Circumferential Flow Research Articles

A new reciprocating straight propulsion for high propulsive hydrodynamic efficiency

The majority of underwater vehicles currently use screw propellers as propulsion method. Despite screw propellers are being promoted to increase the efficiency through better designs and technologies, the circumferential flow caused by the rotation of screw propeller results in wasted energy. This paper proposes an ideal reciprocating straight propulsion paradigm that eliminates this waste by implementing straight backward thrust based on a foldable mechanism. This mechanism can implement a maximized propulsion during the propelling stroke and a minimized resistance during recovery by folding and unfolding the mechanism, which can be adjusted passively via the relative motion between the thruster mechanism and water avoiding using sensors and actuations. This principle makes the reciprocating straight propulsion simple and reliable to be achieved in practice. Besides, a modularized propulsion system with four identical independently thrusters based on the proposed mechanism was proposed, achieving various motion modes in underwater vehicles. The proposed propulsion mechanism was theoretically analyzed and verified through simulations and prototype tests. In mooring tests, the thrust provided by the proposed mechanism is similar to the simulation results. The propulsion performance indicator of an underwater vehicle with the proposed propulsor reached 66 %. The mechanism could turn even with one-sided propulsion.

Computational Investigation of the Operating Mechanism of the Ranque–Hilsch Vortex Tube

Abstract The Ranque–Hilsch vortex tube is a device that splits an incoming flow into two outgoing streams, but with the peculiar property that one stream exits at a lower total temperature than the incoming flow and the other at a higher total temperature. This temperature separation is accomplished without any moving parts, electronics or external power supplied to the device. Despite the passage of nearly a century since discovery of the effect, there remains a dearth of understanding regarding the mechanism responsible for the phenomenon. In fact, the literature contains competing theories with little evidence providing support. A promising technique to discern the responsible mechanisms for the energy transfer from the ultimately cold stream to the ultimately hot stream is to define a stream tube in a computational simulation of the flow that propagates upstream from the exits such that the stream tube interface separates the hot flow from the cold flow. In this article, we apply this method to a three-dimensional, full-volume analysis of the flow within a vortex tube using a computational simulation that was thoroughly validated against experiments on a physical replica of the computational geometry. In this novel study, the integral form of the energy equation was used to quantify all forms of the energy transfer within the vortex tube. The results demonstrate that the phenomenon of temperature separation is attributable primarily to viscous work in the radial direction due to the circumferential flow, with a lesser contribution from heat transfer in the radial direction.

A study on the internal vortex structure within a single-blade pump via numerical methods and particle image velocimetry experiments

This study investigates the performance and internal flow characteristics of a single-blade centrifugal pump through a comprehensive analysis integrating performance tests, Particle Image Velocimetry (PIV) tests, and numerical simulations. Across the operational speed range of 1470–2940 rpm, the predicted pump (head-flow rate curve)performance error between the numerical simulation results and the test results of the pump underrated flow conditions is found to be only 3.4%, demonstrating the high accuracy of the selected numerical method in predicting both performance metrics and internal flow structures. Key findings highlight the presence of significant circumferential and axial secondary flows in the region where the blade wraps back, resulting in the formation of high-intensity vortex structures and subsequent energy dissipation. The interaction of the blade's trailing jet with the volute casing's tongue induces periodic changes in the intensity and spatial size of these vortex structures. Furthermore, pronounced reverse vortex pairs are identified within the volute casing, attributed to axial non-uniformity in impeller outflow. These vortex pairs are associated with the preferential accumulation of solid particles, potentially contributing to wear in the volute casing of single-blade centrifugal pumps. The revelation of the evolution characteristics of vortex structure in single-blade centrifugal pumps provides theoretical support for reducing pressure pulsation and radial force of single-blade centrifugal and provides a potential solution to the technical difficulties of low efficiency and poor stability of single-blade centrifugal pumps. Overall, this study provides valuable insights into optimizing the design and operational efficiency of single-blade centrifugal pumps by elucidating their complex flow dynamics and performance characteristics under varying operational conditions.

