Straight Inlet Research Articles

The effect of emergent vegetation on flow, bedload transport, and bed morphology in a diffluence-confluence unit on a meandering channel

A diffluence-confluence unit on a meandering channel, coupled with the broadening of the divergence zone and meander circulation, promotes sediment deposition on the convex bank, forming shoals to stimulate vegetation growth, which results in water level elevation, velocity reduction, and bank stabilization. Despite these significant impacts, current research on the influence of this channel remains limited. This study conducts a series of flume experiments to quantify the influence of vegetation in a such channel on flow hydraulics, bedload transport, and bed morphology, and their inter-links. The results reveal that increased vegetation cover density subtly influences the flow depth in straight inlet reaches, triggers higher flow depth and fluctuations in the left anabranch, and induces uneven velocity distribution, especially below the crest of the curved channel. Centrifugal forces and vegetation-induced water levels shape the transverse water surface slope, resulting in a downward concave trend and unique slopes within each anabranch. The bedload transport capacity rapidly increases until an armoring layer forms, a process expedited by vegetation, particularly in high discharge conditions. This vegetation effect, amplified with higher density, enhances bedload transport rate and size but is lessened by increased discharge, which also reduces fluctuations during armoring layer formation. The statistical parameters of bed morphology at the grain-scale and structure-form-scale indicate that denser vegetation reshapes erosion dynamics across anabranches, intensifying downstream scouring and propelling the sediment deposition zone, especially under high discharge. Furthermore, the flow bifurcation ratio intensifies with escalating vegetation cover density and is assessed by a modified model consider vegetation effects with heightened precision. The apex scour depth downstream of the unit, induced by the confluence of water from both anabranches, can be characterized as a function of the dimensionless discharge and vegetation density. Concurrently, a refined model for bedload transport rate, influenced by the turbulent kinetic energy arising from emergent vegetation in this intricate reach, is proposed with high accuracy.

Numerical investigation on the effect of feed operating parameters and inlet structure on a cyclone utilizing flow splitting for performance enhancement

The shunting technique is regarded as one of the most crucial approaches for suppressing localized secondary flow within a cyclone. This study employs the Reynolds stress model and discrete phase model to investigate the impact of inlet structure and feed operating parameters on the performance of enhanced cyclone with split flow (ECSF), aiming to further enhance its efficiency. The findings demonstrate that the optimum feed velocity of ECSF is 29 m/s, which surpasses that of Lapple cyclone at 23 m/s. In addition, both a contracting inlet and multiple inlets contribute to enhancing the separation efficiency of ECSF. Specifically, ECSF with a contracting inlet exhibits a total separation efficiency of 86.8% for 2.5 μm particles, representing an improvement of 12.3% compared to ECSF with a straight inlet configuration. The enhancement in separation efficiency achieved through the implementation of the four-inlet design is even more pronounced. The segregated particles are directed into the discharge pipe via either underflow or bypass flow, and the trajectory of particle entry into the discharge pipe is closely associated with their cross-sectional positioning prior to entering the cylinder.

Experimental research on similarity deviation between prototype and model pumping systems

To investigate the reasons for the flowrate deviation of the prototype pumping systems between the measured value onsite and the calculated one by the similarity law, the energy characteristic relationship of the prototype and model pumping systems under different working conditions was compared and analyzed. It was pointed out that the hydraulic loss in the outlet passages caused by the residual velocity circulation is not similar. Using the method of vessel-mounted ADCP and water level gauges to measure the flowrates and heads of pumping stations, the energy characteristics of three typical pumping stations were obtained, and the comparisons with the characteristic curves of the pumping systems predicted by similarity law are made. It was found that there was a deviation between the two in most cases, and the similarity deviation of the elbow inlet and siphon outlet passages was greater than that of the straight pipe inlet and outlet passages. Meanwhile that the larger the blade angle (or the higher the rotational speed of pump), the greater the similarity deviation. Therefore, in the design of the pumping system, the energy characteristics of the model pumping system cannot be simply converted by the similarity law to predict the characteristics of the prototype pumping system, but the influence of different factors on the similarity deviation between the prototype and model pumping system should be considered carefully.

