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Lateral flow immunoassay (LFIA) is extensively utilized for point-of-care testing due to its ease of operation, cost-effectiveness, and swift results. This study investigates the flow dynamics and reaction mechanisms in LFIA by developing a three-dimensional model using the Richards equation and porous media transport, and employing numerical simulations through the finite element method. The study delves into the transport and diffusion behaviors of each reaction component in both sandwich LFIA and competitive LFIA under non-uniform flow conditions. Additionally, the impact of various parameters (such as reporter particle concentration, initial capture probe concentrations for the T-line and C-line, and reaction rate constants) on LFIA performance is analyzed. The findings reveal that, in sandwich LFIA, optimizing parameters like increasing reporter particle concentration and initial capture probe concentration for the T-line, as well as adjusting reaction rate constants, can effectively enhance detection sensitivity and broaden the working range. Conversely, in competitive LFIA, the effects are inverse. This model offers valuable insights for the design and enhancement of LFIA assays. [ABSTRACT FROM AUTHOR]

The solution of the general differential equation of non-uniform fluid flow in prismatic and non-prismatic channels is proposed using dimensionless criteria (e.g., Froude numbers based on depth and width of the flow, as well as changes in the average width per unit length of the flow). [ABSTRACT FROM AUTHOR]

Heterogeneous flow pathways through the soil determine the transport of dissolved and particle-bound nutritional elements like phosphorus (P) to ground and surface waters. This study was designed to understand the spatial patterns of P in agriculturally used soils and the mechanisms causing P accumulation and depletion at the centimetre scale. We conducted dye tracer experiments using Brilliant Blue on a loamy Stagnosol in North-Eastern-Germany. The plant-available P was analysed using double lactate extraction (DL-P). The plant-available P content of the topsoil was significantly higher than that of the subsoil in all three replicates (p < 0.001). The topsoil's stained areas showed significantly higher P contents than unstained areas (p < 0.05), while the opposite was found for the subsoil. The P content varied enormously across all observed soil profiles (4 to 112 mg P kg−1 soil) and different categories of flow patterns (matrix flow, flow fingers, macropore flow, and no visible transport pathways). The P contents of these transport pathways differed significantly and followed the order: Pmatrix flow > Pfinger flow > Pno visible transport pathways > Pmacropore flow. We conclude that P tends to accumulate along flow pathways in the topsoil in the observed fertilized and tilled mineral soil. In contrast, in the subsoil at a generally lower P level, P is depleted from the prominent macroporous flow domains. [ABSTRACT FROM AUTHOR]

Cohesive sediment particles are ubiquitous in environmental flows. The cohesive properties of clay promote the formation of clay flocs and gels and relatively small suspended clay concentrations can enhance or suppress turbulence in a flow. Furthermore, flows are naturally non‐uniform, varying in space and time, yet the dynamics of non‐uniform open‐channel clay suspension flows is poorly understood. For the first time, the adaptation time and length scales of non‐uniform clay suspension flows were quantified using novel experiments with spatially varying but temporally uniform flow. Different levels of turbulence enhancement and attenuation were identified as the flow decelerates or accelerates. Results highlight that decelerating clay suspension flows crucially have a longer adaptation time than accelerating clay suspension flows. This is explained by the longer timescale required for the formation of bonds between cohesive particles in turbulence attenuated flows after deceleration than the rapid breakdown of bonds in turbulent flows after acceleration of clay suspension flows. This hysteresis is more pronounced for higher concentration decelerating flows that pass through a larger variety of clay flow types of turbulence enhancement and attenuation. These different adaptation time scales and associated clay flow type transitions are likely to affect clay flow dynamics in a variety of fluvial and submarine settings. Plain Language Summary: Flows in natural environments, such as rivers, estuaries, seas, and oceans, can transport sediment in suspension. The suspended sediment can increase or decrease turbulence in a flow, depending on the sediment concentration. Clay has the ability to form bonds between the individual particles and therefore even small concentrations are sufficient to alter turbulence levels in a flow. The amount of alteration of turbulence is known for uniform, constant flow conditions, but in natural environments, flows are often non‐uniform. For example, flow variations can occur due to changes in river width or bed slope. The influence of these variations on clay suspension flows is unknown. New physical experiments were conducted where clay suspension flows were decelerated and accelerated. As the flow decelerates, turbulence in the flow is reduced and bonds between the suspended clay particles are established. Turbulence increases as the flow accelerates and clay bonds are broken. Decelerating flow requires more time to adjust to changes in velocity than accelerating flow, as establishing the bonds between clay particles requires more time than breaking them. This means that, especially for the decelerating flows, the influence of a change in velocity is noticeable further downstream. Key Points: Comparable to uniform flow, the combination of flow velocity and clay concentration influences the clay flow type in non‐uniform flowsAccelerating clay‐laden flows adapt faster to velocity changes than decelerating flows; breaking clay bonds is easier than establishing themAdaptation timescales grow with clay concentration for decelerating clay‐laden flows passing through a larger variety of clay flow types [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the possibility of using the empirical formulas to determine the roughness coefficient in gravel-bed streams, the bed slopes of which range from 0.006 to 0.047. Another aim was to determine the impact of taking into account the conditions of non-uniform flow on the application of these formulas and to develop the correlation relationships between the roughness coefficient and water surface slope and also between the roughness coefficient and friction slope in order to estimate the roughness coefficient n in gravel-bed streams.

