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Few studies have focused on abutments located on curved channels; previous studies have typically focused on straight channels. The present study experimentally examined the local scour that occurs around abutments of different lengths placed on inner and outer banks along a curved channel under clear-water scour flow conditions. The local scour around an abutment in a curved channel is a function of the upstream Froude number, flow intensity, the angle of the bend curvature and the ratios of abutment length to flow depth, abutment length to abutment width and abutment length to channel width. The maximum scour depth around the abutments placed on the outer bank was 1.45 times the scour depth on the inner bank. An empirical equation was developed containing all the dimensional parameters for equilibrium scour depth. The average percentage error of the proposed equation was 2%. [ABSTRACT FROM AUTHOR]

Gravity currents modify their flow characteristics in the presence of an obstacle. Also, the flow path to the dam reservoirs is not always direct. Since no studies have addressed the feedback between the hydrodynamics of a gravity current in a curved channel and the location effects of the obstacle, in this research, a Lock-exchange density current flows in a 120 ∘ bending channel. The numerical simulation has been performed using OpenFOAM software. The models include no-obstacle curved channel and a curved channel with an obstacle in different positions concerning the increased radius of the curved channel. Results indicated that the obstacle directed the concentration towards the banks, with its maximum value tending from the outer to the inner bank, especially in the tail. The tail longitudinal velocity maximized near the channel bed in areas far from the obstacle, and in the outer bank in areas near it. The secondary flow reduces its lowest and most different pattern observed around the obstacle. In displacing the latter, if the front has at a certain distance, the secondary flow does not change much, but if it has at the channel end, the post-obstacle secondary flow would increase as the obstacle neared the Lock. [ABSTRACT FROM AUTHOR]

This study attempts to analyze the effect of diverse parameters of the peristaltic flow of second grade dusty fluid through a curved configuration. Stream function conversions are used to model the separate system of equations for the dust particles and fluid. The Perturbation technique is used to get the analytical solutions and the results are verified through graphs. It is noticeable that the trapped bolus, compresses both the dust particles and fluid with an increase in 'the second grade parameter'. Moreover, a surge in 'the Reynolds number' Re effects the bolus trapped in the lower portion of the channel for fluid. Decrement in the velocity is observed with a rise in 'the wave number' - and 'the second grade parameter' α1. [ABSTRACT FROM AUTHOR]

Curved channels and aquatic vegetation are commonly present in the riverine environment. In this study, the effects of vegetation density and distribution on the hydrodynamic characteristics of a mixed layer developed over a 180-degree curved channel were investigated through flume experiments. Wooden sticks were used to simulate rigid vegetation distributed along the half side of the channel, and a 200 Hz acoustic Doppler velocimeter (ADV) was employed to measure the three-dimensional instantaneous velocity at five selected cross sections along the curved channel. Experimental results show that the vegetation covering the half of the channel significantly affects the hydrodynamic structure of the curved channel flow, and the unequal vegetation resistance induces the K-H instability at the vegetation and non-vegetation interface, resulting in a standard hyperbolic tangent function of streamwise velocity distribution along the lateral direction. The influence of curve position on turbulence kinetic energy is far greater than that of vegetation density and vegetation distribution. The peak value of turbulent kinetic energy is comprehensively affected by vegetation density and distribution, and the peak position of turbulent kinetic energy at the interface is changed by different vegetation distribution. The combined effect of the curve and the partly covered vegetation increases the mixing between the water bodies, enhancing turbulent kinetic energy, and vegetation along the concave bank plays a more significant role. For turbulent bursting, the inward and outward interactions are mainly bursting events in the vegetation area, while ejections and sweeps are dominant in the non-vegetation area. However, the critical vegetation condition to initiate large-scale coherent structure (LSS) in the mixed layer and the influence of flexible vegetation need to be further studied in the future. [ABSTRACT FROM AUTHOR]

