Values Of Skin Friction Research Articles

Unsteady Mixed Bioconvection Flow of Eyring–Powell Nanofluid with Motile Gyrotactic Microorganisms Past Stretching Surface

The provided mathematical analysis aims to scrutinize the behavior of gyrotactic microorganisms to depict their role in heat and mass transfer in an unsteady mixed convection stretched flow of special Eyring–Powell nanofluid loaded by nanoparticles and gyrotactic microorganisms with simultaneous impact of Lorentz forces and zero nanoparticle flux condition at boundary. A two-phase type is presented for modeling the nanofluid. Thought of microorganisms is adopted just to stabilize the pendant nanoparticles due to bioconvection which has been promoted by combined impacts of both buoyancy and magnetic field forces. The controlling highly nonlinear partial differential equations with the auxiliary conditions have been mutated into ordinary differential equations via a convenient similarity approach. Governing mutated equations have been solved computationally by means of fifth-order Runge–Kutta–Fehlberg scheme with 10−6 tolerance level, the numerical calculations were presented. Further, our computations illustrate that a significant impact of unsteady parameter by examining the factor values of skin friction and the local density numbers. While A parameter leads to weaken skin friction, it boosts the local density number. The coefficient of heat and motile microorganism transfer rates strengthen, when mixed convection parameter λ improves. While base fluid parameter ϵ weakens the rate of heat transfer, it enhances the local density number. In addition, comparison was provided between Newtonian and non-Newtonian Powell–Eyring fluid on velocity and temperature distributions to confirm the methodology. Comparison with given results for special conditions is presented and seen to be highly satisfactory.

Radiative MHD flow of hybrid nanofluid past a porous stretching cylinder for heat transfer enhancement

AbstractThe current study investigates heat transfer enhancement due to the radiative magnetohydrodynamics (MHD) flow of a hybrid nanofluid past a porous stretching cylinder under the influence of variable viscosity as well as suction. The nonlinear partial differential equations governing the proposed physical model are transformed into nonlinear ordinary differential equations by applying suitable similarity transformation. The scaled‐down system is solved numerically by the fourth‐order Runge–Kutta method along with shooting technique for the achievement of asymptotic boundary condition. The velocity and temperature profiles are obtained for various physical factors of the problem, namely, magnetic interaction factor , Reynolds number , volume fraction factor of copper , variable viscosity , and radiation factor , together with suction , by fixing the Prandtl number of the core fluid (ethylene glycol) constant at 25.825. The numerical values of skin friction and the rate of heat transfer are obtained and tabulated. To validate the proposed physical model, numerical simulations are provided with comparison. The paper highlights the effects of physical factors, namely, radiation, variable viscosity, and suction parameters, on the flow of a hybrid nanoflluid for heat transfer enhancement.

Heat and mass transfer of magnetohydrodynamic Casson fluid flow over a wedge with thermal radiation and chemical reaction

AbstractA numerical computation to analyze the heat and mass transfer mechanism of a magnetohydrodynamic radiative Casson fluid flow over a wedge in the presence of Joule heating, viscous dissipation, and chemical reaction is carried out in this study. The flow‐governing partial differential equations are transformed as ordinary differential equations by relevant similarity transformations and subsequently resolved by Runge–Kutta numerical approach with a shooting technique. The characteristics of momentum, thermal, and concentration border layers due to various influencing parameters are graphically outlined and numerically computed by MATLAB software. We present comparative solutions to construe the relative outcomes of Casson fluid versus Newtonian fluid. Computational outcomes of friction factor and Nusselt and Sherwood numbers are tabulated with suitable interpretations. An increase in skin friction values is noted due to an increment in the thermal Grashof number, whereas a decrease is observed due to the chemical reaction parameter. The Casson fluid displays a superior heat transfer mechanism than the Newtonian fluid. Obtained outcomes are in good agreement with the prevailing literature in the limiting case.

Effect of variable thermal conductivity on the MHD boundary-layer of Casson-nanofluid over a moving plate with variable thickness

The effect of variable thermal conductivity on the characteristics of heat transfer and mechanical properties of a moving surface on a Casson nanofluid flow as a coolant has been studied in this paper. We used similarity transformation method to transform the equations of the governing boundary-layer into ODE which are solved numerically using a mix of fourth order Runge-Kutta method and find root technique. Different values relevant parameters have been studied on the features of velocity, temperature, and the profiles of concentration and discussed in details for different values of various parameter as shape parameter, heat source parameter, radiation parameter, and magnetic parameter. The results were compared with previous published researches and obtained it in a good agreement and the results were tabulated. Furthermore, Nusselt number, Sherwood number, and the skin friction values with different parameters were calculated and the influence of theses physical quantities on the mechanical properties on the surface are analyzed and discussed in details.

