Showing papers on "Streamlines, streaklines, and pathlines published in 2020"

Numerical study on mixed convection of a non-Newtonian nanofluid with porous media in a two lid-driven square cavity

Abstract: In the present numerical study, mixed flow of the non-Newtonian water/Al2O3 nanofluid with 0–4% nanoparticles volume fractions (φ) inside a two-dimensional square cavity with hot and cold lid-driven motion and porous media is simulated at Richardson numbers (Ri) of 0.01, 10 and 100 and Darcy numbers (Da) of 10−4 ≤ Da ≤ 10−2 using Fortran computer code. The obtained results for temperature domain, velocity, Nusselt number and streamlines indicate that by increasing Richardson number and decreasing axial velocity parameter of walls and similarity of flow behavior to natural flow mechanism, variations of velocity are reduced, which is due to the reduction in fluid momentum. By increasing Darcy number, penetrability of fluid motion enhances and fluid lightly moves along the cavity. Figuration of streamlines at lower Richardson numbers highly depends on the Darcy number changes. In case (2), due to the counterflow motion and buoyancy force, distinction of flow domain profiles is more obvious. On the other hand, this issue causes more velocity gradients and vortexes in special sections of cavity (central regions of cavity). In case (2), the behavior of streamlines is affected by some parameters such as variations of Darcy number, nanoparticles volume fraction and Richardson number more than case (1). By increasing Darcy number, flow lightly passes among hot and cold sources and leads to improve the heat transfer. Moreover, reduction in flow penetrability in cavity results in the reduction in fluid flow in its direction, sectional distribution and regions with higher temperature. Consequently, in these regions the growth of thermal boundary layer is more significant. In case (2), at lower Richardson numbers compared to higher ones, the affectability of lid-driven motion contrary to buoyancy force caused by density variations is less because of higher fluid momentum. At Ri = 0.01, because of the strength of lid-driven motion, flow direction is compatible with lid-driven motion. Also, temperature distribution is not uniform, and in these regions, fluid has the minimum velocity which leads to the enhancement of dimensionless temperature. In both studied cases, the increment of nanoparticles volume fraction as well as Darcy number and reduction in Richardson number result in the improvement of temperature distribution and decrease in dimensionless temperature.

Study of Two-Phase Newtonian Nanofluid Flow Hybrid with Hafnium Particles under the Effects of Slip

Abstract: This paper investigates the role of slip in a two-phase flow of Newtonian fluid. The nano-size Hafnium particles are used in the base fluid. The fluid under consideration is studied for two cases namely (i) fluid phase (ii) phase of particles. Both cases are examined for three types of geometries. The governing equations are simplified in nondimensional form for each phase along with boundary conditions. The resulting equations have been analytically solved to get exact solutions for both fluid and particle phases. Different features of significant physical factors are discussed graphically. The flow patterns have been examined through streamlines.

Spectral quasi linearization simulation of radiative nanofluidic transport over a bended surface considering the effects of multiple convective conditions

Abstract: This article enlightens on the hydrothermal performance of radiative nanofluid flow over a curved stretched surface. The curved surface is coiled inside a circular segment of radius R. The surface has been presumed to be permeable and slippery. Effects of multiple convective conditions i.e. convective conditions at the surface caused by both heat and mass transport are incorporated to explore the outcomes. The permeability characteristic of the surface that affects the hydrothermal integrity of the flow has been discussed in detail. The leading equations are renovated into its non-dimensional form by applying similarity conversion. After then, the spectral quasi linearization method (SQLM) is introduced to solve those foremost nonlinear ordinary differential equations (ODEs). Residual error analysis is depicted to show the convergence rate of SQLM. The impact of the pertinent factors on the flow is illustrated through graphs and tables. Several streamlines and three-dimensional plots are provided to enrich the result section. Results assured that temperature reduces for curvature parameter, but intensifies for both thermal and mass Biot numbers. Nanofluidic motion increases for curvature parameter and declines for slip factor. Curvature parameter and Lewis number provide reduction in mass transfer, whereas thermal and mass Biot numbers, slip parameters provide the enhancement. Heat transfer is enhanced for curvature parameter, thermal and mass Biot number.