Effect of flow direction on circumferential velocity, radial velocity, and flow resistance characteristics of rotating gap structures

A rotating gap structure is a type of viscous flow resistance using two disks where the rotation of one disk drives the fluid within the gap, generating rotational inertia. This inertia, combined with viscous friction, determines the flow resistance characteristic curve (pressure drop vs flow rate, or Δp-Q curve). By adjusting the disk's rotational speed, the rotational inertia and the Δp-Q curve can be modified. This paper examines how the radial flow direction (positive and negative) affects the circumferential velocity, radial velocity, and the Δp-Q curve of the rotating gap structure through theoretical modeling and experiments. Results show that radial flow direction and rate influence the symmetric distribution of radial velocity and the linear distribution of circumferential velocity, altering the main components of the Δp-Q curve: the viscous flow resistance curve (Δpvis-Q) and the rotational inertia flow resistance curve (Δprot-Q). The study found that the slope of the Δpvis-Q curve is smaller for positive flow than for negative flow due to differences in radial velocity distribution. Additionally, the circumferential velocity is weakened in positive flow and enhanced in negative flow, resulting in a smaller slope of the Δprot-Q curve for positive flow. These factors cause the Δp-Q curve to deviate from linearity, with greater deviation at higher rotational speeds. Finally, experimental verification was conducted, and the measured Δp-Q curve closely matched the theoretical calculations.

Optimization Study of the Structural Parameters of an Artificial Percolation Intake Riverbed Based on a Numerical Orthogonal Test

Research on water abstraction techniques in sandy rivers is crucial for addressing water scarcity issues in northern China. This study introduces an artificial percolation water intake riverbed structural model designed to prevent sand intake and facilitate the extraction of clear water from sandy rivers, the main function of which is to artificially construct a helical flow field to realize the separation of water and sand and, at the same time, percolate the water. In this paper, we use a numerical orthogonal test method to study the influence of structural parameters and their combinations on water extraction by percolation, and the preferred combination of structural parameters. The main conclusions of this paper are as follows: Under the condition of certain structural parameters of the artificial riverbed, the single-width flow rate has an important effect on the mean circumferential flow rate of the vortex tube and the vortex tube seepage volume. The effect of different structural parameters on the mean circumferential flow rate of the vortex tube and the vortex tube seepage varies in magnitude. The longitudinal slope of artificial riverbed i had the greatest and most significant effect on the mean circumferential flow rate of the vortex tube, and each structural parameter had some effect on the vortex tube seepage Q but not to a significant level. When the sand content of the water flow is 15 kg/m3 and the maximum sand grain size of the suspended mass is 2 mm, the optimal structural parameter combinations of the artificial riverbed under different working conditions are as follows: Combination 20 is the optimal structural parameter combination for q = 0.3 m2/s; Combination 24 is the optimal structural parameter combination for q = 0.6 m2/s; and Combination 24 is the optimal structural parameter combination for q = 0.9 m2/s. The present study is of great significance for understanding the influence of each structural parameter and its combination on the effect of the water intake and sand discharge of an artificial percolation intake riverbed, and for optimizing the combination of the structural parameters of an artificial percolation intake riverbed.

Numerical Simulation Study of an Artificial Percolation Riverbed and Its Hydraulic Characteristics under Different Reynolds Numbers

