Showing papers in "Journal of Applied Fluid Mechanics in 2016"
TL;DR: In this article, the magnetohydrodynamic (MHD) three-dimensional boundary layer flow of an incompressible Casson fluid in a porous medium is investigated and heat transfer characteristics are analyzed in the presence of heat generation/absorption.
Abstract: The magnetohydrodynamic (MHD) three-dimensional boundary layer flow of an incompressible Casson fluid in a porous medium is investigated. Heat transfer characteristics are analyzed in the presence of heat generation/absorption. Laws of conservation of mass, momentum and energy are utilized. Results are computed and analyzed for the velocities, temperature, skin-friction coefficients and local Nusselt number.
83 citations
TL;DR: In this article, the stagnation point flow of an incompressible non-Newtonian fluid over a non-isothermal stretching sheet is investigated and a mathematical analysis is presented for a Casson fluid by taking into the account of variable thickness and thermal radiation.
Abstract: The stagnation-point flow of an incompressible non-Newtonian fluid over a non-isothermal stretching sheet is investigated. Mathematical analysis is presented for a Casson fluid by taking into the account of variable thickness and thermal radiation. The coupled partial differential equations governing the flow and heat transfer are transformed into non-linear coupled ordinary differential equations by a similarity transformation. The transformed equations are then solved numerically by Runge-Kutta-Fehlberg method along with shooting technique. The effects of pertinent parameters such as the Casson fluid parameter, wall thickness parameter, velocity power index, velocity ratio parameter, Prandtl number and radiation parameter have been discussed. Comparison of the present results with known numerical results is shown and a good agreement is observed.
74 citations
TL;DR: In this article, the effect of thermal radiation on the two-dimensional boundary layer flow of an electrically conducting micropolar fluid and heat transfer subject to a transverse uniform magnetic field over a curved stretching sheet coiled in a circle of radius has been studied.
Abstract: The two-dimensional boundary layer flow of an electrically conducting micropolar fluid and heat transfer subject to a transverse uniform magnetic field over a curved stretching sheet coiled in a circle of radius has been studied. The effect of thermal radiation is also considered using linearized Rosseland approximation. For mathematical formulation of the flow equations, curvilinear coordinates system is used. The governing partial differential equations describing the flow phenomena and heat transfer characteristics are reduced to ordinary differential equations by means of suitable transformations. The system of differential equations is solved numerically by shooting method using Runge-Kutta algorithm combined with the Newtons-Raphson technique. Some physical features of the flow and heat transfer in terms of fluid velocity, angular velocity, temperature profile, the skin-friction coefficient, couple wall stress and the local Nusselt number for several values of fluid parameters are analyzed, discussed and presented in graphs and tables. Comparison of the present results with the published data for the flat surface i.e. ( → ∞) is found in good agreement.
72 citations
TL;DR: In this paper, a numerical study of oscillatory magnetohydrodynamic (MHD) natural convection of liquid metal between vertical coaxial cylinders is carried out, where the inner and outer cylinders are maintained at uniform temperatures, while the horizontal top and bottom walls are thermally insulated.
Abstract: A numerical study of oscillatory magnetohydrodynamic (MHD) natural convection of liquid metal between vertical coaxial cylinders is carried out. The motivation of this study is to determine the value of the critical Rayleigh number, Racr for two orientations of the magnetic field and different values of the Hartmann number (Harand Haz) and aspect ratios A. The inner and outer cylinders are maintained at uniform temperatures, while the horizontal top and bottom walls are thermally insulated. The governing equations are numerically solved using a finite volume method. Comparisons with previous results were performed and found to be in excellent agreement. The numerical results for various governing parameters of the problem are discussed in terms of streamlines, isotherms and Nusselt number in the annuli. The time evolution of velocity, temperature, streamlines and Nusselt number with Racr, Har, Haz, and A is quite interesting. We can control the flow stability and heat transfer rate in varying the aspect ratio, intensity and direction of the magnetic field.