This article presents a new approach to determining the viscosity of Newtonian fluid. The approach is based on the analysis of the secondary Dean flow in a curved channel. The study of the flow patterns of water and aqueous solutions of glycerin in a microfluidic chip with a U-microchannel was carried out. The advantages of a microfluidic viscometer based on a secondary Dean flow are its simplicity, quickness, and high accuracy in determining the viscosity coefficient of a liquid. A viscosity image in a short movie represents fluid properties. It is revealed that the viscosity coefficient can be determined by the dependence of the recirculation angle of the secondary Dean flow. The article provides a correlation between the Dean number and the flow recirculation angle. The results of the field experiment, presented in the article, correlate with the data obtained using computational fluid dynamics and allow for selecting parameters to create microfluidic viscometers with a U-shaped microchannel. [ABSTRACT FROM AUTHOR]

The mean flow characteristics in a curved channel are really different from those in a straight channel. The main cause is the existence of secondary flow within the flow in the curved channel. This paper will discuss the differences in mean flow characteristics due to changes in the bed topography in the curved channel. Acoustic Doppler Velocimetry (ADV) measurements have helped to analyse characteristics of the mean flow on flat and eroded beds in a 180° curved channel. Sand (mean diameter d50 = 0.001 m and specific gravity Gs = 2.65) was selected as the bed material. The condition of flow in the approach section was steady and uniform with 0.159 m depth. One of the mean flow characteristics in the curved channel is the free surface superelevation due to the presence of centrifugal force. The second is the circular motion toward the inner-bank region at the lower layer and toward the upper layer outer-bank region. The cause of the circulation is the difference in centrifugal forces between the two layers. The magnitude of velocity near the bed surface is more significant than the flow near the water surface. This causes erosion in the outer bank region and deposition in the inner bank region. In general, tangential velocity vθ in flat bed is greater than its tangential velocity in eroded bed. The maximum velocity path in a flat and eroded bed of the curved channel resembles a sinusoidal curve, where the minimum value is located at 90° and 120° of the curve. [ABSTRACT FROM AUTHOR]

In this paper, a Stokes-Brinkman model is developed to study a transverse flow through a rough curved channel containing a porous medium. The analytical expression of the flow rate, for a given mean pressure drop, is obtained as a function of the parameters specifying the surface roughness, the channel permeability and the channel radius of curvature. The study shows that the transverse flow through the porous curved channel is decreased by the surface roughness. Further to that, we have shown that the surface roughness has greater impact on the rough curved channel flow, when compared to a straight rough channel flow with the same permeability. The Stokes and Darcian flow limits pertaining to the rough curved channel flow have been examined, and it is found that the roughness effect is relatively significant in the Stokes flow limit. [ABSTRACT FROM AUTHOR]

A theoretical study has been developed to explore peristaltically deformable curved channel flow of Sisko nanofluid with double-diffusive (thermal and concentration) convection. Such consideration supports the flow of fluid in biological vessels and arteries to transport the food contents, oxygen, waste products, heat, blood and several other nutrients to the body. The flow stream is regulated and restricted in laminar region by considering long wavelength (d ≪ λ → ∞) and low Reynolds number (Re → 0) in terms of velocity, temperature, concentration and nanoparticle volume fraction fields. Moreover the mathematical expressions are listed for mixed convection and viscous dissipation aspects. The outcomes of influential dynamic parameters are sketched as graphical flow patterns with focus towards double-diffusive convection. Computational technique NDSolve in Mathematica is employed. The results for classical Newtonian fluid are captured as a special case of this analysis. The upshots of this investigation can be supportive for an enhancement of gastrointestinal movements and pumping in several engineering devices. [ABSTRACT FROM AUTHOR]

