Viscous Dissipation Term Research Articles

Investigating thermal conduction dynamics in ternary Carreau–Yasuda nanofluids under convective boundary conditions and exponential heat source/sink effects

The analysis of the Carreau–Yasuda nanofluid (CYNF) across a stretching surface has practical applications in several fields, such as heat exchange, engineering, and material science. Scholars may discover novel perspectives for increasing heat transfer performance, establishing advanced materials, and enhancing the efficiency of multiple engineering systems by studying the behavior of CYNF in this particular instance. The energy transfer through trihybrid CYNF flow with the effect of magnetic dipole across a stretching sheet is examined in the present study. The ternary hybrid nanofluid (THNF) has been prepared by the addition of ternary nanoparticles (NPs) in the water (50%) and ethylene glycol (50%). Titanium dioxide (TiO2), silicon dioxide (SiO2), and aluminum oxide (Al2O3) are used in base fluid. The fluid velocity and heat transfer are examined under the impact of Darcy–Forchheimer, chemical reaction, convective condition, activation energy, and exponential heat source. The fluid flow has been stated in form of velocity, energy, and concentration equations. The set of modeled equations is simplified to non-dimensional form of ordinary differential equations (ODEs) by using similarity substitutions. Numerically, the system of lowest order ODEs is calculated through the parametric continuation method. It has been noticed that the temperature field augments against the variation of viscous dissipation and heat source term. Furthermore, the magnetic dipole has significant impact to enhance the thermal curve of THNF whereas falloffs the velocity profile. It can be noticed that the energy propagation rate enhances with the rising numbers of ternary NPs, from 1.22% to 5.98% (nanofluid), 2.30% to 9.61% (hybrid nanofluid), and 3.23% to 11.12% (trihybrid nanofluid).

Investigation of irreversible losses in subsonic compressor cascade flow field: A study on viscous dissipation and temperature gradient term in entropy production rate

The entropy generation rate is a widely employed loss characterization approach in the design and optimization of fluid machinery. This approach is utilized to quantitatively determine various types of losses in the flow field, and it is considered that the temperature gradient term in the entropy generation rate can characterize irreversible losses. This research paper aims to address the question of whether the temperature gradient term in entropy production rate can represent the irreversible losses in a flow field. By employing the Reynolds-Averaged Navier-Stokes (RANS) numerical simulation method, the flow field of a subsonic compressor cascade, both with and without wall heating, was investigated. Statistical analysis was conducted to examine the contributions of viscous dissipation, the temperature gradient term in entropy production rate, wall shear stress work, and global power loss. The study reveals the distribution differences of viscous dissipation and the temperature gradient term in entropy production rate within the separated flow region. The research results demonstrate that, under wall heating conditions, viscous dissipation increased by approximately 45%, and the ratio of the temperature gradient term to global power loss increased from 4% to 125%, exceeding the mechanical energy loss in the flow field. The distribution of the temperature gradient term within the separated flow region cannot be explained by irreversible losses, and it exhibits significant discrepancies with the distribution of viscous dissipation losses. Therefore, the temperature gradient term in entropy production rate cannot represent the local irreversible losses, whereas viscous dissipation serves as an accurate measure of local irreversible losses. The research results provide theoretical support for accurately determining the irreversible losses in the flow field.

Heat transfer analysis of nanofluid flow with entropy generation in a corrugated heat exchanger channel partially filled with porous medium

