scholarly journals Effects of g-jitter and radiation on three-dimensional double diffusion stagnation point nanofluid flow

2020 ◽  
Vol 41 (11) ◽  
pp. 1707-1722
Author(s):  
M. H. A. Kamal ◽  
N. A. Rawi ◽  
A. Ali ◽  
S. Shafie

Abstract The unsteady double diffusion of the boundary layer with the nanofluid flow near a three-dimensional (3D) stagnation point body is studied under a microgravity environment. The effects of g-jitter and thermal radiation exist under the microgravity environment, where there is a gravitational field with fluctuations. The flow problem is mathematically formulated into a system of equations derived from the physical laws and principles under the no-slip boundary condition. With the semi-similar transformation technique, the dimensional system of equations is reduced into a dimensionless system of equations, where the dependent variables of the problem are lessened. A numerical solution for the flow problem derived from the system of dimensionless partial differential equations is obtained with the Keller box method, which is an implicit finite difference approach. The effects studied are analyzed in terms of the physical quantities of principle interest with the fluid behavior characteristics, the heat transfer properties, and the concentration distributions. The results show that the value of the curvature ratio parameter represents the geometrical shape of the boundary body, where the stagnation point is located. The increased modulation amplitude parameter produces a fluctuating behavior on all physical quantities studied, where the fluctuating range becomes smaller when the oscillation frequency increases. Moreover, the addition of Cu nanoparticles enhances the thermal conductivity of the heat flux, and the thermal radiation could increase the heat transfer properties.

2019 ◽  
Vol 1 (2) ◽  
pp. 58-61
Author(s):  
MOHAMAD HIDAYAD BIN AHMAD KAMAL ◽  
NORAIHAN AFIQAH RAWI ◽  
ANATI AHMAD ALI ◽  
SHARIDAN AHMAD SHAFIE

The fundamental research near a boundary layer nanofluid flow at a stagnation point region with thermal radiation effect is conducted under microgravity environment. The mathematical formulation is modified from physical law to represent the physical characteristic of the flow and the system of the equation are solved numerically using Keller box method. The flow is analyzed in terms of physical quantities of principal interest such as skin friction and Nusset number. Parameters consider in this flow such as curvature ratio, amplitude of modulation, frequency of oscillation, nanoparticles volume friction and thermal radiation is analyzed numerically and presented graphically. From the analysis, g-jitter effect will produce a fluctuating result to the skin frictions and Nusset number indicate the singularity solution in the flow. The existing of nanoparticles and thermal radiation is found to increase the rate of heat transfer of the flow.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amir Reza Mogharrebi ◽  
Ali Reza D. Ganji ◽  
Khashayar Hosseinzadeh ◽  
So Roghani ◽  
Armin Asadi ◽  
...  

Purpose The purpose of the study is to indicate a three-dimensional convective heat transfer properties evaluation of magnetohydrodynamics nanofluid flow, comprising motile oxytactic microorganisms and nanoparticles, passing through a rotating cone. Design/methodology/approach The imposed technique for solving the governing equations is the Runge–Kutta fifth-order method. The main point of this survey is to diagnosis the influence of diverse factors on velocity, temperature distributions and concentration profile. Furthermore, appending the magnetic field, thermal radiation and viscous dissipation in calculations; also, simultaneous involvement of heat absorption and excretion has been represented as novelties. Findings The results elucidate that by changing the Peclet number from 1 to 2, the dimensionless concentration of the microorganisms has been diminished by about 34.37%. In addition, variation of the magnetic parameter from 0 to 1 has been resulted in reducing the temperature distribution by about 3.11%. Originality/value Recently, attention has been absorbed to adding the motile microorganisms to nanofluid for enhancement of heat transfer and avoiding aggregation of particles. In this regard, the hydrothermal flow of microorganisms has been investigated in this study.


2020 ◽  
Vol 66 ◽  
pp. 157-171 ◽  
Author(s):  
Najiyah Safwa Khashi'ie ◽  
Norihan Md Arifin ◽  
Ioan Pop ◽  
Roslinda Nazar ◽  
Ezad Hafidz Hafidzuddin ◽  
...  

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amin Noor ◽  
Roslinda Nazar ◽  
Kohilavani Naganthran ◽  
Ioan Pop

Purpose This paper aims to probe the problem of an unsteady mixed convection stagnation point flow and heat transfer past a stationary surface in an incompressible viscous fluid numerically. Design/methodology/approach The governing nonlinear partial differential equations are transformed into a system of ordinary differential equations by a similarity transformation, which is then solved numerically by a Runge – Kutta – Fehlberg method with shooting technique and a collocation method, namely, the bvp4c function. Findings The effects of the governing parameters on the fluid flow and heat transfer characteristics are illustrated in tables and figures. It is found that dual (upper and lower branch) solutions exist for both the cases of assisting and opposing flow situations. A stability analysis has also been conducted to determine the physical meaning and stability of the dual solutions. Practical implications This theoretical study is significantly relevant to the applications of the heat exchangers placed in a low-velocity environment and electronic devices cooled by fans. Originality/value The case of suction on unsteady mixed convection flow at a three-dimensional stagnation point has not been studied before; hence, all generated numerical results are claimed to be novel.


Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 784 ◽  
Author(s):  
Nurul Amira Zainal ◽  
Roslinda Nazar ◽  
Kohilavani Naganthran ◽  
Ioan Pop

The hybrid nanofluid under the influence of magnetohydrodynamics (MHD) is a new interest in the industrial sector due to its applications, such as in solar water heating and scraped surface heat exchangers. Thus, the present study accentuates the analysis of an unsteady three-dimensional MHD non-axisymmetric Homann stagnation point flow of a hybrid Al2O3-Cu/H2O nanofluid with stability analysis. By employing suitable similarity transformations, the governing mathematical model in the form of the partial differential equations are simplified into a system of ordinary differential equations. The simplified mathematical model is then solved numerically by the Matlab solver bvp4c function. This solving approach was proficient in generating more than one solution when good initial guesses were provided. The numerical results presented significant influences on the rate of heat transfer and fluid flow characteristics of a hybrid nanofluid. The rate of heat transfer and the trend of the skin friction coefficient improve with the increment of the nanoparticles’ concentration and the magnetic parameter; however, they deteriorate when the unsteadiness parameter increases. In contrast, the ratio of the escalation of the ambient fluid strain rate to the plate was able to adjourn the boundary layer separation. The dual solutions (first and second solutions) are obtainable when the surface of the sheet shrunk. A stability analysis is carried out to justify the stability of the dual solutions, and hence the first solution is seen as physically reliable and stable, while the second solution is unstable.


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