This paper compares the aerodynamic characteristics of a central-spillage diverterless hypersonic inlet (i.e., bump inlet, Form 1) with a side-spillage inlet (Form 2) under on/off design conditions when faced with non-uniform inflow. Both forms are designed for a flight Mach number of 6.0 and a cruise altitude of 24.0 km. Numerical methods are introduced and validated. Integrated design results indicate that based on identical contraction ratios, Form 2 is 27.8% lower in height, 28.3% shorter in length, and 34.4% smaller in the windward projection area than Form 1. This provides the evidence that the side-spillage strategy will suppress the external drag less. Then, the aerodynamic performance is investigated under various upstream/downstream boundary conditions (inflow speed range: Mach 2.0~6.0; backpressure fluctuation range: 1~110.0 times the freestream static pressure). The evaluation methods for non-uniform flow fields are first introduced in this paper. Form 2 has a relatively stronger shock system, which allows it to suppress 4.52% more of the pressure fluctuation from the downstream combustion chamber than Form 1. The inlet start margin is widened by approximately 250% due to the self-adaptive flow spillage ability established by the side-spillage strategy. Furthermore, the compression efficiency, internal shock system, spillage ability, etc., are analyzed in detail. In summary, the side-spillage flow organization strategy has better potential for designing wide-ranging air-breathing flight vehicles. [ABSTRACT FROM AUTHOR]

When constructing a low-noise submarine, it is crucial to consider the non-cavitating noise from the propeller. Non-cavitating noise reduction is crucial for submarine stealth and survivability. Recently, several studies have been conducted on the use of flexible propellers as a means of reducing non-cavitating noise. However, there are no studies on the use of flexible propellers with adaptive characteristics to reduce noise in wake fields. Thus, this study investigated the noise reduction effect of adaptive characteristics on non-cavitating noise for the flexible propeller in the wake field. Numerical investigations on the main propeller variables were conducted based on the proposed procedure using fluid-structure interaction and acoustic analysis models. The results were compared with those of rigid propellers to determine the possible reasons for noise reduction. Finally, the acoustic analysis results of the flexible propeller were compared with those of the rigid propeller to reveal the effectiveness of the adaptive characteristics.

The influence of flow channels on the leaching behavior of toxic elements in contaminated soil cannot be neglected in a column percolation test. This study presents a visualization of the flow channel formed in the soil and evaluated the relationship between the leaching behavior of soil components and flow. We conducted column percolation tests with two types of filling methods (Compaction and No compaction) and used X-ray computed tomography to visualize the soil structure and non-uniform flow. Additionally, the variations of flow in a cross section of water were evaluated using hydraulic conductivity based on differential pressure. Under No compaction, a flow occurred throughout the soil column at the beginning of the water passage, but a non-uniform flow emerged as the liquid–solid ratio increased; under Compaction, a non-uniform flow was formed from the beginning of water passage. The leaching behavior of the major components and toxic elements from soil with high adsorptive properties was significantly affected by the filling method up to a liquid–solid ratio of 2. These results suggest that the non-uniform flow formed in the column percolation test has a significant impact on the leaching of soil components.

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Taking a certain oil tanker propeller as the research object, and using Schnerr-Sauer cavitation model based on Rayleigh-Plesset equation and the realizable k-ε two-layer turbulence model, the cavitation pattern around the propeller in non-uniform flow conditions is simulated by using the computational fluid dynamics (CFD) software STAR-CCM+. Through effective and reasonable mesh densification of the propeller blade tip area, the tip vortex cavitation is successfully captured with a small number of meshes. The comparison between numerical calculation and test results shows that the whole process of cavitation inception, development, and collapse in wake flow can be accurately reproduced. The back-sheet cavitation pattern at each phase angle is in good agreement with the test results and the difference of cavitation area between calculation and the experiment is within 5%. Although the numerical method can capture the tip vortex cavitation, it cannot accurately predict the unsteady characteristics and spatial structure of the tip vortex cavitation. Based on the above results, it can be concluded this numerical methodology is suitable for simulating cavitation flows around propeller in non-uniform flow.