68 citations
TL;DR: In this paper, the authors examined the convective heat transfer of nanofluid past a wedge subject to first-order chemical reaction, heat generation/absorption and suction effects.
Abstract: The aim of the present study is to examine the convective heat transfer of nanofluid past a wedge subject to first-order chemical reaction, heat generation/absorption and suction effects. The influence of wedge angle parameter, thermophoresis, Dufour and Soret type diffusivity are included. The local similarity transformation is applied to convert the governing nonlinear partial differential equations into ordinary differential equations. Shooting method integrated with fourth-order Runge-Kutta method is used to solve the ordinary differential equations. The skin friction, heat and mass transfer rates as well as the effects of various parameters on velocity, temperature and solutal concentration profiles are analyzed. The results indicate that when the chemical reaction parameter increases, the heat transfer coefficient increases while the mass transfer coefficient decreases. The effect of chemical reaction parameter is very important in solutal concentration field compared to velocity and temperature profiles since it decreases the solutal concentration of the nanoparticle.
64 citations
TL;DR: In this paper, the effects of governing parameters, namely, Hartmann number, solid volume fraction, the different values of the heat source length and the different locations of a localized heat source on the streamlines and isotherms contours as well as maximum temperature, Nusselt number and average Nussellt number along the heat sources were considered.
Abstract: Numerical investigation for heat transfer with steady MHD natural convection cooling of a localized heat source at the bottom wall of an enclosure filled with nanofluids subjected to changeable thermal boundary conditions at the sidewalls has been studied in the a presence of inclined magnetic field. Finite difference method was employed to solve the dimensionless governing equations of the problem. The effects of governing parameters, namely, Hartmann number, solid volume fraction, the different values of the heat source length and the different locations of the heat source on the streamlines and isotherms contours as well as maximum temperature, Nusselt number and average Nusselt number along the heat source were considered. The present results are validated by favorable comparisons with previously published results. The results of the problem are presented in graphical and tabular forms and discussed. It is found that an increase in the Hartmann number results in a clear reduction in the rate of heat transfer; however, the increase in Rayleigh number enhances the nanofluid flow and heat transfer rate.
49 citations
TL;DR: In this paper, a simulation of the inlet-combustor interaction and flow structure through a scramjet engine at a flight Mach number M = 6 with parallel injection (strut with circular inlet) is presented.
Abstract: A numerical analysis of the inlet-combustor interaction and flow structure through a scramjet engine at a flight Mach number M = 6 with parallel injection (Strut with circular inlet) is presented in the present research article. Three different angles of attack (α=-4°, α=0°, α=4°) have been studied for parallel injection. The scramjet configuration used here is a modified version of DLR scramjet model. Fuel is injected at supersonic speed (M=2) through a parallel strut injector. For parallel injection, the shape of the strut is chosen in a way to produce strong stream wise vorticity and thus to enhance the hydrogen/air mixing inside the combustor. These numerical simulations are aimed to study the flow structure, supersonic mixing, and combustion phenomena for the three different types of geometries along with circular shaped strut configuration.
48 citations
TL;DR: In this article, an investigation of hydromagnetic natural convection flow with heat and mass transfer of a viscous, incompressible, electrically conducting, chemically reactive and optically thin radiating fluid past an exponentially accelerated moving vertical plate with arbitrary ramped temperature embedded in a fluid saturated porous medium is carried out.
Abstract: Investigation of unsteady hydromagnetic natural convection flow with heat and mass transfer of a viscous, incompressible, electrically conducting, chemically reactive and optically thin radiating fluid past an exponentially accelerated moving vertical plate with arbitrary ramped temperature embedded in a fluid saturated porous medium is carried out. Exact solutions of momentum, energy and concentration equations are obtained in closed form by Laplace transform technique. The expressions for the shear stress, rate of heat transfer and rate of mass transfer at the plate for both ramped temperature and isothermal plates are derived. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. It is found that, for isothermal plate, the fluid temperature approaches steady state when 1.5 t . Consequently, the rate of heat transfer at isothermal plate approaches steady state when 1.5 t .