Numerical Simulation on the Influence of Inlet Flow Characteristics on the Performance of a Centrifugal Compressor

Although inlet bent pipes are usually adopted due to limited installation space, the influences of different bend pipes on the inlet flow characteristics and performance of centrifugal compressors are still unclear. The numerical simulation of a centrifugal compressor is established and validated by experimental results with the case of a straight inlet pipe. Then, the internal flow characteristics of the centrifugal compressor with a 90-degree bent pipe (p90) and Z-shaped bent pipe (pz) are simulated and discussed. The results show that the adoption of two inlet bent pipes reduces the performance of the centrifugal compressor to a certain extent, which reduces more greatly with pz, with a maximum reduction of 6.82% in pressure ratio and 14.83% in efficiency, respectively. The pressure ratio and efficiency reduction of the centrifugal compressor both increase with the increment of distortion degree, which maintains the increasing trend as the flow rate increases, and the maximum distortion degree of p90 and pz reaches 0.0351 and 0.0479, respectively. The reduction degree of the pressure ratio shows a power–law relationship with the distortion degree, while the reduction degree of efficiency shows an exponential relationship with it. The flow characteristics at the outlet section of the inlet pipe affect the flow field distribution at the inlet of the impeller, and the distortion area ranges of the total pressure and axial velocity at the inlet of the impeller are near 72°–144° in the circumferential direction for p90, while those of pz are close to 108°–180° and 288°–360°. When the flow with a high distortion degree enters the impeller, a large area with high turbulent kinetic energy is formed in the downstream flow channel, resulting in an increase in the flow loss.

Numerical investigation of microchannel heat sinks with different inlets and outlets based on topology optimization

Topology optimization can generate better structures of microchannel with improved cooling performance. In this paper, microchannel heat sinks with five different inlet and outlet structure combinations are optimized using bi-objective topology optimization based on the density method. The layouts of channels are optimized to minimize the power dissipation and total heat generation at the same time. The results show that the straight line inlet and outlet with extension areas (SE) can reduce 20%-50% power dissipation when realizing the same heat transfer performance compared with traditional one channel inlet and one channel outlet (OC). Effects of Reynolds number, the ratio of solid and fluid thermal conductivity and the dimensionless heat generation coefficient in fluid domains are also investigated. The simple channels can be obtained with higher ratio of solid and fluid thermal conductivity and/or higher dimensionless heat generation coefficient in fluid domains. With optimization further considered in the inlet and outlet regions, better overall performance can be obtained. Finally, the 2D optimized structures are further validated by three-dimensional numerical simulation. It is found that the optimized design can realize 53.28% increment of Nusselt number with 40.89% reduction in pressure drop compared with traditional microchannel heat sinks.

Computational Fluid Dynamics (CFD) modelling of the effect of distributor plate geometry in the bubbling fluidized bed reactor

Air distribution is the primary factor that influences the performance of fluidized beds. To understand the hydrodynamics and operation of a fluidized bed, an assessment of the airflow and its distribution is essential. The design and operation of the fluidized bed are complex therefore numerical models have been proposed to predict the behaviour of fluidized beds. Although fluidisation has been studied fundamentally, systematic investigation of air maldistribution due to fluidised bed reactor design and geometry has not been characterised. The effect of four distributor plates (Plate A, B, C and D with 8.67%, 6.12%,4,2% and 2.4% open area, respectively) and the two fluidised bed reactors (straight inlet and bend inlet reactors) on the fluidisation hydrodynamics have been investigated. OpenFOAM™ v1712 was used to develop a computational fluid dynamic (CFD11CFD- computational Fluid dynamics) model to predict the behaviour of a bubbling fluidised bed. The determination of these characteristics will allow for an improved CFD model and optimisation of an industrial fluidised bed granulator. The model was validated with experimental data. Plate pressure drops of 76 Pa,121 Pa,296 Pa and 886 Pa were achieved with plates A, B, C and D respectively. High bed pressure drops were observed for plate It was therefore concluded that the pitch and open area percentage of the distributor has an effect on both the plate and bed pressure drop. Particles with 1.3 mm diameter fluidised quicker with minimum fluidisation velocity range between 0.3 and 0.8 m/s. There was an agreement between the model and experiments for plate and bed pressure drop and bed expansion. Air maldistribution was observed for bend inlet reactor.