The application of image velocimetry to measure surface streamflow velocities requires meticulous preparation, including surveying and securing both the existence of floating features on the water surface, and, as in every hydrometry method, appropriate hydraulic conditions (e.g., uniform flow, turbulent velocity profile, etc.). Though these requirements can be easily satisfied when all stages involved in image velocimetry are prepared and executed by specialists, this is not guaranteed when the video footage is recorded by citizens. This kind of spontaneously obtained data are frequently the only available information of extreme flood events; therefore, and despite their non-scientific origin and standardization, these data are very important for hydrology. In this study, we evaluate image velocimetry under a variety of conditions, including conditions resembling citizen videos. Furthermore, we conclude on the manual analysis as a means of verification of the accuracy of the velocity estimations. An interesting finding from the case study with non-uniform flow conditions was that the surface velocities occurring at the middle section of the river, estimated using large-scale particle image velocimetry algorithms, exhibited a significant error, whereas the manual estimation was more accurate. This finding calls for further investigation and a more careful approach in similar conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Applying fluctuation to the cyclone boundaries to consider the actual condition. • Dominant frequency in non-uniform flow is independent of the vortex finder height. • Enlarging the vortex finder length increases the vortex power in the cylinder zone. • Applying the oscillations has strengthened the vortex power in non-uniform flow. • In non-uniform flow, the efficiency is independent of the vortex finder length. This study has been investigated the effect of the height variation of the cyclone components under the non-uniform flow. Oscillating flow is an approach to consider the real flow condition in the use of cyclones as an inlet air filter for the internal combustion engine. Accordingly, an oscillating flow with an inlet velocity of 15 (m/s) along with a range of pressure based on the motor inlet is applied to the cyclone's dirty and clean outlets. Seven cyclone models including a base model, and models with height change in vortex finder, cylinder, and cone have been created and gridded. The numerical solution has been run using the Large Eddy Simulation and the Eulerian–Lagrangian model. Having validated, the flow field and cyclone performance have been considered. The results indicate that under the non-uniform flow, a decrease in the vortex finder height and an increase in the height of the cyclone's cylinder and cone minimize the pressure drop. Applying oscillations along with the 30% change in the vortex finder height increases vortices power in the cone, cylinder, and vortex finder zones by 4.23, 8.99, and 21.42 percent, respectively. Additionally, the efficiency dependence on the change in length of cyclone components under the uniform flow is much higher than that of under the non-uniform flow. [ABSTRACT FROM AUTHOR]

The critical depth is a hydraulic factor of the flow, it plays a particularly important role in studying and designing for open channels, especially during identification of water surfaces and analyzing to determine the phenomenon of a hydraulic jump in open channel. In practice, when calculating the critical depth, only the rectangular and isosceles triangle channels have the theory equation, in other circumstances in calculating by semi empirical equations. This paper presents the general method to compute the critical depth of trapezoidal channel, the case study methodology was chosen to analyze the application of existing formulas and then offering a new equation to compute the critical depth based on the optimization algorithm in MS Excel software. This new equation will help to obtain more accurate result, which relative error of the equation is less than 0.61%, this equation has a simple structure, easy to calculate with small errors to meet the conditions to quickly calculate the critical depth, this equation is also suitable for teaching–learning and studying in the field of hydraulics.

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective. [ABSTRACT FROM AUTHOR]

Oil-water two-phase flow widely exists in the oil production and transportation. The flow pattern presents obvious complexity due to non-uniform distribution of water and oil. When the onshore oilfields are on a middle-late stage of oil recovery, the oil production gradually decreases and the water-cut increases. Accurate measurement of oil-water two-phase flow is a significant issue to improve oil production performance and optimize oil reservoir management. Therefore, we propose a distributed four-sector conductance cross-correlation sensor to realize the flow pattern classification and the measurement of flow velocity and water holdup for low-velocity and high water-cut oil-water flows in a 20 mm inner diameter pipe. The geometry dimension is optimized according to the sensitive field distributions of the sensor. In the flow loop test of vertical upward oil-water two-phase flow, the output signals measured from upstream and downstream electrodes are used to figure out three flow patterns combining with a high-speed camera, and the cross-correlation velocity. Then we use the kinematic wave theory to connect the relationship between the cross-correlation flow velocity and the mixture flow velocity considering water- cut and flow patterns. In addition, according to Maxwell equation, we calculate the water holdup. Finally, a drift velocity model based on three flow patterns is constructed to measure the oil phase superficial velocity. [ABSTRACT FROM AUTHOR]

Schizothorax oconnori Lloyd is a local endemic species, one of the most frequently observed species in the Tibet plateau, China, and the representative species of cold-water fish in the Yarlung Zangbo River basin. Knowing the flow velocity preference of fish is essential for understanding the mechanics of their locomotion, and part of the biological foundation required for habitat restoration. The flow velocity preference of Schizothorax oconnori swimming upstream was investigated using a four-channel flume. The flow fields in each channel were nearly uniform, but the flow velocity varied by channel. Test fish swam upstream, of their own volition, into a channel and were recorded by PIT (Passive Integrated Transponder) antennas as they entered the channel. The proportion of fish entering each channel was recorded and changes in activity level during the experiment were analyzed to detect diurnal and nocturnal cycles of activity. The choice among channels made by the test fish differed significantly, indicating that Schizothorax oconnori display a preference for flow velocity. Furthermore, it was demonstrated that the preference for flow velocity varied by season, with a preference for relatively high velocity in late July and a relatively low velocity in late August. This variation in preference may be attributed primarily to different feeding strategies in the two seasons and to differing maximum flow velocities in the two experiments. Due to fatigue, or acclimation to the constant flow field, fish activity decreased significantly after 10 h. Schizothorax oconnori was more active at night than during the day, attributed to its benthic nature and the relatively high light level in the shallow flume. Based on our findings, we make the following recommendations for fish passage design: (1) The flow field should be non-uniform to accommodate a flow preference that varies with season, and which helps prevent fatigue; (2) Avoid excessively long fish passageways and provide a combination of water depth and shading that provides a satisfactory light level.