AbstractHeat exchanger research is mainly exploited to develop and optimize new engineering systems with high thermal efficiency. Passive methods based on nanofluids, fins, wavy walls, and the porous medium are the most attractive ways to achieve this goal. This investigation focuses on heat transfer and entropy production in a nanofluid laminar flow inside a plate corrugated channel (PCC). The channel geometry comprises three sections, partially filled with a porous layer located at the intermediate corrugate channel section. The physical modeling is based on the laminar, two‐dimensional Darcy–Brinkman–Forchheimer formulation for nanofluid flow and the local thermal equilibrium model for the heat equation, including the viscous dissipation term. Numerical solutions were obtained using ANSYS Fluent software based on the finite volume technique and the appropriate meshed geometries. The numerical results are validated with theoretical, numerical, and experimental studies. The simulations are performed for CuO–water nanofluid and AISI 304 porous medium. The coupled effects of porous layer thickness (δ), Reynolds number (Re), and nanoparticle fraction (φ) on velocity, streamlines, isotherm contours, Nusselt number (Nu), and entropy generation (S) are analyzed and illustrated. The simulation results demonstrate that heat transfer enhancement in clear PCC can be achieved using a porous layer insert. For the porous thickness range of [0.1–0.6], the corresponding range of average Nusselt number increase is [35.7%–176.9%], and the average entropy generation is [105.4%–771.9%]. The effect of the Reynolds number is more important in a porous duct than in a clear one. For δ = 0.4 and φ = 5%, the increase of Re in the range of [200–500] induces an increase in average Nusselt number in the range of [80.9%–108.4%] and average entropy in [222.9%–309.1%] comparatively to clear PCC. The effect of φ is practically the same for porous and clear channels. For φ = 5%, the increase on average Nu is about 9%, and entropy generation is 5%. Accordingly, important improvements in heat transfer in PCC can be achieved through the combined effect of flow Reynolds number and porous layer thickness.

Modelling internal erosion using 2D smoothed particle hydrodynamics (SPH)

This paper presents a stabilised multi-phase smoothed particle hydrodynamics (SPH) model applicable to seepage-induced internal erosion and the resulting deformation in soils. Based on the continuum mixture theory, a new single-layer SPH model in the u-w-p formulation is derived for the mathematical description of the erodible porous material. A new modified constitutive model is formulated to account for the influence of erosion on the mechanical behaviour of soils. Extensions of a first-order consistent boundary condition as well as the diffusion algorithm for hydro-mechanical coupling in SPH are also proposed to accommodate the analysis of erosion-transport process. A novel viscous dissipation term is designed to mitigate the numerical instability commonly encountered in coupled problems. In contrast to existing stabilisation terms in the SPH literature, which operate on both the bulk component and shear component, this new stabilisation term offers the possibility to increase the dissipation of unphysical oscillation due to the shear deformation. The proposed method is validated through a series of benchmark tests. The results demonstrate the effectiveness of the proposed approach in addressing the coupled problem in porous materials involving multi-phase flow, phase interaction/transfer, and large deformation with enhanced accuracy, stability, and robustness.

A thermal energy analysis of binary (Go-Co/H2O) and ternary (Go-Co-Zro2/H2O) nanofluids based on characterization and thermal performance

Hybrid or binary nanofluids have superior mechanical and thermal characteristics but the tri-hybrid nanofluids comprise of more embellished thermal properties, better physical strength, and enhanced stability. The present work characterizes the thermal and physical aspects of the hybrid and tri-hybrid nanofluids. The nano-composition of graphene oxide ( Go) and cobalt ( Co) is used in the amalgamation of hybrid nanofluid Go-Co/H2O, whereas the addition of zirconium oxide ( ZrO2) in this mixture gives rise to the ternary Go-Co-ZrO2/H2O hybrid nanofluid. The activation energy and viscous dissipation terms are also amended in the governing equations. The mathematical framework consists of a complex natured dynamical system. However, a numerical algorithm based on finite-difference discretization is developed which can solve the system numerically via the MATLAB software. A comparison with the existing literature is provided in order to validate the numerical procedure. From the outcomes, it is noticed that the temperature of hybrid as well as tri-hybrid nanofuid increases rapidly with change in concentration of zirconium oxide and cobalt. Temperature increases up to 20% by taking 0.1 volume fraction of both zirconium oxide and cobalt. Porous medium and activation energy resist the flow and concentration respectively. A comparative judgment evidently reveals that tri-hybrid Go-Co-ZrO2/H2O nanofluid has a substantial effect on temperature as equated to hybrid or pure nanofluid.