47 citations
TL;DR: In this paper, the effect of magnetic field on the viscosity of Fe3O4-water magnetic nanofluid experimentally was investigated and the results showed that the viscoverage increased with increasing of nanoparticle volume fractions and decreased with temperature enhancement with or without of magnetic fields.
Abstract: This article investigates the effect of magnetic field on the viscosity of Fe3O4-water magnetic nanofluid experimentally. Experiments were done in the volume fraction range 0 to 1 vol% and the temperature ranges from 25 to 45 ̊C. The results showed that the viscosity increased with increasing of nanoparticle volume fractions and decreased with temperature enhancement with or without of magnetic field. Also, it is observed that the viscosity of the magnetic nanofluid increases with enhancement of magnetic field strength. Thus, magnetic field is a basic factor that influences the viscosity of the magnetic nanofluids and magnetic nanofluid flow can be controlled by applying a magnetic field.
46 citations
TL;DR: In this paper, a numerical investigation on mixed convection in a lid-driven square cavity has been performed in the presence of the uniform magnetic field, where three different lengths of heater are varied along bottom and left walls simultaneously.
Abstract: A numerical investigation on mixed convection in a lid-driven square cavity has been performed in the presence of the uniform magnetic field. From the left-bottom corner of the cavity, three different lengths of heater are varied along bottom and left walls simultaneously. The finite volume method is employed to solve the governing equations. It is observed that the heater length in the x-direction is more effective than that of in the y-direction on the heat transfer and on the flow pattern. The magnetic field affects the average heat transfer rate more on vertical heaters than on the horizontal heaters.
44 citations
TL;DR: In this article, the authors focused on the study of heat and mass transfer characteristics of an unsteady MHD boundary layer flow through porous medium over a stretching sheet in the presence of thermo-diffusion and diffusionthermo effects with thermophoresis, thermal radiation and non-uniform heat source/sink.
Abstract: This paper is focused on the study of heat and mass transfer characteristics of an unsteady MHD boundary layer flow through porous medium over a stretching sheet in the presence of thermo-diffusion and diffusionthermo effects with thermophoresis, thermal radiation and non-uniform heat source/sink. The transformed conservation equations are solved numerically subject to the boundary conditions using an optimized, extensively validated, variational finite element analysis. The numerical code is validated with previous studies on special cases of the problem. The influence of important non-dimensional parameters, namely suction parameter ( ), magnetic parameter (M), unsteadiness parameter (α), Soret parameter (Sr), Dufour parameter (Du) thermophoretic parameter ( ), space dependent (A1) and temperature dependent parameters (B1) and radiation parameter(An) on the velocity, temperature and concentration fields as well as the skinfriction coefficient, Nusselt number and Sherwood number are examined in detail and the results are shown graphically and in tabular form to know the physical importance of the problem. It is found that the imposition of wall fluid suction ( >0) in the flow problem has the effect of depreciating the velocity, temperature and concentration boundary layer thicknesses at every finite value of η. This deceleration in momentum, thermal and concentration profiles is because of the fact that suction is taken away the warm fluid from the surface of the stretching sheet.
TL;DR: In this article, an upper-convected Maxwell (UCM) fluid flow over a melting surface situated in hot environment is studied and the influence of melting heat transfer and thermal stratification are properly accounted for by modifying the classical boundary condition of temperature to account for both.