This paper compares the aerodynamic characteristics of a central-spillage diverterless hypersonic inlet (i.e., bump inlet, Form 1) with a side-spillage inlet (Form 2) under on/off design conditions when faced with non-uniform inflow. Both forms are designed for a flight Mach number of 6.0 and a cruise altitude of 24.0 km. Numerical methods are introduced and validated. Integrated design results indicate that based on identical contraction ratios, Form 2 is 27.8% lower in height, 28.3% shorter in length, and 34.4% smaller in the windward projection area than Form 1. This provides the evidence that the side-spillage strategy will suppress the external drag less. Then, the aerodynamic performance is investigated under various upstream/downstream boundary conditions (inflow speed range: Mach 2.0~6.0; backpressure fluctuation range: 1~110.0 times the freestream static pressure). The evaluation methods for non-uniform flow fields are first introduced in this paper. Form 2 has a relatively stronger shock system, which allows it to suppress 4.52% more of the pressure fluctuation from the downstream combustion chamber than Form 1. The inlet start margin is widened by approximately 250% due to the self-adaptive flow spillage ability established by the side-spillage strategy. Furthermore, the compression efficiency, internal shock system, spillage ability, etc., are analyzed in detail. In summary, the side-spillage flow organization strategy has better potential for designing wide-ranging air-breathing flight vehicles.

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ship design involves many calculations to provide a propulsion system with the appropriate speed. Prioritizing speed-resistance calculations affects main engine, gearbox, propeller, and other auxiliary system selection. Here, the propeller is most intriguing. Since the propeller operates in a fluid domain, internal and external factors affect it. Despite being designed for service speed, water flow can affect the efficiency of a propeller at the ship's stern. Under open-water circumstances, a ship's hull affects a propeller's hydrodynamic performance. The effect usually decreases propeller efficiency, so it's important to know how ship hull and propeller design interact before production. To overcome this issue, researchers test towing tanks extensively. Computational Fluid Dynamics, which is efficient and cost-effective, is also commonly used. This study examines the hydrodynamics of a fishing vessel's highly skewed model propeller. The objective of this study was to assess the propeller's efficiency under uniform and non-uniform flow conditions and investigate an alternative method for dividing the inlet area, which has not been studied in the literature. The study has effectively met its goals, producing satisfactory error margins for both operating conditions. This research significantly contributes to understanding the relationship between hull configuration and propeller design, particularly in non-uniform flow scenarios. • An alternative method for partitioning the inlet area for a propeller CFD analysis. • Hydrodynamic performance prediction of a highly skewed propeller. • Ship hull wake distribution impacts on propeller efficiency. • Comparison of physical test and CFD results for a highly skewed propeller. • Rapid propeller numerical analysis setup for non-uniform flow inlet. [ABSTRACT FROM AUTHOR]

Regenerative cooling is considered one of the most effective cooling methods used in liquid rocket engines and has been widely studied in recent years. But the effect of the non-uniform flow in cooling channels caused by inlet and outlet manifolds did not attract much attention. In this paper, we carried out the coupled flow and heat transfer of combustion and regenerative cooling in a LOX/Methane (LOX means liquid oxygen) engine and compared the results with and without manifolds. Then, three different configurations of the inlet and outlet manifolds were also discussed. The results show that the parameters averaged in the circumferential direction are less affected by the manifolds. However, the existence of the manifolds will make the distribution of mass flow rate as well as wall temperature non-uniform along the circumferential direction. In addition, when the angles between inlet and outlet are 0°, 90° and 180°, the maximum temperature difference along the circumference of throat increases by 90.1%, 151.2% and 229.5%, respectively, compared with that without manifolds. This indicates that the larger the angle between inlet and outlet, the greater the non-uniformity of mass flow rate and wall temperature along the circumferential direction. As a result, extra thermal stress will be generated which could cause some negative effects on the rocket engines. [ABSTRACT FROM AUTHOR]

The application of image velocimetry to measure surface streamflow velocities requires meticulous preparation, including surveying and securing both the existence of floating features on the water surface, and, as in every hydrometry method, appropriate hydraulic conditions (e.g., uniform flow, turbulent velocity profile, etc.). Though these requirements can be easily satisfied when all stages involved in image velocimetry are prepared and executed by specialists, this is not guaranteed when the video footage is recorded by citizens. This kind of spontaneously obtained data are frequently the only available information of extreme flood events; therefore, and despite their non-scientific origin and standardization, these data are very important for hydrology. In this study, we evaluate image velocimetry under a variety of conditions, including conditions resembling citizen videos. Furthermore, we conclude on the manual analysis as a means of verification of the accuracy of the velocity estimations. An interesting finding from the case study with non-uniform flow conditions was that the surface velocities occurring at the middle section of the river, estimated using large-scale particle image velocimetry algorithms, exhibited a significant error, whereas the manual estimation was more accurate. This finding calls for further investigation and a more careful approach in similar conditions.

