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1

Investigations of Couette flow unsteady radiative convective heat transfer in a vertical channel using the generalized method of lines (MOL)

Sowayan Ahmed S.

International Journal of Applied Mechanics and Engineering

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2022

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Vol. 27, no. 3

199--211

EN

This study describes a very efficient and fast numerical solution method for the non-steady free convection flow with radiation of a viscous fluid between two infinite vertical parallel walls. The method of lines (MOL) is used together with the Runge-Kutta ODE Matlab solver to investigate this problem numerically. The presence of radiation adds more stiffness and numerical complexity to the problem. A complete derivation in dimensionless form of the governing equations for momentum and energy is also included. A constant heat flux condition is applied at the left wall and a transient numerical solution is obtained for different values of the radiation parameter (R). The results are presented for dimensionless velocity, dimensionless temperature and Nusselt number for different values of the Prandtl number (Pr), Grashof number (Gr), and the radiation parameter (R). As expected, the results show that the convection heat transfer is high when the Nusselt number is high and the radiation parameter is low. It is also shown that the solution method used is simple and efficient and could be easily adopted to solve more complex problems.

2

Thermal performance enhancement of the mixed convection between two parallel plates by using triangular ribs

Jehhef K. A., Badawy F. A., Hussein A. A.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

11--30

EN

This paper aims to investigate the mixed convection between two parallel plates of a vertical channel, in the presence of a triangular rib. The non-stationary Navier-Stokes equations were solved numerically in a two-dimensional formulation for the low Reynolds number for the laminar air flow regime. Six triangular ribs heat-generating elements were located equidistantly on the heated wall. The ratio of the ribs to the channel width is varied (h / H = 0.1, 0.2, 0.3 and 0.4) to study the effect of ribs height effects, the ratio of the channel width to the ribs height is fixed constant at (H / w = 2) and the ratio of the channel height to the ribs pitch is fixed at (W/p=10). The influence of the Reynolds number that ranged from 68 to 340 and the Grashof number that ranged from 6.6 ×103 to 2.6 ×104 as well as the Richardson number chosen (1.4, 0.7, 0.4 and 0.2) is studied. The numerical results are summarized and presented as the profile of the Nusselt number, the coefficient of friction, and the thermal enhancement factor. The contribution of forced and free convection to the total heat transfer is analyzed. Similar and distinctive features of the behavior of the local and averaged heat transfer with the variation of thermal gas dynamic and geometric parameters are investigated in this paper. The results showed that the Nusselt number and friction factor increased by using the attached triangular ribs, especially when using the downstream ribs. Also, the results revealed that the Nusselt number increased by increasing the ratio of the ribs to the channel width.

3

Convective flow of hydromagnetic couple stress fluid with varying heating through vertical channel

Makhalemele C. R., Rundora L., Adesanya S. O.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

107--127

EN

This article addresses the impact of magnetic field induction on the buoyancy-induced oscillatory flow of couple stress fluid with varying heating. Modelled equations for the incompressible fluid are coupled and nonlinear due to the inclusion of viscous heating and thermal effect on the fluid density. Approximate solutions are constructed and coded on a symbolic package to ease the computational complexity. Graphical representations of the symbolic solutions are presented with detailed explanations. Results of the present computation show that the effect of induced magnetic field on the oscillatory flow and heat transfer is significant and cannot be neglected.

4

Effects of viscous dissipation and wall conduction on steady mixed convection Couette flow of heat generating / absorbing fluid

Ajibade A. O., Umar A. M.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 4

12--35

EN

This article theoretically investigated mixed convection flow of heat generating/absorbing fluid in the presence of viscous dissipation and wall conduction effects. The flow is considered to be steady in a vertical channel with some boundary thickness. One of the plates is heated while the other is kept at ambient temperature. The governing flow equations were solved analytically using Homotopy Perturbation Method (HPM). The influences of the governing parameters were captured in graphs, tables and a table was constructed for validation of the work. It is worthwhile to stress that, both the velocity and temperature profiles decrease near the heated plate with an increase in boundary thickness (d) while the reverse cases were observed toward the cold plate. The velocity profile increases near the heated plate with increase in mixed convection parameter (Gre) and decreases towards the cold plate. Rate of heat transfer has been observed to decrease with increase in boundary plate thickness (d) while the critical value of (Gre) increases with growing boundary plate thickness. The study therefore established the importance of boundary plate thickness in mixed convection investigation.

5

Theoretical studies of the ellipsoidal-shaped particles’ behaviourin the channel of pneumo-electric separator bumping into its walls

Kovalyshyn S., Dadak V.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

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2016

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Vol. 5, No 3

147--152

EN

It is widely known that during the post-harvest handling of a number of crops pneumatic separators are often used. It is proved that in order to improve separation process by using an air flow becomes possible through the use in the separation channels an electric field of corona discharge as additional working body. The electric field makes an additional force effect on the particles of the separated mixture. Since the seeds of cultivated plants and weeds belong to different species, their electrical properties interact with the working bodies of pneumatic separators in different ways that enables quality improvement of seed mixtures separation. We consider the ellipsoidal particles’ behaviour under the influence of gravity, electric power and air flow in pneumo-electric separator channel taking into account their bumping into the walls. We also worked out the differential equations that reflect the mathematical model of the particles under the totality of these forces. This model describes the movement of particles in the pneumo-electric separator channel and allows at any time to calculate the coordinates of trajectories. Based on their analysis we can explore the influence of the controlled process parameters on the pneumo-electric separation and determine their optimal parameters under which the separation of the investigated seed mixtures is the most effective and the components of which are of ellipsoid shape.

