Channel Velocity Research Articles

Investigation Influence of Channel Transport on Output Characteristics in Sub-100nm Heterojunction Tunnel FET

In this paper, the influences of channel transport on the output characteristic in sub-100nm heterojunction tunnel FET have been investigated through TCAD simulation. The calibrated tunneling and transport parameters with experiment have been adopted. The influences of the parameters characterizing channel transport, i.e., mobility, channel length, and saturation velocity, are analyzed in detail under different biases. It is found that the channel transport has stronger impact on the performance of the device biased in the linear region and with smaller mobility, longer channel, and higher saturation velocity. The saturation drain voltage can be reduced by improving the mobility and reducing the saturation velocity. However, the latter will reduce the current simultaneously. What’s more, considering quantum confinement, the variation in performance of the device induced by the change of mobility is still visible after some optimization strategies are used.

МАГНІТОГРАФІЧНІ ТА CПЕКТРАЛЬНІ ДОСЛІДЖЕННЯ СОНЯЧНИХ МАГНІТНИХ ПОЛІВ В АСТРОНОМІЧНІЙ ОБСЕРВАТОРІЇ КИЇВСЬКОГО НАЦІОНАЛЬНОГО УНІВЕРСИТЕТУ ІМЕНІ ТАРАСА ШЕВЧЕНКА В 1975–1980 рр.

In 1975, at the Astronomical Observatory of the Taras Shevchenko National University of Kyiv, a magnetograph of the full vector of the SIBIZMIR design was installed and began to operate, and this initiated the creation of a new promising scientific direction at the observatory – the measurement of solar magnetic fields by both magnetographic and spectral-polarization methods. This article provides a brief chronology of the events in the first 5 years of the existence of the new direction, as well as the most important scientific results during this period. Вased on the experience of observations obtained at the Kyiv observatory, it was concluded that this magnetograph in the Kyiv’s astroclimate can not provide such scientifically valuable data as those magnetographs used in other observatories far outside large cities. In particular, although in Kyiv the sensitivity of measurements in the longitudinal magnetic field channel was quite high – about 5 G in the longitudinal field channel and 75 G in the transverse field channel, “noise” in the radial velocity channel reached 0.3 km/sec, which is about an order of magnitude higher than in the Crimea magnetograph. Another reason for the limited use of the magnetograph in the Kyiv observatory was that in the late 1970s significant problems with the calibration of magnetographic measurements became apparent, as a result of which such measurements in the areas of sunspots could have errors of 200–300%. However, in parallel with magnetographic research, spectral-polarization studies were also developed, and they allowed to obtain the most important results. In particular, the new data were obtained on the existence of magnetic fields with a strength of » 10 kG in active regions on the Sun, on the discreteness of the strengths in subtelescopic structures with very strong fields, as well as data on the significant suppression of turbulent motions in them. The corresponding conclusions were confirmed and detailed by new research in the following years.

INVESTIGATION OF A SELF-ACTUATED, GRAVITY-DRIVEN SHUTDOWN SYSTEM IN A SMALL LEAD-COOLED REACTOR

Passive safety systems in a nuclear reactor allow to simplify the overall plant design, beside improving economics and reliability, which are considered to be among the salient goals of advanced Generation IV reactors. This work focuses on investigating the application of a self-actuated, gravity-driven shutdown system in a small lead-cooled fast reactor and its dynamic response to an initiating event. The reactor thermal-hydraulics and neutronics assessment were performed in advance. According to a first-order approximation approach, the passive insertion of shutdown assembly was assumed to be influenced primarily by three forces: gravitational, buoyancy and fluid drag. A system of kinematic equations were formulated a priori and a MATLAB program was developed to determine the dynamics of the assembly. Identifying the delicate nature of the balance of forces, sensitivity analysis for coolant channel velocities and assembly foot densities yielded an optimal system model that resulted in successful passive shutdown. Transient safety studies, using the multi-point dynamics code BELLA, showed that the gravity-driven system acts remarkably well, even when accounting for a brief delay in self-actuation. Ultimately the reactor is brought to a sub-critical state while respecting technological constraints.