The direct extraction of clear water from a sandy river is a difficult task and can only be achieved through specific engineering measures. This paper proposes an artificial percolation riverbed structure for extracting clean water from sandy rivers, using a numerical simulation to study the flow field distribution characteristics of the structure under clean water conditions. The main conclusions are as follows: When the percolation vortex tube opening rate is 1.4%, the vortex tube with or without opening the percolation hole has little influence on the distribution characteristics of the flow field in the artificial riverbed, and the purpose of water extraction can be achieved while constructing a helical flow field. The axial flow velocity and circumferential flow velocity of the vortex tube cross-section under different Reynolds numbers show the distribution of a low-flow velocity close to the center of the vortex tube, and a high-flow velocity close to the vortex tube side-wall area. The average axial flow velocity and average circumferential flow velocity of the vortex tube show a trend of increasing and then decreasing distribution along the axial axis of the vortex tube in the direction of the sediment transport flume. The mean axial flow velocity of the vortex tube along the axis of the vortex tube toward the sediment transport flume and the mean circumferential flow velocity both show a distribution trend of increasing and then decreasing. At the junction of the vortex tube and the sediment transport flume, there are obvious pressure changes, and the pressure changes drastically under the same horizontal line. Along the direction of the bottom line of the vortex tube, the pressure at the vortex tube is obviously greater than that at the sediment transport flume. The vortex of the artificial percolation riverbed is mainly concentrated in the vicinity of the vortex tube, and the maximum value of the vortex intensity generally occurs at the junction of the vortex tube and the sediment transport flume. With the increase in the Reynolds number, the vortex intensity has an overall increasing trend, and the distribution of the vortex is more complex. This study helps to elucidate the distribution characteristics of the flow field in the artificial percolation riverbed, and it provides a reference basis for the future study of the flow field of artificial percolation riverbeds of sandy rivers.

Flow Structure and Periodic Processes in a Disc-Shaped Vortex Chamber of a Hydrodynamic Cavitator

Introduction. The essence of the acoustic – cavitation processes is that the liquid is passed through sound with a pressure at the wave surface of more than 3 bar that causes local breaks of the liquid in the vacuum phase of the wave and the collapse in the manometric phase. The opposite walls of each cavern in the collapse approach at a speed exceeding two speed of sound, due to which a high energy density is achieved at the meeting point, and what is especially valuable is the mutual transitions of energies from one form to another, unattainable under normal conditions, and, moreover, as inside cavitation area and near it. The novelty of the work is confirmed by the results of a periodic information and patent analysis, and by four patents received for inventions on the topic under consideration.Aim of the Study. The study is aimed at improving the acoustic-cavitation qualities of a disk-shaped vortex chamber used as a liquid whistle.Materials and Methods. In the study, there were used numerical modeling of flows in the FlowVision program, experimental determination of flow rates using a pitot tube, film method, removal of frequency response using SpectraPLUS 5.0, and visualization of flows and processes on optically transparent devices by the method of color indicators in stroboscopic lighting high-speed video shooting.Results. The mechanism of sound generation and noise in the flow transiting through the device has been found. The corrective effect of pump pulsations f = 300 Hz on the sound generation mechanism was revealed. The disc-shaped character of the device, which encloses the input flow in cross section from three directions, contributes to creating a more expressive acoustic signal, forming two conjugate torus vortices along the shell that ensures uniformity of the circumferential flow, attenuation of longitudinal high-frequency oscillations f = 200 kHz, and the creation of periodic zones of increased pressure along the shell. The concentrated tangential entrance to the device determines the central asymmetry of the flows in it and a number of processes that create acoustic noise.Discussion and Conclusion. The frequency of the useful acoustic signal in the vortex chamber is proportional to the speed of the transit flow, and the amplitude is proportional to the dimensions of the device. Along with the useful signal created by the interaction of the peripheral and input parts of the transit flow, noise of similar frequencies is created in the device. Other sources of noise generation are due to the presence of a concentrated tangential input. The formation of two conjugate torus vortices along the shell can be used as a means of controlling the process of interaction between parts of the transit flow. The disc-shaped vortex chamber combines the functions of sound generation and the ability to create a centrifugal field, which expands its technological capabilities.

Study on the influence of labyrinth seal structure on the performance of shrouded stator cascades with inter-stage cavities

Numerical simulations of a shrouded stator cascade with an inter-stage cavity were conducted using validated numerical methods to investigate the impact of different labyrinth seal structures and positions on the aerodynamic performance of the stator cascade. The study discussed the development trends of secondary flow motion and corner separation within the cascade under different labyrinth seal structures, evaluated the stator performance using total pressure loss coefficient and entropy-based loss coefficient, and revealed the interaction between cavity leakage flow and mainstream flow. The results indicate that individually changing the labyrinth seal structure or position has a negligible impact on stator performance, but simultaneously altering both the structure and position of the labyrinth seal can effectively reduce stator losses. The structure case 1-position case 2 labyrinth seal structure can reduce total pressure loss by 6.25%, while structure case 4-position case 4 reduces entropy increase loss coefficient by 7.67%. Additionally, it was found that changing the labyrinth seal structure and position can increase the circumferential velocity and momentum of cavity leakage flow at the cavity outlet, enhance the resistance of cavity leakage flow to circumferential secondary flow within the stator passage, and reduce stator losses. Altering the structure and position of the labyrinth seal effectively reduces the cavity leakage vortex at the leading edge of the cascade during the mixing process of cavity leakage flow with the mainstream, causing the passage vortex to move rearward axially.

