Trapezoidal Channel Research Articles

Effect of downward seepage on turbulence and morphology in mobile boundary sinuous channel

The porous boundary of alluvial channels allows water to interact with the surrounding groundwater. With reduction in groundwater level, transfer of water from the main channel to the groundwater is significant and referred to as downward seepage. The action of downward seepage causes morphological alteration along the sinuous alluvial channel. Laboratory experiments were conducted for no-seepage and seepage conditions to study the effect of downward seepage on turbulence and bed morphology in rectangular and trapezoidal sinuous channels. The deformation along the streambed and bank of the sinuous channels showed remarkable alterations with seepage. Downward seepage caused excess sediment transport in the sinuous channels showing high erosion along banks and streambed. With increased flow rate and downward seepage, prominent depositionalzones near inner region and erosion zones near outer region of the bend were observed in sinuous channel with rectangular cross section. Sinuous channel with trapezoidal cross section showed less morphological change as the side slope was almost equal to the angle of repose of the sand. However, with the application of downward seepage, the streambed of the channel has lowered in elevation, indicating sediment transport. Mean streamwise velocity at the center of the bend showed an average percentage increase in 26% in the rectangular channel and about 20% in the trapezoidal channel with downward seepage. The Reynolds shear stress estimated with downward seepage has increased near the channel bed, indicating high momentum flux. Higher bed shear stress was indicated near the channel bed with downward seepage, which results in downstream sediment transport.

NUMERICAL STUDY OF TURBULENT HEAT TRANSFER PROCESS IN DIFFERENT WAVY CHANNELS WITH SOLID AND PERFORATED BAFFLES

This study numerically investigated the effects of different baffle arrangements on heat transfer enhancement and flow in channels with different wave profiles. Four different wave profiles - rectangular, trapezoidal, triangular, and circular - were considered for the wavy channels. Analyses were made on the solid and perforated baffles that were installed vertically in the channel's central area to determine their hydrodynamic performance and convective heat transfer. Pressure-velocity coupling in discretized equations was handled with the SIMPLE algorithm, and analyses were carried out using the ANSYS Fluent solver. The standard <i>k-ε</i> turbulence model was used to solve the simulations. In this study, the channel geometry, the baffle arrangement, and the Reynolds number (4000 ≤ Re ≤ 12,000) were changed. The wavy surfaces were preserved at <i>T<sub>ω</sub></i> = 360 K. The results were presented with different dimensionless parameters such as Nusselt number (Nu), friction factor (<i>f</i>), and thermal performance factor (TPF). Analyses indicated that the Nu number increased with increasing Re in all channel flows. In all wave profiles, the highest heat transfer was obtained in the solid baffle arrangement. The heat transfer increased by 2.12 times in the rectangular channel with solid baffle at Re = 4000 compared to the channel without a baffle. The highest average Nusselt number and relative friction factor were obtained about 143.34 and 1.24, respectively, in rectangular profile with solid baffle at Re = 12,000. The variation of the friction factor differed according to the wave profile and the baffle arrangement. The triangular profile with two-perforation baffles had the lowest TPF value, 1.09, and the rectangle profile with a solid baffle had the highest TPF value, 2.02. The results of the present study showed that the flow and heat transfer behaviors were similar in trapezoidal and circular channels.

Automatic water level regulator with flexible working bodies in form of partition structure for trapezoidal channels

To improve the designs of hydraulic automatic water level regulators with flexible working bodies for channels, the object of research was developing and studying an innovative design of an autoregulator of the water level with flexible working bodies in the form of a partition structure for trapezoidal channels. The study℉s main purpose was to create a design for trapezoidal channels that do not allow channel narrowing and provides automatic level control, draining excess water, washing deposits in front of the partition, and determining its throughput. The developed design consists of a gate with flexible working bodies and a water level regulator combined with it. The article presents a theoretical formula for determining the flow rate of lateral water flows through the gate of the water level autoregulator. Experimental studies were carried out on an experimental installation by the method of physical modeling using the criterion of geometric similarity of the model and nature. As a result of these studies, simpler formulas were obtained for determining the flow rate of lateral water flows through the gate and a formula for determining the total flow rate of water passing through the gate of the water level autoregulator with flexible working bodies for trapezoidal channels for use during operation.