Experimental Study on the Negative Skin Friction of the Pile Group Induced by Rising and Lowering the Groundwater Level

Negative skin friction (NSF) has been one of the important factors in the design of pile foundation; especially, the influence of water level on the pile negative skin friction should be paid attention. In this paper, a series of model tests were carried out to analyze the bearing characteristic of the pile group influenced by groundwater level. The pile axial force and negative skin friction, settlement, and soil pore pressure were investigated. The results showed that both the water level rising and lowering cycle could increase the axial force of the pile along the upper part of the pile, yet reducing it along the lower part of the pile; both the axial force and the negative skin friction of the pile presented a feature of time effect; the value of negative skin friction was positively correlated with that of the pile head load, and the neutral plane ranged from 0.57 L to 0.64 L as the water level changed; the soil featured settling in layers, and the change of pore water pressure was accordant with the water level changing regulation.

Thermal variable conductivity features in Buongiorno nanofluid model between parallel stretching disks: Improving energy system efficiency

In present investigation, the axisymmetric analysis for the Casson nano-material has been analyzed due to two parallel stretchable disks. The novel thermophoresis and Brownian aspects of nanofluid are studied by using Buongiorno nanofluid model. Similarity transformations are applied on the system of governing equations that renovate it into the problem into proper dimensionless form. The homotopic procedure is suggested for the determination of solution. The role of numerous parameters on dimensionless velocity and temperature are observed in very effective way. To study the effect of Brownian motion and thermophoresis diffusion parameter, Buongiorno model is adopted. Radial and axial velocity profile has increasing behavior for stretching ratio and Casson parameter. As the value of Biot number and thermophoresis parameter enhanced, the concentration profile also enhances and concentration profile declines due to increase in value of Brownian motion parameter. Temperature profile decreases as the value of Reynolds number and Prandtl number increased. The values of Sherwood number, Nusselt number and Skin friction are calculated at upper and lower disk to understand the behavior of stretching disks.

Characteristics of Magnetohydrodynamics Nanofluid Flow in the Presence of Porous Medium Towards a Stretching Sheet with a Convective Boundary Condition

With the effects of variable viscosity and convective boundary conditions, the contemporary studies work ambitions to investigate the together effects of the magnetic field and porous medium on non-Newtonian nano fluid flow to a stretching layer. In this latest work, to examine the impact of thermophoresis and Brownian motion, the nanofluid model is utilized. To lessen the basic governing coupled non-linear PDE’s for velocity (momentum), temperature (energy), and nanoparticle concentration to an assortment of ordinary non-linear differential equations, the necessary transformations are used. Utilizing the fourth-fifth order Runge-Kutta-Fehlberg strategy, the resulting reshaped conditions are tackled mathematically. The effects on the dimensionless temperature, velocity, nanoparticle concentration profiles of various engineering parameters are discussed and graphically analyzed. The numerically computed values of skin-friction, coefficients of heat transfer rate and mass transfer are tabulated. The numerical findings got are contrasted and the outcomes recently detailed as unique instances of the current examination and viewed as in reasonable consistence.

Numerical study of the nanofluid thin film flow past an unsteady stretching sheet with fractional derivatives using the spectral collocation Chebyshev approximation

In this work, a mathematical model of fractional-order in fluid will be analyzed numerically to describe and study the influence of thermal radiation on the magnetohydrodynamic flow of nanofluid thin film which moves due to the unsteady stretching surface with viscous dissipation. The set of nonlinear fractional differential equations in the form of velocity, temperature and concentration which describe our proposed problem are tackled through the spectral collocation method based on Chebyshev polynomials of the third-kind. This method reduces the presented model to a system of algebraic equations. The effect of the influence parameters which governs the process of flow and mass heat transfer is discussed. The numerical values of the dimensionless velocity, temperature and concentration are depicted graphically. Also, computations of the values of skin-friction, Nusselt number and Sherwood number have been carried out and presented in the same figures. Finally, our numerical analysis shows that both the magnetic and the unsteadiness parameters can enhance the free surface temperature and nanoparticle volume fraction.

