Drag Heat Research Articles

Entropy Generation in Magneto-Casson Nanofluid Flow Along an Inclined Stretching Sheet Under Porous Medium with Activation Energy and Variable Heat Source/Sink

The current paper deals with the study of magneto-convective and chemically reactive Casson nanofluid flow along an inclined permeable stretching surface embedded in a fluid-saturated uniform porous medium. As a novelty of the work, entropy generation analysis in the presence of multiple slips at the surface and a nonuniform heat source/sink is carried out. Moreover, viscous dissipation, Arrhenius activation energy, Joule dissipation and thermal radiation are included in the investigation. To the best of authors’ knowledge, no such study on Casson nanofluid is reported yet in the literature. Dimensionless similarity transformations have been introduced to convert the regulating model PDEs into ODEs in dimensionless form. As the model equations are highly nonlinear in nature, shooting technique based on the Runge-Kutta Cash-Karp method is used to solve those equations numerically. The updated values of the initial guesses are computed with the help of secant iteration. Profiles for fluid velocity, temperature, nanoparticle concentration and entropy generation have been drawn to explain the impacts of several important parameters on momentum, thermal and mass fields. However, the surface drag force, heat and mass transport rates at the solid wall are illustrated using numerical data displayed in tabular form. Also, a linear regression model is derived for the local Nusselt number and the related physical parameters. Moreover, a comparison table is presented to confirm the correctness of the obtained results. A fantastic correlation of the present results with the existing results is reported. Graphical results reveal that for the rising values of the angle of inclination parameter and magnetic parameter velocity profiles are declined, but for the growing values of Eckert number and thermal radiation parameter temperature profiles are enhanced.

Direct Numerical Simulation of Drag Reduction and Heat Transfer Enhancement by Wall Oscillation in Turbulent Concentric Annular Pipe Flow

In fluid engineering, the reduction of the skin-friction drag and the enhancement of the heat transfer are of importance in turbulent flows. In the present study, we made direct numerical simulations of the concentric annular turbulent pipe flow controlled by the wall oscillation control technique for the skin-friction reduction and heat transfer enhancement. The concentric annular pipe is widely used, and we expected to obtain the control effect by using the different radius of the inner and outer cylinders. Two types of control methods are shown: the wall oscillation technique and the traveling wave-like wall oscillation. In the wall oscillation, the friction drag decreases at all the frequencies, and the similarity between momentum and heat transport is maintained. In the traveling wave, the wave speed significantly affects the friction drag and the heat transfer. In some cases, the dissimilarity between momentum and heat transport is also confirmed.

A Review of Recent Advances in Superhydrophobic Surfaces and Their Applications in Drag Reduction and Heat Transfer.

Inspired by the superhydrophobic properties of some plants and animals with special structures, such as self-cleaning, water repellent, and drag reduction, the research on the basic theory and practical applications of superhydrophobic surfaces is increasing. In this paper, the characteristics of superhydrophobic surfaces and the preparation methods of superhydrophobic surfaces are briefly reviewed. The mechanisms of drag reduction on superhydrophobic surfaces and the effects of parameters such as flow rate, fluid viscosity, wettability, and surface morphology on drag reduction are discussed, as well as the applications of superhydrophobic surfaces in boiling heat transfer and condensation heat transfer. Finally, the limitations of adapting superhydrophobic surfaces to industrial applications are discussed. The possibility of applying superhydrophobic surfaces to highly viscous fluids for heat transfer to reduce flow resistance and improve heat transfer efficiency is introduced as a topic for further research in the future.