Characterization of a 3D Printed Self-Powered Micropump Mould for Microfluidics Application

The number of words should not exceed 350 Self-powered infusion micropump is a non-mechanical micropumps for microfluidics application. A three- dimensional (3D) printing is an intelligent additive manufacturing technique that permits cheap, fast and accurate geometrically complex designs. In this study, a self-powered infusion micropump master mould was fabricated using stereolithography (SLA) 3D printing technique and was characterized accordingly. Furthermore, polydimethylsiloxane (PDMS) self-powered micropump from the 3D printed mould was successfully replicated using soft lithography technique. Optical microscope with i-Solution Lite imaging software was used for micropump mould dimensions characterization. It was found was that the smallest average percentage difference of 4.26 % was measured for straight inlet channel’s width between the actual mould and the computer-aided design (CAD). The average coefficient of variance (CV) for all micropump components dimensions was 3.22. It was found that the SLA 3D printing reduced manufacturing time and costs by 30.43 % and 82.84 % respectively in comparison to the standard SU-8 mould. In conclusion, SLA 3D printing technology is a viable alternative to master mould fabrication in self-infusion micropump production since it accurately reproduced the design from the CAD input.

Air Flow Analysis and Effect of Angle on Rotation Vane Blade Through 90-Degree by Computational Fluid Dynamic

The effects of different angles of rotation vane blades on the flow characteristics in a pipe bend were numerically examined in this work using computational fluid analysis (CFD). The model's geometry included a straight inlet pipe of 1 m length, a 90° pipe bend with a 0.1 m cross-section diameter, a straight outlet pipe of 1 m length, and the installation of rotating vane blades at 10° and 33° angles. The simulation's input parameters include fluid viscosity (0.000017894 kg/m.s), fluid density (1.225 kg/m3), and inlet fluid velocity (10, 14, 20, 24, 26, and 30 m/s). The simulations' output parameters include velocity and pressure measured at two points: section A-A (before the pipe bend) and section B-B (after pipe bend). The findings demonstrate that the velocity and pressure distribution is somewhat uneven at section B-B owing to the presence of the rotating vane. The most efficient rotation vane blade angle is 10° since it has the lowest velocity, static pressure, and pressure drop.

Design and Optimization of the Inlet Header Structure in Microchannel Heat Exchanger Based on Flow Distribution Uniformity

The flow distribution in a printed circuit heat exchanger (PCHE) is of great theoretical and practical significance in the Brayton cycle power generation system. For the straight barrel inlet header PCHE, when S-CO2 flows in the PCHE, the structural types and working parameters of the inlet header and diversion zone may lead to differences in the flow distribution in each channel of the PCHE. This flow distribution difference affects the thermal hydraulic characteristics of the PCHE. A numerical simulation method was applied to explore the flow uniformity of the PCHE and the overall performance and analyze the influence of the type of straight barrel inlet header PCHE. Within each layer, the flow showed an uneven flow distribution, and the optimized inlet header was the tapered type. The results showed that when the taper angle varies from 6° to 9°, the flow distribution in each layer is relatively uniform. The comprehensive heat transfer performance of the straight-channel PCHE can be improved by 17.3–19.7%. Finally, the response surface and a genetic algorithm were combined to optimize the inlet header. The heat transfer performance of the optimized PCHE was improved by 19.7%.

Preparation of Drug-Loaded Liposomes with Multi-Inlet Vortex Mixers.

