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Haemodynamics is a branch of fluid mechanics which investigates the features of blood when it flows not only via blood vessels of smaller/larger diameter, but also under normal as well as abnormal flow states, such as in the presence of stenosis, aneurysm, and thrombosis. This review aims to discuss the rheological properties of blood, geometry of constrictions, dilations and the emergence of single-layered fluid to four-layered fluid models. To discuss further the influence of the aforesaid parameters on the physiologically important flow quantities, the mathematical formulation and solution methodology of the two-layered and four layered arterial blood flow problems studied by the authors (Afiqah and Sankar in ARPN J Eng Appl Sci 15:1129--1143, 2020, Comput Methods Programs Biomed 199:105907, 2021. https://doi.org/10.1016/j.cmpb.2020.105907) are recalled. It should be pointed out that the increasing resistive impedance to flow in three distinct states encompassing healthy, anaemic, and diabetic demonstrates that the greater the restriction in the artery, very few blood is carried to the pathetic organs, leading to subjects' death. It is also discovered that the pulsatile nature of blood movement produces a dynamic environment that poses a slew of intriguing and unstable fluid mechanical state. It is hoped that the intriguing results gathered from this literature survey and review conducted may help the medical practitioners to forecast blood behaviour mobility in stenotic arteries. Furthermore, the physiological information gathered from the available clinical data from the literature on patients diagnosed with diabetes and anaemia may be beneficial to doctors in deciding the therapeutic procedure for treating some particular cardiovascular disease. [ABSTRACT FROM AUTHOR]

The stability of fractional-order visco-elastically damped linear system Bagley Torvik equation is analyzed in this paper. The fundamental novelty of this paper is the application of Caputo derivative. Prevailing sufficient spectral conditions are considered to guarantee the stability of linear models. Laplace transform, and Mittag-Leffler functions are utilized to develop the results. Furthermore, asymptotical stability of linear fractional-order models are also achieved through spectral values of the characteristic polynomials. Numerical examples are given to display the effectiveness of suggested method. [ABSTRACT FROM AUTHOR]

The impacts of radiation, mass transpiration, and volume fraction of carbon nanotubes on the flow of a Newtonian fluid past a porous stretching/shrinking sheet are investigated. For this purpose, three types of base liquids are considered, namely, water, ethylene glycol and engine oil. Moreover, single and multi-wall carbon nanotubes are examined in the analysis. The overall physical problem is modeled using a system of highly nonlinear partial differential equations, which are then converted into highly nonlinear third order ordinary differential equations via a suitable similarity transformation. These equations are solved analytically along with the corresponding boundary conditions. It is found that the carbon nanotubes can significantly improve the heat transfer process. Their potential application in cutting-edge areas is also discussed to a certain extent. [ABSTRACT FROM AUTHOR]

This paper considers a mathematical model that accounts for the hematological disorders of blood in its flow in human arteries. Blood is described as a Newtonian fluid but with its viscosity as a function of the hematocrit, plasma viscosity, and shape factor of the red blood cells. The artery is modeled as a flexible circular pipe with the blood flow as oscillatory. This model is solved using HAM (Homotopy Analysis Method), an approximate analytical method, and we computed expressions for wall shear stress (WSS) and volumetric flow rate. With the help of publicly available data, blood flow in the human femoral artery for male and female populations aged 19 to 60 and above years is simulated for healthy, anemia, and polycythemia cases. The model projected a significant difference in the mean volumetric flow rates in the conditions mentioned above. Results also indicated that the mean WSS of healthy and anemic populations are not significantly different. However, a significant difference in the mean has been observed in healthy and polycythemic conditions. Furthermore, a 33.3% decrease in hematocrit value from that in the normal range (taken as 0.45) of a healthy population has increased the flow rate by 33.5%. For a value 33.3% above 0.45, there is a decrease of 42.7% in the flow rate.