Computational and sensitivity analysis of a dual purpose solar chimney for buildings

The solution(s) to issues of electric power availability is a great concern in many places in both underdeveloped and developing countries. A solution to this problem is proposed in the use of the Solar Chimney (SC). In this study the potentials of using the Solar Chimney is analysed as a means of improving the power problem and providing ventilation at the same time in building in Nigeria. The Solar chimney (SC) being a natural flow device that uses solar irradiation to cause buoyancy in flowing air by means of the addition of heat, thereby converting the solar thermal energy of the sun into kinetic energy in the flowing air. The SC had been developed for the purpose of ventilation for over two millennia now, while the SC has also been developed in recent time for power generation. In this study computational analysis was carried out using the ANSYS Fluent CFD package together with a statistical package “Design Expert” to carryout sensitivity analysis to determining the potentials of the SC system for buildings. A 23 factorial experiment was simulated and analysed on a 4 m × 4 m × 4 m room. Results revealed by the simulated factorial experiments that the effect of interactions of parametric factors of the SC, chimney height, width and Solar heat flux, were of great importance. The power output from the SC is about 25 W/m2, with a channel velocity of 1.5 m/s. The room temperature was maintained as its initial value of 300 K, with an increase in room average velocity to about 1.5 m/s.

Proof-of-Concept Experiment of Microfluidic Flow Sensor Based on Microcavity- Secondary-Flow Observation

We propose a new type of microfluidic flow sensor, where the velocity measurements are not done on the fluid sample itself but on a second, immiscible fluid in contact with the sample. This allows us to use a low-cost, straight-forward, and well-developed particle tracking velocimetry on samples otherwise unsuitable for tracer particles. Our proof-of-concept experimental setup consists of a microfluidic device with the main channel filled with the sample and rectangular side-cavities, adjacent and opened to the main channel, filled with immiscible fluid with tracer particles. The flow in the main channel induces a circular secondary flow of the cavity liquid. We observed and analyzed the side-cavity particle movement and found that its characteristic parameters show a good linear correlation with flow velocity in the main channel over the whole observed range, from approx. $600~\mu \text{m}$ /s (volumetric flow rate $\Phi _{v} \cong 200$ nl/min, Reynolds number $\textit {Re} \cong 10^{-3}$ ) to approx. $3500 ~\mu \text{m/s}\left ({\Phi _{v} \cong 1200~ \text{nl/min}, ~\text{Re} \cong 10^{-2}}\right)$ .

Invasive Carp Reproduction Phenology in Tributaries of the Upper Mississippi River

AbstractInvasive Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella are expanding throughout the upper Mississippi River (UMR) basin. Spawning has occurred in the main‐stem UMR but could be limited to high‐discharge events when dam operations create a free‐flowing river. Alternatively, naturally free‐flowing tributaries could offer alternative habitat for successful reproduction. Our objectives were to examine temporal and spatial variation in adult gonad development, ichthyoplankton densities, and back‐calculated spawn dates of invasive carp collected in three UMR tributaries. We compared ichthyoplankton densities between the upstream and mouth reaches of tributaries and densities between the UMR and adjacent tributaries. Ichthyoplankton samples were collected every 10 d, and adult invasive carp were sampled monthly at nine sites throughout the Des Moines, Skunk, Iowa, Cedar, and Mississippi rivers during April–October 2014 and 2015. Peaks in adult gonadosomatic index, an increase in postspawn females, and ichthyoplankton collections suggested that peak spawning occurred during late May through June, when water temperatures were 18–30°C and channel velocities were at least 0.7 m/s. However, reproduction occurred as late as August in some tributaries. Ichthyoplankton densities were highest in the Des Moines River among tributaries, but tributary densities were similar to the UMR densities, suggesting that both tributaries and main‐stem sites provide suitable spawning locations. Invasive carp reproduction in UMR tributaries provides additional sources of potential recruitment for further population expansion upstream in the UMR and should be considered when devising plans for controlling populations along the leading edge of the invasion.

Large-eddy simulation of the flow in a fluidic oscillator

Large-eddy simulations are performed to investigate the internal dynamics of a fluidic oscillator over a range of Reynolds numbers Red = 3000 – 30000. The device represents Φ-shaped configuration providing a strongly unsteady flow due to periodic oscillations based on the Coanda effect. Computational results for a mesh convergence study are presented. The conducted analysis of statistical characteristics of the flow has shown that the flow velocity in the feedback channels increases with an increase in the Reynolds number. The obtained results, such as the frequency of vibrations and the depth of the jet, perfectly match the experimental data.