Performance improvement of multi-blade centrifugal fan based on impeller outlet flow control

The impeller of the multi-blade centrifugal fan significantly impacts the fan's internal flow field and aerodynamic performance. To improve the axial flow distribution along the impeller and suppress the blade passage backflow at the impeller outlet of multi-blade centrifugal fans, a method of variable chord length blade design is proposed. Simultaneously, optimization models are established with static pressure and efficiency as objectives. By altering the control points of the Bezier curve, the leading-edge profile of the impeller is optimized. The results indicate that using variable chord length blades can expand the operating range of the multi-blade centrifugal fan. The maximum flow rate improvement reaches 10.6%. Significant enhancements in the aerodynamic efficiency of the multi-blade centrifugal fan are observed at low flow rates, with a maximum improvement of 4.9%. The variable chord length blade design method enables adjustment of the axial flow distribution at the impeller outlet to better match the impeller's flow requirements. This leads to increased outlet flow on both the shroud and hub sides of the impeller, consequently reducing the backflow area on both sides and improving the blade passage backflow phenomenon. Moreover, variable chord length blades facilitate a more uniform circumferential flow distribution at the impeller outlet, reducing the diversion pressure of the volute tongue, mitigating flow separation within the blade passage, weakening the interaction between the impeller and the volute tongue, and lowering energy losses in the impeller–volute tongue regions. Consequently, this enhances the aerodynamic performance of multi-blade centrifugal fans.

Numerical investigation of energy dissipation and vortex characteristics on the S-shaped region of a reversible pump-turbine

In order to meet the regulation needs of power system, the pump-turbine is prone to operate in the S-shaped region during frequent start-up, leading to unit vibration and grid connection failure. In this paper, the S characteristic experiment was carried out, and the entropy production, unstable flow and vortex structure under turbine, runaway, turbine breaking, reverse pump conditions with optimum guide vane opening are detailed analyzed. The relationship between the energy dissipation and flow field characteristics is clarified. The results show that the runner entropy production is the largest in all components, and the wall entropy production is greater than the fluctuating entropy production under turbine condition. With the decrease in discharge, the fluctuating entropy production and wall entropy production first increase and then decrease, reaching the maximum values in the runaway condition. The circumferential movement trend of water enhances, and forms circumferential flow in the vaneless region. The separation vortex formed on the blade suction surface extends from the blade inlet to the middle of the flow channel, inducing a high entropy production. Under the turbine braking condition, the tangential velocity increases rapidly in the vaneless region. The circumferential flow develops into water ring, blocking the water flows into the runner. Under the reverse pump condition, the water flows in the opposite direction, with negative tangential and streamwise velocities. The absolute flow angle becomes obtuse, and a large-scale reverse vortex is formed. The runner inlet is blocked by the water ring, and the flow channel is almost completely filled with the low-speed region. The proportion of the guide vanes entropy production reaches maximum. Unstable flow leads to the increase in vorticity. Separation vortex, bypassed vortex, and reverse flow vortex leads to an increase in VST, forming a high VST region at corresponding positions. Due to the rotational motion accompanying the development of separated vortex, it leads to the increase in CFT. In addition, the circumferential flow and water ring have higher tangential velocities, which can lead to high CFT regions.