Outlining the influence of thermal and solutal stratifications on mixed convection second grade fluid flow near an irregular cylinder with induced magnetic field

In this analysis, thermal and solutal stratifications in three-dimensional mixed convection flow of second grade fluid along an irregular cylinder through porous medium is demonstrated. Effect of induced magnetic induction is considered to deal many technological and scientific problems like crude oil purification, plasma confinement, rotating magnetic stars and power generation. The flow narrating continuity, magnetic flux, momentum, magnetic induction, concentration and heat equations are modeled in the form of PDEs. Set of dimensionless conversions are introduced to replace non-linear PDEs into a set of ODEs. To predict numerical solution of considering model, we used an efficient numerical technique Bvp4c. The consequential outcomes are sketched for unlike values of dimensionless parameters. Parameters like mixed convection, second grade parameter, magnetic parameter, porosity parameter and buoyancy ratio parameter are initiated to control the flow field. Further, temperature and solutal stratification parameters, Prandtl, magnetic Prandtl and Schmidt numbers are found to control energy, magnetic induction and concentration distributions. Skin drag coefficients, heat and mass fluxes are investigated for inflating values of some sundry parameters. For justification of the model, we compared present numerical outcomes with previous published results.

Significance of heat conduction in binary reactive flow of Walter’s B fluid with radiative flux and activation energy

The prime objective of binary chemical reaction (BCR) is concentrated on the study and optimization of chemical reaction to accomplish finest reactor design and performance, which elaborated the interfaces of flow phenomena, reaction kinetics and heat and mass transport. The reactor performance is likely to be linked to the reaction operating constraints and feed composition through the aforementioned factors. The applications of BCR are generally in the petroleum and petrochemical regions, but with the help of chemical engineering and reaction chemistry concepts, it could be used in different areas, like waste treatment, chemical pharmaceuticals, nanoparticles in advanced materials, microelectronics, enzyme technology, biochemical engineering, living systems, renewable energy systems, sustainable development, environment/pollution prevention, as well as to optimize a different reaction framework via simulation and modeling methodology. Owing such physical applications in mind, this research deals with the binary chemical reactive flow of non-Newtonian fluid (Walter’s B) subject to activation energy. Stagnation point is accounted. Radiative flux and ohmic heating effects are considered in the development of energy expression. Concentration and microorganism equations are considered. The governing system is altered to ordinary one through the important similarity variables. Results are obtained through bvp4c technique. All results are discussed graphically. Furthermore, surface drag force (skin friction) and heat and mass transfer (Nusselt and Sherwood) rates are calculated and displayed graphically. Significant results are listed in conclusion.

Effects of uniform injection and suction through perforated pentagonal cylinders on the flow and heat transfer

PurposeThe purpose of this paper is to study the effects of uniform injection and suction through a perforated pentagonal cylinder on the flow field and heat transfer.Design/methodology/approachThe finite-volume method has been used to solve the ensemble-averaged Navier-Stokes equations for incompressible flow at moderate Reynolds number (Re = 22,000) with the k-ɛ turbulence model equations.FindingsA computational fluid dynamics analysis of turbulent flow past a non-regular pentagonal cylinder with three different aspect ratios aspect ratios has been carried out to investigate the effects of uniform injection/suction through the front and all surfaces of the cylinder. It is found that flow field parameters such as drag coefficient, pressure coefficient and Nusselt number are affected considerably in some cases depend on injection/suction rate (Γ) and perforated wall position.Research limitations/implicationsTo optimize the efficiency of the injection and suction through a perforated surface, both wide-ranging and intensive further studies are required. Using various perforation ratios and injection/suction intensities are some possibilities.Practical implicationsControl of the vortex shedding and wake region behind bluff bodies is of vital interest in fluid dynamics. Therefore, applying uniform injection and suction from a perforated bluff body into the main flow can be used as a drag reduction mechanism, thermal protection and heat transfer enhancement.Originality/valueThis study provides unique insights into the active flow control method around pentagonal cylinders that can be useful for researchers in the field of fluid dynamics and aeronautics.