Hall effect on MHD transient free convection flow of chemically reactive Casson fluid with heat source/sink past an infinite vertical cylinder

This article presents an analytical investigation of the effect of Hall current, magnetic field, and chemical reaction on an unsteady MHD transient free convection heat and mass transfer flow of viscous incompressible, electrically conducting Casson fluid past an infinite vertical cylinder subject to heat source and sink. Closed-form solutions are obtained by employing Laplace transform and inverted using Mellin-Fourier integral and presented them in terms of Bessel functions and modified Bessel functions. To get an insight into the model, we have depicted the graphs of velocity, temperature and concentration profiles for various values of the pertinent flow parameters. The values of Sherwood number, Nusselt number, and skin friction are calculated and presented in the tabular form. Further, we have also considered a special case and investigate the velocity profiles of the Newtonian fluid for both heat source and sink as the Casson parameter α → ∞. From the investigation, it is perceived that with an increase in the values of chemical reaction parameters the species concentration and the velocity of the Casson fluid get reduced while its reverse trend has been observed on Sherwood number and skin friction. With an increase in the Prandtl number the fluid temperature decreases whereas, the Nusselt number increases. A crossing over point is observed in velocity distribution for the Hall current parameter. This fluid flow model will be applicable in geophysics, mining industry, chemical and biomedical engineering such as underground energy system, electromagnetic material production, and automotive fuel level indication, etc.

Numerical Solutions for Convective Boundary Layer Flow of Micropolar Jeffrey Fluid with Prescribe Wall Temperature

The steady two dimensional convective boundary layer flow of micropolar Jeffrey fluid past a permeable stretching sheet is studied in this paper. The governing boundary layer equation in the form of partial differential equations are transformed into nonlinear coupled ordinary differential equations and solved numerically using an implicit finite-difference scheme known as Keller-box method. The effects of Prandtl number, Deborah number, and material parameter with the boundary condition for microrotation, n = 0 (strong concentration of microelements) on the velocity, microrotation, temperature profiles as well as the skin friction and heat transfer coefficients are presented and discussed. An excellent agreement is observed between the present and earlier published results for some special cases. The results revealed that, the effect of Deborah number and stretching parameter are increased the heat transfer coefficient while the opposite trend is observed for the effects of material and velocity slip parameters. It was also observed that, the values of skin friction increased with the increment on the values of all studied parameters.

CNTs-Nanofluid flow in a Rotating system between the gap of a disk and cone

In the current article, the focus of the study is the rate of heat transfer in three-dimensional coordinates. The cone-disk apparatus is assumed with rotating disk and stationary cone or may be taken with a stationary disk and rotating cone, or both of them co-rotating, or counter-rotating, along single-wall carbon nanotubes (SWCNTs) and multiple wall carbon nanotubes (MWCNTs) of water-based. By the definition of well-known thermal physical possessions of CNTs heat transfer enhancement at both the cone-disk surfaces is investigated. Further magnetism (MHD) is enforced perpendicular to the flow of nanofluid between the cone and the disk surface. The conical gap section is considered moderate for the better result of heat transfer. The modeled equations for the nonlinear problem are solved through an analytical approach Homotopy analysis method (HAM). On behalf of graphical outcomes of velocity, concentration, and temperature profiles the HAM BVPh 2.0 package has been used. Moreover numerical values of skin friction, Nusselt number are calculated through the effect of SWCNTs and MWCNTs at both the cone and disk surface with a moderate apex angle. On behalf of the concentration equation, the Sherwood number is also deliberate in the present analysis.

Impact of heat generation/absorption of magnetohydrodynamics Oldroyd-B fluid impinging on an inclined stretching sheet with radiation

In this paper, we have investigated thermally stratified MHD flow of an Oldroyd-B fluid over an inclined stretching surface in the presence of heat generation/absorption. Similarity solutions for the transformed governing equations are obtained. The reduced equations are solved numerically using the Runge–Kutta Fehlberg method with shooting technique. The influences of various involved parameters on velocity profiles, temperature profiles, local skin friction, and local Nusselt number are discussed. Numerical values of local skin friction and local Nusselt number are computed. The significant outcomes of the study are that the velocity decreases when the radiation parameter R_{d} is increased while the temperature profile is increased for higher values of radiation parameter R_{d} in case of opposing flow, moreover, growth in Deborah number beta_{2} enhance the velocity and momentum boundary layer. The heat transfer rate is decrease due to magnetic strength but increase with the increased values of Prandtl and Deborah numbers. The results of this model are closely matched with the outputs available in the literature.

Interaction of Al2O3-Ag and Al2O3-Cu hybrid nanoparticles with water on convectively heated moving material

PurposeThe aim of present work is to study the flow and heat transport structures of hybrid nanoparticles in a moving material. Two types of hybrid nanoparticles have been chosen namely Al2O3-Cu and Al2O3-Ag nanoparticles (90%) within 10% of pure water.Design/methodology/approachLeading governing equations are transformed through similarity technique and then computed for numerical illustration by applying RKF method.FindingsThe author observed that the skin friction value of Al2O3-Cu/water case is lesser in comparison to the values of Nusselt number for Al2O3-Ag/water nanoparticles.Originality/valueThere exist no such study which addressed such phenomenon.