Heat transfer characteristics of supercritical pressure hydrocarbon fuels in rotating trapezoidal channels

Heat transfer characteristics of supercritical pressure hydrocarbon fuels in rotating trapezoidal channels

Automatic partition structure for trapezoidal channels

Based on the analysis of existing and proposed designs of automatic gate structures, as well as the design of an automatic water level regulator on the canal developed earlier with F.A.Kadirov, a design of a mobile automatic partition structure in the form of an automatic shutter for channels of a trapezoidal section of irrigation systems was developed. And also, based on model studies conducted by the author, the flow coefficient is determined, and a formula for determining the throughput of this design is given. This design is made in the form of a gate, which is a container formed by a rigid bottom, pressure, and spillway parts of the flexible rubberized meliorative fabric, passing into flexible side elements. The level control in front of the partition structure is carried out with the help of a level controller. This partition structure does not require large expenditures; it can be portable or stationary, it is not metal-intensive, lightweight, transportable, combines the functions of stabilizing the required water level in the channel, dumping excess water, fin, and debris, and provides the necessary water inflow into the discharge channels.

MANIPULATION OF FLOOD CONTROL CHANNEL PROFILE IN THE KEK LIKUPANG, PANTAI PULISAN, INDONESIA

Flood, erosion, and sedimentation have become classic problems in the river. The two main parameters that significantly affect the phenomenon of flood are flow and sediment. Flood and sediment transport cause aggradation and degradation of the river bed, bring the bad influence to the construction in the river and environment. Therefore, it becomes important to conduct the manipulation of flood control channel profile in the selected area of Special Economic Area (KEK) that is Likupang, Pantai Pulisan. This research intends to obtain the design of channel shape and dimension for controlling the disasters that are influenced by the factors of environment, water resources, and climate change. One of the urgent factors in this research is to produce a design/recommendation for minimizing the negative impact that is triggered by floods and sediment transport, so it causes the disaster of geology and ecology. To reach the research aim, we carried out the survey of the existing conditions for determining the suitability of the analysis that will be used. The dimension of rainfall and watershed characteristics becomes the input in the HEC-HMS software for obtaining the design flood. Additionally, there is carried out the measurement/mapping of the river geometry. This is used in the application of HEC-RAS that will simulate the real-time flow condition in the field. Based on the analysis results of the flood control channel profile manipulation, there is obtained the dimension of multi-stage trapezoid channel with an upper width (La) of 10 m, lower width (Lb) of 1 m, and depth (h) of 3 m that can flow the design flood in amount of 36.5 m3/s (Q25). This information is a recommendation/reference in determining the management method of the environment and water resources in the Special Economy Area (EK) in the Likupang tourism-Pantai Pulisan as a super-priority tourism destination in making effort of disaster mitigation that is influenced by the factors of environment, water resources, and climate change.

Design and Analysis of a Novel Opposite Trapezoidal Flow Channel for Solid Oxide Electrolysis Cell Stack

High efficiency, raw material availability, and compatibility with downstream systems will enable the Solid Oxide Electrolysis Cell (SOEC) to play an important role in the future energy transition. However, the SOEC stack’s performance should be improved further by utilizing a novel flow-field design, and the channel shape is a key factor for enhancing gas transportation. To investigate the main effects of the novel channel design with fewer calculations, we assumed ideal gas laminar flows in the cathode channel. Furthermore, the cathode support layer thickness and electrical contact resistance are ignored. The conventional channel flow is validated first with mesh independence, and then the performance difference between the conventional and novel designs is analyzed using COMSOL Multiphysics. The process parameters such as velocity, pressure, current density, and mole concentration are compared between the conventional and novel designs, demonstrating that the novel design significantly improves electrolysis efficiency. Furthermore, it directly increased the concentration of product hydrogen in the novel channel. In addition to enhancing convection and diffusion of reaction gases in neighboring channels, the simple structure makes it easy to manufacture, which is advantageous for accelerating commercial use of the novel design.