Influence of inclined magnetic field on the flow of condensed nanomaterial over a slippery surface: the hybrid visualization

Abstract: Nanofluids are of great interest for its inflated heat transport rate. A novel conviction of hybrid nanosuspension with an enhanced model under inclined magnetic field along with its thermophysical properties is analyzed in this work. Surface slip plus permeable texture of the sheet aid us to have excellent points of the flow. The prime equations are renewed to ODE with the assistance of similarity transportation and subsequently solved numerically. A hybrid nanofluid with $${\text{Ag}}$$ and $${\text{CuO}}$$ nanoparticles as well as $${\text{CuO}}$$ for usual nanofluid with base fluid water are taken to explore salient attribute and parameters. Several graphs, streamlines, and contour plots are presented to convey the impact of inclined magnetism of hybrid condensed structure of the flow. Reduced frictional coefficient and heat transports are calculated and reviewed. This investigation shows that heat transport rate of hybrid nanofluid is better than nanofluid under inclined magnetic field and for suitable angle of inclination. Temperature amplifies owing to magnetic parameter, injection, and magnetic field inclination, whereas reverse is true for suction. The novel outcomes of this investigation will advance the field of condensed nanostructure and nanomaterials.

Finite element analysis of hybrid nanofluid flow and heat transfer in a split lid-driven square cavity with Y-shaped obstacle

Abstract: The constructal design-based model is reported to analyze the thermal control and heat augmentation inside a split lid-driven square cavity. A Y-shaped obstacle is placed within the cavity, which is filled with Al2O3–Cu–water hybrid nanofluids. The concept of the split-lid-driven cavity is utilized for the first time. The governing flow mathematical structure is obtained in terms of a system of partial differential equations and converted to a non-dimensional form through dimensionless variables. The numerical experiments are performed by employing a Galerkin finite element scheme for different values of involved physical parameters. The effects of pertinent parameters on the streamlines, isotherms, dimensionless temperature, and Nusselt numbers are investigated for different values of the Richardson number. Due to the simultaneous motion of the split-lids, the streamlines and isotherms show symmetrical distribution. The local Nusselt number increases with the moving split-lids and attains the maximum value when both lids meet. The average Nusselt number decreases with an increase in the Richardson number. It is important to note that the Y-shaped obstacle enhances the heat transfer rate in the cavity.

Impacts of heated rotating inner cylinder and two-phase nanofluid model on entropy generation and mixed convection in a square cavity

Abstract: A numerical study is carried out on mixed convection and entropy generation of Al2O3/water nanofluid due to a rotating cylinder inside a square cavity. The numerical computations are performed taking the non-homogenous model of Buongiorno into consideration. The inner moving rotating circular cylinder is maintained at a constant hot temperature Th and the other left and right vertical walls of the cavity are maintained at a constant cold temperature Tc. The bottom and top horizontal walls are maintained as adiabatic. The Galerkin weighted residual method is implemented to numerically solve the governing equations. The Rayleigh number (104 ≤ Ra ≤ 107), angular rotational velocity (0 ≤Ω≤ 600) nanoparticles loading (0 ≤ ϕ ≤ 0.04) and the dimensionless radius of rotating cylinder (0.1 ≤ R ≤ 0.4) are the governing parameters of this study. Numerical results for the streamlines, isotherms, isentropic lines, nanoparticle loading, local and average Nusselt number and Bejan number are obtained and presented graphically. A detailed discussion of the results is performed to highlight the physics of the problem.

Mathematical Analysis on an Asymmetrical Wavy Motion of Blood under the Influence Entropy Generation with Convective Boundary Conditions

Abstract: In this article, we discuss the entropy generation on the asymmetric peristaltic propulsion of non-Newtonian fluid with convective boundary conditions. The Williamson fluid model is considered for the analysis of flow properties. The current fluid model has the ability to reveal Newtonian and non-Newtonian behavior. The present model is formulated via momentum, entropy, and energy equations, under the approximation of small Reynolds number and long wavelength of the peristaltic wave. A regular perturbation scheme is employed to obtain the series solutions up to third-order approximation. All the leading parameters are discussed with the help of graphs for entropy and temperature profiles. The irreversibility process is also discussed with the help of Bejan number. Streamlines are plotted to examine the trapping phenomena. Results obtained provide an excellent benchmark for further study on the entropy production with mass transfer and peristaltic pumping mechanism.