What Rayleigh numbers are achievable under Oberbeck–Boussinesq conditions?

The validity of the Oberbeck–Boussinesq (OB) approximation in Rayleigh–Bénard (RB) convection is studied using the Gray & Giorgini (Intl J. Heat Mass Transfer, vol. 19, 1976, pp. 545–551) criterion that requires that the residuals, i.e. the terms that distinguish the full governing equations from their OB approximations, are kept below a certain small threshold $\hat {\sigma }$ . This gives constraints on the temperature and pressure variations of the fluid properties (density, absolute viscosity, specific heat at constant pressure $c_p$ , thermal expansion coefficient and thermal conductivity) and on the magnitudes of the pressure work and viscous dissipation terms in the heat equation, which all can be formulated as bounds regarding the maximum temperature difference in the system, $\varDelta$ , and the container height, $L$ . Thus for any given fluid and $\hat {\sigma }$ , one can calculate the OB-validity region (in terms of $\varDelta$ and $L$ ) and also the maximum achievable Rayleigh number ${{Ra}}_{max,\hat {\sigma }}$ , and we did so for fluids water, air, helium and pressurized SF $_6$ at room temperature, and cryogenic helium, for $\hat {\sigma }=5\,\%$ , $10\,\%$ and $20\,\%$ . For the most popular fluids in high- ${{Ra}}$ RB measurements, which are cryogenic helium and pressurized SF $_6$ , we have identified the most critical residual, which is associated with the temperature dependence of $c_p$ . Our direct numerical simulations (DNS) showed, however, that even when the values of $c_p$ can differ almost twice within the convection cell, this feature alone cannot explain a sudden and strong enhancement in the heat transport in the system, compared with its OB analogue.

Integral methods for friction decomposition and their extensions to rough-wall flows

A primary objective of integral methods, such as the momentum integral method, is to discern the physical processes contributing to skin friction. These methods encompass the momentum, kinetic energy and angular momentum integrals. This paper reformulates existing integrals based on the double-averaged Navier–Stokes equations, and extends their application to flows over rough walls. Our derivation yields distinct decompositions for the bottom-wall viscous friction coefficient, denoted as $C_S$ , and the roughness element drag coefficient $C_R$ . The decompositions comprise three terms: a viscous term, a turbulent term and a roughness (dispersive) term – regardless of the flow configuration, be it channel or boundary layer. Notably, when these integrals are evaluated for laminar flow scenarios, only the viscous term remains significant. In addition, we elucidate the spatial distributions of the terms within these decompositions. To demonstrate the practicality of our formulations, we apply them to analyse data from direct numerical simulations of turbulent half-channel flows. These flows feature aligned and staggered cubical roughness at various packing densities. Our analyses, based on kinetic-energy-oriented decompositions, reveal that when the surface coverage density $\lambda _p$ is small, the dominant terms within the decompositions are the viscous and turbulent terms. With increasing $\lambda _p$ , the viscous dissipation term decreases, while the turbulent production term increases and then decreases. These variations arise from a subdued near-wall cycle and the development of a shear layer at the height of the cubes.

Three-dimensional shock–flame interactions: effect of wall friction

Multi-dimensional numerical simulations were performed to study the interactions between shock wave and premixed flame. The three-dimensional (3D) fully-compressible, reactive Navier–Stokes equations were solved using a high-order numerical method on a dynamically adapting mesh. The effect of wall friction on the shock–flame interaction was examined by varying wall boundary condition on sidewall. The simulations agree with previous experiment in terms of flame perturbation and flame evolution. The results show two effects of wall friction on flame–shock interaction: (1) flame stretching and (2) damping of local flame perturbation very close to the no-slip wall. The stretch effect leads to non-uniform development of the perturbated flame and consequently a significantly higher growth rate in both global flame perturbation and averaged pressure in the no-slip case compared to the free-slip case. By contrast, the damping effect locally moderates the flame perturbation in close proximity to the no-slip wall because less vorticity is deposited on this part of flame during shock–flame interaction. Quantitative analysis of vortex dynamics suggests that vorticity generation that is produced by baroclinic torque and enhanced by the dilation term during shock–flame interaction causes a growth of flame perturbation via Richtmyer–Meshkov instability. Nevertheless, the vorticity generation is greatly weakened in close proximity to the no-slip wall by the viscous torque and viscous dissipation terms due to friction.