Customized Design of a Proposed Alignment at MAU Yola Campus in Civil 3D Using Nigerian Federal Ministry of Works Highway (FMWH) Manual

This study testedthe capability of Civil3D to design acarriageway using FMWH Manual. Forthis purpose, the guidelines outlined in the manual were accommodated. The route under consideration is a proposed dual carriageway alignment at Modibbo Adama University (MAU) Yola, Adamawa State, Nigeria. Methodology focused on field work, data acquisition, and roadway alignment design. Data for this project was obtained directly from the field using conventional ground survey method, Google Earth, GARMIN GPSMAP64 Hand Held GPS, and Kern-Swiss K1-M 292272 Theodolite. Reduce level was computed using Microsoft excel and the output was imported into the design software (Autodesk Civil 3D V.2023) as a dot csv (.csv) data file known as PENZD.csv.A simple horizontal circular curve with a radius of 200m was designed at chainage 0+268.55 to 0+290.41 between two tangents. Two Sag curves at chainages 0+160.95 and 0+655.33 were designed for the vertical alignment. A trapezoidal channel was provided to discharge storm water and also, a single cell box culvert to be sited at chainage 0+524 to 0+532.5. Equally, a pipe culvert was proposed at 0+722 to 0+723. QR Code for data used is also presented. The results indicate that the designed alignment was adequate and economical based on FMWH Manual.

Determination of Hydraulic Roughness Coefficients of Some Vegetated Species in Awka, Nigeria

In this study, selected types of grasses were studied to determine their hydraulic roughness coefficient and to select the most suitable grass for erosion control. The experiments were performed in twelve trapezoidal open channels measuring 5 m x 0.12 m x 0.03 m at different flow depths (0.001m, 0.002m, 0.003m, 0.004m and 0.005m) and at varying bed slope (0.2%, 0.3%, and 0.4%). Overall, Bahama grass showed the highest Manning’s n-value due to its deep root system and creeping nature. For each slope, the degree of submergence, Reynolds number, and flow depth increases as Manning’s n decreases. As the flow depth increases, the Reynolds number increased while the drag coefficient, Cd decreases.

Heat transfer enhancement for corrugated facing step channels using aluminium nitride nanofluid - numerical investigation

The present work carries out a three-dimensional numerical analysis study of Aluminium Nitride (AlN)-water hybrid nanofluid enhanced heat transfer in laminar forced convection flow heat exchanger with four different channels, flat, backward facing step, triangle and trapezoidal facing step channels. The influence of different Reynolds number (100≤ Re ≤1500) and different solid nanoparticles volume fraction (1% and 4%) on the heat transfer and fluid flow were numerically investigated. The numerical analysis was carried out by using a laminar model of ANSYS-Fluent CFD code and the governing equations were resolved using the finite volume method. The results indicate that the thermal conductivity of the nanofluids increases with the increase values of both the nanoparticles volume fractions and Reynolds number, compared with base fluids. Likewise, the pressure drop showed slightly increased due to the increased of both parameters. The use of high nanoparticles volume fractions (4% volume) nanofluid corresponded with the use of four different channel designs resulted in heat transfer augmentation about 30% when compared to that pure water for the trapezoidal channel.

Prediction of the conjugate depth of the hydraulic jump in the trapezoidal channel using Random Forest regression

Prediction of the sequent depths of the hydraulic jump in the trapezoidal channel using the theoretical equation is a challenging task. Therefore, existing studies have attempted to solve the task by conducting experiments or using semi-empirical calculations. The paper proposes a novel method that applies Buckingham's Pi theory and the Random Forest regression to improve the prediction accuracy of the sequent depths of the hydraulic jump in the trapezoidal channel. The study has shown that Machine Learning models can be efficient for the determination of the geometrical features of the jump and have high ability in many real projects.