Combination of baffling technique and high-thermal conductivity fluids to enhance the overall performances of solar channels

In the present study, two-phase flow and forced-convection heat transfer of hydrogen gas (H2) in a solar finned and baffled channel heat exchanger (SFBCHE) is studied numerically. The effect of different obstacles in the channel is addressed. A H2 heat transfer fluid (HTF) having a high thermal conductivity with the baffling technique is implemented to enhance the overall performance of a solar channel. In the initial step, the results from the proposed numerical model were compared with the experimental data of a smooth channel, and then against data with a baffled channel. After checking the validity of our model, the same numerical approach was used for studying thermal-fluid characteristics of the channel with the new fluid. A hydrothermal analysis is presented for a range of Reynolds number (Re) from 5000 to 25,000. At the lowest Re = 5000, the thermal enhancement factor (TEF) is about 1.25. This value increases to 2.16, or 73.46%, when Re = 10,000. This increase in the TEF values continues as Re increases. The largest Re = 25,000 gives the highest TEF value, as it is about 4.18, which is 2.75 times greater than that given for the case of using the conventional gaseous fluid (air). Therefore, our proposed structure for the SFBCHE with high H2 HTF flow velocity leads to improve the values of dynamic pressure (Pd) and heat transfer (Nu), while reducing the skin friction (f) values, which increases the overall TEF of the channel. In addition, all performance values are greater than unity (or 1.00). This reflects the importance of the H2 HTF baffling and finning technique in improving the hydrodynamic thermal-energy performance of solar heat exchangers. The suggested model of SFBCHE filled with an H2 HTF having a high thermal conductivity allows a considerable enhancement in the overall thermal performances which can be employed in various thermal types of equipment, such as solar energy receivers, automotive radiators, and cooling in chemical industries.

Numerical investigation of induced magnetic field and variable mass diffusivity on double stratified Jeffrey fluid flow with heat and mass flux boundary conditions

AbstractThe investigation explores the influence of the induced magnetic field and variable mass diffusivity on an unsteady incompressible mixed convective double stratified and chemically reactive flow of Jeffrey fluid through a porous medium with heat, and mass flux boundary conditions. The system of flow field nonlinear partial differential equations is reduced into coupled nondimensional ordinary differential equations using appropriate similar variables, then worked out a numerical solution via shooting technique along with Rung‐Kutta fourth‐order scheme. The results are analyzed for various physical flows, heat and mass transfers, induced magnetic field, and skin friction against disparate prominent parameters via graphs and tables. It is recognized that the temperate of the fluid is enhanced with thermal stratification; however, the concentration of the fluid is decreased with magnetic Reynold's number. The comparison of numerical values of skin friction with the existing literature for limiting sense.

Assessment of Pile Capacity Using Bidirectional Static Load Test (BDSLT)

Bidirectional Static Load Test (BDSLT), an innovative load test method, two static load tests performed simultaneously in opposite directions, adopting sacrificial hydraulic cells was globally used in the deep foundation industry. This paper presents the results of value engineering and optimization of the foundation design for the proposed pile tests from the Dubai Creek Harbour Project on plot no. A004, Dubai, UAE. The main objective of this load test was to proof-load the test pile to its ultimate capacity using the BDSLT method. For this purpose, 4 × 900 tons of capacity hydraulic cell/jacks was utilized. Two test piles of 1500 mm diameter were used, namely PTP1 and PTP2. Five levels of Geokon USA model 4200 vibrating wire-type strain gauges comprising four units at each level were also installed on the test pile to measure strain at nominated locations, and from that, load and unit skin frictions were derived. Results indicate that the skin friction was increased from values reported before pile testing. Pile capacities were optimized using the skin friction values obtained from the load test results.

