Documents published in Scipedia

• Hydromagnetic double-diffusive mixed convection in trapezoidal enclosure due to uniform and nonuniform heating at the bottom side: Effect of Lewis number

  M. Uddin, M. Rahman, M. Khan, R. Saidur, T. Ibrahim

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  This paper presents unsteady numerical results of double diffusive mixed convection flow in a trapezoidal enclosure with the uniform magnetic field effect applied in negative horizontal direction. At the bottom wall, the uniform and non-uniform heat and mass are applied while the heat and mass absorbed uniformly at the top wall. Other side walls are impermeable and adiabatic. The top wall moves along x-axis direction with a constant velocity. The transport phenomenon of this problem can be expressed by the coupled governing equation derived from the conservation of mass and momentum along with the energy equation for temperature and concentration. The finite element method (FEM) based on Galerkin weighted residual technique is used to compute the numerical result from these governing equations. The numerical computation is carried out for Lewis number (Le = 0.1–50) and Richardson’s number (Ri = 0.1–100). Computed numerical results of mass, temperature and velocity distribution are expressed graphically as iso-concentration lines, isotherm lines and streamlines respectively. Average Sherwood and Nusselt number values are used to show the mass and heat transfer rate from the heated and concentrated surface of the enclosure. It is found from the analysis that mass transfer strongly depends on Lewis number. Heat and mass transfer for uniformly heated and concentrated bottom wall is larger than the non-uniformly heated and concentrated bottom wall. Finally, a correlation has been done for average Nusselt and Sherwood numbers for both of the cases.

  Abstract
  This paper presents unsteady numerical results of double diffusive mixed convection flow in a trapezoidal enclosure with the uniform magnetic field effect applied in negative [...]

  • 0
  •  read

• Simultaneous effects of slip and MHD on peristaltic blood flow of Jeffrey fluid model through a porous medium

  M. Bhatti, M. Abbas

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  In this article, the simultaneous effects of slip and Magnetohydrodynamics (MHD) on peristaltic blood flow of Jeffrey fluid model have been investigated in a non-uniform porous channel. The governing equation of blood flow for Jeffrey fluid model is solved with the help of long wavelength and creeping flow regime. The solution of the resulting differential equation is solved analytically and a closed form solution is presented. The impact of all the physical parameters is plotted for velocity profile and pressure rise. Nowadays, Magnetohydrodynamics is applicable in various magnetic drug targeting for cancer diseases and also very helpful to control the flow. The present analysis is also described for Newtonian fluid (λ1→0)(λ1→0) as a special case of our study. It is observed that magnitude of the velocity is opposite near the walls due to slip effects whereas similar behavior has been observed for magnetic field.

  Abstract
  In this article, the simultaneous effects of slip and Magnetohydrodynamics (MHD) on peristaltic blood flow of Jeffrey fluid model have been investigated in a non-uniform porous [...]

  • 0
  •  read

• Exact solution for thermal boundary layer in Casson fluid flow over permeable shrinking sheet with variable wall temperature and thermal radiation

  K. Bhattacharyya, M. Uddin, G. Layek

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  An analysis of thermal boundary layer in the flow of Casson fluid over a permeable shrinking sheet with variable wall temperature and thermal radiation is made. Using similarity transformations, self-similar nonlinear ODEs are obtained from the governing equations. Dual exact solutions of transformed velocity and energy equations are obtained. From the plotted results it can be observed that the temperature inside the boundary layer decreases with Casson parameter and wall mass transfer parameter in first solution and it increases in second solution. Whereas, temperature decreases for larger values of Prandtl number, radiation parameter and power-law exponent for inverse variation along the sheet in both solutions and it enhances with power-law exponent for direct variation along the surface. Also, thermal boundary layer thickness reduces with stronger thermal radiation and inverse variation of wall temperature along the surface and it becomes thicker with direct variation of wall temperature. The rate of heat transfer is less with increasing values of power-law exponent for direct variation along the sheet and for inverse variation it is higher. In graphical representation of temperature field, temperature overshoot is observed in certain cases. So, in some situations heat absorption at surface occurs instead of heat transfer from surface.