Entropy production in the flow of Bingham-Papanastasiou fluid having temperature and shear rate-dependent viscosity

This article comprehensively examines entropy production in a peristaltic flow of Bingham-Papanastasiou fluid in an asymmetric wavy wall channel. The viscosity of the fluid is selected to depend on the temperature in addition to the shear rate. Furthermore, viscous dissipation is considered. The equations governing momentum and energy are adjusted to incorporate the existence of a nonlinear correlation between stress and strain rate. The energy dissipation caused by viscosity in the energy equation exhibits variation between Newtonian and non-Newtonian fluids due to their distinct rheological behaviors and response to shear forces. Newton’s law of viscosity states that the viscous dissipation term for Newtonian fluids follows a simple linear relationship between shear stress and shear rate. In contrast, non-Newtonian fluids exhibit more complex rheological behaviors, with the correlation between shear stress and shear rate described by various constitutive equations, depending on the specific type of non-Newtonian behavior. Consequently, the energy equation for non-Newtonian fluid flow problems becomes more intricate and nonlinear compared to the energy equation for Newtonian fluids, resulting in a more challenging analysis. Modeling of the equations is traditionally obtained using all steps involved in analyzing peristaltic flow. Using MATLAB's bvp5c solver, the obtained coupled set of differential equations is numerically solved. The research explores how the Bingham number and stress growth exponent parameters affect different dimensionless variables, including velocity, streamlines, temperature, axial pressure gradient, entropy production, and the Bejan number.

The influence of cooling medium and cooling channel on heat transfer of textured seal in presence of viscous dissipation

When operating at high speed, the mechanical seal produces a large amount of frictional heat on the seal face. If the heat is not dissipated in time, it could lead to the thermal failure of the seal face. In the field of tribology research, the technology of textured surface is a method to enhance the heat dissipation rate. Numerical analysis is carried out based on the SST k-ω turbulence model and the energy equation with viscous dissipation term, and the results are validated by the experimental data published in the reference. In a wide range of rotational speeds, cooling medium with varied Pr numbers is employed to confirm the performance of textured side-wall in heat transfer enhancement. The shape of the seal chamber is also changed to provide guidance for the design of the cooling channel. The results show that a larger Pr number increases the heat transfer enhancement of the textures; it is advisable to utilize a cooling channel that gradually decreases in size; and the flushing should not be perpendicular to the stator; additionally, it is important to ensure that the cooling channel is not too narrow. By means of appropriate design, the maximum temperature of seal face can be reduced by over 40 °C (22.2 %) at 20,000 rpm.

Insight into blade tip vibration and deformation characteristics of boiler circulation pumps induced by tip leakage vortex under different tip clearances

For circulating pumps in large power plant boilers, tip leakage flow is the main cause of blade fatigue. To investigate the correlation between tip leakage vortex and blade fatigue, in this paper, the bidirectional fluid structure coupling method is used to simulate the full flow field of the boiler circulating pump under different tip clearance sizes. The accuracy of the delayed detached vortex simulation method is verified by combining the external characteristics and vibration characteristics of the pump. It is obtained that tip leakage vortex is the main cause of blade tip vibration and deformation. Under deep stall conditions, the increase in tip clearance size suppresses the vibration displacement of the blade leading edge, while the opposite is true under optimal conditions. After decomposing tip leakage vortex, it is found that the compression–expansion term played a major role in the deformation of the blade tip, while the viscous dissipation term and the stretching term mainly affected the vibration frequency. At optimal working conditions, the main frequency of blade vibration is basically consistent with the main frequency of vortex generation. In deep stall condition, as the tip clearance size increases, the amplitude of the vibration main frequency decreases and the number of harmonic frequencies decreases, while the optimal condition is the opposite.

