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Papers by Mohamed Ridouane

Heat and Mass Transfer, 2006

Coupled laminar natural convection with radiation in air-filled square enclosure heated from belo... more Coupled laminar natural convection with radiation in air-filled square enclosure heated from below and cooled from above is studied numerically for a wide variety of radiative boundary conditions at the sidewalls. A numerical model based on the finite difference method was used for the solution of mass, momentum and energy equations. The surface-to-surface method was used to calculate the radiative heat transfer. Simulations were performed for two values of the emissivities of the active and insulated walls (ɛ1=0.05 or 0.85, ɛ2=0.05 or 0.85) and Rayleigh numbers ranging from 103 to 2.3×106 . The influence of those parameters on the flow and temperature patterns and heat transfer rates are analyzed and discussed for different steady-state solutions. The existing ranges of these solutions are reported for the four different cases considered. It is founded that, for a fixed Ra, the global heat transfer across the enclosure depends only on the magnitude of the emissivity of the active walls. The oscillatory behavior, characterizing the unsteady-state solutions during the transitions from bicellular flows to the unicellular flow are observed and discussed.

International Journal of Numerical Methods for Heat & Fluid Flow, 2006

Purpose – The aim of this work consists of studying numerically the coupling between natural conv... more Purpose – The aim of this work consists of studying numerically the coupling between natural convection and radiation in a tall rectangular cavity by examining the effect of the emissivity of the walls, ɛ, the Rayleigh number, Ra, and the inclination of the cavity, , on the flow characteristics and the existence ranges of the multiple solutions obtained. Design/methodology/approach –

International Journal of Heat and Fluid Flow, 2006

This paper addresses turbulent natural convection of air confined in an isosceles triangular encl... more This paper addresses turbulent natural convection of air confined in an isosceles triangular enclosure representing conventional attic spaces of houses and buildings with pitched roofs and horizontally suspended ceilings. The values to be considered are H = 0.86 m and 2.73 m for the height while the values 1.72 m and 5.46 m were assigned to the width, W, such as the aspect ratio H/W remains 0.5. The third dimension of the cavity is considered long enough for the flow to be considered 2D. The base wall is heated at 20°C and the inclined walls are cooled at 0°C. This combination of factors leads to large Rayleigh numbers equal to 1.58 · 10 9 and 5 · 10 10 . Turbulence is modeled by a low-Reynolds-number k-e model. The system of governing equations, subject to the proper boundary conditions is solved with the finite volume method. Second-order-accurate QUICK and SIMPLE schemes were used for the discretization of the convective terms and the pressure-velocity coupling, respectively. The velocity and temperature distributions were calculated at different locations in the cavity and their mean quantities are presented. The local and average Nusselt numbers and the wall shear stresses are also presented. Since to the knowledge of the authors, no previous results on turbulent thermal convection in this geometry exist, the validation of the numerical code was performed by comparing velocity and temperature profiles against recent experimental measurements, obtained for a square cavity. Satisfactory agreement was observed.

Journal of The Saudi Pharmaceutical Society

The analytical transfer is a complete process that consists in transferring an analytical procedu... more The analytical transfer is a complete process that consists in transferring an analytical procedure from a sending laboratory to a receiving laboratory. After having experimentally demonstrated that also masters the procedure in order to avoid problems in the future. Method of transfers is now commonplace during the life cycle of analytical method in the pharmaceutical industry. No official guideline exists for a transfer methodology in pharmaceutical analysis and the regulatory word of transfer is more ambiguous than for validation. Therefore, in this study, Gauge repeatability and reproducibility (R&R) studies associated with other multivariate statistics appropriates were successfully applied for the transfer of the dissolution test of diclofenac sodium as a case study from a sending laboratory A (accredited laboratory) to a receiving laboratory B. The HPLC method for the determination of the percent release of diclofenac sodium in solid pharmaceutical forms (one is the discovered product and another generic) was validated using accuracy profile (total error) in the sender laboratory A. The results showed that the receiver laboratory B masters the test dissolution process, using the same HPLC analytical procedure developed in laboratory A. In conclusion, if the sender used the total error to validate its analytical method, dissolution test can be successfully transferred without mastering the analytical method validation by receiving laboratory B and the pharmaceutical analysis method state should be maintained to ensure the same reliable results in the receiving laboratory.

Journal of Thermophysics and Heat Transfer, 2007

ABSTRACT The present paper investigates a promising avenue for the intensification of turbulent f... more ABSTRACT The present paper investigates a promising avenue for the intensification of turbulent free convection in square cavities using an adequate selection of binary gas mixtures. Five binary gas mixtures have considered helium (He) as the primary gas component and carbon dioxide (CO2), methane (CH4), nitrogen (N-2), oxygen (O-2), and xenon (Xe) the secondary gas components. In the thermodynamic context, the thermophysical properties viscosity, thermal conductivity, density, and isobaric heat capacity depend on three quantities: temperature, pressure, and molar gas composition. The finite volume method is the vehicle used to perform the numerical calculations of the enlarged set of conservation equations, wherein turbulence is modeled with a low-Reynolds k-epsilon model. The turbulent velocity and temperature fields for each binary gas mixture and air were calculated at different locations in the cavity and presented in terms of streamlines and isotherms for Ra = 2 x 10(9). The results culminate with the allied convective coefficient h(m)/B varying with the molar gas composition w in the w domain [0, 1] for each binary gas mixture. Values of the maximum allied convective coefficients h(m,max)/B attained at the correlative optimal molar gas compositions w(opt) are easily extracted from a graphical display.

Numerical Heat Transfer Part A-applications, 2006

This article addresses buoyant air circulation inside attic spaces of houses and buildings with s... more This article addresses buoyant air circulation inside attic spaces of houses and buildings with sloped roofs and horizontally suspended ceilings. Depending on the season of the year, two different heating/cooling scenarios may occur. In order to counteract the excessive heat transmission that takes place during the winter and summer seasons, heavily insulated, vertical side walls of variable height h are placed at the hot/cold intersection between the active walls. As a result, the shape of the enclosure switches from an isosceles triangular enclosure to a trapezoidal enclosure, but having two insulated side walls. The finite-volume method is employed to perform the numerical computations.

Numerical Heat Transfer Part A-applications, 2004

The radiation effect of gray surfaces on multiple steady-state solutions obtained in a square enc... more The radiation effect of gray surfaces on multiple steady-state solutions obtained in a square enclosure filled with air has been investigated numerically, by a finite-difference procedure. The bottom and top surfaces of the cavity are, respectively, heated and cooled at constant temperatures, while its vertical walls are adiabatic. Parameters of the problem are the Rayleigh number (10 3 Ra 2:5 Â 10 6 ) and the surface emissivity (0 e 1). The results obtained show that surface radiation alters significantly the existence range of the solution and the average heat transfer through the horizontal walls of the cavity. The parameter e is found to reduce considerably the critical Rayleigh number characterizing the transition toward the oscillatory convection.

Journal of Heat Transfer-transactions of The Asme, 2006