  Abstract
  An analysis of thermal boundary layer in the flow of Casson fluid over a permeable shrinking sheet with variable wall temperature and thermal radiation is made. Using similarity [...]

  • 0
  •  read

• A numerical parametric study of mechanical behavior of dry contact slipping on the disc–pads interface

  A. Belhocine, W. Omar

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The aim of this contribution was to present a study based on the determination and the visualization of the structural deformations due to the contact of slipping between the disc and the pads. The results of the calculations of the contact described in this work relate to displacements, Von Mises stress on the disc, and contact pressures on the inner and outer pad at various moments of simulation. We first proceed to view the meshed models and predicting variations of tensile or compressive stress normal to the plane and shear stress in rotating disc and ring bodies. One precedes then the influence of some parameters on the computation results such as rotation of the disc, the smoothness of the mesh, the material of the brake pads and the friction coefficient entering the disc and the pads, the number of revolutions and the material of the disc, the pad groove.

  Abstract
  The aim of this contribution was to present a study based on the determination and the visualization of the structural deformations due to the contact of slipping between [...]

  • 0
  •  read

• Dual-well potential field function for articulated manipulator trajectory planning

  A. Badawy

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  A new attractive potential field function is proposed in this paper for manipulator trajectory planning. Existing attractive potential field constructs a global minimum through which maneuvering objects move down the gradient of the potential field toward this global minimum. The proposed method constructs a potential field with two minima. The purpose of these two minima is to create a dual attraction between links rather than affecting each link by the preceding one through kinematic constraints.

  Abstract
  A new attractive potential field function is proposed in this paper for manipulator trajectory planning. Existing attractive potential field constructs a global minimum through [...]

  • 0
  •  read

• Exploring delay causes of road construction projects in Egypt

  R. Aziz, A. Abdel-Hakam

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  Construction delays are a common phenomenon in civil engineering projects in Egypt including road construction projects. Therefore, it is essential to study and analyze causes of road construction delays. This paper studied a list of construction delay causes gathered from literature having different types of construction, different countries, different periods and different numbers of delay causes and delay groups. A questionnaire and personal interviews have formed the basis of this paper listing 293 delay causes. The questionnaire survey was distributed to 500 construction participants and 389 were received who represent consultants, contractors and site/design engineers excluding the owner representing the government in road projects as one party only. Relative Importance Index (RII) is calculated and according to the highest values the top twenty and the least twenty delay causes of construction projects in Egypt are determined. A case study is analyzed and compared to the most important delay causes in the paper. The test results reveal good correlation of causes and groups between contractors and site/design engineers and between consultants and site design engineers and a somewhat low correlation between contractors and consultants. So there are no root causes that can be taking for granted to be most or least effective delay causes. Proposed model for predicting actual road construction project duration was developed, a real case study tested the accuracy of proposed model. According to the analysis of case study, the most contributing causes and groups to delays were discussed, and some future recommendations were proposed in order to control and minimize delays in road construction projects. These findings can be helpful for project managers to mitigate the road construction delays in Egypt. In order to effectively overcome the road construction delays in developing countries, suggestions are made for fundamental and large‐scale reforms in procurement systems and stakeholders’ management. Also, this paper is useful for both researchers and road construction parties and allows detailed and repeatable analysis of the progress of a road construction project in order to facilitate and achieve a competitive level of time, cost and quality for effective road construction projects.

  Abstract
  Construction delays are a common phenomenon in civil engineering projects in Egypt including road construction projects. Therefore, it is essential to study and analyze causes [...]

  • 0
  •  read

• Effect of partial slip on an unsteady MHD mixed convection stagnation-point flow of a micropolar fluid towards a permeable shrinking sheet

  . Aurangzaib, K. Bhattacharyya, S. Shafie

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The objective of the present study was to investigate the partial slip effect on an unsteady two-dimensional mixed convection stagnation point flow towards a permeable shrinking sheet. The governing equations are reduced to a system of non-dimensional partial differential equations using a semi-similarity transformation, before being solved numerically by using Keller-box method. The features of the flow characteristics for different values of the governing parameters are analysed and discussed. The results indicate that the momentum, thermal and concentration boundary layer thicknesses increase with increasing mixed convection parameter for opposing flow, whereas the opposite effect is observed for assisting flow. The results also show that the surface velocity is higher when there is slip at a sheet compared to its absent. Further, the study indicates that the boundary layer thicknesses become thicker and thicker with increasing shrinking parameter, while the opposite effect is observed with increasing Hartmann number. Comparison with previously published work for special cases is performed and found to be in excellent agreement.