Finite volume method for mixed convection flow of Ag-ethylene glycol nanofluid flow in a cavity having thin central heater

Abstract: The article focuses on the mixed convective flow of Ag–ethylene glycol nanofluid. The analysis is carried out for a cavity having center as heated. The relatively moving side walls of cavity are retained at low constant temperature while constant heat source is examined in the bottom wall. The rest of the bottom and top walls remain insulated. Cattaneo–Christov heat flux is implemented in the analysis of heat transfer. Heat transfer rate is dig out for the case of Fourier’s heat flux, as for the case of Cattaneo–Christov heat flux it gives implicit expression, which is difficult to analyze and simplify. The problem is analyzed numerically via projection method. Higher heat transfer is observed for the Fourier’s law as compare to Cattaneo–Christov heat flux. The results are expressed by isotherms, streamlines, velocity field, and average Nusselt numbers.

A computational analysis of heat transport irreversibility phenomenon in a magnetized porous channel

Abstract: The purpose of this paper is to evaluate the temperature, the Dirichlet conditions have been considered to the parallel horizontal plates. The model of generalized Brinkman-extended Darcy with the Boussinesq approximation is considered and the governing equations are computed by COMSOL multiphysics.,In the current study, the thermodynamic irreversible principle is applied to study the unsteady Poiseuille–Rayleigh–Benard (PRB) mixed convection in a channel (aspect ratio A = 5), with the effect of a uniform transverse magnetic field.,The effects of various flow parameters on the fluid flow, Hartmann number (Ha), Darcy number (Da), Brinkman number (Br) and porosity (e), are presented graphically and discussed. Numerical results for temperature and velocity profiles, entropy generation variations and contour maps of streamlines, are presented as functions of the governing parameter mentioned above. Basing on the generalized Brinkman-extended Darcy formulation, which allows the satisfaction of the no-slip boundary condition on a solid wall, it is found that the flow field and then entropy generation is notably influenced by the considering control parameters. The results demonstrate that the flow tends toward the steady-state with four various regimes, which strongly depends on the Hartman and Darcy numbers variations. Local thermodynamic irreversibilities are more confined near the active top and bottom horizontal walls of the channel when increasing the Da and decreasing the Hartmann number. Entropy generation is also found to be considerably affected by Brinkman number variation.,In the present work, we are presenting our investigations on the influence of a transverse applied external magnetohydrodynamic on entropy generation at the unsteady laminar PRB flow of an incompressible, Newtonian, viscous electrically conducting binary gas mixture fluid in porous channel of two horizontal heated plates. The numerical solutions for the liquid velocity, the temperature distribution and the rates of heat transport and entropy generation are obtained and are plotted graphically.

Vector Field Topology of Time-Dependent Flows in a Steady Reference Frame

Abstract: The topological analysis of unsteady vector fields remains to this day one of the largest challenges in flow visualization. We build up on recent work on vortex extraction to define a time-dependent vector field topology for 2D and 3D flows. In our work, we split the vector field into two components: a vector field in which the flow becomes steady, and the remaining ambient flow that describes the motion of topological elements (such as sinks, sources and saddles) and feature curves (vortex corelines and bifurcation lines). To this end, we expand on recent local optimization approaches by modeling spatially-varying deformations through displacement transformations from continuum mechanics. We compare and discuss the relationships with existing local and integration-based topology extraction methods, showing for instance that separatrices seeded from saddles in the optimal frame align with the integration-based streakline vector field topology. In contrast to the streakline-based approach, our method gives a complete picture of the topology for every time slice, including the steps near the temporal domain boundaries. With our work it now becomes possible to extract topological information even when only few time slices are available. We demonstrate the method in several analytical and numerically-simulated flows and discuss practical aspects, limitations and opportunities for future work.