Abstract: An upper-convected Maxwell (UCM) fluid flow over a melting surface situated in hot environment is studied. The influence of melting heat transfer and thermal stratification are properly accounted for by modifying the classical boundary condition of temperature to account for both. It is assumed that the ratio of inertia forces to viscous forces is high enough for boundary layer approximation to be valid. The corresponding influence of exponentially space dependent internal heat generation on viscosity and thermal conductivity of UCM is properly considered. The dynamic viscosity and thermal conductivity of UCM are temperature dependent. Classical temperature dependent viscosity and thermal conductivity models are modified to suit the case of both melting heat transfer and thermal stratification. The governing non-linear partial differential equations describing the problem are reduced to a system of nonlinear ordinary differential equations using similarity transformations and completed the solution numerically using the Runge-Kutta method along with shooting technique (RK4SM). The numerical procedure is validated by comparing the solutions of RK4SM with that of MATLAB based bvp4c. The results reveal that increase in stratification parameter corresponds to decrease in the heat energy entering into the fluid domain from freestream and this significantly reduces the overall temperature and temperature gradient of UCM fluid as it flows over a melting surface. The transverse velocity, longitudinal velocity and temperature of UCM are increasing function of temperature dependent viscous and thermal conductivity parameters. At a constant value of melting parameter, the local skin-friction coefficient and heat transfer rate increases with an increase in Deborah number.
TL;DR: In this paper, the flow of micropolar fluid over an unsteady stretching surface with convective boundary condition was investigated and its influence on the flow and heat transfer characteristics was examined.
Abstract: This article is concerned with the flow of micropolar fluid over an unsteady stretching surface with convective boundary condition. The governing partial differential equations are first converted into ordinary differential equations using appropriate transformations and then solved for the series solutions. Influence of micropolar parameter, unsteadiness parameter, boundary parameter, Prandtl number and Biot number on the flow and heat transfer characteristics is examined. Numerical values of local Nusselt number and skin friction coefficient are presented and analyzed. It is observed that temperature is an increasing function of Biot number.
TL;DR: In this paper, the effects of heat and mass transfer in the presence of thermal radiation, internal heat generation and Dufour effect on an unsteady magneto-hydrodynamic mixed convection stagnation point flow towards a vertical plate embedded in a porous medium are analyzed.
Abstract: The objective of this paper is to analyze the effects of heat and mass transfer in the presence of thermal radiation, internal heat generation and Dufour effect on an unsteady magneto-hydrodynamic mixed convection stagnation point flow towards a vertical plate embedded in a porous medium. The non-linear partial differential equations governing the flow are transformed into a set of ordinary differential equations using suitable similarity variables and then solved numerically using shooting method together with Runge- Kutta algorithm. The effects of the various parameters on the velocity, temperature and concentration profiles are depicted graphically and values of skin- friction coefficient, Nusselt number and Sherwood number for various values of physical parameters are tabulated and discussed. It is observed that the temperature increases for increasing values of the internal heat generation, thermal radiation and the Dufour number and hence thermal boundary layer thickness increases.
TL;DR: In this article, the effect of Hall current on the criterion for the onset of MHD convection in a porous medium layer saturated by a nanofluid is investigated, and the exact analytical expression for critical Rayleigh Darcy number is obtained in terms of various non-dimensional parameters.
Abstract: In this study, the effect of Hall current on the criterion for the onset of MHD convection in a porous medium layer saturated by a nanofluid is investigated. The model used for nanofluid combines the effect of Brownian motion and thermophoresis, while for a porous medium Brinkman model is used. A physically more realistic boundary condition than the previous ones on the nanoparticle volume fraction is considered i.e. the nanoparticle flux is assumed to be zero rather than prescribing the nanoparticle volume fraction on the boundaries. Using linear stability theory, the exact analytical expression for critical Rayleigh Darcy number is obtained in terms of various non-dimensional parameters. Results indicate that the magnetic field, Hall current, porous medium and nanoparticles significantly influence the stability characteristics of the system. The increase in the Hall current parameter, the Lewis number, the modified diffusivity ratio and the concentration Rayleigh Darcy number is to hasten the onset of convection while the magnetic Darcy number, the porosity parameter and the Darcy number has stabilized on the onset of convection.