The multi-inlet vortex mixer (MIVM) has emerged as a novel bottom-up technology for solid nanoparticle preparation. However, its performance in liposome preparation remains unknown. Here, two key process parameters (aqueous/organic flow rate ratio (FRR) and total flow rate (TFR)) of MIVM were investigated for liposome preparation. For this study, two model drugs (lysozyme and erythromycin) were chosen for liposome encapsulation as the representative hydrophilic and hydrophobic drugs, respectively. In addition, two modified MIVMs, one with herringbone-patterned straight inlets and one with zigzag inlets, were designed to further improve the mixing efficiency, aiming to achieve better drug encapsulation. Data showed that FRR played an important role in liposome size control, and a size of <200 nm was achieved by FRR higher than 3:1. Moreover, increasing TFR (from 1 to 100 mL/min) could further decrease the size at a given FRR. However, similar regularities in controlling the encapsulation efficiency (EE%) were only noted in erythromycin-loaded liposomes. Modified MIVMs improved the EE% of lysozyme-loaded liposomes by 2~3 times at TFR = 40 mL/min and FRR = 3:1, which was consistent with computational fluid dynamics simulations. In summary, the good performance of MIVM in the control of particle size and EE% makes it a promising tool for liposome preparation, especially for hydrophobic drug loading, at flexible production scales.

Numerical analysis on the cavitation characteristics of a pump with an inducer in non-uniform inflow

This study aims to investigate the mechanism of the cavitation characteristics influenced by the non-uniform inflow. A condensate pump with an inducer is investigated. The performance and the cavitation characteristics are experimentally tested. Both the cavitating and non-cavitating flow fields are carefully analyzed based on the numerical results. For a better understanding of cavitation characteristics, a comparison of the pumps with an annulus inlet casing and a straight inlet casing is conducted and analyzed. The results show that the uniformity of the inflow induced by the annulus inlet casing has little effect on the pump performance while it affects the cavitation characteristics. Under the design point, the cavitation morphology for the two different inlet casings is quite similar at the same outlet pressure. There exist three primary features at the outlet section of the annulus inlet casing: the circumferential components, the uneven axial velocity, and some typical streamwise vortex structures. Based on the secondary flow theories, it is found that the non-uniformity induced by the annulus inlet casing mainly influences the development of the secondary flow close to the hub, and the negative induced streamwise vorticity would gradually decay along the radial direction. The different inlet casings make the main contribution to the vorticity transportation around the attached cavitation region. The difference in the cavitation characteristics for the straight inlet and annulus inlet casing is mainly attributed to the different flow losses in the inlet casings and the non-uniformity of the magnitude of the relative velocity and the angle of attack due to the secondary flow.

CFD Simulation on the Flow Inside a Fish Culture Tank

Aquaculture is an important sector for providing a food source. Technology may help the development of aquaculture including in the design of the fluid flow condition beneficial for aquaculture tank design and its operational parameters. In this study, the use of Computational Fluid Dynamics (CFD) to provide local fluid flow information was demonstrated. In the first case, the fluid flow condition generated by two different inlet orientations, namely the straight inlet and the angled inlet was investigated. The significant difference in the fluid flow pattern was observed by the help of the velocity streamlines. In the second case, the transient CFD simulation was used to determine the transient temperature distribution for the two different inlet orientations. The result also shows the significant different in the distribution which closely related to the generated fluid flow by both inlet orientations.

Linear stability of flow in a 90° bend

This paper considers two-dimensional flow in a channel that consists of straight inlet and outlet branches and a circular 90° curved bend. An incompressible viscous fluid flows through the elbow under the action of a constant pressure gradient between the inlet and outlet. Navier–Stokes equations were solved numerically using a high-fidelity spectral/hp element method. In a range of Reynolds numbers, an adaptive selective frequency damping method was used to obtain steady-state flow. It was found that three separation bubbles and vortex shedding can exist in the bend. The modal stability of two- and three-dimensional perturbations was investigated. The critical Reynolds number of two-dimensional disturbances was found by extrapolation from lower Reynolds number results. It is much greater than the three-dimensional one, but the two-dimensional flow could be subcritically unstable with respect to the externally imposed small-amplitude white noise. For three-dimensional perturbations, the dependence of critical Reynolds numbers on the bending radius was obtained. For the case of a moderate bending radius, a neutral curve is provided and eigenfunctions are studied in detail. Three-dimensional instability can be caused by a periodic or monotonically growing mode, and these unstable modes relate to recirculation bubbles that occur after the bend.

