Inlet Structure Research Articles

Overwash‐dominated stratigraphy of barriers with intermittent inlets

AbstractThe morphodynamics and structure of barriers with persistent tidal inlets have been well studied. In contrast the stratigraphy and functioning of barrier systems with ephemeral inlets is poorly understood. This article examines the barrier‐inlet systems of two intermittently closed open lagoons or temporarily open closed estuaries on the east coast of South Africa. Multiple geophysical surveys using ground‐penetrating radar (GPR) were correlated with exposed sections of the barrier where inlet formation revealed the internal stratigraphy. Stratigraphic observations were placed in the context of the contemporary wave dynamics and mesoscale geomorphic evolution. The integrated databases reveal an absence of migrating channel features. Instead the stratigraphy is dominated by landward dipping sheets of alternating high‐ and low‐amplitude reflectors. These correlate with gravel, shell debris and heavy mineral‐lined beds formed by overwash processes. Where ephemeral inlet structures are preserved in the stratigraphy, their fills comprise aggrading, high‐amplitude reflectors, linked to washover infilling of the inlet mouth. Multiple small channels in the more distal portions of the barrier in georadar stratigraphy are related to channelized washover flow.These barriers often breach during high swell and are subsequently sealed during fairweather wave conditions. Time series analysis of waves and satellite imagery shows a link between storms from the south and breach events. This is consistent with the truncations in subsurface images and inferred barrier lowering by overwash channelling. These barriers experience quasi‐stable oscillations in their landward and seaward shore position, punctuated by periods of barrier rollover associated with the most intense storms. As overwash is responsible in part for both the constructive and destructive phases of the barrier, these barriers have low preservation potential. Persistent rollover driven by overwashing will terminate once accommodation space is eliminated and the barriers are eroded by storm activity. © 2019 John Wiley & Sons, Ltd.

Optimal Configuration of an Underdrain Delivery System for a Stormwater Infiltration Trench

AbstractPerformance of a green infrastructure (GI) tree trench comprising planters, an underground rock infiltration bed, inlet structures collecting runoff, and a perforated underdrain pipe delive...

Development Methods for the Formulation of Community Empowerment-Based Oxbow Stream Utilization Models in Citarum River

Citarum River stretches wide and long through village and city lands with straight, winding paths, and meanders. In the meander section, sediment deposits occur which result in the stunted flow causing floods or overflowing water out of the river. To overcome this problem, river shortcuts were constructed to straighten the stream, which results in disconnected reaches called oxbow rivers. This study presents a method development of a community empowerment-based oxbow rivers utilization which taking a case study on one of the ten oxbow rivers located along the Citarum River. The selected oxbow river is the one that located in Cibarangbang, Baleendah Village of West Java province with a length of 860.36 m, 10 m width, river bank height of 4.97 m and area of 100 ha. The utilization of oxbows is aimed to address technical and socio-economic problems through either of these three main approaches: 1. oxbow river as a means of conservation/revitalization of rivers by maintaining the function of oxbow lakes as a water reservoir, e.g., by making an impoundment, an inlet and outlet structures, a maintenance road, etc; 2. utilizing the area for public infrastructure and facilities through land reclamation; 3. using the area as a tourism site.

Experimental study of the air emission effect in the tangential and the multi-stage spiral inlet

Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.

Effect of light phase inlet structure on liquid-liquid cyclone reactor for isobutane alkylation catalyzed by ionic liquid

The liquid-liquid cyclone reactor (LLCR) is a new and promising device suitable for the fast reaction and separation for the liquid-liquid system, such as isobutene alkylation catalyzed by acidic ionic liquids. The effect of the number and the width of light phase inlet structures of LLCR on the mixing and separation performance was investigated. The Euler-Euler model and Reynolds Stress Model were used as the multiphase model and the turbulence model, respectively. The mean local turbulence dissipation rate, mean residence time and separation efficiency of Type O (dual-inlet), Type A (tetra-inlet with half width) and Type B (dual-inlet with half width) were obtained to compare the mixing and separation performance. The results showed that both the mixing performance and the separation performance improved with the increasing number of light phase inlet. The width reduction of light phase inlet could result in the decrease of the droplet breakup, the increase the mass of transfer time and the separation efficiency.