TL;DR: In this article, transition flow past a circular cylinder in the lower subcritical regime (Re = 3900) has been analyzed using Large Eddy Simulation (LES) coupled to Smagorinsky and dynamic sub grid scale models.
Abstract: Transitional flow past a circular cylinder in the lower subcritical regime (Re = 3900) has been analysed using Large Eddy Simulation (LES) coupled to Smagorinsky and dynamic sub grid scale models. These simulations have been carried out using a parallel multiblock structured finite volume code which is based on SIMPLE algorithm. The predictions are validated against detailed measurement data for mean as well as turbulence quantities. The present LES prediction in general agree reasonably well with the measurement data in the near wake region but deviates from the measurement data in the far wake region which may be due to the coarse resolution of the grid in this region. The influence of the SGS model on mean flow quantities as well as on the flow structures are also discussed.
TL;DR: In this article, the peristaltic transport of Phan-Thien-Tanner fluid in an asymmetric channel induced by sinusoidal peristALTic waves traveling down the flexible walls of the channel is investigated in a wave frame of reference moving with the velocity of the wave by using the long wavelength and low Reynolds number approximations.
Abstract: This paper deals with peristaltic transport of Phan-Thien-Tanner fluid in an asymmetric channel induced by sinusoidal peristaltic waves traveling down the flexible walls of the channel. The flow is investigated in a wave frame of reference moving with the velocity of the waveby using the long wavelength and low Reynolds number approximations.The nonlinear governing equations are solved employing a perturbation method by choosing W e as the perturbation parameter. The expressions for velocity, stream function and pressure gradient are obtained. The features of the flow characteristics are analyzed through graphs and the obtained results are discussed in detail. It is noticed that the peristaltic pumping gets reduced due to an increase in the phase difference of the traveling waves. It is also observed that the size of the trapping bolus is a decreasing function of the permeability parameter and the Weissenberg number. Furthermore, the results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the nonNewtonian fluid phenomena, especially the Peristaltic flow phenomena.
TL;DR: In this article, the peristaltic transport of an incompressible non-Newtonian fluid in an elastic tube was studied and the flux was determined as a function of inlet, outlet, external pressures, yield stress, amplitude ratio, and the elastic properties of the tube.
Abstract: This paper is concerned with the peristaltic transport of an incompressible non-Newtonian fluid in an elastic tube. Here the flow is due to three different peristaltic waves and two different types of elastic tube. The constitution of blood suggests a non-Newtonian fluid model and it demands the applicability of yield stress fluid model. Among the available yield stress fluid models for blood, the non-Newtonian Casson fluid is preferred. The Casson fluid model describes the flow characteristics of blood accurately at low shear rates and when it flows through small blood vessels. Long wavelength approximation is used to linearize the governing equations. The effect of peristalsis and non-Newtonian nature of blood on velocity, plug flow velocity, wall shear stress and the flux flow rate are derived. The flux is determined as a function of inlet, outlet, external pressures, yield stress, amplitude ratio, and the elastic properties of the tube. Furthermore, it is observed that, the yield stress, peristaltic wave, and the elastic parameters have strong effects on the flux of the non-Newtonian fluid, namely, blood. One of the important observation is that the flux is more when the tension relation is an exponential curve rather than that of a fifth degree polynomial. Further, in the absence of peristalsis and when the yield stress tends to zero our results agree with the results of Rubinow and Keller (1972). This study has significance in understanding peristaltic transport of blood in small blood vessels of living organisms.
TL;DR: In this paper, an attempt has been made to carry out a numerical analysis to investigate the cavitation effect in a Francis turbine, where three dimensional numerical study approach of unsteady and SST turbulence model is considered for the numerical analysis under multiphase flow such as cavitating flow.