활어 이송용 스크류원심 임펠러 블레이드 입구 형상에 따른 펌프 수력 및 흡입 성능

A screw centrifugal pump is a non-clog type pump known as the sewage pump to transfer solids such as rags, hair, clusters of stringy material, and digested sludge applications. With the large and open channel from suction to discharge, the screw centrifugal pump shows better solids transferring capability, even the sensitive products such as food (tomato, potato), live fish, eel, shrimp. However, the impeller blade inlet of screw centrifugal pump with the high rotation speed can damage the live fish or food. Therefore, in this study, the impeller blade inlet shapes are investigated for their influence on the performance of the live fish transfer pump. The straight, concave, and convex blade inlet shapes are created. Numerical analysis was conducted to study the pump hydraulic and suction performances according to the impeller blade inlet shapes of the screw centrifugal pump.

Numerical simulation of S-shaped inlet under the intake total pressure distortion

During the development of the stealth fighter, the S-shaped inlet enters the designer’s vision because it has better stealth than bump inlet and straight inlet. During the use of the S-shaped inlet, due to its structural reasons, secondary flow is likely to occur in the curved section, which directly causes the flow state to be changeable and complicated. Therefore, this paper takes the S-shaped inlet as the research object to analyzes the steady flow field simulation under uniform inlet condition and distortion inlet condition and analyze the flow field of the airflow and the total pressure of each section under the S-shaped inlet by changing the intake distortion conditions with CFX software. The results show that although the S-shaped inlet will occur total pressure distortion under uniform intake. However, when the S-shaped inlet work under certain flight conditions, the level of total pressure distortion will be smaller than the uniform inlet condition, which can improve the air intake performance. Finally, it can be inferred that with use of the S-shaped intake port, the deterioration of distortion may be prevented under certain specific intake conditions.

Numerical analysis of non-aligned inputs M-type micromixers with different shaped obstacles for biomedical applications

Fluid mixing in lab-on-a-chip devices at laminar flow conditions result in a low mixing index. The reason is dominant diffusion over the convection process. The mixing index can be improved by certain changes in the micromixer structural design like introducing obstacles in the path of fluid flow. These obstacles will make dominant the advection process over the diffusion process. The main contribution of this work is based on proposing the novel hybrid type micromixer design for enhancing the mixing quality. Three non-aligned M-type and non-aligned M-type with obstacles passive type micromixers are analyzed by COMSOL5.5. These designs are hybrid types because different structural changes are combined in a single design for mixing improvement. First of all the straight non-aligned inlets, M-type passive micromixer (SMTM) is analyzed. It is observed that mixing performance is improved because of M-shaped mixing units and non-aligned inlets. This improvement is deemed to be not enough so different shaped obstacles are introduced in the micromixer design. These designs based on obstacles are named horizontal rectangular M-type micromixer, square M-type micromixer, and vertical rectangular M-type micromixer. The mixing index for SMTM, square M-type micromixer, horizontal rectangular M-type micromixer, and vertical rectangular M-type micromixer at Reynolds number Re = 60 is respectively given by 71.1%, 83.21%, 84.45%, and 89.99%. The mixing index of vertical rectangular M-type micromixer was 59.34% − 87.65% for Re = 0.5–100. Vertical rectangular M-type micromixer is concluded with the better-mixing capability design among the proposed ones. Based on these simulation results, the vertical rectangular M-type micromixer design can be utilized for mixing purposes in biomedical applications like nanoparticle synthesis and biomedical sample preparation for drug delivery.

Validation setup for the investigation of aeroacoustic and vibroacoustic sound emission of confined turbulent flows

Confined flows induce sound at certain flow conditions, which can be annoying in electric vehicles due to the absence of combustion noise. Noise in internal flow may occur due to unfavorable flow-guiding geometries caused by the complex packaging required in engine compartments of modern vehicles. The flow-induced sound is emitted at duct openings (e.g., ventilation inside the passenger cabin). It also originates from the vibroacoustic emissions of the flow-guiding structure excited by the flow. We propose a modular validation procedure for aeroacoustic simulations of confined flows. The experimental setup includes the vibroacoustic emission of the involved flow-guiding structure. The test rig consists of a sensor system, a high-pressure blower, modular pipe sections, and absorbers, which decouple the system from blower noise and avoid acoustic reflections at the pipe exit. A sufficiently long straight inlet section ensures fully developed flow conditions entering the investigated region. For capturing the vibroacoustic sound radiation of the flow-guiding structure, the measurement object and the surrounding microphones are encapsulated in a wooden box, lined with micro-perforated plates. Measurement results of a straight pipe and a pipe with a half-moon-shaped orifice are presented. Additionally, the sound generation is reproduced by Lighthill's aeroacoustic analogy applying a hybrid approach.