Flow Field and Combustion Characteristics in Localized Stratified Swirling Tubular Flame Burner: Numerical Investigation

ABSTRACTA three-dimensional numerical simulation of a localized stratified tubular flame burner is carried out by using propane as fuel. The characteristics of the flow field, species distribution, flame structure, and stability limit are investigated. Results show that in the cold flow field, a specific distribution of species is formed due to the unique inlet structure and the effects of vortex breakdown, in which propane is mainly distributed near the wall, while oxygen is uniformly distributed in the burner. At the burning state, propane and oxygen are mixed at the inlet section of the burner and produce a stratified mixture from fuel lean to fuel rich, thus forming a flame that is similar to a triple flame, which plays an important role in promoting the combustion stability. Based on the localized stratification property and the effect of precessing vortex core, the main reaction takes place in the fuel-rich region (Lewis number <1 for C3H8 as fuel). Hence, the tubular flame easily forms and is hardly extinguished. In addition, the flow field promotes the chemical enthalpy supply to the reaction zone, thereby enhancing combustion. Essentially, this type of burner does not require a uniform premixed gas to establish the tubular flame which differs from the typical tubular flame burner. The stability limit of the localized stratified tubular flame is greatly improved compared with that of the rapidly mixed tubular flame, especially under lean conditions.

Effect of Inlet Structures on the Performance of Oil Supply System of a Variable Speed Rotary Compressor

Variable speed rotary compressors are now increasingly favored in the market of household air-conditioners in China due to its advantage of energy saving and system stability. Oil supply system plays a pivotal role in high efficiency and good reliability of a variable speed rotary compressor. This paper presents an investigation of the effect of inlet structures on the performance of oil supply system of a variable speed rotary compressor by means of numerical simulation and experiment. The method of volume of fluid (VOF) has been employed in the simulation model and a novel experimental test rig is designed to perform oil flow rate measurements in order to validate the simulated results. With the help of numerical simulation, oil flow patterns in oil pump can be visualized and oil supply rate under different working conditions can be predicted. Good agreement between the simulated oil flow rates and the experimental data has been achieved. The results indicate that oil supply rate increases with an increase in oil level height, oil viscosity as well as the rotating speed. Vertical oil suction pipe with a tapered port contributes to oil pumping in comparison with a straight suction pipe and no suction pipe. Additionally, the minimum rotational speed at which oil starts to flow out of the oil pump increases with the oil inlet diameter and the increment of oil inlet diameter allows the improvement oil pumping performance at a high rotating speed.

Prediction of water velocities in circular aquaculture tanks using an axisymmetric CFD model

Computational fluid dynamics (CFD) software was used to construct two-dimensional axisymmetric simulations of the turbulent flow inside 1.5, 5, 9.15 and 10 m tanks containing rotating water. The water rotation was induced mathematically by either placing a rotating cover on the surface of the water or locating a tangential water inlet near the top of the side wall. Central and side drains evacuated the water from the tank when using an inlet. The rotating cover produced a forced vortex in the tanks similar to the one observed in actual rearing tanks when the majority of the flow is leaving via the side drain. The predicted flow structure in tanks with an inlet can be divided into three regions: a narrow region along the side wall where the rotating water is moving down toward the floor, a thin boundary layer along the floor where the rotating water is moving radially inward, and a large region in the bulk of the tank where radial and axial velocities are small and the tangential velocity is independent of elevation but varies with radial position. Calculations were performed with the k-ε (RNG) and Reynolds stress turbulence models. Converged solutions were easier to obtain with the k-ε (RNG) model but only the Reynolds stress model could predict the strong vortex which is experimentally observed to form in the central portion of the tank as the flow leaving via the center drains is increased. The simulations predict that the thickness of the floor boundary layer is proportional to the tank diameter and that the radial velocity within the floor boundary layer is maximum at an elevation equal to about 10% of the boundary layer thickness. At any given radial position, the maximum value of the radial velocity next to the floor is between 15 and 45% of the tangential velocity in the bulk of the tank. Predicted shear stresses along bounding surfaces were used to obtain correlations for the side-wall and floor friction coefficients in terms of the Reynolds number. These correlations were in turn substituted in an overall moment balance to obtain an analytical model for predicting the maximum tangential velocity Vθw near the side wall of multi-drain rearing tanks. The predictions of the analytical model are in excellent agreement with Vθw values reported in the literature for tanks with diameters ranging from 1.5–15 m and indicate that the drag from inlet structures is non-negligible. The results demonstrate that the axisymmetric CFD model can simulate the main features of the rotating flow inside circular tanks and provide valuable boundary-layer information that is difficult to obtain experimentally.