Effect of porous slab thickness and Darcy number on thermohydraulic transport characteristics of Ag–TiO2/water hybrid nanofluid flow‐through partially porous wavy channels

AbstractThe present article investigates the effect of varying porous slab thicknesses (S = 0–0.4) and Darcy number (Da = 10−6–10−2) on the thermohydraulic performance of three different corrugated channels (triangular, sinusoidal, and trapezoidal) embedded with partially filled porous media. Ag–TiO2/water hybrid nanofluid ( = 0–0.04) is taken as coolant flowing at Re = 400. Results revealed that the thermal performance (average Nusselt number, Nuavg and enhancement ratio, ER) augments with the increase in porous slab thickness and decrease in Darcy number. However, the hydraulic performance reduces (i.e., an increase in pressure drop). To check the viability of the cooling system performance factor (PF) is evaluated which demonstrates variation in thermal performance considering pressure drop penalty also. It is demonstrated that among all configurations, the trapezoidal channel with porous slab thickness (S = 0.4) and Darcy number (Da = 10−4) gives maximum enhancement thermal performance (110%) considering water as a coolant ( = 0). Furthermore, enhancement in thermal performance by 210% is noticed as volume concentration of hybrid nanofluid varies from 0% to 4%. It is also evident that the value of PF for all corrugated channels is lower than 1 indicating the nonviable system. However, for the case of the partially porous plane channel the maximum PF = 1.07.

Impact of Process-Induced Inclined Sidewalls on Gate-Induced Drain Leakage (GIDL) Current of Nanowire GAA MOSFETs

The shape of the channel cross section in rectangular nanowire (NW) gate-all-around (GAA) MOSFETs turns trapezoidal due to process variations. In this article, the impact of process-induced inclination of sidewalls on gate-induced drain leakage (GIDL) current in the trapezoidal channel NW GAA MOSFETs has been systematically investigated using experimental and calibrated TCAD simulation results. The GIDL current has also been analyzed against the variation in other device parameters, such as channel length, height, and width. The lateral band-to-band tunneling (L-BTBT) mechanism at the channel/drain junction has been considered in simulations to obtain the GIDL current. The investigation reveals that the GIDL current increases up to two times if the process-induced sidewalls inclination angle increases from 0° to 20°.

Numerical Simulation Research on the Diversion Characteristics of a Trapezoidal Channel

Open-channel bifurcations are the most common water diversion structures in irrigation districts. In irrigation water conveyance, water transport efficiency and sedimentation are primary concerns. This study accordingly analyzes the influence of open-channel bifurcations on water delivery in irrigation areas. Herein, the three-dimensional flow at an open-channel bifurcation was studied via numerical simulations using FLOW-3D software and including 15 sets of working conditions. The hydraulic characteristics of the recirculation zone and flow structures in the vicinity of the open-channel bifurcation were analyzed. Equations for the flow diversion width of the surface and bottom layers in the trapezoidal channel were then obtained. The flow diversion widths along the water depth were found to differ between trapezoidal and rectangular channels. The results also show that open-channel bifurcations considerably influence the flow velocity in the main channel. The flow velocity in the recirculation zone of open-channel bifurcations was small, but the pulsation velocity and the turbulent kinetic energy were large. The energy dissipated in this area was relatively large, which was not conducive to channel water delivery. This study provides a reference for channel optimization and operation management in irrigation districts.

Estimation of Boundary Shear Stress Distribution in a Trapezoidal Cross-Section Channel with Composite Roughness

The estimation of boundary shear stress distribution in a channel is a challenge in some hydraulic or environment investigations. A new partition model of a trapezoidal cross-section in a prismatic channel with composite roughness has been introduced based on a concept of a standardized cross-section using the “zero-shear stress” division lines. Based on this new model, an “equal local-region velocity” assumption, which can be regarded as an improvement of Einstein’s (1942) “equal velocity” assumption, has been proposed that is based on a discussion on the mechanism of energy transfer and velocity distribution at two sides of a dividing line. This assumption along with some empirical treatments have been employed to establish a new method to estimate the boundary shear stress of a side-wall or bed. Comparisons show that the proposed method can be applied to composite roughness cases and provides better prediction performance compared to other methods.