Abstract: Cavitation is undesirable phenomena and more prone in reaction turbines. It is one of the challenges in any hydro power plant which cause vibration, degradation of performance and the damage to the hydraulic turbine components. Under the present study, an attempt has been made to carry out a numerical analysis to investigate the cavitation effect in a Francis turbine. Three dimensional numerical study approach of unsteady and SST turbulence model are considered for the numerical analysis under multiphase flow such as cavitating flow. The performance parameters and cavitating flow under different operating conditions have been predicted using commercial CFX code. Three different operating conditions under cavitation and without cavitation with part load and overload conditions of the turbine for a plant sigma factor are investigated. The results are presented in the form of efficiency, pressure fluctuation, vortex rope and vapor volume fraction. It has been observed that variation in efficiency and vapor volume fraction is found to be nominal between cavitation and without cavitation conditionsat rated discharge and rated head. Turbine efficiency loss and vapor bubbles formation towards suction side of the runner blade are found to be maximum under overload condition. However, the pressure pulsation has been found maximum under part load condition in the draft tube. The simulation results are found to be in good agreement with model test results for efficiency. The locations of cavitating zone observed wellwith the result of previous studies.
TL;DR: In this paper, the authors examined the non-aligned stagnation point flow and heat transfer of an EthyleneGlycol and water based nano fluid towards a stretching surface utilizing hematite (Fe3O4) as a heat enhancing agent.
Abstract: This article examines the non-aligned stagnation point flow and heat transfer of an EthyleneGlycol and water based Nano fluid towards a stretching surface utilizing hematite (Fe3O4) as a heat enhancing agent. Resulting differential equations of the physical problem are solved numerically using Mid-point integration as a basic scheme along with Richardson extrapolation as an enhancement scheme. Influence of the flow governing parameters on the dimensionless velocity and temperature profile are expressed through graphs. Skin frictions co-efficient and Nusselt numbers are tabulated. It is observed that Ethylene-based nano fluids have higher local heat flux than water-based nano fluids. Computed numerical results of skin friction co-efficient are in good agreement with the existing available literature for the limited case.
TL;DR: In this article, the characteristics of hydromagnetic flow over a slendering stretching sheet in slip flow regime were determined by using similarity transformations and Nachtsheim-swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method.
Abstract: The objective of this study is to determine the characteristics of hydromagnetic flow over a slendering stretching sheet in slip flow regime. Steady, two dimensional, nonlinear, hydromagnetic laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness in the presence of variable magnetic field and slip flow regime is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and their effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.
TL;DR: In this article, the steady laminar boundary layer flow and heat transfer over a permeable exponentially stretching/shrinking sheet with generalized slip velocity is studied, where appropriate similarity variables are used to transform the governing nonlinear partial differential equations to a system of nonlinear ordinary differential equations.
Abstract: In this paper, the steady laminar boundary layer flow and heat transfer over a permeable exponentially stretching/shrinking sheet with generalized slip velocity is studied. The flow and heat transfer induced by stretching/shrinking sheets are important in the study of extrusion processes and is a subject of considerable interest in the contemporary literature. Appropriate similarity variables are used to transform the governing nonlinear partial differential equations to a system of nonlinear ordinary (similarity) differential equations. The transformed equations are then solved numerically using the bvp4c function in MATLAB. Dual (upper and lower branch) solutions are found for a certain range of the suction and stretching/shrinking parameters. Stability analysis is performed to determine which solutions are stable and physically realizable and which are not stable. The effects of suction parameter, stretching/shrinking parameter, velocity slip parameter, critical shear rate and Prandtl number on the skin friction and heat transfer coefficients as well as the velocity and temperature profiles are presented and discussed in detail. It is found that the introduction of the generalized slip boundary condition resulted in the reduction of the local skin friction coefficient and local Nusselt number. Finally, it is concluded from the stability analysis that the first (upper branch) solution is stable while the second (lower branch) solution is not stable.