A theoretical analysis of a viscous flow in a corrugated curved channel enclosing a porous medium is carried out. The alignment of the corrugations of the outer and the inner curved walls is taken arbitrarily, and the corrugations are considered to be sinusoidal in nature with periodicity. The flow problem is described by Darcy–Brinkman model, derived in the curvilinear coordinates. The effects of the channel curvature, the wall corrugations and the medium permeability are studied through the boundary perturbation technique, for small corrugation amplitude. A substantial effect of the porous medium on the flow is observed when compared to that of the flow in a corrugated curved channel with clear conduit, especially for low permeability medium. Flow enhancement is found to take place for small corrugation wavenumbers, and maximum augmentation is realized for the completely out-of-phase alignment of the two corrugated curved walls. However, the flow reduces for large enough wavenumbers, and the alignment of corrugated curved walls eventually becomes irrelevant, with no influence on the flow. For low permeability medium, the results also show no effect of the wall alignment on the flow. In general, the effect of the channel curvature on the corrugated curved channel flow is discussed relative to a corrugated straight channel flow to demonstrate the implications of the wall geometry enclosing the porous medium. [ABSTRACT FROM AUTHOR]

The main objective of this research paper is to perform a parametric comparison of gas flow (air and hydrogen) through a curved channel in terms of thermodynamic based environmental and sustainability analysis. For this analysis, the following sustainability indicators which are i) exergetic efficiency (ee), ii) waste exergy ratio (wer), iii) environmental effect factor (eef) and iv) exergetic sustainability index (esi) are defined and estimated in terms of the channel aspect ratio (AR), Dean Number (De) and reference temperature (T 0). Consequently, it is found that ee and esi rise with the increment of De and AR of the curved channel and with the decrease of T 0. However, wer and eef show the opposite behavior. As an important conclusion, air flow through the channel is found to be more exergetic than that of hydrogen under the boundary conditions assumed for the problem. The ee and esi increases with the rise of De while rising with the decrement of T 0. For air, maximum ee and esi values are obtained to be 99.9% and 751.69 incase De is 207.1 and T 0 is 243 K. Adding that, for hydrogen, the maximum ee and esi values have been estimated to be 99.8% and 710.5 while De is 202.3 and T 0 is 243 K. The ee and esi increase with the rise of AR. For air, the maximum ee and esi values are found to be 97.9% and 45.8 while De is equal to 207.1 and AR is 5.5. Also, for hydrogen, the maximum ee and esi values have been calculated to be 97.5% and 38.6 while De is 202.3 and AR is 5.5. • Thermodynamic based sustainability analysis determines environmental effects. • Gas flow in a curved duct is promising with its significant efficiency. • Dean number and channel aspect ratio effect gas flow through a curved duct. • Air or hydrogen flow through a curved duct is a sustainable solution for industry. • The exergetic sustainability indexes of the air and hydrogen have been compared. [ABSTRACT FROM AUTHOR]

A numerical work is performed to investigate the thermal-hydraulic performance in a curved channel of a journal bearing equipped with oblique horseshoe baffles. Water, a working fluid, is passed through the curved channel at a constant temperature condition of 358 K. The effects of different parameters of baffles, that is, attack angle (α = 45°, 60°, and 90°) and the number of baffles (NB = 9 and 13 baffles), are examined. Influences of design parameters on heat transfer and friction performances are studied and displayed in terms of the Nusselt number, the friction factor, the Nusselt number enhancement ratio, and the thermal-hydraulic performance factor (THPF). The numerical simulations present the flow structures of the tested channel in terms of velocity, isotherms, turbulent kinetic energy, and vorticity contours. The numerical results reveal that the adopted geometry of the curved channel with baffles yields a significant enhancement of heat transfer rate over the plain channel (without baffles), which is approximately 2.5 to 3.8 times. Also, the results show that the best condition to achieve maximum heat transfer is at angle α = 90°, NB = 13, and Re = 5000, compared with other conditions. Furthermore, the maximum THPF of the curved channel using baffles is 4.4 at the same condition. The results confirmed that the geometry of the baffles inside the curved channel has a remarkable impact on heat transfer improvement, accompanied by a reasonable increase in friction losses. [ABSTRACT FROM AUTHOR]