Experimental and numerical investigation of residual stress distribution in Al-6061 tubes under using tubular channel angular pressing process by new trapezoidal channel

Tubular channel angular pressing (TCAP) method is an appropriate severe plastic deformation (SPD) techniques for the generation of ultra-fine grained (UFG) and nanostructured (NS) tubes. In forming methods, the measurement of residual stresses is very important due to their significant effects on the processed samples. Therefore, determining the residual stresses created by the TCAP method in metals is of great importance. In this research, the distribution of residual stresses in Al-6061 tubes under the TCAP process, was studied experimentally and numerically. For this purpose, first the TCAP process was applied on Al-6061 tubes and after that the residual stresses generated in the TCAPed tubes were measured. Sachs method was used experimentally to measure the residual stresses. Sachs method is one of the destructive, convenient and efficient methods for measuring the residual stresses of axisymmetric cylindrical samples. Residual stresses measured by Sachs method in the processed samples showed that the tensile and compressive residual stresses were created on the external and internal tube surfaces, respectively. In addition, a good agreement was existed between the results of the numerical simulation and experimental methods for measuring the residual stress distribution.

Heat transfer in a rotating lateral outflow trapezoidal channel with pin fins under high rotation numbers and Reynolds numbers

Existing heat transfer research on wedge-shaped channels with pin fins at the trailing edge has mainly focused on Reynolds numbers below 40,000. Larger inlet parameters are rarely considered, resulting in uncertainties in this aspect. Therefore, in this study, the heat transfer characteristics in a rotating lateral outflow trapezoidal channel with pin fins, which is a typical model of the internal cooling passage in a turbine blade, were experimentally investigated under the Reynolds number range of 10,000–110,000, rotation number range of 0–0.5, and speed range of 0–1000 rpm. The differences in the heat transfer at different entry conditions were compared. For the non-rotating condition, the heat transfer at a high Reynolds number (110,000) was four to nine times that at a low Reynolds number (10,000). For the rotating conditions, when the dimensionless parameter X/D (coordinate in radial direction/channel hydraulic diameter) was greater than seven for the inner surface and equal to eight for the outer surface, the heat transfer on the leading surface exceeded that of the trailing surface. Moreover, the critical rotation number, which varied with X/D, was noted on the leading surface. Finally, the heat transfer under a high Reynolds number and high speed were investigated. The findings under a high Reynolds number were similar to those under a low Reynolds number. The research of this paper supplements the heat transfer of wedge-shaped pin fins channel at the trailing edge of turbine blade under the condition of high Reynolds number and rotation number.

A Field-Based Evaluation of the Reliability of Empirical Formulae for Quantifying the Longitudinal Dispersion Coefficient in Small Channels

The majority of formulae for predicting in-channel mixing by longitudinal dispersion are based on empirical evidence from medium to large rivers, whereas small creeks and streams are under-represented despite their hydrological and ecological importance. In this study, twenty-six formulae for predicting the longitudinal dispersion coefficient (Kx) were evaluated for their applicability to small channels using field measurements and hydraulic modeling. Predicted values for Kx, following guidelines recommended in the original publications for the formulae, were compared to measured dispersion coefficients obtained from sodium-chloride plumes injected into two small channels (a concrete-lined, trapezoidal channel and a small, natural stream) based on fitting the Hayami solution to the one-dimensional advection-dispersion equation (ADE) to each plume. The predicted Kx coefficients from the formulae were also utilized to create model-simulated plumes, which were compared to those measured well downstream of the point of injection. The findings demonstrate that the predictive accuracy of the twenty-six formulae was extremely variable; none were able to predict the dispersion process in the small channels with better than ± 50% accuracy. These results show that “universal” formulae are plagued with a large degree of uncertainty and should be used with caution when applied to small channels, although more robust predictions are possible with some formulae if site-specific data are available for calibration.

