This paper examines the effects of thermal buoyancy on momentum and heat transfer characteristics of symmetrically and asymmetrically confined cylinder submerged in incompressible Poiseuille liquid. The detailed flow and temperature fields are visualized in term of streamlines and isotherm contours. The numerical results have been presented and discussed for the range of conditions as 10 ≤ Re ≤ ≤ 40, Richardson number 0 ≤ Ri ≤ 4, and eccentricity factor 0 ≤ ε ≤ 0.7 at Prandtl number Pr = 1, and blockage ratio B = 20%. The representative streamlines and isotherm patterns are presented to interpret the flow and thermal transport visualization. When the buoyancy is added, it is observed that the flow separation diminishes gradually and at some critical value of the thermal buoyancy parameter it completely disappears resulting a creeping flow. Additionally, it is observed that the down vortex requires more heating in comparison to upper vortex in order to be suppressed. In the range 1.5 ≤ Ri ≤ 4, two counter rotating regions appear above the cylinder and on the down channel wall behind the cylinder. The total drag coefficient, C D , increases with increasing Richardson number at (ε = 0). Moreover, an increase in eccentricity factor from 0 to 0.3 increases C D by 37% at Re = 10, and 30% at Re = 20 for Ri = 4. An increase in eccentricity factor form 0 to 0.4 increases local Nusselt number by 20.4% at Re = 10, and 18.6% at Re = 30 for Ri = 4.

Knowledge of the fluid dynamic characteristics in a stirred vessel is essential for reliable design and scale-up of a mixing system. In this paper, 3D hydrodynamics in a vessel agitated by a Rushton turbine were numerically studied (with the help of a CFD computer program (CFX 13.0)). The study was carried out covering a wide Reynolds number range: 10 4 -10 5 . Computations, based on control volume method, were made using the k-ε model. Our main purpose was to investigate the effect of vessel configuration and agitation rates on the flow structure and power consumption. Three types of vessels were used: unbaffled, baffled and a vessel with slots placed at the external perimeter of its vertical wall. The effect of slot length has been investigated. The comparison of our predicted results with available experimental data shows a satisfactory agreement.

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In this paper, three-dimensional numerical simulations are carried out to investigate and analyze the gradual effects of thermal buoyancy strength on laminar flow of an incompressible viscous fluid and heat transfer rate inside a 180° curved channel of square cross-section. The governing equations of continuity, momentum and energy balance are obtained and solved numerically using finite volume method. The effect of Dean number, De, and Richardson number, Ri, on dimensionless velocity profiles and Nusselt number are examined for the conditions: De = 125 to 150, Ri = 0 to 2 at Pr = 1. The mean results are illustrated in terms of streamline and isotherm contours to interpret the flow behaviors and its effect on heat transfer rate. Dimensionless velocity profiles and the local Nusselt number at the angle 0° and 90° are presented and discussed. Also, the average Nusselt number on surfaces of curved duct is computed. The obtained results showed that by adding thermal buoyancy to computed domain, some early Dean vortices are observed at the angle 0° and new sort are observed at 90°. Furthermore, increase in Dean number increases the heat transfer rate. In other hand, increase in Richardson number decreases the average Nusselt number of 180° curved duct.

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Realizing the growing importance and availability of motor vehicles, we observe that the main source of pollution in the street canyons comes from the dispersion of automobile engine exhaust gas. It represents a substantial effect on the micro-climate conditions in urban areas. Seven idealized-2D building configurations are investigated by numerical simulations. The turbulent Schmidt number is introduced in the pollutant transport equation in order the take into account the proportion between the rate of momentum turbulent transport and the mass turbulent transport by diffusion. In the present paper, we attempt to approach the experimental test results by adjusting the values of turbulent Schmidt number to its corresponding application. It was with interest that we established this link for achieving our objectives, since the numerical results agree well with the experimental ones. The CFD code ANSYS CFX, the k, e and the RNGk-e models of turbulence have been adopted for the resolutions. From the simulation results, the turbulent Schmidt number is a range of 0.1 to 1.3 that has some effect on the prediction of pollutant dispersion in the street canyons. In the case of a flat roof canyon configuration (case: runa000), appropriate turbulent Schmidt number of 0.6 is estimated using the k-epsilon model and of 0.5 using the RNG k-e model.