A catalyst grain in a fixed-bed reactor is surrounded by an non-uniform flow because the reactant concentration changes as the reaction mixture moves through the bed. A problem was considered in which a spherical grain is in an non-uniform flow with a linear dependence of the reactant concentration on the longitudinal coordinate of the reactor in the presence of pore-diffusion resistance in the catalyst grain. For a first-order reaction, an analytical solution for the reactant concentration distribution within the grain was obtained. It was shown that, in comparison with a grain in a uniform flow, the reactant concentration increases in the frontal hemisphere of the grain and decreases in its rear hemisphere, and the grain performance remains unchanged because the increase in the reaction rate in the frontal hemisphere is compensated by its decrease in the rear hemisphere. [ABSTRACT FROM AUTHOR]

Traditional osculating axisymmetric flow (OA) theory is widely used in the inverse design of generalized shock waves. However, this theory is only applicable to uniform incoming flows. In this paper, a novel method called micro osculating axisymmetric flow (MOA) method is proposed to solve the inverse problem of the 3D generalized shock wave design under non-uniform incoming flows. This method constructs a series of micro osculating planes (MOPs) along the shock wave surface in spanwise and streamwise directions. Actual 3D flows are then approximated by 2D axisymmetric flows in each MOP. Thus, the new method breaks the restriction of no lateral velocities or pressure gradients in the traditional method. An internal conical shock wave at a 4° angle of attack and the other one in an external conical flow of a 10° cone half-angle are obtained by the novel method to validate its feasibility and applicability. Numerical simulation results of the two cases indicate that the 3D shock wave geometries completely match the target. A streamwise integration of the inward turning wavecatcher inlet and outward turning waverider forebody is also presented. This integration shows the remarkable application prospects of the MOA method in the field of air-breathing hypersonic propulsion. • A novel method for 3D shock wave design under non-uniform flows is proposed. • CFD results demonstrate the MOA method is effective to reconstruct 3D shock waves. • A streamwise integration of wavecatcher inlet and waverider forebody is presented. [ABSTRACT FROM AUTHOR]

Steady uniform and non-uniform flows through an array of emergent and slightly submerged square cylinders are experimentally investigated with a specific focus on transverse seiche waves induced by vortex shedding. The study is first and foremost aimed at assessing the effect of streamwise flow non-uniformity on seiche waves. Its secondary purpose is to investigate the change in seiche magnitude, when initially emerged cylinders become slightly submerged. Thirdly and lastly, the effect of seiche waves on mean velocities and velocity fluctuations is quantified. The lock-in process between waves and vortex shedding is unaltered by flow non-uniformity and by a change from cylinder emergence to submergence. For non-uniform flows, this results in the co-existence of two differently oscillating transverse waves close to each other. Relative wave amplitude is found to be mainly influenced by relative submergence in the case of submerged cylinders, and by Froude number and oscillation mode in the case of emergent cylinders. Finally, seiche waves modify the streamwise mean velocity, when cylinders are emergent. [ABSTRACT FROM AUTHOR]

A new methods were presented to estimate streamflow with the aid of low-cost optical, infrared, and microwave imagery in a controlled experimental hydraulic channel. The River Experiment Center in Andong, Korea was used as a test site for calibration and validation. The suggested methodologies uses the remotely sensed channel width and the derived channel cross sections coupled with simple hydraulic models. Two basic models were applied for comparison; 1) the Manning's equation for uniform flow analysis and 2) an iterative method based on the energy equation that assumes non-uniform flow. The non-uniform condition for the 2nd method is achieved by using a water structure, specifically, a weir, to form a backwater effect. Under the assumption of ideal uniform flow, both methods show similarly reasonable performance, with 14.5% error on average against the in-situ channel flow observations. However, under non-uniform flow, the uniform flow approach, i.e., the 1st method, exhibits overestimated channel flow (62.6% error) compared to the non-uniform analysis method, i.e., the 2nd method (15.8% error on average). [ABSTRACT FROM AUTHOR]