Surface dense discharge from rectangular and trapezoidal channels

In this paper, the effect of channel geometry on the characteristics of surface dense jets was experimentally investigated. Their geometric properties for various densimetric Froude numbers were studied for rectangular and trapezoidal channels. A simple innovative image processing technique was implemented to study flow trajectory, jet width, plunge point location, impact point, and location of ultimate discharge mixing zone. For small Froude numbers, Frd≤20, it was observed that the channel geometry was an important parameter influencing the dense flow behavior. The plunge point and impact point for the trapezoidal section were 1.37 and 1.53 times more than the rectangular section, linearly proportional to densimetric Froude number. Longer trajectory in trapezoidal channels leads to better dilution at the impact point. The comparisons showed when the objective was to achieve higher mixing, the trapezoidal section was preferable. However, in terms of the ultimate mixing location, both sections were the same. The closer the shape of the channel to the best hydraulic section (semi-circle section), the geometrical parameters and mixing characteristics would be more appropriate. The non-dimensional equations were determined based on dimensional analysis and regression with R2 > 0.9 in the rectangular section and R2 > 0.8 in the trapezoidal section, which are beneficial to design and optimization of marine outfalls on large scales.

Reinforced Metal Bipolar Plate Structure with Stiffening Rib Channel for Proton Exchange Membrane Fuel Cell

Clean energy has become a concern because fossil fuels are the primary cause of climate change and air pollution. A proton exchange membrane fuel cell (PEMFC) is an environmentally friendly vehicle's alternative energy source. Bipolar plates, gaskets, gas diffusion layers, and a membrane electrode assembly (MEA) constitute a PEMFC. The bipolar plate accounts for a large portion of the fuel cell stack cost. Metallic bipolar plates are utilized in vehicle fuel cell stacks because of its low fabrication cost, high manufacturability, mechanical strength, and low weight. Despite the benefits, a thin metal plate's major drawbacks are deformation and corrosion resistance.Stamping metallic plates form trapezoidal cross-section channels, whereas machined graphite bipolar plates can form rectangular cross-section channels. These trapezoidal channels make dimensional errors such as draft angle and fillet radius. Besides, the spring back effect makes shape errors in the manufacturing process. Many kinds of research are conducted to understand the impact of channel tolerances on the performance of PEMFCs. Mainly, inhomogeneous compression in the gas diffusion layer results from channel deformation caused by unevenly distributed clamping force and shape inaccuracy of the metal bipolar plates. High contact resistance and non-uniform reactant gas distribution would result from inhomogeneous compression of GDL.A reinforced metal bipolar plate structure with a stiffening rib channel is proposed in this work to reduce bipolar plate deformation and improve gas transfer. Stiffening ribs are imprinted on the top of the channel. The geometric parameters of the stiffening ribs are shown in Fig. 1. Four geometric design parameters are selected in this study, the distance between the ribs d1, length of the rib l1, height of the rib l2, width of the rib l3. The stainless steel with a thickness of 0.1mm, 50mm×50mm active area, is used. The influence of stiffening ribs on mechanical and fluid characteristics is investigated through numerical analyses and experiments. The static structural analysis illustrated the deformation of the bipolar plates and GDL under the clamping force. The stiffening rib design improves the structure's mechanical strength, lowering bipolar plate deformation. When the endplates clamp the stack, the stiffening rib supports more stress to prevent deformation. The flow distribution in the flow field channel and GDL was then visualized using computational fluid analysis. Stiffening ribs increase the velocity of the reactant. Enhanced under rib convection makes reactant gas evenly distributed. In addition, stiffening ribs causes a convective flow beneath the rib, which improves PEMFC performance. Finally, single-cell studies proved that the modeling results are valid. Under the same operating conditions with the same geometry to the model, electrochemical reactions are investigated to decouple the leading cause of the resistances. The ohmic resistance decreases with the robust structural stiffening ribs, and the mass transport resistance decreases with the well-distributed reactants flow. Figure 1