Stabilized Production of Lipid Nanoparticles of Tunable Size in Taylor Flow Glass Devices with High-Surface-Quality 3D Microchannels.

Nanoparticles as an application platform for active ingredients offer the advantage of efficient absorption and rapid dissolution in the organism, even in cases of poor water solubility. Active substances can either be presented directly as nanoparticles or can be integrated in a colloidal carrier system (e.g., lipid nanoparticles). For bottom-up nanoparticle production minimizing particle contamination, precipitation processes provide an adequate approach. Microfluidic systems ensure a precise control of mixing for the precipitation, which enables a tunable particle size definition. In this work, a gas/liquid Taylor flow micromixer made of chemically inert glass is presented, in which the organic phases are injected through a symmetric inlet structure. The 3D structuring of the glass was performed by femtosecond laser ablation. Rough microchannel walls are typically obtained by laser ablation but were smoothed by a subsequent annealing process resulting in lower hydrophilicity and even rounder channel cross-sections. Only with such smooth channel walls can a substantial reduction of fouling be obtained, allowing for stable operation over longer periods. The ultrafast mixing of the solutions could be adjusted by simply changing the gas volume flow rate. Narrow particle size distributions are obtained for smaller gas bubbles with a low backflow and when the rate of liquid volume flow has a small influence on particle precipitation. Therefore, nanoparticles with adjustable sizes of down to 70 nm could be reliably produced in continuous mode. Particle size distributions could be narrowed to a polydispersity value of 0.12.

Sculpturing wafer-scale nanofluidic devices for DNA single molecule analysis.

We present micro- and nanofluidic devices with 3D structures and nanochannels with multiple depths for the analysis of single molecules of DNA. Interfacing the nanochannels with graded and 3D inlets allows the improvement of the flow and controls not only the translocation speed of the DNA but also its conformation inside the nanochannels. The complex, multilevel, multiscale fluidic circuits are patterned in a simple, two-minute imprinting step. The stamp, the key of the technology, is directly milled by focused ion beam, which allows patterning nanochannels with different cross sections and depths, together with 3D transient inlets, all at once. Having such a variety of structures integrated in the same sample allows studying, optimizing and directly comparing their effect on the DNA flow. Here, DNA translocation is studied in long (160 µm) and short (5-40 µm) nanochannels. We study the homogeneity of the stretched molecules in long, meander nanochannels made with this technology. In addition, we analyze the effect of the different types of inlet structures interfacing short nanochannels. We observe pre-stretching and an optimal flow, and no hairpin formation, when the inlets have gradually decreasing widths and depths. In contrast, when the nanochannels are faced with an abrupt transition, we observe clogging and hairpin formation. In addition, 3D inlets strongly decrease the DNA molecules' speed before they enter the nanochannels, and help capturing more DNA molecules. The robustness and versatility of this technology and DNA testing results evidence the potential of imprinted devices in biomedical applications as low cost, disposable lab-on-a-chip devices.

Design of a Three-Dimensional Hypersonic Inward-Turning Inlet with Tri-Ducts for Combined Cycle Engines

The operation of a propulsion system in terms of horizontal takeoff/landing and full-speed range serves as one of the main difficulties for hypersonic travelling. In the present work, a three-dimensional inward-turning inlet with tri-ducts for combined cycle engines is designed for the operation of three different modes controlled by a single rotational flap on the compression side, which efficiently simplifies the inlet structure and the flap control mechanism. At high flight speed between Mach 4 and 6, the pure scramjet mode is switched on, whereas both the ejector and the scramjet paths are open for a moderate Mach number between 2 and 4 with a larger throat area guaranteeing the inlet startability. In the low flight speed range with Mach number below 2, the additional turbojet path will be turned on to supply air for the turbine engine, whereas the other two paths remain open for spillage. Numerical simulations under different operation modes have proven the feasibility and good performance of the designed inlet, e.g., a nearly full mass flow ratio and a total pressure recovery around 0.5 can be achieved at the cruise speed. Meanwhile, the inlet works properly at low flight speeds which overcomes the typical starting problem of similar inlet designs. In the near future, wind tunnel experiments will be carried out to validate our inlet design and its performance.