Mathematical modelling of streamwise velocity profile in open channels using Tsallis entropy

This study derived the vertical distribution of streamwise velocity in wide-open channels by maximizing Tsallis entropy, in accordance with the maximum entropy principle, subject to the total probability rule, and the constraints based on the conservation of mass, momentum, and energy. Entropy maximizing leads to a highly nonlinear differential equation for velocity, which was transformed into a relatively weaker nonlinear equation and then solved analytically using a non-perturbation approach that yielded a series solution. The convergence of the series solution was proved using both theoretical and numerical procedures. For the velocity profile assessment, we calculated the Lagrange multipliers and the entropy index by solving a system of nonlinear equations using the Gauss-Newton method after approximating the constraint integrals using Gauss-Legendre quadrature rule. The derived velocity profile was validated for some selected sets of laboratory and field data and was compared with the existing velocity profiles based on Rényi, Tsallis, and Shannon (with additional constraints) entropies. We found that the incorporation of additional constraints and the effect of the entropy index improved the velocity profile compared to the existing Tsallis and Rényi entropy-based velocity equations. Further, it was observed that the proposed model and the Shannon entropy-based model with additional constraints behaved the same for most of the data sets considered, as the corresponding values of the entropy index were close to 1, which is in agreement with the theoretical consideration. The methodology reported in this study can also be employed for addressing other open channel flow problems, such as sediment concentration and shear stress distribution.

Particle motion in pressure-driven suspension flow through a symmetric T-channel

Particle motion is studied in pressure-driven suspension flow through a bifurcating channel of square cross-section. Particles and suspending liquid are neutrally buoyant, i.e. of the same density ρ. Experimental particle trajectories are compared with the computed single-phase flow. The flow is in a symmetric T-junction, with each outgoing stream making a right angle relative to the incoming stream. All branches have the same cross-section and length, with L/D=29, where L is the length of each branch, and D is the side length. Particle trajectories are obtained by two-camera imaging for solid volume fraction 0 < ϕ ≤ 0.30. Inertia is characterized by the bulk, Re=ρDU/η, and particle scale Reynolds numbers, Rep=Re(d/D)2, where d is the diameter of the particles, U is the mean velocity in the inlet channel and η is the liquid viscosity. In this work, d/D=O(0.1) and Re=200. For the pure liquid, spiraling vortices are found in the outlet channels, emanating from near the bifurcation, and these flow structures are largely unchanged for ϕ ≤ 0.1, leading to spiraling motions of the particles. Particle tracks are compared against computed tracer motion in the pure fluid flow, and for dilute ϕ agree qualitatively well, with some deviation due to the particles’ finite size. For larger ϕ, the flow deviates strongly from that of pure fluid, keeping Re=200 based on the suspension effective viscosity. Vortices are damped for ϕ=0.2 and disappear for ϕ=0.30. Particle interactions with the wall and each other appear to dissipate energy at a higher rate than predicted by the effective viscosity.

Structure and kinematics of shocked gas in Sgr B2: further evidence of a cloud–cloud collision from SiO emission maps

ABSTRACTWe present SiO J = 2–1 maps of the Sgr B2 molecular cloud, which show shocked gas with a turbulent substructure comprising at least three cavities at velocities of $[10,40]\, \rm km\, s^{-1}$ and an arc at velocities of $[-20,10]\, \rm km\, s^{-1}$. The spatial anticorrelation of shocked gas at low and high velocities, and the presence of bridging features in position-velocity diagrams suggest that these structures formed in a cloud–cloud collision. Some of the known compact H ii regions spatially overlap with sites of strong SiO emission at velocities of $[40,85]\, \rm km\, s^{-1}$, and are between or along the edges of SiO gas features at $[100,120]\, \rm km\, s^{-1}$, suggesting that the stars responsible for ionizing the compact H ii regions formed in compressed gas due to this collision. We find gas densities and kinetic temperatures of the order of $n_{\rm H_2}\sim 10^5\, \rm cm^{-3}$ and $\sim 30\, \rm K$, respectively, towards three positions of Sgr B2. The average values of the SiO relative abundances, integrated line intensities, and line widths are ∼10−9, $\sim 11\, \rm K\, km\, s^{-1}$, and $\sim 31\, \rm km\, s^{-1}$, respectively. These values agree with those obtained with chemical models that mimic grain sputtering by C-type shocks. A comparison of our observations with hydrodynamical simulations shows that a cloud–cloud collision that took place $\lesssim 0.5\, \rm Myr$ ago can explain the density distribution with a mean column density of $\bar{N}_{\rm H_2}\gtrsim 5\times 10^{22}\, \rm cm^{-2}$, and the morphology and kinematics of shocked gas in different velocity channels. Colliding clouds are efficient at producing internal shocks with velocities $\sim 5\!-\!50\, \rm km\, s^{-1}$. High-velocity shocks are produced during the early stages of the collision and can readily ignite star formation, while moderate- and low-velocity shocks are important over longer time-scales and can explain the widespread SiO emission in Sgr B2.