We study the flow behavior of a Newtonian fluid in a planar 4:1 contraction channel using two numerical methodologies: the two-relaxation time lattice Boltzmann method (TRT-LBM) and the finite element method (FEM). To confirm the validity of the TRT-LBM, hydrodynamic quantities such that velocity, pressure, and vortex are carefully investigated at the wide ranges of Reynolds numbers (Re = 0.1–100). At first, we analyze the velocity along the channel. The results of TRT-LBM look reasonable and also coincide with the analytical solution and FEM results. Richer features are observed in the pressure profile along the flow direction. At low Reynolds numbers, the one-step change of the slope in the pressure profile is observed near the contraction region. The slope gradually grows up with the increase of Reynolds numbers, and eventually, this evolves the two-step change. Non-monotonic behavior is observed in the characteristics of the vortex. The size of the vortex non-linearly decreases as the Reynolds number increases. Also, the center of the vortex gradually moved toward the corner of the channel as an increase of Reynolds numbers with non-linearity. Not only the velocity and the pressure profiles but also the characteristics of the vortex quantitatively coincide in TRT-LBM and FEM results. Through this study, we confirm the robustness of the TRT-LBM as a simulation tool to investigate inertial flow in a planar contraction geometry. [ABSTRACT FROM AUTHOR]

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Heat transfer effect on peristaltic Newtonian flow in an annular region of eccentric cylinders is considered. An approximate solution for temperature and velocity is obtained using perturbation technique. For constant flow rate, the variation of pressure gradient and velocity with respect to several non-dimensional parameters is studied using graphical representation. It is seen in these graphs that velocity, pressure gradient and temperature enhance with raise in eccentricity and amplitude ratio. Heat diffuses with faster rate with depletion in area of cross section eccentric annulus through parameter inner cylinder radius. Also, velocity rises with increase in heat transfer parameters such as Grashof number and heat transfer co-efficient. Thus velocity of peristaltic flow in eccentric annulus enhances rapidly in presence of heat transfer compared to absence of heat transfer. A study of peristaltic flow in concentric annulus in presence of heat transfer is obtained analytically and compared with present study at eccentricity equal to zero, to validate the approximate solution. It is seen that flow rate increases more in case of eccentric annulus compared to concentric in presence of heat transfer. Present study has application in endoscope, which is important to diagnose problems in internal organs. Also, the variation of pressure gradient helps to maintain flow rate which is essential during insertion of catheter into artery.

Stoke's problems significantly impact several domains, including industrial manufacturing, geophysical flows, chemical engineering, and heat conduction. Stoke's second problem deals with the movement of a semi-infinite viscous incompressible fluid caused by an oscillating flat plate. Thus, this work examines Stoke's second problem for an unsteady hydromagnetic surface-driven flow along an infinite flat plate in the presence of thermal radiation and heat dissipation. The governing momentum and energy equations form an emerging nonlinear system of partial differential equations through dimensionless proxies. MAPLE 2022 is employed to solve the resulting system of nonlinear partial differential equations that control the flow both analytically and numerically in specific situations. The analytical solutions are displayed graphically, along with variations of skin friction and Nusselt number at the plate. It has been observed that momentum and thermal slips significantly diminished the flow characteristics to cause damping flow rate and temperature distributions. Rising the values of Magnetic and velocity slip parameters, an oscillatory motion is observed in skin friction. This is due to the periodic and wavy nature of the boundary wall. Furthermore, a rise in the Prandtl number and radiation value correspondingly boosted the wall heat gradient profiles. Finally, this study will assist industry and engineering in understanding the sensitivity of their working fluids to parameter variations and for the exact prediction of their base fluids.