Effects of Hall, ion slip, viscous dissipation and nonlinear thermal radiation on MHD Williamson nanofluid flow past a stretching sheet

This work aims to explore the effects of ion slip and Hall current on the flow of MHD Williamson nanofluid over a stretching plate in the presence of chemical reaction, viscous dissipation, ohmic (Joule) heating, nonlinear thermal radiation, and heat generation/absorption. After using appropriate similarity transformations, the highly nonlinear governing partial differential equations are transformed to a system of ordinary differential equations. The subsequent non-linear problems are treated to numerical results by reducing the converted nonlinear ODE in to first order. The fifth-order Runge–Kutta method along with the shooting approach is implemented using the python programming tool to analyze the problem. Graphical representations have been used to investigate the impacts of the derived physical parameters on the temperature, velocity, and concentration distributions of nanoparticles with the goal of giving each parameter a physical interpretation. The study of the effects of various physical parameters on the skin friction coefficient, the local Nusselt number and the Sherwood number was finally explained with the help of graphs and tables. It is discovered that when the Williamson parameter increases, both the principal and secondary velocity profiles decline but the temperature and concentration profiles rise. Both the Hall parameter and ion slip effect produce similar results with increasing principal velocity profile and decreasing secondary velocity, temperature and concentration profiles. Furthermore, it is seen that the temperature and concentration profiles increase in response to an increase in the nonlinear thermal radiation parameter. The increment in Eckert number (viscous dissipation term) also showed enhancements in temperature and concentration profiles. Additionally, the primary skin friction coefficient and rate of mass transfer are accelerated by raising the magnetic field parameter, Williamson parameter, or Darcy number, but the heat transfer rates are slowed down in the boundary layer. Lastly, the obtained results were cross-referenced with earlier findings, considering specific assumptions, to establish the credibility of the results. The comparison revealed that the new results provided valuable and profound insights into the studied phenomenon.

Influence of cavitation on vortical structures and energy loss in a waterjet pump

Cavitation-induced vortex and energy loss are critical topics in the field of hydraulic machinery. Through a combination of experimental and numerical analysis, this paper investigates how blade loading affects vortical structures and energy loss during cavitation in a waterjet pump. The flow rate and cavitation conditions changed blade tip pressure loading, which significantly affected the trajectories of the primary tip leakage vortex cavitation and secondary tip leakage vortex cavitation. A considerable pressure gradient at the attached cavity closure region leads to a wall reentrant jet and a side-entrant jet, resulting in an attached vortex under the cavitation developing stage and severe stage. The development of the attached vortex leads to the shedding of attached cavities. Furthermore, the blade tip pressure difference loading significantly alters the distribution of tip leakage vortex and gives rise to a perpendicular leakage vortex (PLV). The PLV entrains the shedding cavities and forms a perpendicular cavitation vortex. These complex vortical structures induced by cavitation inevitably enhance enstrophy and lead to entropy production in the pump. The entropy production terms of viscous dissipation, turbulent dissipation, and the wall effect react differently to the development of cavitation. As the cavitation stages developed and became more severe, wall entropy production (S3) decreased. While turbulent dissipative entropy production S2 due to mixing losses occurring in the tip region increased sharply, which dominates the total entropy production S and results in an increase in S.

Numerical modeling of Carreau–Yasuda fluid with induced magnetic field in a heated curved channel having ciliary walls

Cilia motion is commonly located in mammalian cells of living organisms which continually grow and feature conspicuously. The ciliary apparatus is associated with cell cycle movement and proliferation, and cilia play a dynamic part in human and animal growth and everyday life. The motivation of these applications, this article is to present a metachronal wave analysis for non-Newtonian Carreau–Yasuda fluid inside a curved channel with ciliated walls. Hall effect is encountered in the momentum equations to measure the magnetic field while the viscous dissipation and thermal radiation terms are considered to address the energy analysis. The curvilinear coordinates are used due to the curved nature of flow geometry in the derivation of flow equations. The computations for axial velocity, pressure rise, temperature field, mass concentration, and stream function are carried out under low Reynolds number and long wavelength approximation in the wave frame of reference by utilizing appropriate numerical implicit finite difference method (FDM). The implementation of numerical procedure and graphical representation of the computations are accomplished using MATLAB language. Furthermore, the skin friction and Nusselt number at the channel walls are determined for a variety of critical parameter assessments.