• The paper focus on the effects of non-uniform inflow on small modular reactor coolant pump. • The difference of the performance, inner flow and hydrodynamics are compared. • Non-uniform inflow exacerbates the flow separation and the asymmetry of the flow field. • The complex vortex structure induced by non-uniform flow has a great influence on pump operation. Small reactors have broad application prospects due to their advantages of safety, economy, and portability. In the first circuit of a small reactor nuclear power plant, the steam generator is directly connected to a reactor coolant pump, and there is a non-uniform flow situation, which has not been studied. Taking the small modular reactor coolant pump as the research object, the influence of non-uniform inflow on the internal flow and hydrodynamic characteristics of the small modular reactor coolant pump was investigated using CFD numerical simulation methods, and was verified by experiment. Firstly, the basic structural parameters of key hydraulic components are determined based on the design input parameters, and the initial model of the impeller and diffuser of the small modular reactor coolant pump is modeled. The channel-head, impeller, diffuser, and casing are modeled using three-dimensional software; Secondly, the hydrodynamic performance of the small modular reactor coolant pump was experimented, and the experimental results verified the reliability of the numerical simulation; After comparing the external characteristics of the straight-pipe small modular reactor coolant pump coupling model and channel-head small modular reactor coolant pump coupling model, it was found that the head and efficiency of the straight-pipe model were better than channel-head model, indicating that non-uniform inflow had a certain impact on the performance of the small modular reactor coolant pump. Finally, the internal flow states of the straight-pipe model and the channel-head model were compared and analyzed from the perspectives of pump internal flow field, pump internal velocity and pressure distribution. The results showed that the sudden contraction of the direct connection between the channel-head and the small modular reactor coolant pump and the short length of the direct connection caused the inlet flow of the pump to be non-uniform, which adversely affected the hydrodynamic and internal flow characteristics of the pump. This study provides a certain idea for the research on the suppression of non-uniform inflow from small modular reactor coolant pumps and the improvement of non-uniform inflow from small modular reactor coolant pumps. [ABSTRACT FROM AUTHOR]

The tip clearance has an important effect on the performance of an engine compressor. While the impact of tip clearance on a concentric compressor has been widely explored in previous research, the flow field distribution of an eccentric compressor has only been minimally explored. Both the steady and unsteady computational fluid dynamics (CFD) methods have been widely used in the studies of concentric axial-compressors, and they have similar simulation results in terms of flow field. However, they have been rarely applied to axial-compressors with non-uniform tip clearance to investigate their flow field. In this paper, ANSYS CFX is used as CFD software, and both steady and unsteady CFD methods are applied to study a single rotor of ROTOR67 to investigate the compressor characteristic line and flow field under different eccentricity conditions. The results show that non-uniform tip clearance creates a non-uniform flow field at the inlet and tip regions over the whole operating range. The circumferential position where the flow coefficient and the axial velocity are the smallest occurs at a position close to the maximum tip clearance and is located on the side deviating toward the direction of rotation of the rotor. Compared with steady CFD, unsteady CFD has better predictive capability for the flow field distribution in axial compressors with non-uniform tip clearance.

We conducted an experiment to clarify nitrogen gas behavior at low pressures during reflux condensation in a pressurized water reactor (PWR) with the rig of safety assessment/large scale test facility (ROSA/LSTF) at Japan Atomic Energy Agency. The primary pressure was lower than 1 MPa under the constant core power of 0.7% of the volumetric-scaled (1/48) PWR nominal power, unlike a previous related test with the LSTF. Steam generator (SG) secondary-side collapsed liquid level was maintained at a certain liquid level above the SG U-tube height. Nitrogen gas was injected stepwise into each SG inlet plenum at a certain constant amount. The primary pressure and the degree of subcooling of the SG U-tubes were largely dependent on the amount of nitrogen gas accumulated in the SG U-tubes. Nitrogen gas accumulated from the outlet towards the inlet of the SG U-tubes. Non-uniform flow behavior was observed among the SG U-tubes with nitrogen gas ingress. The RELAP5/MOD3.3 code indicated remaining problems in the predictions of the primary pressure and the degree of subcooling of the SG U-tubes depending on the number of nitrogen gas injection. We investigated further the applicability of the RELAP5 code with different models for the SG U-tubes to the prediction of the non-uniform flow behavior through sensitivity analyses.

Non-contacted double-walled-straight-tube heat exchanger has been designed for the Lead-Bismuth Eutectic (LBE) loop KYLIN-II, the flow rate and temperature distribution dramatically influence the performance of heat exchanger. The Computational Fluid Dynamics (CFD) and numerical heat transfer method has been used to build the three-dimensional model of the heat exchanger. Adopting the SST (Shear Stress Transport) k-omega model the flow rate and temperature distribution of the heat exchanger model has been calculated. The numerical simulation result shows that the non-uniform LBE flows don’t affect TH performance of HX filled with powder in the gap between two tubes. [ABSTRACT FROM AUTHOR]

In overbank flow due to the interaction mechanism between the main channel and floodplain, the flow property of the compound sections gets affected. The complexity is more when the compound channels have non-prismatic floodplains. Additional complexity occurs during the interaction between the subsections as well as due to non-uniformity of flow through converging parts of the compound channel. For prediction of flow, calculation of energy loss parameters from section to section is an important task for river engineers. In this paper, an experimental investigation for the energy losses of converging compound channels for different flow depths along the converging path is performed. The loss of energy due to contraction and compound geometry for a compound channel is evaluated, and the dependency of energy loss for such channels is analyzed. A generalized multivariable regression model has been developed to predict the energy slope with high accuracy. Using the expression of the energy loss concept, the discharge capacity in the converging compound is found to provide good results as compared to other standard model exists in the literature. [ABSTRACT FROM AUTHOR]