Numerical Modelling of Flow Characteristics in an Asymmetric Trapezoidal Compound Channel with Vegetation Patches

Vegetation is an important component of rivers, present naturally alongside the banks. In this research study, three-dimensional computational fluid dynamics (CFD) code ANSYS FLUENT was used to solve the Reynolds Averaged Navier-Stokes equations and to simulate flow features in an asymmetric vegetated compound channel. Three-dimensional flow characteristics and turbulence properties were captured well by the Reynolds stress turbulence model (RSM). A total of five flow cases were considered in this work. Among these, four cases were of circular vegetation patches present on the floodplain edge and one was of non-vegetated asymmetric trapezoidal compound channel. Impact of vegetation patch density, patch center to center (c/c) spacing and flow blockage area has been investigated on various flow features and compared with flow characteristics in a channel without vegetation. Flow features include mean and depth-averaged velocities, secondary flows, Reynolds shear and normal stresses, turbulence intensities and turbulent kinetic energy. The results show that the presence of vegetation patches along the floodplain imparted flow resistance which shifted the zone of higher velocities towards outer wall of main channel and floodplain. Increased velocities in the main channel up to 24.8% was observed for larger flow blockage (aD, where a is the density of the vegetation patch and D is the diameter of patch) and smaller normalized c/c spacing (L/D, where L is the c/c spacing between two patches and D is the diameter of patch) of patches. Large transverse shear stresses existed around the vegetated zone due to the gradient of velocities and vortices in the main channel and floodplain. Floodplain, especially vegetated zone acquires less Reynolds stresses and turbulence making it favorable for deposition of sediments and growth of ecological species.

The history of dynamics and stellar feedback revealed by the H I filamentary structure in the disk of the Milky Way

We present a study of the filamentary structure in the emission from the neutral atomic hydrogen (HI) at 21 cm across velocity channels in the 40′′ and 1.5-km s−1 resolution position-position-velocity cube, resulting from the combination of the single-dish and interferometric observations in The HI/OH/recombination-line survey of the inner Milky Way. Using the Hessian matrix method in combination with tools from circular statistics, we find that the majority of the filamentary structures in the HI emission are aligned with the Galactic plane. Part of this trend can be assigned to long filamentary structures that are coherent across several velocity channels. However, we also find ranges of Galactic longitude and radial velocity where the HI filamentary structures are preferentially oriented perpendicular to the Galactic plane. These are located (i) around the tangent point of the Scutum spiral arm and the terminal velocities of the Molecular Ring, around l ≈ 28° and vLSR ≈ 100 km s−1, (ii) toward l ≈ 45° and vLSR ≈ 50 km s−1, (iii) around the Riegel-Crutcher cloud, and (iv) toward the positive and negative terminal velocities. A comparison with numerical simulations indicates that the prevalence of horizontal filamentary structures is most likely the result of large-scale Galactic dynamics and that vertical structures identified in (i) and (ii) may arise from the combined effect of supernova (SN) feedback and strong magnetic fields. The vertical filamentary structures in (iv) can be related to the presence of clouds from extra-planar HI gas falling back into the Galactic plane after being expelled by SNe. Our results indicate that a systematic characterization of the emission morphology toward the Galactic plane provides an unexplored link between the observations and the dynamical behavior of the interstellar medium, from the effect of large-scale Galactic dynamics to the Galactic fountains driven by SNe.

Application of the Correlation Velocity Measurements for Hydrodynamic Investigations of Turbulent Coolant Flow in Nuclear Reactor Elements

The method of correlation measurement of the coolant flow rate, widely used for operational diagnostics of nuclear power plants, can be extensively used in research practice. The aim of this work was to apply a correlation method based on the conductometric measurement system with wire-mesh sensors for measuring a coolant flow rate.Insignificant concentration of a salt solution (NaCl or Na2SO4 ) creates a gradient of the conductivity in the flow, which is used as a passive scalar measured by the system. Authors used turbulent pulsations at the interface of two concurrent flows with identical velocities in a square channel as a signal source for the correlation method. The paper presents the methodology of the tests, test facility description, signalto-noise ratio estimation, the results of digital signal processing and comparison of the measured velocities in the model with the flowrate‒averaged velocity determined by the use of flowmeters. The measured velocity values give acceptable agreement for the turbulent flow modes. It was shown that the measurement accuracy drops sharply for low-Reynolds flows.The obtained results were used for flowrate measurements in core-imitator channels of the nuclear reactor test model. The presented paper is an approbation of this approach for its application as part of an test model of a nuclear reactor in order to determine the each duct flow rates in the channels of the core simulator using wire mesh sensors.

