor and the chemical reaction factor.

Experimental study of swirling flow pneumatic liquid-carrying characteristics in the vortex tool inserted tube under liquid loading conditions

Liquid unloading by vortex tool is one of the most important applications of swirling flow pneumatic conveying. However, due to swirl decay, the evolution of gas–liquid flow patterns and the dynamic characteristics of pressure drop downstream of the vortex tool are much more complex than those in non-swirling flow. In this study, the gas–liquid flow patterns and pressure drop inside the vortex tool inserted tube (ID = 60 mm) under liquid loading conditions were experimentally studied and compared with those of the plain tube. With the superficial gas velocities ranging from 0.5 to 6.0 m/s and superficial liquid velocities of 0.01, 0.02, and 0.04 m/s, the effects of the structural parameters and stages of vortex tools on the pressure drop were discussed. The experimental results reveal that three distinct swirling flow patterns can be identified downstream of the vortex tool, namely swirling gas column flow, swirling churn flow and swirling annular flow. The insertion of vortex tool facilitates an earlier transition of the churn flow to the annular flow, and the induced swirling flow can restrain the liquid from falling back. The helix angle of the corkscrew deflector has a more significant effect on the pressure drop than its length. By reducing the helix angle from 54° to 45°, the total pressure drop and downstream pressure gradient are significantly decreased, even lower than those of the plain tube. But the series combination of 54° and 45° vortex tools results in a significant increase in the downstream pressure gradient. Additionally, at low gas flow rate, negative frictional pressure drop occurs in both plain tube and vortex tool inserted tube. Hence, the new friction factor correlations were established respectively for the positive and negative friction regions in the cases of the tube with and without vortex tool, and most of the frictional pressure gradient predictions are within an error band less than 20%.

Swirl Effects On Gas-Liquid Upward Vertical Pipe Flow

Abstract When swirl is added to gas-liquid upward vertical pipe flows (e.g. inside an inline swirl separator), the classical flow patterns are modified by the centrifugal forces which act pushing the gas towards the center of the pipe and the liquid towards the wall. If the swirl is strong enough, this leads to the formation of a gas column in the center of the pipe, which can be either stable or intermittent. It was observed experimentally that the behavior of the gas column is strongly dependent on the dynamics of the gas-liquid flow upstream of the addition of swirl. In this video, a high speed camera was used to record the gas-liquid flow upstream and downstream of a swirl-generating element for different flow rates of liquid and gas, covering multiple non-swirling (upstream) and swirling flow patterns (downstream). The video: (i) shows the different swirling gas-liquid flow patterns and their dynamic behavior; (ii) analyzes the connection between the dynamics of the swirl patterns and the gas-liquid patterns upstream of the swirl element, via synchronized recordings of the two locations.

Pseudoaneurysm of the brachial artery in an infant due to vaccination: a case report

BackgroundPseudoaneurysm is a known complication of penetrating arterial injuries such as catheterization, gunshot wounds, and open fractures. Vaccination is an effective method for preventing multiple, serious, infectious diseases in children. Common adverse reactions related to vaccination include fever, swelling, redness, and pain. Brachial pseudoaneurysm after vaccination has not been previously reported.Case presentationHerein we describe a novel case of brachial pseudoaneurysm after vaccination in a child aged 1 year and 3 months. A pulsatile mass was formed in the medial left arm of the infant 10 days after vaccination at a community hospital and gradually grew larger. Preoperative images depicted an eccentric aneurysm in the brachial artery and a swirling flow pattern in the mass. The pseudoaneurysm was excised, and vein graft interpositioning was successfully performed. There were no short-term or long-term complications during the follow-up period.ConclusionsBrachial pseudoaneurysm is a rare complication of vaccination via intramuscular injection. Medical staff should avoid puncture wounds to the brachial artery during vaccination, especially in infants.

Two-phase flow pattern identification in horizontal gas–liquid swirling pipe flow by machine learning method

Gas–liquid two-phase swirling flow has been widely used in nuclear industry. Its flow pattern is fundamental to investigate the two-phase flow. Although flow patterns of non-swirling flow in a horizontal pipe have been investigated for a long history, flow patterns of swirling flow in the pipe are rarely reported. In this paper, gas–liquid two-phase flow patterns of swirling flow generated by a vane-type swirler inside a horizontal pipe were investigated by a visualization experiment. Five swirling flow patterns were observed and recorded by the backlight imaging method. Then image processing method was used to obtain void fraction, and the statistical analysis (CDF and PDF) of void fraction for each swirling flow patterns was performed. Owing to the distinguished and stable feature of PDF signals, four parameters describing the characteristics of PDF signals have been proposed as the indicator of machine learning method. Finally, five algorithms of machine learning method have been used to identify the swirling flow patterns, and RUSBoost tree algorithm performs best with an accuracy of 97.4%.

