Abstract: 2D simulation is carried out to determine exactly the effect of blockage ratio on the flow and mixed convection heat transfer characteristics of Newtonian fluid across a square cylinder confined in horizontal channel, the numerical study is investigated in the range of these conditions: Re = 10 to 30, Ri = 0 to 1 and blockage ratio β = 1/10 to 1/2. The flow structure and temperature field are visualized in terms of streamlines and isotherm contours. The total drag coefficient and average Nusselt number are also reported to show the combined effects of thermal buoyancy, Reynolds number and blockage ratio on the hydrodynamic flow forces and heat transfer rate. The obtained results showed that the effect of thermal buoyancy on fluid flow and heat transfer becomes more pronounced by decreasing the blockage ratio.
Abstract: In this paper, we numerically examine the mixed convective flow around a confined tandem heated circular cylinders embedded in a vertical channel in order to determine exactly the effects of opposing thermal buoyancy and distance between cylinders (S) on the behavior of fluid flow and heat transfer rate. The dimensionless governing equations involving momentum, continuity and energy are obtained and solved in a steady laminar flow regime for the conditions: Re = 5 to 40 and S = 0 to 5d, at fixed values of Prandtl number Pr = 1, Richardson number Ri = 1 and blockage ratio β = 1/5. The fluid flow and temperature field are illustrated in terms of streamline and isotherm contours. The average Nusselt number is also computed to quantify the effect of fluid flow and heat transfer characteristics on amount of heat transfer rate.
Abstract: 2D simulations of incompressible fluid in plan channel of waved bottom wall is carried out in this paper to understand and to determine correctly the effects of the Reynolds, Prandtl and Richardson numbers on the fluid flow and heat transfer of waved channel wall. The governing equations involving continuity, momentum and energy are solved numerically based on commercial code which called ANSYS-CFX. The results are presented and discussed for the range of following conditions as: Re = 60 to 250, Pr = 0.7 to 30, Ri = 0 to 1 at fixed value of blockage ratio. The numerical results showed that increase in Richardson number and/ or Prantl number For Reynolds number limited between 60 and 200 increases tightly the heat transfer rate. For the value 250 of Reynolds number increase in the buoyancy strength reduces the value of heat transfer rate.
Abstract: Film cooling is vital for gas turbine blades to protect them from thermal stresses and high temperatures due to the hot gas flow in the blade surface. Film cooling is applied to almost all external surfaces associated with aerodynamic profiles that are exposed to hot combustion gases such as main bodies, end-walls, blade tips and leading edges. In a review of the literature, it was found that there are strong effects of free-stream turbulence, surface curvature and hole shape on film cooling performance also blowing ratio. The performance of the film cooling is difficult to predict due to the inherent complex flow fields along the surfaces of the airfoil components in the turbine engines. From all what we introducing the film cooling is reviewed through a discussion of the analyses methodologies, a physical description, and the various influences on film-cooling performance. Initially Computational analysis was done on a flat plate with hole inclined at 55° to the surface plate. This study focuses on the efficient computation of film cooling flows with three blowing ratio. The numerical results show the effectiveness cooling and heat transfer behavior with increasing injection blowing ratio M (0.5, 1, and 1.5). The influence of increased blade film cooling can be assessed via the values of Nusselt number in terms of reduced heat transfer to the blade. Predictions of film effectiveness are compared with experimental results for a circular jet at blowing ratios ranging from 0.5, 1.0 and 1.5. The present results are obtained at a free stream turbulence of 10%, which are the typical conditions upstream of the effectiveness is generally lower for a large stream-wise angle of 55°.
Abstract: This paper presents a comprehensive computational work on hydrodynamic and thermal phenomena of upward flow separation around a confined circular cylinder by aiding/opposing thermal buoyancy. For that purpose, let us consider a confined flow of Non-Newtonian power-law fluid around a heated/cooled circular cylinder in a two-dimensional vertical channel. The effects of thermal buoyancy and power-Law index on the flow separation and the average Nusselt number are studied for the conditions: (10 ≤ Re ≤ 40), (0.4≤ n ≤ 1.2), (-0.5 ≤ Ri ≤ 0.8), Pr = 50 and blockage ratio β = 0.2. In the steady flow regime the results show that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to grow. The adding buoyancy effect delays the separation in different power-law indices gradually and at some critical value of the buoyancy parameter it completely disappears resulting a stuck flow around a cylinder, whereas the opposing buoyancy effect causes an earlier wake behind cylinder. Moreover, the recirculation length is calculated to support the above finding. The decrease in the power-Law index increases the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the aiding/opposing thermal buoyancy condition.
Abstract: In order to improve the cooling effectiveness of the film, a numerical study was conducted to study the effects of different film-cooled angles on surface heat transfer. In this work CFD simulation has revealed the difference of injection angles ranging from 35°,45°,55°,65° and 90° with different blowing, where the low blowing ratios are represented by M = 0.5, and the high blowing ratios by M = 1.0 and 1.5. And the turbulence closure is done with the help of the k - ω shear stress transport (SST) turbulence model. It is found that the stream-wise variations in the angles of the holes do not really provide a significant change in the adiabatic film cooling effectiveness results. On the other hand, the results indicate that the hole of angles 35°and 45° improved the centerline and laterally averaged adiabatic effectiveness, and the effectiveness decrease particularly at high blowing ratios.
Abstract: This paper examines the effects of thermal buoyancy on momentum and heat transfer characteristics of confined square cylinder submerged in incompressible power-law fluid. The detailed flow and temperature fields are visualized in terms 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 ≤ 1), and power-law index (0.4 ≤ n ≤ 1.2) at Prandtl number Pr = 50, at fixed value of blockage ratio β = 25%. The results showed that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to diminish for the value Re = 40. The thermal buoyancy delays the flow separation in different power-law indexes gradually and at some critical value of the buoyancy parameter it completely disappears resulting a creeping flow around a cylinder. Moreover, the recirculation length and skin friction are calculated to support the above finding. The decrease in the power-Law index promotes the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the superimposed thermal buoyancy condition.
Abstract: This paper deals with a numerical investigation in order to predict correctly the combined effects of aiding thermal buoyancy and rheological flow behavior of power-law fluids on downward flow and heat transfer rate inside of 180° curved duct. The governing equations involving the momentum, continuity and the energy are solved in two-dimensions using the package called ANSYS-CFX. The computational results are depicted and discussed for the range of conditions as: Re = 40 to 1000, Ri = 0 to-1 and n = 0.4 to 1.2 at fixed value of Prandt number of Pr = 1. To interpret the found results, the flow structure and temperature field are shown in form of streamlines and isotherm contours. The average Nusselt number of the inner and outer walls of curved channel is calculated to determine the role of Reynolds number, Richardson number and power-law index. It is found that increase in strength of aiding buoyancy creates a counter rotating region in angle of 90 degrees of the duct.
Abstract: In this study, we addressed the impact of magnetic field on fluid flow and heat transfer of an in compressible Carreau fluid over exponentially stretching sheet in addition with fluid and dust particle suspension. Thermal radiation and non-uniform heat source/sink were included to develop heat transport phenomena. Dusty fluids have various applications such as processing of material, nuclear heat treatment, cooling process, treatment of waste water etc. The relevant governing equations are converted into ordinary differential equation using similarity transformation the transformed ordinary differential equations are then solved numerically by shooting technique along with Runge-Kutta method The effect of certain parameters on the dimensionless velocity and temperature are presented graphically. The physical quantities of the flow such as the friction factor and Local Nusselt number were calculated. It was found from the study that the velocity slip parameter increases the temperature profiles.