Papers by Keyword: Laminar Flow

Abstract: In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are compared for various cases. The value of the Reynolds number which the flow transits from steady to unsteady has been compared for the different cross sectional shapes.

Abstract: At the small town of Silsoe, UK , under the leadership of engineer Richards the model was made up with edge of the cube 6 m, used for research of wind on the model. Cube named Silsoe took over many laboratories in the world and diminished cube was tested in the wind tunnel. The aim of our study was to compare recently built the wind tunnel Faculty of Civil Engineering in Bratislava with other sites in the world. Suitable for this purpose served just cube model Silsoe of the edge of 200 mm, which was tested in the wind tunnel of Faculty of Civil Engineering and subsequently also in the workplace at VZLU Prague. The model coefficients were measured the pressure on the cladding of cube and compared with the other measurements. The test results are presented in this paper.

Abstract: Abstract-Flow over two offset square cylinders in a confined channel is simulated for different Reynoldsnumber to reveal the forced convection heat transfer from the heated square cylinders to the ambientfluid. The bottom of the cylinder is maintained at constant temperature. The distance between thecylinder in normal direction as well as transverse direction are fixed as 2d and the blockage ratio is fixedas 0.167. Heat transfer from the cylinders to the ambient fluid as well as conducted within solid wallthrough conjugate interface boundary investigated in connection with Reynolds number are reportedfor both steady and periodic flow. Simulation is carried out for Reynolds number varies from 10 to100 for the fluid as air with Prandtl number as 0.71. The isotherm contours, local Nusselt number andaverage Nusselt number are reported for various Reynolds number. The stagnation zone results higherNusselt number than remaining walls and rear wall results lowest Nusselt number. The downstreamcylinder results higher Nusselt number than the upstream cylinder. The top and bottom surfaceNusselt number from upstream and downstream cylinder are not analogous to single cylinder placed ina channel.

Abstract: In the present numerical investigation, the flow field of confined slot air jet in a rectangular computational domain is reported. In the present work the flow field parameters like reattachment length, vortex center and horizontal velocity profiles for various Reynolds numbers and for various aspect ratios are presented .The present study reveals that the vortex centers are moving in a downstream direction with increase in Reynolds number. The reattachment length is directly dependent on the Reynolds numbers. In case of vortex dynamics, the vortex size is indirectly dependent on the inlet jet width. In the present investigation, SIMPLE algorithm is used to solve the governing equations. It is concluded that the aspect ratio and the Reynolds number are playing dominant roles in flow field of the present computational domain.

Abstract: This paper presents the numerical studies of an irregular surface – a circular dimpled surface with different patterns of dimple arrangement (i.e., inline and staggered) and to identify the one that gives maximum heat transfer rate under laminar flow conditions. The comparative studies are made with a flat plate. The studies are carried out with inlet velocities 1 m/s and 49 m/s at laminar flow regimes. The investigations revealed that heat transfer rate increases as the air flow velocity increases and it decreases as the air flow velocity is decreased. Also, air flow contact with heated plate plays a vital role in heat transfer rate. Based on the study, it is concluded that the heat transfer rate depends on the surface area, air flow velocity and the air flow contact with the heated plate. At air velocities 1 m/s and 49 m/s, the heat transfer rate is highest for the circular dimple with staggered pattern under the laminar flow conditions.

Abstract: This study examines the design of heat exchanger made of copper tube for cooling electric vehicle car battery system and the effects of base fluid and nanofluid (as coolants) channeling inside the heat exchanger to increase heat transfer between the compartment of the electric vehicle car and the heat exchanger and comparison between them. The nanofluid (CuO/pure water) was prepared by dispersing a nanoparticle (CuO) in base fluid (pure water). nanofluid (CuO/pure water) with a nominal diameter of 50 nm at volume concentrations (0.27 Vol. %) at batteries’ compartment temperature was used for these investigations. The analysis showed that secondary cooling system by means of nanofluid (CuO/pure water) has advantages in improving the thermal conductivity and heat transfer coefficient, better from base fluid (pure water) also in Nusselt number. This results work on reducing the electric power loss in the form of thermal energy from batteries. This led to increase in the efficiency of the electric vehicle car battery, hence also improved the performance of the EV car and battery lifetime.

Abstract: In the present paper, we have described in-depth numerical study of the basic fluid mechanics problem of yield stress fluid flow with regularization model of Berovier and Engelman in a cylindrical vessel not chicaned equipped with an anchor stirrer by using computational fluid dynamics (CFD) based on the finite volumes method discretization of Navier - Stokes equations formulated in variables (U.V.P). We study the effect of inertia and the yield stress influence by the variation of Hedström number on the flow; we have analyzed also the influence of rheological parameters on the hydrodynamic flow behavior, such as the velocity components and the power consumption.

Abstract: Mixing is one of the important processes to the many industries. Fluid mixing process typically involves three phases of fluid in the form of liquids, gases and solids. To obtain a desired type of mixing, one of the devices that can be use is a static mixer. In this study, a perforated plate static mixer with circle grid fractal design with two grades of porosity which are 50% and 75% will introduce. The purpose of implementing the two grades porosity of perforated plate in this study is to determine a performance of the two static mixers. In order to achieve the objective, the simulations of mixing fluid were carried out by using ANSYS CFX software. The simulation was carrying out primarily in cylindrical pipe with insertions of circle grid perforated plate. Three levels of laminar flow had been used which is Reynolds numbers (Re) equal to 100, 200 and 400. The performance of circle grid perforated plate static mixer will be evaluated by determining the Coefficient of Variation (COV). The simulation results also were compared in term of homogeneity level of mixing fluids to the Kenics static mixer. Based on the simulation results, the value of COV at selected plane in pipeline simulated for Kenics static mixer and the two grades porosity of perforated plate at Re = 400 are 0.000703, 0.0247and 0.00427 respectively. Since the values of COV between 0.01 and 0.05 are a reasonable target for many industry applications, the results for new approach of static mixer represent completely homogeneous mixing fluid for this application. Definitely this new approach of circle grid perforated plate with fractal design gave better results because of lower number of inserts and simple design of static mixer.

Abstract: To investigate the influence of the roughness characteristics of the metallic gasket on the gas leakage rate, a mathematical model of a rough surface based on the Gauss distribution function and exponential auto-correlation function was built. According to this model, a 3D geometrical model of a sealing clearance with two rough surfaces was configured. Effect of the roughness parameters on the gas sealing performance was numerical analyzed, and through the comparison with the classical smooth parallel plate leakage model, the relationship between the leakage rate and the roughness parameters of the sealing surfaces was built. Furthermore, the relationship between contact pressure and the leakage rate for the different roughness surfaces was studied based on the current model. The results show the methodology proposed in current work is effective in predicting the actual sealing performance of static seal structure.

Abstract: Based on the critical condition of fire liftoff about exhaust flow, the critical condition of fire liftoff caused by man-made interfering jet flow on the laminar flow condition was researched. The calculative formula for critical condition of fire liftoff caused by man-made interfering jet flow on the laminar flow condition was acquired. And the experiments were designed to validate the formula. The results show that the formula was accord with the experiments. It could be used for engineering application.