Surface Potential-Based Analytical Modeling of Electrostatic and Transport Phenomena of GaN Nanowire Junctionless MOSFET

This article presents a comprehensive analytical investigation of electrostatic and transport phenomena of GaN nanowire (NW) junctionless (JL) MOSFET. The evolution of the proposed model involves the solution of quasi 2-D Poisson equation with appropriate boundary conditions to obtain effective surface potential as a function of gate voltage. The mobile carrier density derived from the surface potential model is used to formulate the core transport model as well as to analyze the electrostatic characteristics for various physical device parameters. Short channel effect and certain nonideal effects including velocity saturation, mobility degradation, and channel length modulation have been incorporated in the core transport model. The impact of physical device parameters including channel length, NW radius, and oxide thickness on the performance metrics of the device such as subthreshold slope (SS), drain-induced barrier lowering (DIBL), and threshold voltage has been rigorously investigated. Upon analyzing the transport properties of the device, steep SS of 68 mV/dec, DIBL of 27 mV/V, and switching figure of merit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$= {g}_{m}/\text {SS}$ </tex-math></inline-formula> ) of 0.16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({\mu }\text {S}/{\mu }\text {m})/(\text {mV}/\text {dec})$ </tex-math></inline-formula> have been attained which makes the GaN NW JL MOSFET a promising candidate for emerging low-power application. The results of this work exhibit very good agreement with 3-D TCAD simulation and reported experimental results and thereby enhancing the reliability of the proposed model.

Microfluidic Quantification of Blood Pressure and Compliance Properties Using Velocity Fields under Periodic On–Off Blood Flows

To monitor variations of blood samples effectively, it is required to quantify static and dynamic properties simultaneously. With previous approaches, the viscosity and elasticity of blood samples are obtained for static and transient flows with two syringe pumps. In this study, simultaneous measurement of pressure and equivalent compliance is suggested by analyzing the velocity fields of blood flows, where a blood sample is delivered in a periodic on-off fashion with a single syringe pump. The microfluidic device is composed of a main channel (mc) for quantifying the equivalent compliance and a pressure channel (pc) for measuring the blood pressure. Based on the mathematical relation, blood pressure at junction (Px) is expressed as Px = kβ. Here, β is calculated by integrating the averaged velocity in the pressure channel (&lt;Upc&gt;). The equivalent compliance (Ceq) is then quantified as Ceq = λoff · Q0/Px with a discrete fluidic model. The time constant (λoff ) is obtained from the transient behavior of the averaged blood velocity in the main channel (&lt;Umc&gt;). According to results, Px and Ceq varied considerably with respect to the hematocrit and flow rate. The present method (i.e., blood pressure, compliance) shows a strong correlation with the previous method (i.e., blood viscosity, elasticity). In conclusion, the present method can be considered as a potential tool for monitoring the mechanical properties of blood samples supplied periodically from a single syringe pump.

Large eddy simulation of turbidity currents in a narrow channel with different obstacle configurations

Turbidity currents are frequently observed in natural and man-made environments, with the potential of adversely impacting the performance and functionality of hydraulic structures through sedimentation and reduction in storage capacity and an increased erosion. Construction of obstacles upstream of hydraulic structures is a common method of tackling adverse effects of turbidity currents. This paper numerically investigates the impacts of obstacle’s height and geometrical shape on the settling of sediments and hydrodynamics of turbidity currents in a narrow channel. A robust numerical model based on LES method was developed and successfully validated against physical modelling measurements. This study modelled the effects of discretization of particles size distribution on sediment deposition and propagation in the channel. Two obstacles geometry including rectangle and triangle were studied with varying heights of 0.06, 0.10 and 0.15 m. The results show that increasing the obstacle height will reduce the magnitude of dense current velocity and sediment transport in narrow channels. It was also observed that the rectangular obstacles have more pronounced effects on obstructing the flow of turbidity current, leading to an increase in the sediment deposition and mitigating the impacts of turbidity currents.