Design of A Micro Hydro Power Plant Based on The Vortex Flow of Water

This research focuses on the gravitational creation of a water vortex stream, which is a novel technique in hydropower engineering. The water enters a wide straight inlet and then through a vertical conical tube, creating a vortex that exits at the shallow basin's centre floor. The blades of the turbine can spin in the vortex, which generates electricity from a generator. The gravitational vortex turbine is the name for this kind of turbine. The turbine is driven by the vortex's dynamic force rather than the pressure differential. Since no discretization of the flow domain is needed, this study relies on simulation to provide the specifics of water vortex creation. The computational fluid dynamics (CFD) models' boundary conditions are added depending on the experiment configuration. Two different hole sizes for water discharge were tested in two different environments. The first condition's effect shows that the vortex heights in the experiment and CFD agree. The final vortex height of the CFD model differs from the experiment outcome in the second condition. More turbulent flow has set in as the discharge hole becomes larger, creating more errors in the CFD model's prediction of water vortex formation.

Effect of the flow upstream the impeller inlet on flow instability of a centrifugal pump

Under part-load conditions, flow instability phenomena in a hydraulic machinery could lead to strong pressure fluctuations and vibrations, posing a great threat to the safety of the units. This paper analysed unsteady flow in a centrifugal pump (specific speed of 39 min−1·m3s− 1·m) with different inlet geometries under part-load conditions. An advanced turbulence model, PANS (partially averaged Navier-Stokes), acting as a bridge from RANS to DNS, is applied for numerical simulations. The results indicated the pump with a straight inlet pipe reached higher values of pump head and efficiency near the design point than the test pump with a non-straight inlet pipe. According to the characteristic curves, hump phenomenon was observed at 0.75ϕbep for the pump having a straight inlet pipe, while it occurred at 0.5ϕbep for the test pump. Under the condition of a low flow rate i.e. ϕ=0.5ϕbep, there is strong pre-swirling flow upstream impeller inlet for the test pump, which contributes to the propagation of rotating stall cells; But energy loss in the impeller inlet of the pump with straight inlet pipe is slightly higher than that in the test pump due to the presence of the stationary stall cells, which causes large energy loss in the impeller and the passage upstream impeller inlet. Further, rotating stall cells are captured in the impeller in both pumps under the condition of ϕ=0.75ϕbep.

Towards optimal aerodynamic design of wind catchers: Impact of geometrical characteristics

This paper presents a detailed parametric analysis of the impact of geometrical characteristics of wind catchers on their flow features to enhance the effectiveness of cross-ventilation strategies of buildings. The following geometrical characteristics are evaluated in detail: (i) ceiling tilt angle, (ii) radius of the outer-corner bend, (iii) leeward-side tilt angle, (iv) straight inlet extension length, (v) nozzle-shaped inlet extension radius, and (vi) radius of the inner-corner bend. In addition, the impact of using guide vanes in the bend of wind catchers is systematically investigated. High-resolution coupled (outdoor wind flow and indoor airflow) 3D steady RANS CFD simulations are performed for 40 different wind catcher geometries. The CFD simulations are based on a grid-sensitivity analysis and are validated by comparing with two wind-tunnel measurements. The results show that the use of straight and nozzle-shaped inlet extensions can significantly increase the airflow rate. The maximum increase is about 23%, which is achieved for the straight inlet extension length S/D = 1 (D is wind-catcher depth). Guide vanes are also found to effectively improve the flow uniformity inside wind catchers and significantly enhance the airflow rate. This enhancement can go up to 29% when guide vanes are implemented in combination with a straight inlet extension with S/D = 0.375. The results of the present study support the optimal aerodynamic design of wind catchers.