The basic aim of this research is to investigate the main features of the peristaltic flow of Johnson-Segalman fluid in a curved flow channel in the presence of a homogeneous-heterogeneous reaction. The fluid is considered electrically conducting with a radial magnetic field effect. The constitutive relation for energy is formulated with the addition of viscous dissipation and nonlinear thermal radiation. The slip and flexible wall boundary conditions are taken into consideration. The lubrication technique is used for the mathematical the modelling of the problem. The solution of the resulting nonlinear system of ODE's is computed numerically through NDSolve command of Mathematica, and graphical results are prepared for flow variables. It has been clearly noticed that flow is accelerated in the planer medium as compared to the curved channel, and the velocity of the fluid increases with a larger Weissenberg number. Moreover, the thermal profile has an inverse relation to the parameters, i.e., radiation, temperature ratio, and curvature. Furthermore, it is also observed that the magnitude of heat transfer coefficient rises significantly when a comparatively less curved channel is utilized, however, a reduction in concentration profile is witnessed in this case. Alternative impact of homogeneous and heterogeneous reactions on concentration profile are observed through graphical results. Application of the study include the usage of peristaltic pump in chemical industry and in pharmacology industry for the purpose of drug deliveries. [ABSTRACT FROM AUTHOR]

This paper aims to examine variable viscosity effects on peristalsis of Sisko fluids in a curved channel with compliant characteristics. Viscous dissipation in a heat transfer is studied. The resulting problems are solved using perturbation and numerical schemes to show qualitatively similar responses for velocity and temperature. A streamline phenomenon is also considered. [ABSTRACT FROM AUTHOR]

This paper evaluates a new methodology for calibration of hydrodynamic models based on the theory of statistical design of experiments. An Eulerian-Eulerian hydrodynamic homogeneous model, integrated by the commercial software CFX Ansys Inc., is used to perform the numerical experiments. For the screening step, the fractional factorial experimental design 27-2 was used, followed by a Draper-Lin design of second order to find the optimum point in the calibration. A new method is introduced to generate the level of points to the center and to carry out the test of lack of fit. In this work, we develop a validated methodology for the calibration of deterministic hydrodynamic models with several factors, suggesting a second-order regression model for forecasting the optimum point of the simulations, with acceptable accuracy in predicting the response variable. [ABSTRACT FROM AUTHOR]

Impact of radially varying applied magnetic field on the peristaltic transport of a Carreau–Yasuda (CY) fluid through a curved channel is examined. Analysis is performed when the no-slip condition does not hold. Long wavelength and low Reynolds number approximations are taken into consideration in the mathematical formulation of the problem. Both differential equation and boundary condition are nonlinear. Resulting nonlinear equation subject to the nonlinear boundary conditions are numerically solved with Runge–Kutta fourth order with numerical Shooting. Impacts of sundry parameters on the quantities of interest are analyzed through plots. Results show that plots of the axial velocity are not symmetric about the center line for flow through curved conduits. Consequently the fluid flowing through a curved channel exerts additional stress on the inner wall of the curved channel. Such symmetry is restored when we move from curved to straight channel. Maximum fluid velocity decreases with an increase in the strength of applied magnetic field and the velocity slip parameter. Further the stress at the inner wall reduces by increasing the value of curvature parameter. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical model to predict the lateral distribution of streamwise velocity for flow in a curved channel with vertical sides, based on the depth-integrated Navier–Stokes equations. The model includes the effects of bed friction, lateral turbulence and secondary flows, where the additional secondary flow is approximated by a linear function of the lateral distance, as demonstrated by the limited data which are available. Two analytical solutions for the depth-averaged velocity are obtained, one for a flat bed and another for a bed with a transverse slope. Two parameters (denoted by m and n herein), which define the secondary flow, have been examined to analyze how they affect the velocity distribution in these two cases. Comparison of the analytical results with the limited experimental data available shows that the proposed model predicts the lateral distributions of depth-averaged velocity well. Further studies are needed to validate the values of the model parameters ( m and n ) for bends with different geometric properties. [ABSTRACT FROM AUTHOR]