Power engineering of the tangential supply device of the microturbine of the thermal control system of a promising spacecraft

This paper presents an overview of the current technical problem related to two-phase spacecraft thermal control systems and possible technical applications of thermal energy recovery in the organic Rankine cycle as an integral part of thermal management systems. The design solution involves the integration of a steam microturbine behind an evaporator radiator. The microturbine is a tangential supply device and a radially centripetal impeller of low speed nst40. In this area, there is no reliable data on the design and energy of both the supply device and the impeller. The energy (loss of enthalpy) of the supply device mainly determines the transport of the swirling flow to the impeller and, as a result, the circumferential operation on the turbine. A prototype of a radial microturbine has been developed and presented in order to evaluate the design of the flow part of both the supply device and the impeller. As a result of the analysis, the main determining hydrodynamic areas necessary for hydrodynamic analysis and mathematical elaboration of the flow calculation algorithm with an assessment of energy losses are identified: the flow of a swirling flow of a radial-annular slit; axial-annular slit and tangential supply device. The first two algorithms assume computational modeling, the model of energy losses in a tangential supply device is not amenable to analytical modeling because it includes a sequence (or compatibility) of flows under boundary conditions defined as “local resistances”: the sudden expansion, reversal of the flow, together with a section of radially circumferential flow, the mutual influence of these boundary conditions assumes only an expe rimental assessment of energy losses in a tangential supply device through the loss coefficient of local resistance in the range of changes in geometric and operating parameters. As a result of experimental studies, a database has been proposed on the loss coefficient of tangential microturbine supply devices in the field of the practical range of the existence of operating and design parameters.

A comparative study on rotordynamics characteristics of hole-pattern damping seals with different cavity shapes

PurposeThe purpose of this paper is to improve the seal performance by proper design of the cavity shape of the damping holes, especially the rotordynamics characteristics of the hole-pattern damped seal (HPDS).Design/methodology/approachA new damping seal structure that comprises a circle-shaped cavity and two directional leaf-shaped cavities with a dovetail-shaped diversion groove is proposed. The comparative study on the sealing characteristics of dovetail-shape, leaf-shape and classical circular HPDSs was carried out using ANSYS CFX.FindingsThe dovetail-shaped HPDS significantly outperformed two other damping seal designs in leakage and rotordynamic performance. At a rotating speed of 7,500 rpm, it showed a 25% reduction in leakage, a 23% increase in average effective damping and a 119% increase in average effective stiffness. The cross-coupled stiffness Kxy shifted from positive to negative, reducing circumferential flow. The dovetail's inclined leaf-shaped grooves create a double vortex that slows jet velocity in the seal clearance and alters spiral flow direction, resulting in a uniform pressure distribution and enhanced rotor stability at low frequencies.Originality/valueThis study proposes a novel HPDS with dovetail-shaped diversion grooves. The seal can realize the simultaneous improvement of rotordynamics and leakage characteristics compared to the current seal structure.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0127/

Surface integrity improvement of the ground surface of Inconel 718 fabricated by forging and additive manufacturing using a robotic rotational burnishing method

Given that the surface acts as the primary interface with the surrounding environment, the surface integrity of a component significantly influences its operational effectiveness. In the aerospace industry, materials like Inconel 718 are often utilized for their high-temperature strength despite their poor thermal conductivity and machinability, resulting in inferior surface integrity during grinding procedures. This research proposes an innovative robotic rotational burnishing method that leverages self-generated heat to aid in the post-grinding burnishing process, eliminating the need for an external heat source. The surface integrity achieved through this method undergoes a comprehensive evaluation, encompassing surface topological features, microstructure, and mechanical properties, and is compared with surfaces treated by grinding and slide burnishing. The findings demonstrate that during the rotational burnishing process, the friction between the high-speed rotating burnishing tip and the workpiece surface induces circumferential flow of the surface material, thereby enhancing surface anisotropy. Additionally, this process generates significant heat, further encouraging plastic deformation of the material surface under high burnishing forces. As a result, the surface acquires a compressive residual stress exceeding 1000 MPa and develops a microhardness-strengthened layer with a thickness exceeding 500 μm. Both forging and additive manufacturing techniques for preparing Inconel 718 raw materials yield consistent outcomes. This study not only achieves a fusion of additive, subtractive, and equivalent manufacturing but also validates the applicability of the proposed robotic rotational burnishing method in enhancing surface integrity across materials manufactured by various techniques.