Effect of arrhenius activation energy and medium porosity on mixed convective diluted ethylene glycol nanofluid flow towards a curved stretching surface

The present investigation is a computational attempt to explore the impact of Arrhenius activation of the energy on the mixed convective binary chemical nanofluid dissipative flow over a curved stretching surface through a porous medium. Curvilinear coordinates are opted for mathematical interpretation of the physical flow problem and governing equations are transformed into a set of coupled non-linear differential equations by invoking similarity analysis. The nonlinear coupled system is tackled numerically with the aid of computational software MAPLE. The MAPLE routine program bvp midrich is incorporated for numerical solutions subject to the fixed values of emerging parameters. The impact of prominent parameters on velocity, temperature, concentration distributions along with physical quantities of interest such as surface drag force, heat and mass flux rates are explored through graphs and tables. The key findings of the present investigation include that the Darcy-Forchheimer parameter contribute prominently in fluid flow along with heat and mass transfer.

Parametric research on drag reduction and thermal protection of blunt-body with opposing jets of forward convergent nozzle in supersonic flows

Extreme drag and aerodynamic heat are the main penalties for blunt forebody of supersonic vehicles. This results in shorter flight range and higher fuel consumption, and aerodynamic heat seriously affects the performance of internal electronics. In the current study, the flow field mechanism of a blunt body model with a supersonic opposing jet in a supersonic flow field is numerically study. The physical model is a two-dimensional axisymmetric blunt forebody model with a convergent nozzle structure, and the numerical calculation model is a coupling of the two-dimensional axisymmetric Reynolds average method and the shear stress transport(SST) turbulence model. The calculation results in this paper are compared with the experimental data in the literature, which verifies the accuracy, and the calculation verifies the grid independence. An active flow control method that controls a single pressure parameter is proposed, and the formation process of the opposing jet in the convergent nozzle is considered, and the flow field structure of the opposing jet formed by the convergent nozzle with different nozzle sizes is studied. The results show that a single pressure parameter can control the formation of a supersonic opposing jet to form a long penetration mode and a short penetration mode. The ratio of the ambient pressure to the jet pressure at the stagnation point of the blunt body can directly affect the flow field structure of the opposing jet, and reasonable control of opposing jet parameters is an effective way for thermal protection and drag reduction of blunt body structures.

Influence of autocatalytic chemical reaction with heterogeneous catalysis in the flow of Ostwald-de-Waele nanofluid past a rotating disk with variable thickness in porous media

The present study ventilates shear-dependent viscosity to examine the non-Newtonian rheology of Ostwald-de-Waele nanofluid flow over a rotating disk of variable thickness in a Darcy-Forchheimer permeable medium. Heat transfer phenomenon is witnessed by adding non-uniform heat source-sink with melting heat transfer. The effectiveness of surface catalysis in the process of homogeneous and heterogeneous reactions is also analyzed. The Buongiorno nanofluid model is used for the fluid flow assumptions. The sketched model contains the system of partial differential equations. The procedure of using similarity transformation is adopted to obtain the ordinary differential equations. Simulations are performed to obtain the numerical results via the bvp4c numerical scheme. The numerical values of drag force coefficient and heat transfer rate are the properties of physical interest. Large values of Prandtl number are favorable to boost the heat transfer phenomenon. The thermal profile is increased for both pseudoplastic and dilatant fluid models. The power-law index is more influential than the disk thickness index. Surface catalysis triggers the reaction more efficiently.

Kinetic theory of polydisperse gas–solid flow: Navier–Stokes transport coefficients

The particulate phase stress and solid–solid drag force in the multifluid modeling of polydisperse gas–solid flows are usually closed using kinetic theory. This research aims to establish the hydrodynamic equations and constitutive relations of the multifluid model for polydisperse systems via species kinetic theory, in which the non-equipartition of energy and interphase slip velocity between different species are considered. Whereas previous studies have used approximations, such as Taylor series expansions, to simplify the calculation of collision integrals, the present study, for the first time, solves the collision integrals analytically without any approximations to obtain accurate constitutive relations. Explicit expressions for the constitutive laws are obtained, including the particle stress tensor, solid–solid drag force, heat flux, and energy dissipation rate up to the Navier–Stokes order. The present study offers more complete and mathematically rigorous constitutive laws for the multifluid modeling of polydisperse gas–solid flows.