Heat and mass transfer analysis of viscous liquid flow generated by rotation of disk has generated prodigious interest due to promising utilizations in numerous processes such as thermal energy generation systems, turbine rotators, geothermal energy preservations, chemical processing, medicinal instrumentations, computing devices and so forth. In view of such extraordinary utilizations in numerous engineering procedures existent exertion is excogitated to disclose flowing phenomenon over rotating disk. To raise the importance of current analysis influential physical aspects like magnetic field, permeability, Dufour and Soret diffusion phenomenon are also incorporated. Subsequently, flow field distributions are analyzed for suction and injection cases. Modelling is structured via PDE’s by obliging constitutive conservation laws. Boundary layer approach is executed to reduce complexity of attained partial differential system. Transformations developed by Karman are implemented to convert developed differential framework into ODE’s. Implicitly finite differenced technique known as Keller Box is engaged to find solution of coupled intricate high order ordinary differential equations. Influence of flow controlling parameters on associated distributions are revealed through graphical and tabular representations. The related quantities of engineering interest like coefficients of wall drag force, along radial and tangential directions are also computed. Credibility of presently computed results is established by constructing comparison with previously published literature. It is inferred that magnetic strength parameter enhances tangential and radial components of velocity whereas contrary trend is depicted in axially directed velocity. In addition, temperature and momentum distributions show up surging attribute versus magnetic field parameter. All associated profiles have exhibited decrementing aspects against suction parameter. It is also revealed that increment in Soret tends to produce depreciation in temperature profile whereas concentration distribution is enhanced.

The prime intend behind the current effort is to explicate flow attributes of magnetically influenced Newtonian fluids toward a stretchable sheet under the novel physical impact of oxytactic microorganisms in a comparative manner for free and forced convections. In addition, modified Fourier and Fick’s laws are implemented to examine the change in temperature and concentration distributions in a more realistic manner by accounting thermal and mass relaxation parameters in the flow. The obtained PDEs are reduced into the non-linear ODEs by employing similarity variables. Due to the complexity of parametrically based differential equations, a numerical scheme based on a finite-difference approach is implemented via the MATLAB built-in routine known as BVP4C. Flow-controlling parameter effects on associated distributions are evaluated through graphs and tables. Subsequently, the influence of flow-controlling parameters on associated distributions is revealed through pictures in a comparative manner for different convection regimes. Additionally, the quantities such as heat and mass fluxes along with the density of motile microorganisms are also illustrated. From the thorough analysis of the current investigation, it is inferred that velocity distribution enhances for free and forced convections, whereas the temperature of the fluid diminishes against the mentioned convective regimes. It is manifested that the Nusselt number is more in the situation of free convection instead of the forced convection situation. The magnitude of the skin friction factor is more in case of free convection as compared to the forced convection regime. It is also reported that by uplifting the magnitudes of concentration and thermal relaxation parameters, depreciation in associated heat and mass transfer rate arises. In addition, it is also reported that with the increment in the magnetic field, buoyancy ratio, bioconvection parameters, and Rayleigh number skin friction accelerate, while the behavior is quite opposite in case of stretching the ratio parameter.

The study of an immiscible fluid plays a significant role in the field of petroleum extraction, blood flow in arteries, hydrology, manufacturing process, and reservoir mechanics. These phenomena include immiscible fluids of different densities and viscosities in the same channel. Due to the various practical applications, in the current study, the generalized Couette flow of two immiscible fluids (Newtonian and non‐Newtonian fluids) of different viscosities between two infinite parallel plates under the presence of constant pressure gradient and electroosmosis is addressed. The effects such as electromagnetohydrodynamics, zeta potential, Joule heating, thermal radiation, modified Darcy's law, and chemical reaction have been also considered into account. The dimensional system of equations has been nondenationalized with suitable dimensionless quantities. The resulting nondimensional system of coupled flow equations has been solved analytically. The solutions for the velocity, temperature, and concentration have been presented. The effect of various pertinent fluid flow parameters has been displayed graphically. The current study concludes that both the velocity and temperature profiles decrease with the increase in Hartmann number and radiation parameter, whereas an increase in chemical reaction parameter uplifts the concentration of both fluids. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical and numerical analysis of the length required for roll waves to become stationary in a free-surface laminar flow of a Newtonian fluid. Two types of stability analysis are brought to verify flow stability and obtain parameters for wave growth rate in a Saint-Venant like system. Then, numerical simulations are performed of the free-surface laminar transient flow of glycerin. The Navier-Stokes equations were solved using the finite volumes method, Euler schemes and PIMPLE, and the VoF technique to solve the interface. Boundary conditions were specified to obtain a steady and uniform regime given a Froude number. Then, a sinusoidal perturbation with controllable properties was applied to the inlet velocity. From the numerical results, the spatial development of the roll waves was evaluated, focusing on the establishment length as a function of the Froude number and the perturbation amplitude. The analyses performed allowed the verification of the influence of flow hydraulic regime over the establishment length, and it was possible to obtain a new equation as a function of the perturbation amplitude. [ABSTRACT FROM AUTHOR]