Gas–liquid two-phase flow patterns and pressure drop of decaying swirling flow inside a horizontal pipe

Gas–liquid two phase swirling flow has been widely used in industry. Its flow pattern is fundamental to investigate the two-phase flow. In this paper, two-phase air–water flow patterns and pressure drop of decaying swirling flow generated by vane-type swirler inside a horizontal pipe have been systematically investigated by visualization experiment. The range of superficial gas phase Reynolds number is 17–23902, while superficial liquid phase Reynolds number is 12–37871, and gauge pressure is 0.003–0.17 MPa. The five typical flow patterns in a horizontal swirling flow were characterized based on flow visualizations and fluctuation characteristics of pressure drop signals. Then swirling flow regime map nearby the swirler outlet was proposed. As flow patterns altered along the streamwise direction due to swirl decay, flow pattern maps at different positions were proposed, which indicated the swirling flow patterns gradually transformed to non-swirling flow patterns. Finally, a new model to predict frictional pressure drop of air–water swirling flow inside a horizontal pipe containing vane-type swirler was proposed. This correlation performed well on predicting the frictional pressure drop.

Role of transverse dimples in thermal-hydraulic performance of dimpled enhanced tubes

This study numerically investigates the effects of transverse dimples in thermal and hydraulic performance improvement of Teardrop, Ellipsoidal-0o and Ellipsoidal-45o dimpled tubes under constant surface heat flux (q′′ = 10kW/m2) for turbulent Reynolds numbers (5000 ≤ Re ≤ 40,000). The number of dimples in the transverse direction (Star) are varied from 4 to 8 while maintaining the tube length to pitch (spacing between successive dimples) of 10 for each tube configuration. It is observed from Performance Evaluation Criteria (PEC) that Ellipsoidal-45o-Star 6 dimpled tube (Tube 7), as compared to the smooth tube, enhances the performance by 88.2% at Re = 5000 however, it reduces to 23.9% at Re = 20,000 and becomes negligible at Re = 40,000. The Ellipsoidal-45o dimples generate a non-symmetric wake and create a flow path between downstream dimples. As Star increases the flow momentum increases and a swirl flow pattern is generated and consequently enhances fluid-dimple interaction at low turbulent Re. On the contrary, Teardrop-Star 6 (Tube 2) and Ellipsoidal-0o-Star 6 (Tube 5) perform better at 20000 ≤ Re ≤ 40,000. Tube 5 produces distinct flow streams and enhances the fluid-surfaces interactions at higher Re. Therefore, it is recommended for high turbulent Re.

Computational investigation of magneto-hydrodynamic flow of newtonian fluid behavior over obstacles placed in rectangular cavity

The magneto hydro-dynamic flows are of great importance in the industries such as food processing, power generation and in investigating the behavior of boundary layer convection. In this article, the magneto hydrodynamic flow of Newtonian fluid in rectangular cavity under the effect of applied magnetic filed is investigated. In the rectangular cavity, three semi circular cylinders are placed as obstacles to create unsteadiness in the flow path. Computational fluid dynamics model is built to analyze and observe the flow behavior in presence of 10 Ampere per meter. Furthermore, velocity profiles in vertical and horizontal directions, streamlines patterns, pressure distribution profile, vorticity profile, and viscous stress are presented. These profiles are discussed with and without the presence of strong magnetization force and flow behavior is investigated. The model is designed and compute in COMSOL-Multiphysics. It is concluded that presence of high magnetization force enhance the surface velocity to 1.87 m/s in horizontal direction and 0.86 m/s in vertical direction. Swirling flow pattern in streamlines increase with high magnetic force. The exerted pressure on wall of cavity has augmented to 2.39 Pa with increment in magnetic field. Moreover, obtained results are in complete agreement with already published work.