Analysis of counter flow injection technique at elevated enthalpy hypersonic reacting flows

Large wave drag and high surface heating are common problems encountered at hypersonic speeds and these should be properly dealt for the effective and safe flights. Many studies have been carried out to mitigate these problems by employing various active and passive techniques but most of these computational or experimental studies account lower stagnation enthalpy flows or perfect gas assumption. Hence the current study examines the effect of higher freestream stagnation enthalpy on flow field alteration for counter - jet drag reduction technique for a hemispherical object. Results also includes the real gas effects on flow field, wave drag and wall heat flux. Further the effect of various flow parameters is observed on surface pressure distribution, surface heat flux and drag force for the hypersonic flow over the hemisphere, using the in house developed perfect gas and non - equilibrium N - S flow solvers. Results reveal that the perfect gas assumption overestimates surface properties and wave drag value. Drag coefficient reduces with freestream total enthalpy (Ho) in the presence of real gas effects. Around 30% drag reduction is observed at Ho=1 MJ/kg for Mach number 5 as compared to no - jet case and this reduction increases at higher freestream total enthalpy for same injection pressure ratio. Higher pressure ratio of the jet results in lower surface pressure and Stanton number on the object which gives lower wave drag.

Enhancement in Thermal Energy and Solute Particles Using Hybrid Nanoparticles by Engaging Activation Energy and Chemical Reaction over a Parabolic Surface via Finite Element Approach

Several mechanisms in industrial use have significant applications in thermal transportation. The inclusion of hybrid nanoparticles in different mixtures has been studied extensively by researchers due to their wide applications. This report discusses the flow of Powell–Eyring fluid mixed with hybrid nanoparticles over a melting parabolic stretched surface. Flow rheology expressions have been derived under boundary layer theory. Afterwards, similarity transformation has been applied to convert PDEs into associated ODEs. These transformed ODEs have been solved the using finite element procedure (FEP) in the symbolic computational package MAPLE 18.0. The applicability and effectiveness of FEM are presented by addressing grid independent analysis. The reliability of FEM is presented by computing the surface drag force and heat transportation coefficient. The used methodology is highly effective and it can be easily implemented in MAPLE 18.0 for other highly nonlinear problems. It is observed that the thermal profile varies directly with the magnetic parameter, and the opposite trend is recorded for the Prandtl number.

New similarity variable to transform the fluid flow from PDEs into fractional-order ODEs: Numerical study

The recent research aims to study the fractional-order differential equations of the higher-order. The problems consist of momentum and thermal boundary layers. The similarity variables are introduced to convert the partial differential equations (PDEs) into the fractional-order ordinary differential equations (ODEs). The two nonlinear problems of fractional order ODEs are tackled through the (Fractional Differential equation-12) FDE-12 method. The obtained results show that the fractional-order problems are more nonlinear as compared to the integer-order differential equations. The fractional-order increasing the nonlinearity and consequently more efforts required to obtain the outputs. The impact of the physical parameters in the case of the integer-order and fractional-order are obtained and discussed. It is observed that the impact of the physical parameters more compact in the case of fractional order as compared to the integer-order case. The important features of the drag force and heat transfer rate in the case of the fractional-order boundary value problem also have been analyzed and discussed.

CFD-DEM modeling of filtered fluid-particle drag and heat transfer in bidisperse gas-solid flows

This work extends filtered models to investigate the influence of particle polydispersity on the filtered fluid-particle drag and heat transfer behaviors based on well-resolved computational fluid dynamics-discrete element model (CFD-DEM) simulations. By systematically filtering the CFD-DEM simulation data, it is found that the markers used for the monodisperse systems, (i.e., the filtered slip velocity and the gas phase pressure gradient for the drag correction; the filtered interphase temperature difference for the heat transfer correction) are indispensable in the bidisperse systems. Furthermore, the dependence of the filtered corrections on the particle size ratio and volume fraction ratio is identified. The increase in the proportion of small particles generally corresponds to the reduction of drag and interphase heat transfer corrections. The Sauter mean diameter is applicable to quantify the effect of particle bidispersity. Eventually filtered models of fluid-particle drag and heat transfer corrections for the bidisperse systems are developed.