The history force on a particle depends on background flow and needs to be studied to understand dilute particleladen turbulence. In this study, we numerically investigate the history force on the translating sphere in some nonuniform flows in which the undisturbed streamlines are curved, over a range of the particle Reynolds number being 5 ≤ Rep ≤ 40. For the axisymmetric straining flow, the applicability of the history force model which is based on the result of the uniform flow is highly influenced by the direction of the straining. For the non-axisymmetric shear flows, the history force perpendicular to the particle translating velocity agrees with the model for 5 ≤ Rep ≤ 10. In conclusion, the limited applicability of the history force model is clarified for some non-uniform flows. [ABSTRACT FROM AUTHOR]

The results are presented from an experimental study to investigate three-dimensional turbulence structure profiles, including turbulence intensity and Reynolds stress, of different non-uniform open channel flows over smooth bed in subcritical flow regime. In the analysis, the uniform flow profiles have been used to compare with those of the non-uniform flows to investigate their time-averaged spatial flow turbulence structure characteristics. The measured non-uniform velocity profiles are used to verify the von Karman constant κ and to estimate sets of log-law integration constant Br and wake parameter П, where their findings are also compared with values from previous studies. From κ, Br and П findings, it has been found that the log-wake law can sufficiently represent the non-uniform flow in its non-modified form, and all κ, Br and П follow universal rules for different bed roughness conditions. The non-uniform flow experiments also show that both the turbulence intensity and Reynolds stress are governed well by exponential pressure gradient parameter β equations. Their exponential constants are described by quadratic functions in the investigated β range. Through this experimental study, it has been observed that the decelerating flow shows higher empirical constants, in both the turbulence intensity and Reynolds stress compared to the accelerating flow. The decelerating flow also has stronger dominance to determine the flow non-uniformity, because it presents higher Reynolds stress profile than uniform flow, whereas the accelerating flow does not. [ABSTRACT FROM AUTHOR]

A novel Bump-integrated three-dimensional internal waverider inlet (IWI) design method is presented for high-speed inlet/forebody integration. The low-kinetic-energy (boundary layer) flow generated by a blunted leading-edge and forebody boundary layer represents an extreme challenge in the integration of aircraft forebody and inlet. In this method, such an inlet's flowpath is divided into the entrance shockwave segment, the isentropic compression segment and the isolator. First, a three-dimensional inverse method of characteristics (3D-IMOC) is developed to obtain a compression surface that can generate a requested entrance shock wave in non-uniform upstream flow. This configuration realizes the integration of IWI and aircraft fuselage by incorporating a Bump to remove most of the boundary layer flow. This is followed by a three-dimensional, isentropic compression flow-path with cross sectional areas conforming to the specified Mach number distribution. Finally, a new three-dimensional Bump-integrated IWI was tested in M = 6 wind tunnel, under a rather thick boundary layer upstream flow (37% height of inlet entrance). Both of the experimental data and numerical simulation results show that, the new method of IWI and Bump can overcome serious boundary layer flow problems and improve the inlet performance. [ABSTRACT FROM AUTHOR]

Flows in a compound open-channel (two-stage geometry with a main channel and adjacent floodplains) with a longitudinal transition in roughness over the floodplains are experimentally investigated in an 18 m long and 3 m wide flume. Transitions from submerged dense vegetation (meadow) to emergent rigid vegetation (wood) and vice versa are modelled using plastic grass and vertical wooden cylinders. For a given roughness transition, the upstream discharge distribution between main channel and floodplain (called subsections) is also varied, keeping the total flow rate constant. The flows with a roughness transition are compared to flows with a uniformly distributed roughness over the whole length of the flume. Besides the influence of the downstream boundary condition, the longitudinal profiles of water depth are controlled by the upstream discharge distribution. The latter also strongly influences the magnitude of the lateral net mass exchanges between subsections, especially upstream from the roughness transition. Irrespective of flow conditions, the inflection point in the mean velocity profile across the mixing layer is always observed at the interface between subsections. The longitudinal velocity at the main channel/floodplain interface, denoted $$U_{int}$$ , appeared to be a key parameter for characterising the flows. First, the mean velocity profiles across the mixing layer, normalised using $$U_{int}$$ , are superimposed irrespective of downstream position, flow depth, floodplain roughness type and lateral mass transfers. However, the profiles of turbulence quantities do not coincide, indicating that the flows are not fully self-similar and that the eddy viscosity assumption is not valid in this case. Second, the depth-averaged turbulent intensities and Reynolds stresses, when scaled by the depth-averaged velocity $$U_{d,int}$$ exhibit two plateau values, each related to a roughness type, meadow or wood. Lastly, the same results hold when scaling by $$U_{d,int}$$ the depth-averaged lateral flux of momentum due to secondary currents. Turbulence production and magnitude of secondary currents are increased by the presence of emergent rigid elements over the floodplains. The autocorrelation functions show that the length of the coherent structures scales with the mixing layer width for all flow cases. It is suggested that coherent structures tend to a state where the magnitude of velocity fluctuations (of both horizontal vortices and secondary currents) and the spatial extension of the structures are in equilibrium. [ABSTRACT FROM AUTHOR]