Design of a novel high-efficiency water separator for proton exchange membrane fuel cell system

In the fuel cell system, hydrogen recirculation subsystem is usually used to increase efficiency of hydrogen usage. While the hydrogen recirculation subsystem is a closed circuit that the water might be accumulated, water separator is used necessarily to separate the water and gas at the anode side. As the poor swirling effect caused by the guide vane in commercial separator, a novel water separator for proton exchange membrane fuel cell system is designed and the flow field characteristics of the separator are gained by computational fluid dynamics. The structure of volute inlet and overflow pipe in the novel separator can enhance the swirling flow and increase the tangential velocity. Based on the results, the separation efficiency and steady performance throughout the flow-rate range can be improved by the novel water separator.

Fatigue Tests on ITER PF6 Coil Helium Inlet at 77K

International Fusion Energy Organization (ITER) is one of the most ambitious energy projects in the world today. The poloidal field (PF) coil is cooled down to the required operating temperature (4.2 K) by a forced flow of supercritical helium, which is introduced through the helium inlet. The mechanical reliability requirement on the irregular structure of helium inlet due to the introduction of orifice make the helium inlet one of the critical components of the PF coil cooling system. This paper focuses on the fatigue tests on ITER PF6 coil full-size helium inlet samples to validate whether the fatigue performance of the conduit with the welded inlet can withstand the lifetime of PF6 coil close to the working condition. According to the ITER requirement, the conductor jacket shall withstand a cyclic longitudinal strain (0.95 to 9.5) × 10 -4 during 600 000 cycles at 77K or (1.9-19) × 10 -4 during 30 000 cycles at 77 K, and the equivalent nominal tensile load range we calculated is about (33.5-335) kN. Two samples were designed and prepared to assess the structural design and weld quality. The fatigue test of the sample 1 was carried out with a load range of (33.5-335) kN at 4 Hz and 77 K, and it failed after 593 000 cycles. The scanning electron microscope images and finite element analysis showed that crack initiation area of the fractured sample 1 was at the bottom of the hole. The main reasons were that there were some stress concentrations inside the hole when the tensile load was provided, and the residual burrs assisted the crack initiation. Finally, the modified sample 2 with the completely removed burrs succeed after 600 000 cycles with a nominal load range of (33.5-335) kN. Therefore, it is concluded that the present optimized ITER PF6 helium inlet sample has good fatigue performance and meets the requirements of ITER, which can be utilized for practical applications.

PIV measurement and study on turbulence generator flow field of medium consistency pump

In order to study the flow characteristic in turbulence generator of medium consistency pump, a particle image velocimetry (PIV) test rig was established. 2D-plane flow field was acquired fast and effective by adjusting the angle and position of mirror. For investigating the effect of speed on flow field, velocity and turbulent kinetic energy were measured at speed 80r/min, 130r/min and 200r/min. Dimensionless method was adopted to analyze flow field by quantitative approach. The results showed that on vertical flow plane axial velocities decreased with radius increasing in the region of turbulence generator blade, and axial velocity direction was changed and increased with radius increasing outside the region of turbulence generator blade. Internal flow direction of turbulence generator was at opposite direction with outside flow. Fluid flows from inlet to outlet of turbulence generator blade and then go back to inlet, which forms a circle. On horizontal flow plane, circumferential velocity increase with radius increasing firstly, and then the maximum appears at outer diameter of turbulence generator, and last it decreases gradually. Turbulent kinetic energy increases with rotational speed increasing at inner of turbulence generator flow field, and high turbulent kinetic energy mainly concentrates near the blade inlet and external diameter of turbulence generator. Therefore, in order to achieve better turbulence effect, high turbulent kinetic energy can be obtained by changing the shape of blade inlet structure, increasing the blade outside diameter and improving rotational speed.

Evaluation of three turbulence models in predicting the steady state hydrodynamics of a secondary sedimentation tank

The secondary sedimentation tank (SST) is a sensitive and complicated process in an activated sludge process. Due to the importance of its performance, computational fluid dynamics (CFD) methods have been employed to study the underflow hydrodynamics and solids distribution. Unlike most of the previous numerical studies, in the present investigation, the performance of three different types of turbulence models, standard k-ε, RNG k-ε and Realizable k-ε, are evaluated. Firstly, two-dimensional axisymmetric CFD models of two circular SSTs are validated with the field observations. Next, comprehensive comparisons are presented of the model predictions of the key physical quantities, such as the concentration of effluent suspended solids (ESS), and returned activated sludge (RAS), sludge blanket height (SBH), turbulent properties and flow and concentration patterns.A surprising result shows that the prediction of the ESS concentration is not sensitive to the change of turbulence models; while remarkable prediction difference can be observed in the inlet zone and near-field of sludge hopper and SBH. The results suggest that more observations inside the inlet zone are needed to achieve better model calibration and correct application of the turbulence model, which can be crucial to optimizing the geometry of inlet structure and sludge hopper as well as changing return solids concentration for the operation.