6

Microclimate in cattle barns with functional attic and roof ridge gap

Mazur K.

Journal of Research and Applications in Agricultural Engineering

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2014

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Vol. 59, nr 2

61--66

EN

The aim of this article to present of research results of microclimate parameters in barns with different gravitational ventilation systems and comparison of efficiency of these systems. Two tied-up and three loose-housing barns for dairy cows and one for beef cattle were researched. Tied-up barns had functional attic and duct ventilation, in barns with loose housing systems there were skylights with roof ridge gap. In stalls with ventilation by vertical channels there was not sufficient area of air inflow and outflow. The negative consequence of this was overcoming of recommended internal relative humidity of air (80%) in these stalls. In non-littered barns, with roof- ridge gap ventilation, temperature of air exceeded recommended values of 25oC. The luminance of daily light in stalls with functional attic was below of minimal level, which was described by standards (100 lx).

PL

Celem niniejszego artykułu jest przedstawienie wyników badań parametrów mikroklimatu w oborach z dwoma różnymi systemami wentylacji grawitacyjnej i porównanie skuteczności tych systemów. Zbadano po dwie obory stanowiskowe i wolnostanowiskowe dla krów mlecznych oraz jedną dla bydła mięsnego. Obory stanowiskowe posiadały poddasze użytkowe z wentylacją kanałową, natomiast w pozostałych oborach był świetlik ze szczeliną kalenicową. W oborach z wentylacją pionowymi kanałami nie była zapewniona odpowiednia powierzchnia nawiewu i wywiewu. Negatywnym tego skutkiem było przekroczenie zalecanych wartości wilgotności względnej powietrza (80%) w tych oborach. Temperatura w oborach bezściółkowych z wentylacją kalenicową przekraczała zalecane standardami wartości (25oC). Natężenie oświetlenia dziennego, w oborach z poddaszem użytkowym było poniżej minimalnego poziomu określonego standardami (100 lx).

7

Numerical Simulation of Turbulent Heat Transfer in a Vertical Channel with Discrete Heat Wall

Chesneau X., Zeghmati B., Abide S.

Machine Dynamics Research

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2012

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Vol. 36, No. 1

48-63

EN

Turbulent heat transfer in a vertical channel with discrete heat wall source has been studied numerically. Three different cases were tested according to the heated part of the channel wall. In the first case the flux is applied on the left wall and at the top and the bottom of the right wall separated by an adiabatic zone. The second case, the flux is applied on a zone located on the middle of the left wall and the flux conditions are identical to the first case and in the third case, the right wall is soaked with water. Transfer equations associated to the Launder and Sharma low Reynolds number k-s model are solved using the finite volume method, Thomas and Gauss algorithms. Effects of heat flux density and Reynolds numbers on velocity, air and wall temperature, eddy viscosity, Nusselt and Sherwood numbers were investigated. From these results the driven buoyancy flow for low Reynolds numbers and great Rayleigh numbers affects substantially transfers along the channel. The adiabatic zone influences substantially heat and mass transfer along the channel.

8

A 4th-Order Staggered Compact Finite Difference Method for the Three-Dimensional Incompressible Navier-Stokes Equations

Abide S., Chesneau X., Zeghmati B.

Machine Dynamics Research

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2011

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Vol. 35, No. 1

7-18

EN

The objective of this work is the developement and assessment of a fourth-order compact scheme for the three-dimensional unsteady incompressible viscous flows. The equations of the flow are discretized on a staggered grid and using fourth-order compact scheme for the three directions. The accuracy of the method is demonstrated in the Taylor-Green vortex problem. Finally, the turbulent natural convection in a vertical channel is investigated to validate the numerical methods.

9

Mixed convection flow of micropolar fluid in a vertical channel with symmetric and asymmetric wall heating conditions

Umavathi J. C., Prathap Kumar J.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

141-159

EN

The theory of micro polar fluids due to Eringen is used to formulate a set of equations for the mixed convective flow and heat transfer in a vertical channel. The two boundaries of the channel are kept either at equal or at different temperatures. Through a proper choice of non-dimensional variables and parameters, the governing equations are developed and three types of thermal boundary conditions are prescribed. These thermal boundaries are isothermal-isothermal, isoflux-isothermal and isothermal-isoflux for the left-right walls of the channel. Exact analytical solutions are obtained for the velocity and temperature fields for heat generation/absorption conditions. It is found that the material and source/sink parameters have significant effects on the flow. A parametric study is conducted and the results are presented and discussed. By making the Newtonian solvent more and more micropolar, it is possible to obtain drag reduction.

10

Magnetohydrodynamic fully developed combined convection flow between vertical plates heated asymmetrically

Ghosh S., Nandi D.

Journal of Technical Physics

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2000

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Vol. 41, no 2

173-185

EN

Magnetohydrodynamic (MHD) fully developed flow of a viscous incompressible electrically conducting fluid in a vertical channel during combined convection, with asymmetric heating of the wall, under the influence of a constant pressure gradient and in the presence of an uniform transverse magnetic field, is studied. Exact solution of the governing equation is obtained in a closed form. The solution in dimensionless form contains two pertinent flow parameters, viz. M (the Hartmann number) and Gr(the Grashof number). The limiting cases of a MHD forced and free convection are analyses, what has not beem done earlier in the literature. The occurrence of flow reversal indicates that there arises a flow reversal at the cold wall when r[sub T] = 1 while, for r[sub T] < 1, no flow reversal is possible in the absence of magnetic forces.