Effects of Damköhler Number on Lean Premixed Jet Flames in Crossflow Using Direct Numerical Simulation

ABSTRACT In the present work, lean premixed jet flames in crossflow were studied using direct numerical simulation to explore the effects of Damköhler numbers () on turbulence and flame characteristics. The configuration is based on an experiment, where a jet of lean premixed ethylene-air mixtures ( = 0.6) was injected into a hot vitiated crossflow. The case with a higher and lower Da is denoted as case Da+ and case Da-, respectively. It was found that the turbulence is weakened around the reaction zone of case . In contrast, the turbulence of case is barely influenced by heat release. The vorticity dynamics are examined with the enstrophy transport equation budget terms, and the viscous dissipation term is the main sink for both cases. The windward and leeward flame branches of case are dominated by auto-ignition and premixed flame propagation respectively, while the auto-ignition and flame propagation modes coexist on the leeward flame branch of case . The scalar gradient magnitude in the leeward branch is generally lower compared with the windward branch so that the flame is overall thicker. The normal strain rate is negative, which tends to enhance the scalar gradient, but it becomes positive on the leeward side of case , which is influenced by the alignment between the scalar gradient and the principal strain rates.

Time-dependent squeezing flow of variable properties ternary nanofluids between rotating parallel plates with variable magnetic and electric fields

In this study, forced convective squeezing flow between two rotating parallel plates has been examined. The thermal conductivity depends on the distributions of the temperature and the flow, electric and magnetic fields are considered as time dependent. The worked suspension is ternary hybrid nanofluids which consist of water as a base fluid and graphene, Al2O3 and MWCNT as nanoparticles. The energy equation consists of viscous dissipation, radiation, and Joule heating terms. Suitable transformations are introduced as a first step of the solution methodology and fourth order differential equations are obtained. The resulting system is solved, numerically, and various validation tests are performed. The main outcomes revealed that profiles of the stream function are lower when the squeezing parameter, electric field parameter, or magnetic parameter increases. Also, there is an enhancement in values of the temperature gradients up to 16.78% at the lower plate when the Joule heating parameter is varied from 0 to 6.

Analysis of hydrodynamic characteristics and loss mechanism of hydrofoil under high Reynolds number

Hydrofoil is widely used in hydraulic machinery, the complex shear flow and wake vortex with it can cause energy dissipation of system, affecting the stable operation of the unit. This paper takes the guide vane of a Francis turbine as the research object, and adopts the SST k−ω turbulence model to simulate the complex unsteady flow in a three-dimensional hydrofoil-channel. Entropy production theory is introduced to evaluate the energy dissipation. The effects of attack angle, gap ratio and Reynolds number on the flow loss are studied. The results show that: (1) In the hydrofoil-channel, the dissipation caused by the velocity gradient always dominates the irregular flow of fluid field. So the loss caused by the turbulent dissipation term is the main source of the loss in mainstream zone, accounting for more than 95%, while the loss caused by the viscous dissipation term accounts for only about 2% of the total loss, which can be almost ignored; (2) Changing the attack angle have a significant effect on the flow separation of the suction surface and the shear effect in the wake vortex zone, causing the energy loss to fluctuate accordingly. And 2.5° is the optimal attack angle. On this working condition, the loss decreases to the minimum value of 2.2714W/K and 0.1432 m, a decrease of 57% compared to the initial value; (3) The bottom boundary of channel suppress the development of wing tip vortex, reducing gap ratio will reduce the loss caused by wake vortex to some extent. Among them, S = 0.3 is the optimal gap ratio. Under this operating condition, the loss is 2.2941W/K and 0.1447m, a decrease of 56% compared to the initial value; (4) Affected by flow separation and wake vortexes, more than 80% of energy loss occurs in the middle and downstream zones. The effects of attack angle, gap ratio and Reynolds number on the fluid field are different. Increasing attack angle and flow velocity significantly exacerbate the flow separation and shear flow, while reducing gap ratio would inhibit the adverse flow in downstream wing tip vortex zone.