  Abstract
  The objective of the present study was to investigate the partial slip effect on an unsteady two-dimensional mixed convection stagnation point flow towards a permeable shrinking [...]

  • 0
  •  read

• Drag on a slip spherical particle moving in a couple stress fluid

  E. Ashmawy

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The creeping motion of a rigid slip sphere in an unbounded couple stress fluid is investigated. The linear slip boundary condition and the vanishing couple stress condition are applied on the surface of the sphere. A simple formula for the drag force acting on a slip sphere translating in an unbounded couple stress fluid is obtained. Special cases of the deduced drag formula are concluded and compared with analogous results in the literature. The normalized drag force experienced by the fluid on the slip sphere is represented graphically and the effects of slip parameter and viscosity coefficients are discussed.

  Abstract
  The creeping motion of a rigid slip sphere in an unbounded couple stress fluid is investigated. The linear slip boundary condition and the vanishing couple stress condition [...]

  • 0
  •  read

• Unequal diffusivities case of homogeneous–heterogeneous reactions within viscoelastic fluid flow in the presence of induced magnetic-field and nonlinear thermal radiation

  I. Animasaun, C. Raju, N. Sandeep

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  This article presents the effects of nonlinear thermal radiation and induced magnetic field on viscoelastic fluid flow toward a stagnation point. It is assumed that there exists a kind of chemical reaction between chemical species A and B. The diffusion coefficients of the two chemical species in the viscoelastic fluid flow are unequal. Since chemical species B is a catalyst at the horizontal surface, hence homogeneous and heterogeneous schemes are of the isothermal cubic autocatalytic reaction and first order reaction respectively. The transformed governing equations are solved numerically using Runge–Kutta integration scheme along with Newton’s method. Good agreement is obtained between present and published numerical results for a limiting case. The influence of some pertinent parameters on skin friction coefficient, local heat transfer rate, together with velocity, induced magnetic field, temperature, and concentration profiles is illustrated graphically and discussed. Based on all of these assumptions, results indicate that the effects of induced magnetic and viscoelastic parameters on velocity, transverse velocity and velocity of induced magnetic field are almost the same but opposite in nature. The strength of heterogeneous reaction parameter is very helpful to reduce the concentration of bulk fluid and increase the concentration of catalyst at the surface.

  Abstract
  This article presents the effects of nonlinear thermal radiation and induced magnetic field on viscoelastic fluid flow toward a stagnation point. It is assumed that there [...]

  • 0
  •  read

• MHD flow and heat transfer of couple stress fluid over an oscillatory stretching sheet with heat source/sink in porous medium

  N. Ali, S. Khan, M. Sajid, Z. Abbas

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  This article presents the MHD flow and heat transfer of a couple stress fluid over oscillatory stretching sheet embedded in a porous medium in the presence of heat source/sink. The unsteady flow problem is reduced to two coupled partial differential equations using dimensionless variables. Homotopy analysis method is employed to obtain the solution of these equations. Based on the solution of these equations an extensive analysis is performed to investigate the effects of various flow parameters on velocity and temperature fields, skin friction coefficient and Nusselt number. It is found that the presence of couple stress in viscous fluid increases the amplitude of oscillations in velocity and skin friction coefficient. It is also noticed that temperature increases by increasing heat source parameter. Moreover, the numerical values of local Nusselt number are calculated and shown in tabular form. It is found that the Nusselt number increases by increasing Prandtl number while it decreases by increasing couple stress parameter.

  Abstract
  This article presents the MHD flow and heat transfer of a couple stress fluid over oscillatory stretching sheet embedded in a porous medium in the presence of heat source/sink. [...]

  • 0
  •  read