C43 A CASE REPORT OF A GIANT RIGHT CORONARY ARTERY ANEURYSM: ROLE OF CONTRAST ECHOCARDIOGRAPHY

Abstract A giant coronary aneurysm is rare entity and it is defined if the diameter is 4–fold greater the reference vessel diameter or if it is &amp;gt; 20 mm in diameter. We report the case of a 73–years–old man without prior history of cardiac disease, admitted in Emergency Department for abdominal pain with normal ECG. Abdominal CT scan showed no pathological findings. At thoracic level it was reported a suspected pericardial cyst (75x80 mm), with partial compression of right chambers (Fig. 1). Echocardiography confirmed the presence of a giant round cystic–appearance lesion characterized by the presence of an anechoic space with internal echogenic swirling flow pattern at the level of right atrioventricular groove with mild compressive effect on right chambers. (Fig. 2). The color Doppler mode showed a faint signal, without a clear evidence of flow origin. A bubble test with agitated saline contrast medium injected through antecubital vein, shows no evidence of contrast uptake by the mass. In order to better characterize the lesion, we use echocardiographic contrast agent (SonoVue®), which showed a clear pattern of blood flow inside the mass with a probable origin at a very limited region (Fig. 2a–2b). At that level it was also possible to sample an ECG–synchronized systo–diastolic pulse–wave (PW)–Doppler pattern (peak velocity 125 cm/s), typical for a coronary artery flow. According to these echocardiographic findings, we supposed a giant right coronary aneurysm. Coronary Computed Tomography Angiography with 3D reconstruction showed a giant aneurysm of the right coronary artery at mid–level, preceded by a mild aneurysm of the proximal tract and two small aneurysms of the circumflex artery and diffuse atherosclerosis diseases with significant stenosis on mid left anterior descending artery (LAD). The coronary angiography confirmed the presence of the giant aneurysm in mild tract of right coronary artery preceded by a small one in the proximal tract andthe two small aneurysm of the circumflex artery and a critical stenosis of mid tract of LAD. The patient underwent surgical treatment of the aneurysm and coronary artery bypass graft (Fig. 3). Computed Tomography Coronary Angiography is the best method for coronary artery anatomy and coronary abnormalities. In case of giant coronary abnormalities, the use of echo contrast agent provides further important information about perfusion and/or flow assessment and it helped to clarify the diagnosis.

Tornados and cyclones driven by Magneto-hydrodynamic forces

A numerical analysis is carried out to explore the variety of flow structures induced inside a conducting fluid emerging from the interaction of an electric current source with an external axial magnetic field. Results are obtained for Shercliff (S) numbers up to 1010 and Hartmann (Ha) numbers up to 115, for a single magnetic Prandtl number of Pm=8.6× 10−7. Depending on these numbers, very different swirling flow patterns are predicted. Transitions seem to be solely controlled by two dimensionless ratios Γ=Ha/(PmS)1/2 and N=Ha6Pm/S.For low Γ, vortex-breakdown, tornados and cyclones are obtained. These MHD tornados are found to be very similar in structure to atmospheric tornados. A slight increase in Γ results in the transformation of the tornado into a cyclone which rotates at relatively constant angular velocity. Surprisingly for further increase in Ha, the cyclone is restructured into an inverted tornado. The induced currents are found to be at the origin of this phenomenon. For large N, a Hartmann swirling flow occurs which is associated with almost vertical electric current lines. In this regime, both poloidal and azimuthal flows are damped, and remain mainly present in the forcing region at the edge of the electric current column. These results may be of relevance for the understanding of flow structures in the atmosphere, in aluminum reduction cells, electro-metallurgical processes, and in liquid metal batteries.

Hydrodynamics of Similar Gases in Vortex Mixers: Effect of Physical Properties on the Onset of Instability

The effect of physical properties of gases on the flow hydrodynamics and on the onset of instability was studied to acquire information on how to design fast mixers specific for relevant operations where complete and improved gas mixing is important. To assess the effect of physical properties on the gas flow dynamics in vortex mixers, three gases hydrogen, nitrogen, and argon were chosen because of the viscosity and density differences they provide. Using flow visualization and PIV flow-field characterization techniques, critical Reynolds numbers of flow regime changes were identified from segregated to engulfment flow regimes for three pairs of gases. It was shown that the first critical point of the flow, where the gases have a full rotation in the chamber, depends on the inertial force in terms of dynamic pressure. While hydrogen having the highest kinematic viscosity had a full rotation at Re = 40, nitrogen and argon gases had their full rotation at Re = 70. After these points, a steady rotational flow as a consequence of the balance between the centrifugal and centripetal forces was observed. Similarly, the onset of the engulfment regime was observed earlier for hydrogen, at Re = 150, while it was at Re = 200 for nitrogen and Re = 220 for argon. The present study shows that the gas properties are effective parameters not only on the critical points but also on the shape of the swirling flow pattern formed in the mixer.