Preliminary development and validation of ACENA code for heavy liquid metal-gas two phase flow simulation

To simulate the heavy liquid metal-gas (HLM-gas) two phase flow phenomena that may occur during postulated accidents of Lead-based fast reactors (LFRs), a 2D multiphase fluid dynamics code, ACENA, is preliminarily developed and validated in this study. A brief description of theoretical models, including governing equations, auxiliary models and material properties are listed in this study. The capability of simulating flow and heat transfer characteristics between gas and liquid phases has been examined by typical air-water bubble column experiment, LBE-N2 two phase flow experiment and Lead-Ar heat transfer experiment, and the comparison results show that this code could attain acceptable accuracy in simulating flow and heat transfer characteristics of HLM-gas two phase flow with appropriate interfacial drag coefficient and heat transfer coefficient models.

Axisymmetric hybrid nanofluid flow with heat and mass transfer amongst the two gyrating plates

AbstractThe combined effects of magnetic and electrohydrodynamic on the water‐based iron oxide and CNTs hybrid nanoliquids flow between two rotating plates are examined. The influence of electro‐magneto‐hydrodynamics on the mass and heat transmission characteristics is the main aim of this study. The hybrid nanofluid is synthesized using water as a base fluid in the (Iron oxide) , single and multi‐walled (SWCNTs/MWCNTs) carbon nanotubes (CNTs). The flow model has been arranged in form of PDEs, which are reduced into the system of dimensionless differential equations through a similarity approach. The differential equations are further treated with HAM to get analytic results. The impact of the Reynolds number, magnetic, electric and rotation parameters, on the drag force, mass flux and heat transmission rate has been scrutinized and discussed. The arithmetic consequences are carried out for Nusselt number, Sherwood number and drag force. The heat transmission has been considered to increase with the Reynolds number, magnetic constraint and electric parameter. The electric parameter improving the momentum boundary layer and drop the thermal boundary layer. The outcomes are compared with the existing literature and a closed agreement has found.

Drag and heat transfer characteristics around and through two interactive porous particles

When the concentration of porous particles reaches a certain level, the interactions between the particles can't be ignored. Therefore, this paper numerically investigated the interactions between two porous particles using the lattice Boltzmann method. In this paper, two-dimensional steady flow and heat transfer around and through two porous particles with the same diameters (D) was studied numerically. The effects of Reynolds number (Re), Darcy number (Da), center-to-center distance (expressed as dimensionless form L/D), angle between two porous particles (β) and particles with different permeability on the flow and heat transfer characteristics were investigated in detail. The investigated ranges of the parameters were 10 ≤ Re ≤ 40, 10−6 ≤ Da ≤ 10−2, D ≤ L ≤ 4D and 0° ≤ β ≤ 90°. It is observed that these parameters have significant effects on the flow and temperature fields, drag coefficient and average Nusselt number. The drag coefficient and average Nusselt number of the leading particle (P1) is much larger than those of the trailing particle (P2) in most instances. And the two porous particles show different change tendency to the same changes of these parameters. The effects of Da on P1 are more prominent compared with P2 while the effects of L/D on P2 are more obvious compared with P1. Besides, the drag coefficient of P2 increases with β increasing. In addition, we define drag force ratio and heat transfer enhancement ratio to compare the sensitivity of particles to the changes of Re and/or Da when two particles coexist and when one particle exists alone. The results indicate the heat transfer efficiency of P1 is more sensitive to changes in Da and Re compared with a single porous particle.