In this study, we investigate analytically the importance of different vorticity-production mechanisms contributing to the shock-induced vorticity caused by the interaction of a steady oblique shock wave with a steady, planar, supersonic, laminar mixing layer. The inviscid analysis is performed under the condition of a supersonic post-shock flow, which guarantees that the shock refraction remains regular. Special attention is paid to the vorticity production induced by a change in shock strength along the shock. Our analysis subdivides the total vorticity production into its contributions due to bulk or volumetric compression, pre-shock density gradients and variable shock strength. The latter is the only contribution dependent on the shock-wave curvature. The magnitudes of these contributions are analysed for two limiting cases, i.e., the interaction of an oblique shock wave with a constant-density shear layer and the interaction with a constant-velocity mixing layer with density gradients only. Possible implications for shock/mixing-layer interactions occurring in scramjet combustors are briefly discussed. [ABSTRACT FROM AUTHOR]

Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture aperture distribution. We model a two-dimensional fractured reservoir in which the matrix is impermeable and the fractures are well connected. The fractures obey a power-law length distribution, as observed in natural fracture networks. For the aperture distribution, since the information from subsurface fracture networks is limited, we test a number of cases: log-normal distributions (from narrow to broad), power-law distributions (from narrow to broad), and one case where the aperture is proportional to the fracture length. We find that even a well-connected fracture network can behave like a much sparser network when the aperture distribution is broad enough ( α ≤ 2 for power-law aperture distributions and σ ≥ 0.4 for log-normal aperture distributions). Specifically, most fractures can be eliminated leaving the remaining dominant sub-network with 90% of the permeability of the original fracture network. We determine how broad the aperture distribution must be to approach this behavior and the dependence of the dominant sub-network on the parameters of the aperture distribution. We also explore whether one can identify the dominant sub-network without doing flow calculations. [ABSTRACT FROM AUTHOR]

An increasing number of modern long-span bridges have been built in complex valley terrain, and the influence of non-uniform flows on the vortex-induced vibrations (VIVs) of bridges should be considered. Therefore, this study investigated the multi-mode VIVs of long-span bridges in both the completed bridge stage and erection stage using a taut-strip model under a uniform flow and two types of non-uniform flow. The non-uniform flows were generated by adjusting spires (both their separation distance and shapes) in wind tunnel. The two non-uniform flows were represented by the linear and parabolic wind velocity flow distributions. The characteristics of the vibration responses and wake flows, mechanism of multi-mode VIVs, and aerodynamic differences between different stages and under different incoming flows were discussed. The results indicated that the occurrence of multi-mode VIVs arose from a wake frequency difference covering two or more modal frequencies owing to variations in the wind profile. The non-uniform flows disturb the regular vortices in the wake due to the variable wind velocity and higher turbulence intensity, leading to suppression of the VIV response. [ABSTRACT FROM AUTHOR]

Investigation on non uniform flow behavior among U-tube in steam generator during natural circulation cooling has been conducted using RELAP5. The investigation is performed by modeling the steam generator into multi channel models, i.e. 9-tubes model. Two situations are implemented, high pressure and low pressure cases. Using partial model, the calculation simulates situation similar to the natural circulation test performed in LSTF. The imposed boundary conditions are flow rate, quality, pressure of the primary side, feed water temperature, steam generator liquid level, and pressure in the secondary side. Calculation result shows that simulation using model with nine tubes is capable to capture important non-uniform phenomena such as reverse flow, fill-and-dump, and stagnant vertical stratification. As a result of appropriate simulation of non uniform flow, the calculated steam generator outlet flow in the primary loop is stable as observed in the experiments. The results also clearly indicate the importance of simulation of non-uniform flow in predicting both the flow stability and heat transfer between the primary and secondary side. In addition, the history of transient plays important role on the selection of the flow distribution among tubes. © 2007 Atom Indonesia. All rights reserved

Bed shear stress is an essential parameter in the description of flow motion and sediment transport. Several methods have been proposed to estimate bed shear stress under uniform flow conditions, yet few are applicable to non-uniform flow. A new approach is proposed to compute bed shear stress for non-uniform flow. This approach combines the Saint-Venant method, vertical two-dimensional numerical model and numerical differential method. The computed bed shear stress of this approach shows good consistency with Cardoso and Graf's measured data, with the maximum difference less than 14 %. The new approach is compared with Yang's method, and the maximum difference between these two methods is 25 %. This difference comes from the ignored term in Yang's derivation. By adding the ignored term, the maximum difference reduces to 8 %. This new approach is suitable to calculate bed shear stress in non-uniform flow. [ABSTRACT FROM AUTHOR]