Insight into the motion of ethylene glycol (fluid) conveying magnesium oxide and aluminium oxide nanoparticles with emphasis on “upper branch” and “lower branch” solutions

To address the limitations of nanofluids and combine the physical and chemical characteristics of nanoparticles in a meaningful way, researchers have been focusing on the usage of hybrid nanofluids. A rising number of studies have been conducted in the literature to explore the thermal performance of hybrid nanomaterials. In the current study, dual analysis is carried out to show the impact of theoretical correlations on the heat transfer capabilities of hybrid nanofluids. In this context, a mathematical model for a hybrid nanofluid is developed employing ethylene glycol as a base fluid, conveying magnesia and silver as nanoparticles on an inclined porous stretching/shrinking surface. The thermal transport aspects of a hybrid nanofluid are analyzed in terms of thermal radiation, Ohmic and viscous dissipation, and variable heat source/sink effects. The mathematical model is numerically solved using the bvp4c function in the MATLAB program. The outcomes of controlling factors on the fluid velocity, thermal distributions, as well as friction drag coefficient and heat transfer rate, are illustrated graphically. The findings show that due to remarkable thermal capabilities, the hybrid nanofluid is more effective at transferring heat than ordinary nanofluid. Additionally, the upshots show that the suction and magnetic parameter expands the shrinking range for which the dual solution lives.

Exploring the Dynamics of Viscous Dissipative Fluid past a Super-hydrophobic Microchannel in the Coexistence of Mixed Convection and Porous Medium

This article investigates the theoretical treatment of mixed convection heat enhancement flow for an electrically-conducting and viscous dissipative fluid traveling vertically through a thermodynamic system where the parallel plates are constantly heated in a slit micro-channel due to mixed convection with porous material. One surface had super-hydrophobic slip and a temperature jump, whereas the other did not. The perturbation technique (semi-analytical method) was employed to solve the nonlinear and coupled leading equations. The results were carefully scrutinized, and the effects of the relevant controlling parameters are shown using different plots. It is concluded from this analysis that the fluid temperature and velocity was found to increase as the viscous dissipation term is increased. Similarly, the function of Darcy porous number is to significantly strengthen the fluid velocity, and these effects are stronger at the heated super-hydrophobic surface, whereas mounting level of magnetic field is seen to drastically weaken the fluid motion in the microchannel. Setting Br and A to zero respectively, Gr/Re=1, and Da to 1000, so that the term 1/Da becomes insignificant, Jha and Gwandu (2017)'s work is retrieved, verifying the accuracy of the current analysis. Further, the outcomes of this research can have possible applications in the lubrication industry and biomedical sciences and has proved very useful to designers in increasing the performance of mechanical systems when viscous dissipation is involved, as well as heat transfer in micro-channels, as it is in combustion.

Electro-osmotically generalized bio-rheological fluid flowing through a ciliated passage

In this article, we have investigated a non-Newtonian Jeffrey fluid model, which shows the role of cilia generated metachronal waves in a vertical tube. Electroosmosis effects, a viscous dissipation term is also adopted in this current analysis. The partial differential equations that govern the flow are transformed into a non-dimensional form by considering a low wavelength and small Reynolds number approximations. The obtained set of coupled ordinary differential equations is further solved by using Mathematica solver to get the required flow properties. The current model's output has important heat transfer rate applications in the ciliated channel due to the enhanced viscous dissipation effects, which can be used for the analysis of various areas of biological transport processes such as to design artificial cilia and for the operation of some mechanical devices.