When a liquid fills the semi-infinite space between two concentric cylinders which rotate at different steady speeds, how about the shape of the free surface on top of the fluid? The different fluids will lead to a different shape. For the Newtonian fluid, the meniscus descends due to the centrifugal forces. However, for the certain non-Newtonian fluid, the meniscus climbs the internal cylinder. We want to explain the above phenomenon by a rigorous mathematical analysis theory. In the present paper, as the first step, we focus on the Newtonian fluid. This is a steady free boundary problem. We aim to establish the well-posedness of this problem. Furthermore, we prove the convergence of the formal perturbation series obtained by Joseph and Fosdick in Arch. Ration. Mech. Anal. 49 (1973), 321–380. [ABSTRACT FROM AUTHOR]

A peristaltic endoscope is a device that could locomote through curving and tortuous spaces where it has many real-life applications in different disciplines e.g., in the field of medicine, it helps in the process of catheterization in curved tubes which in turn relieve patient’s pain. The aim of this paper is to study a trapping phenomenon at the centerline of a gap between inner peristaltic endoscope and outer peristaltic tube of a fluid with viscosity variation and a novel phenomenon of separated flow at the boundary of these tubes. For understanding these phenomena, we formulate the flow of a fluid with viscosity variation through the gap between two coaxial peristaltic tubes in cylindrical coordinates with neglecting Reynolds number and wave number. Explicit forms for the velocity field, pressure rise and friction forces on inner and outer peristaltic tubes in terms of radius ratio, flow rate, parameter of viscosity and occlusion have been obtained. A new comparison between a rigid endoscope and a peristaltic endoscope through the gastrointestinal tract has been made for the pressure rising and drag (friction) forces results. Also, we identify type of pumping for various physical parameters of interest. In addition, separated flow points are determined numerically by using computer algebra system.

In this study, we investigated the particle separation phenomenon in a microchannel with a T-shaped cross-section, a unique design detailed in our previous study. Utilizing a co-flow system within this T-shaped microchannel, we examined two types of flow configuration: one where a Newtonian fluid served as the inner fluid and a viscoelastic fluid as the outer fluid (Newtonian/viscoelastic), and another where both the inner and outer fluids were Newtonian fluids (Newtonian/Newtonian). We introduced a mixture of three differently sized particles into the microchannel through the outer fluid and observed that the co-flow of Newtonian/viscoelastic fluids effectively separated particles based on their size compared with Newtonian/Newtonian fluids. In this context, we evaluated and compared the particle separation efficiency, recovery rate, and enrichment factor across both co-flow configurations. The Newtonian/viscoelastic co-flow system demonstrated a superior efficiency and recovery ratio when compared with the Newtonian/Newtonian system. Additionally, we assessed the influence of the flow rate ratio between the inner and outer fluids on particle separation within each co-flow system. Our results indicated that increasing the flow rate ratio enhanced the separation efficiency, particularly in the Newtonian/viscoelastic co-flow configuration. Consequently, this study substantiates the potential of utilizing a Newtonian/viscoelastic co-flow system in a T-shaped straight microchannel for the simultaneous separation of three differently sized particles.