TL;DR: In this article, the position of the vortex core is tracked in these simulations by searching the positions of minimal dynamic pressure and the centre of moment of the horizontal velocity components as function of the axial coordinate.
Abstract: A problem of cyclone separators is the low grade efficiency of small particles. Therefore, a high efficiency cyclone separator has been developed and successfully tested in former work. In this cyclone separator, a vortex stabilizer is used to suppress the vortex core precession. In this article, the pressure and flow field in this cyclone separator are calculated by means of computational fluid dynamics using the commercial software Ansys Fluent 13. The position of the vortex core is tracked in these simulations by searching the position of minimal dynamic pressure and the centre of moment of the horizontal velocity components as function of the axial coordinate. The results are compared with experimental data. It is demonstrated that when using a stabilizer, the vortex is kept in position. Furthermore the maximum of the tangential velocity is found to be larger, which is known to have a positive effect on the separation of small particles in the inner solid body rotation vortex.
TL;DR: In this paper, the authors analyzed the momentum and heat transfer behavior of CuO-water and Al2O3-waternanofluids embedded with micrometer sized conducting dust particles towards a porous stretching/shrinking cylinder at different temperatures in presence of suction/injection, uniform magnetic field, shape of nano particles, volume fraction of micro and nano particles.
Abstract: In this study we analyzed the momentum and heat transfer behavior of CuO-water and Al2O3-waternanofluids embedded with micrometer sized conducting dust particles towards a porous stretching/shrinking cylinder at different temperatures in presence of suction/injection, uniform magnetic field, shape of nano particles, volume fraction of micro and nano particles. The governing boundary layer equations are transformed to nonlinear ordinary differential equations by using similarity transformation. Numerical solutions of these equations can be obtained by using Runge-Kutta Felhberg technique. The influence of non-dimensional governing parameters on the flow field and heat transfer characteristics are discussed and presented through graphs and tables. Results indicates that spherical shaped nano particles showed better thermal enhancement compared with cylindrical shaped nano particles, increase in volume fraction of nano particles helps to enhance the uniform thermal conductivity. But it does not happen by increase in volume fraction of dust particles. Enhancement in fluid particle interaction reduces the friction factor and improves the heat transfer
TL;DR: An analysis of the thermal radiation effects on MHD boundary layer flow past a permeable exponential stretching surface in the presence of Joule heating and viscous dissipation is presented in this article.
Abstract: An analysis of the thermal radiation effects on MHD boundary layer flow past a permeable exponential stretching surface in the presence of Joule heating and viscous dissipation is presented. Velocity and thermal slips are considered instead of no-slip conditions at the boundary. Stretching velocity and wall temperature are assumed to have specific exponential function forms. The governing system of partial differential equations is transformed into a system of ordinary differential equations using similarity transformations and then solved numerically using the Runge-Kutta fourth order method along with shooting technique. The effects of the various parameters on the velocity, shear stress, temperature and temperature gradient profiles are illustrated graphically and discussed in detail. The influence of the slip parameters causes significant fluctuations in velocity of the flow field. Viscous dissipation characterized by Eckert number enhances the temperature of the fluid, as the heat gets transferred from the sheet to the fluid.
TL;DR: In this article, the laminar boundary layer flow and heat transfer of Casson non-Newtonian fluid from an inclined collector plate in the presence of thermal and hydrodynamic slip conditions is analyzed.
Abstract: The laminar boundary layer flow and heat transfer of Casson non-Newtonian fluid from an inclined (solar collector) plate in the presence of thermal and hydrodynamic slip conditions is analysed. The inclined plate surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite-difference scheme. Increasing velocity slip induces acceleration in the flow near the inclined plate surface. Increasing velocity slip consistently enhances temperatures throughout the boundary layer regime. An increase in thermal slip parameter strongly decelerates the flow and also reduces temperatures in the boundary layer regime. An increase in Casson rheological parameter acts to elevate considerably the velocity and this effect is pronounced at higher values of tangential coordinate. Temperatures are however very slightly decreased with increasing values of Casson rheological parameter.