Experimental and Numerical Investigation of Flow in a Newly Developed Vortex Drop Shaft Spillway

AbstractA new shaft spillway composed of an inlet structure that includes inlet swirling-flow-generating piers, an annular weir, a vertical shaft, and an outlet structure is presented. Major factor...

Investigation of the Performance and Flow Behaviors of the Multi-blade Centrifugal Fan Based on the Computer Simulation Technology

The non-uniform flowrate distribution along the axis direction will affect the aerodynamic performance of the multi-blade centrifugal fan. In this article, the bevel cutting design on the blade is adopted. Using this method, the inlet structure is changed and the deviation of the inlet flow of the centrifugal fan is improved. The changed inlet structure reduces the friction and the inlet obstruction, which leads to a more uniform flow distribution, and reduces the impact loss, vortex loss and the drag loss. This paper is focused on the effect of bevel cutting blade on the aerodynamic performance and the flow behaviors of the centrifugal fan, and the bevel cutting area moves along the radial direction and axis direction are also investigated based on the CFD simulation, respectively.

Experimental and numerical analyses on the capacity and the control management of a large flood retention basin situated at the Inn River in Tyrol

The consideration of recent extreme events in flood statistics implies an increase of design flood peaks and discharge loads. With the focus on the 75 km long Tyrolean Inn River reach downstream the regional capital city Innsbruck, the harmonization of the 100-year flood peak and comprehensive 2d-hydrodynamic modelling simulations indicate the need for an extension of the existing flood protection measures. Lateral protection and object protection measures represent the only feasible option due to the confined areal conditions. However, an increase of the channel capacities would worsen the situation for downstream areas demonstrably. In order to counter this impact, it is planned to build several large controlled flood retention basins situated along the Inn River at the valley floor between Innsbruck and the border to Germany. The retention basin “Voldöpp” as one of these flood polders features a maximum capacity of 1.7 million m³ and a maximum design water depth of 3.6 m. According to current planning the inlet structure consists of four uniform weir fields with two gates each. Aims of the presented experimental and numerical analyses are the investigation of the flow characteristics in close range of the inlet structure, the weir capacity and a possible weir control management. Hydraulic model tests are accomplished at the scale 1:35 according Froude similarity and numerical modelling is done with the software FLOW-3D. Preliminary modelling results confirmed the functionality of the inlet structure and pointed out the need of further tests concerning the potential impacts of intense sediment transport and woody debris.

Stress Testing of a Secondary Clarifier with an Adaptive Inlet Structure

Stress Testing of a Secondary Clarifier with an Adaptive Inlet Structure

Numerical investigation of an arc inlet structure extrusion die for large hollow sections

This paper aims to improve the working life of extrusion dies by optimal structure design, which plays an important role in mass production. First, an arc-shaped inlet die structure for an aluminum large-hollow-section profile was developed. Second, a three-dimensional finite-element model of the porthole extrusion process was established using an arbitrary Lagrangian-Eulerian method. Third, the comparison of the formability was analyzed and discussed, including the diversity of extrusion forces and uniformity properties between the proposed design and two traditional design schemes using the same extrusion process. A group of square-profile extrusion dies was used to set up a L16_4_3 orthogonal experimental scheme, considering the side length of profiles, L, with four levels, 110, 100, 90, and 80 mm; inlet angles, α, of the porthole bridge of 0°, 10°, 20°, and 30°; and profile wall thicknesses, t, of 1, 1.5, 2, and 2.5 mm. The results of the orthogonal tests were similar to those of the actual production die model. Two different analysis models reached the same conclusion: the inlet angle or the arc inlet structure has a small effect on the metal flow and the forming distribution, but the arc inlet structure can alleviate the stress load of the dies. The die testing and production validation results indicate that the novel structural design of the arc inlet die will have a long working life.