This study envisions the hydrothermal characteristics of a viscous fluid in a homogenously permeable hexagonal enclosure. Permeability aspects in the flow domain are described by employing the Brinkman-extended Darcy law. A corrugated hexagonal enclosure along with the placement of a star-shaped fin is taken into account. Heated rectangular blocks at horizontal extremities are installed, and sliding sides of the enclosure are considered to be cold to provide convective potential to the flow. In addition, adjoining portions of the heated rectangular blocks are supposed to be adiabatic. The dimensionless governing equations of the resultant problem are derived initially and then solved numerically by implementing the Galerkin finite element approach, and COMSOL is obliged. For this purpose, first, domain discretization is demonstrated in view of 2D elements by performing hybridized meshing. Then, the system of non-linear equations is resolved by a non-linear solver (PARADISO). The grid convergence test is performed to confirm the credibility of the carried out simulations by calculating the average Nusselt number at different refinement levels. A change in associated distributions against the involved physical parameters (Darcy number (Da), Rayleigh number (Ra), and Prandtl number (Pr)) for a wide range is revealed through graphs and tables. Quantities like kinetic energy and heat flux (local and average) are also evaluated through concerned parameters. The results clearly demonstrate that the Darcy number tends to reduce the heat transfer rate. In particular, it is depicted that by increasing the Rayleigh number (Ra), strengthening in the temperature potential arises in the system, thereby magnifying the heat transfer rate. Moreover, it is disclosed that by reducing the Darcy number, kinetic energy shows a decreasing trend.

Simulations of both inert mixing and sustained combustion are analyzed for a cavity flameholder based on corresponding experiments. An M=1 round ethylene jet fuels a cavity with length-to-depth ratio L/D=3.5 and a 45° inclined downstream wall. Oxidizer mixes into the cavity from the M=3 core flow. The simulations reproduce shock angles and wall pressures of the corresponding experiment. The effects that cavity combustion has on the core-flow gas dynamics and cavity entrainment are analyzed in detail. Relative to the inert case, heat release leads to a complex core flow, with upstream boundary layers transiently separating and highly unsteady shocks over the cavity. Their collective effect is the formation of a virtual throat, which decreases the core flow to M=2 above the cavity. Lagrangian trajectories assess the roles that turbulence, combustion, and three-dimensional side-wall boundary layers have on oxidizer entrainment into the cavity. Overall, sustained cavity combustion suppresses entrainment by a factor of about 2. [ABSTRACT FROM AUTHOR]

The present investigation set out to assess the influence of the surface roughness on the flow and thermal mean quantities, around the heated corrugated cylinder in the laminar steady flow. The current investigation has been devoted to a numerical analysis of a two-dimensional steady flow and forced convection heat transfer characteristics over a heated longitudinal sinusoidal shape grooved cylinder, immersed in an unconfined Newtonian fluid. The number of the grooved cavities was chosen to be 10, 20 and 30 grooves, equally distributed around the cylinder circumference with wavelength and wave amplitude of 1/50 and 1, respectively. Moreover, the thermal boundary condition effect has been analyzed by imposing a uniform heat flux and constant temperature on the cylinder periphery as a thermal boundary condition, over a Reynolds number range of (0. 1 ≤ Re ≤ 4 0) and a fixed Prandtl number of 0.715. The numerical procedure is based on the finite volume method. The findings indicate that with increasing groove number, the total drag coefficient of the grooved cylinder reduces markedly compared to the smooth one. This trend is more pronounced as the Reynolds number increases. The effect of the groove number on the pressure coefficients is limited, where the profiles of the grooved cylinder coincide with that of the smooth one over the Reynolds number range. When the Reynolds number varies from 0.1 to 40, the average Nusselt number enhances noticeably by about 86% for the smooth and grooved cylinders. Moreover, the groove number affects significantly the average Nusselt number, where the increased groove number results in a gradual reduction in the average Nusselt number. This attenuation is more pronounced as the Reynolds number increases. To predict the average Nusselt number, a correlation has been proposed. [ABSTRACT FROM AUTHOR]

The present study investigates the influence of uniform magnetic field on the flow of a Newtonian fluid sandwiched between two micropolar fluid layers through a rectangular (horizontal) porous channel. Fluid flow in the every region is steady, incompressible and the fluids are immiscible. Uniform magnetic field is applied in a direction perpendicular to the direction of fluid motion. The governing equations of micropolar fluid are expressed in Eringen's approach and further modified by Nowacki's approach. For respective porous channels, expressions for linear velocity, microrotations, stresses (shear and couple) are obtained analytically. Continuity of velocities, continuity of microrotations and continuity of stresses are employed at the porous interfaces; conditions of no slip and no spin are applied at the impervious boundaries of the composite channel. Numerical values of flow rate, wall shear stresses and couple stresses at the porous interfaces are evaluated by MATHEMATICA and listed in tables. Graphs of flow rate and fluid velocity are plotted and their behaviors discussed. [ABSTRACT FROM AUTHOR]