Systematical study on the aerodynamic control mechanisms of a 1:2 rectangular cylinder with Kirigami scales

Biomimetic flow control is being widely applied. In the present study, a biomimetic flow control method, i.e., Kirigami scales, was applied on a 1:2 rectangular cylinder. The effects of scales' shapes and pasting surfaces on the aerodynamics and circumferential flow patterns of a 1:2 rectangular cylinder were studied. Three scale shapes were investigated with different pasting methods, i.e., elliptical, circular, and triangular scales. The Reynolds number (Re) was set at 1.3–3.1 × 104. The surface pressure distributions and the integrated aerodynamic forces were further analyzed at Re = 1.3 × 104. Results show that pasting the elliptical scales on all surfaces performs best, reaching a 2.4% drag reduction and a 76.4% lift reduction. Moreover, the elliptical and triangular scales on the windward and leeward surfaces can significantly reduce the Re effect. To reveal the control mechanism, the particle image velocimetry technique was employed to obtain the circumferential and wake flow fields. The time-averaged and phase-averaged results indicate that the Kirigami scales can push the interactions of shear layers and the shedding vortices further downstream. The Proper orthogonal decomposition analysis and time-averaged turbulent kinetic energy (TKE) results indicate that the wake vortex shedding is significantly suppressed. The spanwise wake flow field was also investigated. Results show that the spanwise TKE values are significantly reduced. This study further deepened the application of Kirigami scales on the common blunt bodies.

Experimental and numerical investigation on rotating stall flow pattern in a counter-rotating axial compressor

Rotational stall is a common flow instability phenomenon in axial and centrifugal compressors. The experimental and numerical results of the three-dimensional flow field in a low-speed counter-rotating axial compressor operating in deep rotating stall are presented in this paper. The obtained results provide a detailed description of the flow inside and outside the stall cell. The circumferential flow of the reversed flow upstream and downstream is dominated, respectively, by the counter-rotating front and rear row rotors. The reverse flow downstream reenters the rear row rotor and the front rotor at higher blade heights, undergoing repeated work by the rotors. This leads to the formation of a high-pressure region at the leading edge of stall cell, which is essential for maintaining stall conditions upstream of rotors. Stalls primarily occur in the middle and tip regions with elevated pressure, while the downstream stall cell exhibits significant spreading from hub to tip with some circumferential bias.

Flow and Heat Transfer Experimental Study for 3D-Printed Solar Receiving Tubes With Helical Fins at Internal Surface

Abstract 3D-printing technology was applied to fabricate novel solar thermal collection tubes that have internal heat transfer enhancement fins and external surfaces with high solar absorptivity and low emissivity due to the ability to use different materials in one tube. Helical fins were selected to introduce circumferential flow and thus minimize the circumferential temperature difference of the tube that receives sunlight on one side. The structures of the helical fins were previously optimized from computational fluid dynamics (CFD) analysis with the objective of low entropy production rate by looking for high heat transfer coefficient and relatively lower pressure loss. High-temperature alloy, Inconel-718, was used to 3D print the tubes, which can resist corrosion for the potential application of molten chloride salts as heat transfer fluid. Experimental tests were carried out using water as the heat transfer fluid with the high heat flux provided by a tubular furnace heater. The tested Reynolds number ranges from 3.9 × 103 to 6.1 × 104. Heat transfer coefficients of up to 2.8 times that of the smooth tube could be obtained with the expense of increased pressure loss compared to that of the smooth tube. The total system entropy generation can be significantly reduced due to the benefit of heat transfer enhancement that is greater than the expenses of the increased pressure loss. The experimental results of the 3D-printed heat transfer tubes confirmed the CFD-based results of fin optimization. The novel heat transfer tube is recommended for application in concentrating solar power systems.