Irreversibility analysis of Cu-TiO2-H2O hybrid-nanofluid impinging on a 3-D stretching sheet in a porous medium with nonlinear radiation: Darcy-Forchhiemer’s model

Abstract: The current research is conducted to investigate the slip effect and to analyze entropy production in both hybrid nanofluids, and common nanofluids flow past a convectively heated three-dimensional stretching sheet placed in a porous medium. The slip flow is considered in a Darcy-Forchheimer’s scheme by incorporating the nonlinear thermal radiation. Water is taken as base fluid, while Copper and Titanium dioxide nanoparticles are considered. The governing models are overset into dimensionless variables using similarity transformation, and the solution is acquired numerically. The impacts of pertinent factors on the flow, heat transfer, and entropy generation rates are explored. Additional plot portraying the streamlines and isotherms for both nanofluids are presented to examine the hydrothermal behavior. Skin friction and heat transport are discussed with sensible judgment. A comparison with earlier studies is unwrapped to ensure the model’s validity. The results communicate that temperature is enhanced with porosity, whereas velocity is found to be decelerated. Bejan number is decreasing with an increase in the nanoparticle volume fraction of nanoparticles. Furthermore, hybrid nanofluids generate less entropy than common nanofluids.

Inclined magneto: convection, internal heat, and entropy generation of nanofluid in an I-shaped cavity saturated with porous media

Abstract: A numerical investigation of entropy generation due to MHD-free convective of Cu–water nanofluid in a porous I-shaped cavity is reported. The cavity is under Darcy law with inclined uniform magnetic field. The cavity is cooled from the top and a part of bottom wall subjected to uniform heat flux, while the other parts of walls of the cavity are adiabatic. Mathematical pattern formulated employing the single-phase nanofluid approach in governing equations the problem has been solved by finite difference technique. Prime efforts have been concentrated on the impacts of the pertinent parameters on the fluid flow and heat transfer inside the cavity. Numerical data have been plotted in the form of streamlines, isotherms, and average Nusselt numbers. The results show that the Nu number decreases via increasing the Ha number. It increases when the Ra number is increased. The maximum and minimum values of Nusselt occur at B = 0.2 and B = 0.8, respectively. Exerting an angle for magnetic flux leads to the improvement in thermal performance for all amount of B. The effects of Ha, nanofluid volume fraction, heat source size, location and angle of magnetic field on heat transfer, entropy generation, and thermal performance are completely studied and discussed.

Impact of Variable Transport Properties and Slip Effects on MHD Jeffrey Fluid Flow Through Channel

Abstract: The present paper aims at investigating the effects of variable transport properties and slip conditions on the MHD peristaltic mechanism of a Jeffrey liquid. The flow is considered to take place in an axisymmetric channel with compliant walls. The nonlinear momentum and energy equations are solved for small values of variable viscosity and thermal conductivity by utilizing the method of perturbation. Closed-form solutions are found for mass transfer equation. MATLAB programming is employed to get the pictorial representation of various parameters on axial velocity, streamlines, temperature and concentration profiles. The current investigation reveals that an increase in the value of the magnetic parameter reduces the velocity as well as temperature. Moreover, the size of the trapped bolus is seen to be a decreasing function of magnetic and Jeffery parameters.

A theoretical nanofluid analysis exhibiting hydromagnetics characteristics employing CVFEM

Abstract: The heat transfer properties of current liquids are specifically improved by suspending nanocrystalline solid elements smaller than 100 nm in diameter. These liquids are considered as potential working fluids for applications such as car radiators, solar collectors, electronic frost systems, nuclear reactors and heat pipes. Due to such uses, here we formulate CuO–H2O nanofluids in a two-dimensional circular geometry with a rhombus-shaped barrier maintaining the constant temperature of two adjacent high walls. The streamlines and isotherms have been plotted using the control volume finite element method and applying the KKL model for nanofluid simulation. The results were calculated for different concentrations of nanoparticles, Hartmann number and Rayleigh number. It was found that in a large number of volume fraction and Hartmann number, the isotherms near the outer margin are more prominent while the low-volume-concentration isotherms are concentrated near the adiabatic wall of the obstacle. It was also found that there is a temperature gradient in the radial direction at a higher volume fraction and Hartmann number (Ha). The temperature gradient was limited to adiabatic walls of the obstruction in lower volume fraction and Ha. Two similar shapes but differently directed eddies are formed for any value of Ra in streamlines. |Ψmax|nf increases with an increase in the values of Ra from 103 to 105.