Based on the statistical self-similar fractal characteristics of the microstructure of porous media, the total flow rate and permeability of Newtonian fluids in the rough fracture network and rough matrix pores are derived, respectively. According to the connection structure between fractures and pores, the permeability analysis model of fluids in a matrix-embedded fracture network is established. The comparison between the predicted values of the model and the experimental data shows that the predicted values of the permeability of the rough fracture network and the rough matrix pores decrease with the increase in the relative roughness of the fractures and matrix pores, and are lower than the experimental data. Meanwhile, the predicted total flow rate of a rough fractured dual porous media is lower than that of a smooth fractal model and experimental data. In addition, it is also found that the larger the average inclination angle and the relative roughness of the fracture network, the smaller the permeability of the fractured dual porous media, and the relative roughness of the fracture network has a far greater influence on fluid permeability in the fractured dual porous media than the relative roughness of the matrix pores. [ABSTRACT FROM AUTHOR]

Co-extruded multi-layer plastic sheets and polymer structures formed by calendering process or by cold rolling are widely used in the packaging industry and thin-film transistor manufacturing. The different materials are extruded from separate extruders into the single sheet die which delivers a multi-layer sheet with uniform layer thickness at die exit. This multi-layer sheet is then stretched between counter-rotating rolls to obtain final uniform multi-layer sheet. There are many factors which can influence this process. In this article, calendering a single layer Newtonian or Non-Newtonian material has been extended to analyze a two-layer calendering process for an incompressible Viscoplastic and Newtonian fluids as upper and lower layers with different viscosity ratios. To simplify the equations of motion, the lubrication approximation theory is used. The expressions of non-dimensional pressure gradient, pressure and velocity distribution of both layers are obtained analytically by using proper no slip boundary conditions and dimensionless variables. The dimensionless detachment point is approximated by Regula-Falsi (false position) method. The important engineering factors including detachment point, calendered sheet thickness, roll separation force, power input by rolls, torque on each roll, and adiabatic temperature are all computed. In addition, how the viscosity ratios and viscoplastic casson parameter affect these factors have been investigated. Moreover all established results in literature for single layer calendering Newtonian fluids are also validated at casson parameter β tending towards infinity. [ABSTRACT FROM AUTHOR]

Heat and mass transfer analysis of viscous liquid flow generated by rotation of disk has generated prodigious interest due to promising utilizations in numerous processes such as thermal energy generation systems, turbine rotators, geothermal energy preservations, chemical processing, medicinal instrumentations, computing devices and so forth. In view of such extraordinary utilizations in numerous engineering procedures existent exertion is excogitated to disclose flowing phenomenon over rotating disk. To raise the importance of current analysis influential physical aspects like magnetic field, permeability, Dufour and Soret diffusion phenomenon are also incorporated. Subsequently, flow field distributions are analyzed for suction and injection cases. Modelling is structured via PDE's by obliging constitutive conservation laws. Boundary layer approach is executed to reduce complexity of attained partial differential system. Transformations developed by Karman are implemented to convert developed differential framework into ODE's. Implicitly finite differenced technique known as Keller Box is engaged to find solution of coupled intricate high order ordinary differential equations. Influence of flow controlling parameters on associated distributions are revealed through graphical and tabular representations. The related quantities of engineering interest like coefficients of wall drag force, along radial and tangential directions are also computed. Credibility of presently computed results is established by constructing comparison with previously published literature. It is inferred that magnetic strength parameter enhances tangential and radial components of velocity whereas contrary trend is depicted in axially directed velocity. In addition, temperature and momentum distributions show up surging attribute versus magnetic field parameter. All associated profiles have exhibited decrementing aspects against suction parameter. It is also revealed that increment in Soret tends to produce depreciation in temperature profile whereas concentration distribution is enhanced. [ABSTRACT FROM AUTHOR]