Numerical simulation of single-phase flow and heat transfer characteristics of three-petal shaped fuel assembly

Petal-shaped fuel rods are an important means to realize reactor miniaturization and high power density. This paper establishes a numerical analysis model of a triangularly arranged 7-rod bundle with three-petal shaped fuel assembly, analyzes the single-phase flow and heat transfer characteristics under cosine heating conditions, and compares it with a four-petal shaped fuel assembly. The results show that the helical structure of the petal-shaped fuel rods can induce lateral fluid flow, generate secondary flow, and enhance the churning ability between fluids. Its unique structure makes the circumferential heat flow density, temperature, and Nussle number (Nu) on the fuel surface periodically non-uniformly distributed. Compared with the four-petal rod, the three-petal rod performs better in the circumferential direction in terms of heat transfer and temperature distribution uniformity. The related research results provide a theoretical basis for the application of petal-shaped fuel elements in reactors.

Effect of concave‐wall jets with circumferential multi‐inlet on liquid–solid separation

AbstractThis study combined numerical simulation and experiment to explore the influence of the concave‐wall jets with uniformly distributed tangential inlets in the cyclone separator on the liquid–solid separation characteristics and equipment. The results show that as the number of tangential inlets increases, the superposition effect of particle trajectories and flow fields becomes more significant. The superimposed flow field enhances the circumferential flow velocity of the fluid, causing the distribution of the jet along the radial and spanwise directions to shrink, greatly improving the uniformity of particle distribution and turbulent kinetic energy along the circumference, and effectively reducing the impact of particles on local areas near the jet inlet. Since the superposition of circumferential multi‐inlet jets enhances the swirling flow, the local disturbance and wall erosion effects near the jet inlet were reduced. Compared with double inlets, the flow rates of three inlets and four inlets were increased by 50% and 100%, respectively, the maximum turbulent kinetic energy increased by 14.5% and 56.2%, and the maximum escape time of particles was shortened by 3.2 and 3.3 s, respectively, the maximum erosion rates were reduced by 38.4% and 23.6%, respectively, and the separation efficiency and material handling capacity were significantly improved. This study supplemented the theory of concave‐wall jets' superposition characteristics and provided a theoretical basis for applying circumferential multi‐inlet devices in liquid–solid separation equipment.

Blind zones in radiating dispersion at high Péclet number driven by non-Newtonian fluids in porous media

A wide range of environmental, energy, medical and biological processes rely on dispersive transport through complex media. Yet, because of the stagnant and opaque nature of the microscopic system, the role of disordered flow and structure in the dispersive transport of solutes remains poorly understood. Here, we use a circular porous microfluidic system to investigate the radial dispersion in porous media driven by non-Newtonian fluids with strong advection rate (or at high Péclet number) and low-to-moderate Reynolds numbers. We observe for the first time the presence of diffusion ‘blind zones’ in the microstructure for high solution injection velocities. More specifically, an in-depth analysis uncovers that the circumferential flow frame, coformed by obstacles and vortices especially the ‘twin-vortex’ with same rotation direction, is responsible for the diffusion ‘blind zones’ and transport heterogeneity. The vortices are induced by the coupling of microfluidics and porous structures, and correlated to inertial flow-induced instabilities. The trade-off between diffusion efficiency and quality/completeness with respect to the high Péclet number (or high inlet velocity) serves to enhance our comprehension of intricate fluid dynamics and affords a set of principles to aid a diverse range of practical implementations.

Enhancement of Convection and Molecular Transport into Film Stacked Structures by Introduction of Notch Shape for Micro-Immunoassay.

A 3D-stack microfluidic device that can be used in combination with 96-well plates for micro-immunoassay was developed by the authors. ELISA for detecting IgA by the 3D-stack can be performed in one-ninth of the time of the conventional method by using only 96-well plates. In this study, a notched-shape film was designed and utilized for the 3D-stack to promote circulation by enhancing and utilizing the axial flow and circumferential flow in order to further reduce the reaction time. A finite element analysis was performed to evaluate the axial flow and circumferential flow while using the 3D-stack in a well and design the optimal shape. The 3D-stack with the notched-shape film was fabricated and utilized for the binding rate test of the antibody and antigen and ELISA. As a result, by promoting circulation using 3D-stack with notched-shape film, the reaction time for each process of ELISA was reduced to 1 min, which is 1/60 for 96 wells at low concentrations.