Axial performance of micropile groups in cohesionless soil from full-scale tests

Hollow bar micropile (HBMP) groups are used for supporting large loads as an alternative foundation option to large diameter drilled shafts. In such cases, it may be necessary to increase the micropile’s diameter by increasing the drill bit diameter (Db). This paper investigates experimentally and numerically the effect of increasing Dband micropile spacing on the group performance. A field load testing program was conducted on four groups of HBMPs installed in sand; each group comprised four micropiles arranged in a square configuration. All micropiles were constructed with the same size hollow bar, Dh= 51 mm; two groups comprised micropiles constructed with drill bit, Db= 115 mm, and two groups comprised micropiles constructed with drill bit, Db= 152 mm. One group of each set was installed with spacing to micropile diameter ratio, S/Db= 3 and the other group with S/Db= 5. In addition, full 3D finite element model (FEM) was developed and calibrated to simulate the behaviour of micropile groups and to evaluate the failure load for groups that were not loaded to failure. The results demonstrated that micropile groups constructed with the large diameter drill bits displayed higher stiffness and load carrying capacity than the groups constructed with small diameter bits, which confirms the effectiveness of using a larger drill bit. In addition, the group efficiency ratio values at both working load and ultimate capacity were found to be close to unity for all groups. The ultimate skin friction values of grouted micropiles obtained from this study were higher than the values suggested by the US Federal Highway Administration for medium to very dense sand. It was also found that the settlement of the 4-HBMP group increased by 25% to 33% over that of a single HBMP due to group effect.

Non-Newtonian ferrofluid flow over an unsteady contracting cylinder under the influence of aligned magnetic field

In this paper the basic design of the study is comparison between the magnetohydrodynamic (MHD) flow and heat transfer of non-Newtonian (Sodium Alginate) base fluid with three ferroparticles, that is Cobalt ferrite (CoFe2O4), Manganese–Zinc ferrite (Mn−ZnFe2O4) and Nickel–Zinc ferrite (Ni−ZnFe2O4) over an unsteady contracting cylinder. In this inspection the aligned magnetic field effects are taken into consideration. The process of bringing the governing PDE's to the form of ODE's is achieved with the similarity transformations. At this point the changed over conditions are numerically understood by Runge-Kutta method of fourth order with shooting technique. The non-Newtonian behavior is discussed employing Casson model. By means of visual image we explain and interpret the behaviours of several emerging parameters on the velocity and temperature profiles. Calculation for the local skin friction coefficient and local Nusselt number are evaluated and examined for the deserving parameters. Also, it is seen that the alignment of magnetic field helps in advancing the velocity profile. Comparing the nanoparticles it is observed that CoFe2O4 nanoparticle is dominant over the other for the local skin friction values whereas Ni−ZnFe2O4 nanoparticle has higher rate of heat transfer.

Heat and mass transfer effect on a radiative second grade MHD flow in a porous medium over a stretching sheet

A study on heat and mass transfer of a steady laminar boundary layer flow of an electrically conducting fluid of second grade in a porous medium subject to a uniform magnetic field past a semi-infinite stretching sheet with power law surface temperature or power law surface heat flux. The variations in fluid velocity, fluid temperature and species concentration are displayed graphically whereas the numerical values of skin friction, Nusselt number and Sherwood number are presented in tabular form for various values of the pertinent flow parameters. The asymptotic expansions of the solutions for large Prandtl number are also given for the two heating conditions. The temperature distribution decreases with the increase in thermal radiation parameter in case of PST and PHF. The rate of mass transfer at the solid surface increases in the presence of magnetic field and decreases with heavier diffusing species.

Effect of buoyancy and suction on Sisko nanofluid over a vertical stretching sheet in a porous medium with mass flux condition

The present article investigates the flow and heat transfer of Sisko nanofluid over a permeable vertical stretching surface in a porous medium. The effect of buoyancy, suction, and viscous dissipation has been taken into account. Buongiorno’s model of nanofluid consisting of thermophoresis and Brownian diffusion has been considered. Moreover, zero nanoparticle mass flux condition is employed at the boundary which leads to a more realistic physical problem. Using a suitable transformation governing partial differential equations of fluid flow are transformed into a set of nonlinear ordinary differential equations (ODEs). The numerical solution of nonlinear ODEs are obtained using the finite difference technique in MATLAB. The influence of physical parameters viz. buoyancy parameter (λ*), porosity parameter (β*), thermophoresis parameter (Nt*), suction parameter (f), Sisko material parameter (A*), Brinkman number (Br*), Brownian diffusion parameter (Nb*) and Lewis number (Le*) on velocity, temperature and nanoparticle volume fraction are shown graphically. Moreover, to understand the physical phenomenon in the boundary layer region, the numerical values of skin friction and Nusselt number are calculated and presented through table values. It has been found that the Brownian diffusion has a negligible impact on Nusselt number relative to the results obtained in previous studies, where nanoparticle volume fraction on the boundary was actively controlled. The obtained results disclose that the buoyancy parameter increases the velocity of fluid while it reduces the temperature. Suction parameter reduces both velocity and temperature, whereas the porosity parameter reduces velocity and enhances the temperature and nanoparticle volume fraction.