The thermal flow field of Newtonian fluid in novel cavity is investigated numerically. The three different shaped heated ribs namely triangular, rectangular and circular are installed case-wise at lower wall of cavity. The uniformly heated circular cylinder is taken fixed in center of cavity for each case. The no-slip condition is imposed on both the top wall and exterior surface obstacle. The fluid enters from the inlet of a cavity with a specific velocity profile. At outlet, a Neumann condition is taken. The upper wall, inlet and outlet of cavity are taken cold. Thermal flow field individualities are explored by using the energy, momentum and continuity equations. The finite element approach is used to solve these equations. The contour plots, line graphs and tabular data are used to report the ultimate observations on velocity, pressure, temperature and hydrodynamic forces. Particularly, the lift and drag coefficient values are obtained via line integration. The variations pattern in Nusselt for triangular, rectangular and circular ribs at lower wall are shared. It is noticed that the coefficients values towards heated obstacle are higher in magnitude for the case of heated rectangular rib as compared to heated triangular and circular ribs.

The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude δ T , frequency ω and the phase difference θ. The effects of δ T and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number Ri enhances heat transfer and reduces the mass transfer in the system.

Stokes drag on axially symmetric bodies vibrating slowly along the axis of symmetry placed under a uniform transverse flow of the Newtonian fluid is calculated. The axially symmetric bodies of revolution are considered with the condition of continuously turning tangent. The results of drag on sphere, spheroid, deformed sphere, egg-shaped body, cycloidal body, Cassini oval, and hypocycloidal body are found to be new. The numerical values of frictional drag on a slowly vibrating needle shaped body and flat circular disk are calculated as particular cases of deformed sphere.

In this communication, an analytical solution for the thermal transfer of Newtonian fluid flow with quadratic order thermal and velocity slips is presented for the first time. The flow of a Newtonian fluid over a stretching sheet which is embedded in a porous medium is considered. Karniadakis and Beskok's quadratic order slip boundary conditions are taking into account. A closed form of analytical solution of momentum equation is used to derive the analytical solution of heat transfer equation in terms of confluent hyper-geometric function with quadratic order thermal slip boundary condition. Accuracy of present results is assured with the numerical solution obtained by Iterative Power Series method with shooting technique. The impacts of porous medium parameter, tangential momentum accommodation coefficient, energy accommodation coefficient on velocity and temperature profiles, skin friction coefficient and reduced Nusselt number are discussed. The Nusselt number increases with the higher estimations of tangential momentum and energy accommodation coefficients.

In this work, the flow behaviour of two immiscible fluids is analysed through an inclined channel which is made of two rigid plates. The flow model consists of two porous regions of different permeability. Newtonian and micropolar fluids are allowed to flow in the region‐I and region‐II, respectively. The flow of Newtonian and micropolar fluid in respective porous region is governed by the Brinkman's equation. An exact solution of the proposed mathematical model is obtained by using well‐known and appropriate boundary conditions. The expressions for linear velocity, microrotational velocity, flow rate and stresses are evaluated. The effect of various emerging non‐dimensional parameters like viscosity ratio, couple stress parameter, gravitational parameter, Reynolds number, and so on, on linear velocity, microrotational velocity, flow rate and stresses is presented graphically. The results are validated with the help of the previous established results. [ABSTRACT FROM AUTHOR]

Energy conversion in micro/nano-systems is a subject of current research, among which the electrokinetic energy conversion has attracted extensive attention. However, there exist two different definitions on the electrokinetic energy conversion efficiency in literature. A few researchers defined the efficiency using the pure pressure-driven flow rate, while other groups defined the efficiency based on the flow rate with the inclusion of the effect of the streaming potential field. In this work, both definitions are investigated for different fluid types under the periodic electrokinetic flow condition. For Newtonian fluids, the two definitions give similar results. However, for viscoelastic fluids, these two definitions lead to significant difference. The efficiency defined by the pure pressure-driven flow rate even exceeds 100% in a certain range of the parameters. The result shows that in the case of viscoelastic flow, it is incorrect to define the energy conversion efficiency by pure pressure-driven flow rate. At the same time, the reason for this problem is clarified through comprehensive analysis. [ABSTRACT FROM AUTHOR]