Study on the overall energy and exergy performances of a novel water-based hybrid photovoltaic-thermal solar collector

In this work, a novel conceptual water-based hybrid photovoltaic thermal collector design was modeled and numerically simulated using ANSYS Fluent software. The novelty concerns to superimpose a layer of water to the PV module; it will serve to cool the PV cells and also to filter the incoming solar radiation. Water as a natural filter will absorb IR radiations, therefore, it collects thermal energy, besides, it will let the visible radiation pass, reach the PV and generates electricity. Based on the first and second laws of thermodynamics, an analysis of the overall efficiency of the novel hybrid water-based-PVT is performed. The simulations concern the impacts of intrinsic parameters (the height of the cooling channel and water inlet velocity) and extrinsic parameters (the wind velocity, solar irradiation, and the ambient temperature) on the overall energetic and exergetic performances of the PVT. The results show that in terms of energy quantity and quality, the new proposed PVT is superior to previously proposed ones. In addition, a new method to determine the optimal height of the rectangular channel is also proposed and validated.

Numerical study of serpentine flow field designs effect on proton exchange membrane fuel cell (PEMFC) performance

Abstract The design of flow field greatly influences Proton Exchange Membrane Fuel Cell (PEMFC) performance, as it not only distributes the reactants, also removes the product (water) from the cell. Improper water removal blocks the reaction sites, which results in mass transport losses. A complete 3-D numerical model of PEMFC with a single serpentine (1-S), double serpentine (2-S),triple serpentine (3-S) and 3-2-1 serpentine flow fields with round corner was designed with the help of commercial Computational Fluid Dynamics (CFD) code ANSYS FLUENT. Simulations were carried out to investigate the effect of four flow fields on distribution of pressure, mass fraction of H2, O2, current flux density distribution, water content of membrane, and liquid water activity in the flow channels as well as the functioning of cells. Performance properties of proposed four designs were evaluated and found that 3-2-1 serpentine flow field performance is better than the 1-S, 2-S, and 3-S flow fields for the given flow rates of reactants and this 3-2-1 serpentine flow field model was validated with literature experimental data. The results also show that the velocity in channels increases with a decrease in the number of flow passes, which improve the reactions in the catalyst layers, reaction product removal from the cell thus reduces the concentration losses and improves the cell performance.

Comparative analysis of Cu/blood and Cu–CuO/blood nanofluids on a peristaltic flow governed by an asymmetric channel

AbstractContraction and expansion play a crucial role in biomedical applications, such as heart pumping, ovum in the feminine fallopian vessel, blood fluid transport, and so forth. Inspired by these features, the present effort concentrates on the consequences of a thermal slip in the peristalsis of Cu/blood and Cu–CuO/blood nanofluids in asymmetric flow formation. Hence, the microrotation influence of blood flow is considered here. Heat transported through the channel due to perpendicular flow buoyancy effects is also studied. The special effects of thermal radiation, nanoparticle shape, and heat source/sink parameters on the flow are studied in the proposed model. The MATLAB BVP4c condition is utilized to achieve the numerical solutions of the transformed system of nonlinear coupled differential equations. The most important outcome of the present analysis is an enhancement in the evaluation study of the Cu/blood and Cu–CuO/blood nanofluids on the axial velocity, axial spin velocity, pressure gradient, and temperature distributions in the asymmetric channel. Also, another important outcome is observed that the Cu–CuO blood nanofluid strongly has dominated the Cu/blood nanofluid in axial spin velocity.

Transverse velocity in rectangular channel bends: numerical study and development of a prediction formula

Up-welling and down-welling are formed in the inner and outer banks of the river bends, respectively. In this paper, a 3D numerical model is employed in order to study the effective parameters on the maximum value of the up-welling (wU(max)) and down-welling (wD(max)) in rectangular channel bends. A numerical model validated by the existing experimental data is applied to investigate the effects of different parameters on wU(max) and wD(max) over a wide range of flow conditions. The results revealed that the relative depth (water depth/bend radius) and bed resistance are the most effective parameters on wU(max) and wD(max), with a direct relationship. Moreover, based on the numerical results, two formulas are proposed for prediction of wU(max) and wD(max). Accuracy metrics such as root-mean-square error, bias and correlation coefficient indicated that the developed formulas can be applied successfully to approximate wU(max) and wD(max) for engineering application.