Study on the Law of Pseudo-Cavitation on Superhydrophobic Surface in Turbulent Flow Field of Backward-Facing Step

Superhydrophobic surface is regarded as important topic in the field of thermal fluids today due to its unique features on flow drag reduction and heat transfer enhancement. In this study, the pseudo-cavitation phenomenon on the superhydrophobic surface in the backward-facing step turbulent flow field is observed through experiments. The underlying reason for this phenomenon is studied with experimental observation and analysis, and the time variant mechanisms of this phenomenon with various Reynolds number is summarized. The research results indicate that the superhydrophobic surface and the backward-facing step provide the material basis and dynamic condition for the generation of pseudo-cavitation. The pseudo-cavitation induces a large bubble on the superhydrophobic surface below the backward-facing step. The size, position, shape, oscillation amplitude, detachment, and splitting of the large bubble show regularity with the changes of Reynolds number. Meanwhile, the bubble growth, oscillation, detachment, split, and regeneration over time also show regularity. The study of bubble generation and development laws can be used to better control the perturbation of the flow field. Importantly, the present study has meaning in better understanding the flow mechanisms and gas coverage of superhydrophobic surface under condition of backward-facing step, paving the way for studying the flow drag reduction effect of superhydrophobic surface.

Numerical Solution of Laminar Flow and Heat Transfer over a Flat Plate in a Nonuniform Stream.(Dept.M)

The laminar flow and heat transfer over an isothermal flat plate in a free stream with nonuniform velocity have been analysed, fully implicit numerical method (with a hybrid representation for the convective term normal to the streamwise direction) is used for solving the governing equations. Two practical cases are considered. In the first case, a flat plate is located in the laminar wake of an upstream plate. In the second case, a flat plate 18 inserted in the laminar shear layer joining a uniform stream and a quiescent fluid. The dependence of the boundary-layer and heat transfer on the lateral and the downstream shifts of the plate have been investigated. It was found that the nonuniformity of the free stream velocity causes reductions in both the wall shear stress and heat transfer relative to the corresponding values for uniform free stream. These relative reductions decrease with increasing downstream distance along the plate in the upper half of the wake. In the lower half of the wake, these Zeductions increase with distance along the plate. It was also found that the minimum values for drag and overall heat transfer rate at a certain streamwise location correspond to a slight downward shift of the plate from the wake centreline. In the case of shear layer, the relative reductions in the wall shear and heat transfer are more pronounced in the low velocity region. These reductions decrease with increasing downstream distance along the plate. It was found that both the drag and overall heat transfer rate decrease continuously with downstream shift of the plate.

Entropy generation analysis of Falkner–Skan flow of Maxwell nanofluid in porous medium with temperature-dependent viscosity

Entropy generation analysis in steady two-dimensional, viscous, incompressible forced convective Falkner–Skan flow of Maxwell nanofluid over a static wedge embedded in a porous medium with temperature-dependent viscosity is examined. The Buongiorno’s model has been utilised, to get the flow governing higher-order coupled nonlinear partial differential equations (PDEs) from mass, momentum, energy and concentration conservations. Suitable transformations have been done to convert governing PDEs into the coupled non-linear ODEs along with no-slip boundary conditions, which are then solved using the MATLAB programme bvp4c. The influences of diverse flow governing parameters on various flow properties and quantities of physical interest are displayed in graphical mode and discussed. It is found that entropy generation reduces only with Eckert number (Ec), while more entropy is generated for pressure gradient parameter (m), local Deborah number ( $$\beta )$$ , variable viscosity parameter ( $$\delta $$ ) and permeability parameter (K). Entropy generation due to heat transfer irreversibility is prominent with increase in m and $$\delta $$ , but it is not so for other parameters. The drag force on the wedge surface become stronger with $$\beta $$ and m, but it reduces with $$\delta $$ . Rates of heat transfer and mass transfer enhance with m and $$\delta $$ . In addition, surface drag force and heat transfer rate diminish with Brownian motion parameter (Nb) and thermophoresis parameter (Nt).