The current investigation was based on a simulation employing CFD in COMSOL Multiphysics. The base fluid that was used in this simulation was blood. The flow was considered as a laminar, unsteady and incompressible Newtonian fluid, and the Newtonian nature of blood is acceptable at high shear rate. The behavior of blood flow was analyzed with the objective of obtaining pressure, temperature and velocity effects through an arterial stenosis. Two types of nanoparticles were used in this work: silver (Ag) and gold (Au). The equations of mass, momentum and energy were solved by utilizing the CFD technique. A fine element size mesh was generated through COMSOL. The results of this analysis show that velocity changes through confined parts of the artery, the velocity in a diseased region is higher and the velocity decreases before and after the stenotic region. In the heat transfer feature, the upper and lower boundary temperature was set to 24.85 °C and 27.35 °C, respectively. The nanoparticles affected the physical properties of blood, such as thermal conductivity, density, dynamic viscosity and specific heat. The addition of gold and silver nanoparticles prevented overheating because both nanoparticles have a high thermal conductivity, which has a principal role in dissipating temperature quickly. Nusselt number variations were also calculated and the results show that the curve decreases inside the stenosis. It could be concluded that the streamlines show abnormal behavior and recirculation occurs just after the stenosed area at t = 0.7 s and 1 s. These results will help greatly in the treatment of stenosed arteries. [ABSTRACT FROM AUTHOR]

In this work, a numerical study of two dimensional steady, incompressible Newtonian laminar flow of blood through a stenosed (constricted) artery is investigated. The Variational Iteration Method (VIM) is employed to obtain the analytic expressions for the velocity profile and pressure gradient. The results obtained are graphically discussed for mild stenosis (25%) for low Reynolds number in the range 20-100. The significance of the analysis is identified by comparing the results obtained with similar studies in existing literature, and established a good agreement. The results obtained reveal alterations in blood flow due to presence of stenosis in arterial wall and the implications are discussed. [ABSTRACT FROM AUTHOR]

In the present work, the effect of temperature on the rheological properties of the industrialized honey of three different high-trade brands in the northern, central and southern Lima markets was studied. The physicochemical characteristics of water activity, specific gravity, moisture content, brix degrees, refractive index and pH were analyzed. No significant difference was found between the values of the physicochemical properties within and between the groups of the commercial brands analyzed (p> 0.05). The industrialized honey was tested with a Brookfield RVDV-E concentric viscometer using a flat disk spindle at five temperature levels from 20 ºC to 60 ºC, and the influence of temperature with dynamic or absolute viscosity was studied. Through the rheogram, a behavior of a Newtonian fluid was observed. For all samples it was found that the mean absolute viscosity decreases with temperature at 20 ºC (7430 mPa∙s), 30 ºC (2636 mPa∙s), 40 ºC (955 mPa∙s), 50 ºC (440 mPa∙s) and 60 ºC (267 mPa∙s). The dependence of the viscosity with the temperature was described by a mathematical exponential model of three constants proposed in this investigation that gave a good fit, obtaining a coefficient of determination of 0.9999. The activation energy value calculated and within the temperature range tested was 68.73±0.129 kJ.mol-1 . The results obtained in this study are of great interest to the industry that manipulates and formulates edible foods based on this type of product. [ABSTRACT FROM AUTHOR]

Constrained-surface-based stereolithography has recently attracted much attention from both academic and industrial communities. Despite numerous experimental, numerical and theoretical efforts, the fundamental need to reduce the separation force between the newly cured part and constrained surface has not yet been completely solved. In this paper, we develop a fluid dynamics approach, proposed in our previous work, to theoretically model the separation force in 3D printing of a cylindrical part for flat and patterned windows. We demonstrate the possibility of separation force reduction with an accelerated movement of the printing platform. In particular, we investigate behaviors of transient parameter, its reduction rate, and separation force reduction with respect to elevation speed and time. The proposed approach involves deceleration and acceleration stages and allows to achieve the force reduction for the entire printing process. Finally, we provide implicit analytical solutions for time moments when switching between the stages can be done without noticeable increase of separation force and explicit expression for separation force in case of patterned window. [ABSTRACT FROM AUTHOR]