TL;DR: In this paper, Williamson nano fluid flow over a continuously moving surface is discussed when the surface is heated due to the presence of hot fluid under it, and mathematical analysis of various physical parameters is presented and the percentage heat transfer enhancement is discussed due to variation of these parameters.
Abstract: In the present article Williamson nano fluid flow over a continuously moving surface is discussed when the surface is heated due to the presence of hot fluid under it. Governing equations have been developed and simplified using the suitable transformations. Mathematical analysis of various physical parameters is presented and the percentage heat transfer enhancement is discussed due to variation of these parameters. We employed Optimal homotopy analysis method to obtain the solution. It is presented that initial guess optimization will provide us one more degree of freedom to obtain the convergent and better solutions.
TL;DR: It was discovered that the aerodynamic performance of the drone could be further improved by changing the rotating direction of each rotor, and the drone performance increased by 39.58% in terms of lift-to-drag ratio by using this method.
Abstract: Computational fluid dynamics (CFD) study was done on the propeller design of a micro aerial vehicle (quadrotor-typed) to optimize its aerodynamic performance via Shear Stress Transport K-Omega (SST k-ω) turbulence model. The quadrotor model used was WL-V303 Seeker. The design process started with airfoils selection and followed by the evaluation of drone model in hovering and cruising conditions. To sustain a 400g payload, by Momentum Theory an ideal thrust of 5.4 N should be generated by each rotor of the quadrotor and this resulted in an induced velocity of 7.4 m/s on the propeller during hovering phase, equivalent to Reynolds number of 10403 at 75% of the propeller blade radius. There were 6 propellers investigated at this Reynolds number. Sokolov airfoil which produced the largest lift-to-drag ratio was selected for full drone installation to be compared with the original model (benchmark). The CFD results showed that the Sokolov propeller generated 0.76 N of thrust more than the benchmark propeller at 7750 rpm. Despite generating higher thrust, higher drag was also experienced by the drone installed with Sokolov propellers. This resulted in lower lift-to-drag ratio than the benchmark propellers. It was also discovered that the aerodynamic performance of the drone could be further improved by changing the rotating direction of each rotor. Without making changes on the structural design, the drone performance increased by 39.58% in terms of lift-to-drag ratio by using this method.
TL;DR: In this article, a multi-fluid Incompressible smoothed Particle Hydrodynamics (ISPH) model is used to simulate the multifluid flows similar to the fine sediment materials transport (in muddy flows) and water flow mixing process.
Abstract: The Three Gorges Dam (TGD) constructed at the Yangtze River, China represents a revolutionary project to battle against the mage-scale flooding problems while improving the local economy at the same time. However, the large-scale fine-size sediment and pollutant material transport caused by the TGD operation are found to be inevitable and long-lasting. In this paper, a multi-fluid Incompressible Smoothed Particle Hydrodynamics (ISPH) model is used to simulate the multi-fluid flows similar to the fine sediment materials transport (in muddy flows) and water flow mixing process. The SPH method is a mesh-free particle modeling approach that can treat the free surfaces and multi-interfaces in a straightforward manner. The proposed model is based on the universal multi-fluid flow equations and a unified pressure equation is used to account for the interaction arising from the different fluid components. A Sub-Particle-Scale (SPS) turbulence model is included to address the turbulence effect generated during the flow process. The proposed model is used to investigate two cases of multi-fluid flows generated from the polluted flow intrusions into another fluid. The computations are found in good agreement with the practical situations. Sensitivity studies have also been carried out to evaluate the particle spatial resolution and turbulence modeling on the flow simulations. The proposed ISPH model could provide a promising tool to study the practical multi-fluid flows in the TGD operation environment.