Computational Assessment of Hemodynamics Vortices Within the Cerebral Vasculature Using Informational Entropy.

Propper assessment of hemodynamic swirling flow patterns, vortices, may help understand the influence of disturbed flow on arterial wall pathophysiology and remodeling. Studies have shown that vortices trigger pathologic cellular changes within the vasculature such as increased inflammation and cellular apoptosis, leading to weakening of the vessel wall indicative of aneurysm development and rupture. Yet many studies qualitatively assess the presence of vortices within the vasculature or assess only their centermost region (critical point analysis) which overlooks the broader characteristics of flow, leading to a narrow view of vortices. This chapter provides a protocol for utilizing commercially available computational fluid dynamic software (ANSYS-FLUENT) to simulate realistic hemodynamic flow patterns, fluid velocity, and wall shear stress in the complex geometry of the cerebral vasculature, as well as an innovative method for assessing flow vortices. This innovative analytic methodology can identify areas of flow vortices and quantify how the broader bulk-flow (opposed to critical point) characteristics change in space and time over the cardiac cycle. Analysis of such flow structures can be used to identify specific characteristics such as vortex stability and the portion of an aneurysmal sac that is dominated by swirling flow, which may be indicative of vascular pathologies.

Physics-Informed deep learning to predict flow fields in cyclone separators

Cyclone separators are devices whose modeling still represents a significant challenge, despite their vast use as a fundamental component in different industries. Computational Fluid Dynamics (CFD) simulations have been proved to be a suitable tool to predict the swirling flow pattern in such a separator device. Although CFD can be very accurate, the computational resources involved in these simulations restrict its use. In this sense, this work proposes a Physics-Informed Neural Networks (PINN) as a data-driven reduced-order model that respects the flow field behavior and the mass and momentum conservations from the Navier-Stokes Equations. The results show that PINN can capture the complex flow behavior from both velocity and pressure fields. In PINN, momentum conservation is used as output in the training step and respected the same specified tolerance in the simulations. The PINN model’s mass conservation presented the same order of magnitude of the CFD simulations in 96% of the mesh. From our results, one can see that the PINN models are in good agreement with the experimental data and the CFD simulations, with the advantage of being 200 times faster than the CFD simulation.

Experimental and Numerical Studies of Combustion Characteristics in Swirling Fluidized Bed Gasifier Using Palm Cake as Feedstock

In this work, combustion characteristics in swirling fluidized bed gasifier using palm cake as feedstock was studied experimentally and numerically. A 3-D numerical model of reactor was created using ANSYS (Fluent) and was compared with experiment in the same scale. The diameter (D) was 0.20 m, and the reactor length was 1.50 m. The double air inlet pipe with an inner diameter of 46.8 mm was assembled tangentially to the bottom of the reactor. An equivalent ratio (ER) was fixed at ER=0.3. The results showed that the result of experiment and numerical studies is almost similar. For highest temperature of the reactor occurred in combustion zone which is high from reference point (bottom end of the reactor) of 0.25 m for experiment and 0.35 m. for simulation. For swirling flow pattern was occurred at the bottom rather than the top of the reactor. So, the result of numerical studies can predict the phenomena inside the reactor which is similar to experiment test.

A novel particle-to-fluid direct-contact counter-flow heat exchanger for CSP power generation applications: Design features and experimental testing

A novel particle-to-fluid direct-contact counter-flow heat exchanger (PFDCHX) is introduced and investigated. The proposed heat exchanger offers efficient integration with an air-breathing power cycle. A proposed particle-based power tower integrated system using the PFDCHX is presented. The PFDCHX system comprises two main parts: the particle handling unit (PHU) and the direct-contact heat exchanger (DCHX). The PHU delivers solid particles to the pressurized DCHX, a manifold assembly was deployed to separate particles into several separate streams to be injected at the upper end of the DCHX via several distributor pipes. Several enhancement features were considered to prevent particle carryover, including a tangential inlet for the pressurized air (at the bottom end of the DCHX), particle–air disengagement zone (at the top end of the DCHX), and a tapered-shaped heat exchange chamber. Results showed that, for tests with excessive particle flow rate, more than 80% of the temperature rise was achieved within 0.35 m above the air inlet, attributed to the tangential inlet’s swirl flow pattern. The overall temperature rise along the heat exchanger was not significantly influenced by a change in operating air pressure from one barg to three barg.