The pressure driven peristaltic flow of nanofluid in a curved channel is investigated. The flow exploration demeanors the induced magnetic field. Long wavelength and low Reynolds number approach is followed. Numerical solutions are obtained by employing shooting method. The effects of substantial parameters have been portrayed and discussed on the temperature and mass distributions, stream function, magnetic force function, induced magnetic field and pressure rise per wavelength. [ABSTRACT FROM AUTHOR]

In the present article, we have investigated the effects of heat transfer on peristaltic flow of carbon nanoparticles in a curved channel. Governing equations for flow and heat transfer are derived by analysing the effects of curvature of the curved channel and taking inboard the long wavelength and small Reynolds number assumptions. Exact solution is obtained for the stream function, which is used to find the velocity of the fluid flow in the curved channel. Effects of curvature parameter and Grashof number on the velocity and pressure gradient are analysed. The effect of heat transfer through the curved channel is also studied. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the behaviour of two non-mixing fluids flowing in a heated curved channel. In simulating this immiscible fluid flow, a multi-phase model based on VOF approach is developed for steady, turbulent, incompressible fluid flow through curved channel. The analysis examines the influence of centrifugal forces arising from channel curvature on the phase distribution and flow patterns, and their impact on the thermal characteristics. Unique flow features are identified through the interactions between the fluid phases and vortex structures of the immiscible flow in curved channels. The convective heat transfer in curved channel is appraised in relation to the behaviour of fluid components and curved channel flow parameters. Finally, the study presents a Second-Law irreversibility analysis whereby a thermal optimisation technique is developed for immiscible fluid flow through heated curved channels. [Copyright &y& Elsevier]

River courses are rarely straight. Rather, they tend to be meandering. Incision meandering is one of the most common types of meandering discussed in river engineering. The availability of abrasive tools, coverage thickness, appropriate flow velocity, channel geometry, and flow level play a role in the natural phenomenon of bedrock incisions. Any minor change in those parameters, whether internal or external, can significantly impact the bedrock incision. The purpose of this study is to experimentally investigate the bedrock incision under sediment bedload transport along curved channels by varying flow speed with the other parameters kept constant. In this study, a bedrock incision was simulated in an annular flume. Two cases were considered, each with different rotation speeds of the cover lid, using plaster as the bedrock and sediment incision tools. In both cases, sediment motion was the bedload transport. It was found that the sediment deposited along the inner wall differed according to the rotation speed. A uniform transverse slope was found for a rotation speed of 48 RPM and moving bedforms were found for a rotation speed of 40 RPM. The bedrock incision resulted in the formation of the inner channel along the centerline of the flume, which grew more quickly toward the inner wall under the bedforms than under the uniform transverse slope. These findings suggest that the type of bedform has a more significant impact on bedrock incisions than rotation speed. [ABSTRACT FROM AUTHOR]

Structures like blunt-nosed chevrons, log deflectors and double-winged log frames help in modifying the flow regime in the channel by concentrating the flow and increasing navigability. Moreover, they create scour pools in the downstream stilling basin, which can be used either as fish refuge or as an in-stream storage site for previously dredged material. In this respect, the use of wood debris in the channel in the form of wood bundles has gained attention for the ability of these structures to integrate into the surrounding fluvial habitat and to divert the flow partially towards the central part of the channel when placed in curves. Considering the absence of studies dealing with wood bundles as a restoration structure, the aim of this paper is to analyse the scour mechanism and equilibrium scour morphology of wood bundles in straight and curved channels. In doing so, a wide range of hydraulic conditions, structure positions and configurations were tested. Thereafter, dimensional analysis was carried out to derive useful empirical relationships to predict the maximum scour depth and length as well as the maximum dune height based on a novel, equivalent Froude number, which accounts for the effects of channel curvature and structure position. Moreover, the various resulting scour morphology types were classified, and conditions of their existence were determined depending on the abovementioned Froude number and other key hydraulic parameters. [ABSTRACT FROM AUTHOR]