Papers by Keyword: Square Cylinder

Abstract: In this paper, the numerical simulations of laminar mixed convection heat transfer from row of three isothermal square cylinders placed in side-by-side arrangement are carried out to understand the behavior of fluid flow around those cylinders under gradual effect of thermal buoyancy and its effect on the evacuation of heat energy. The numerical results are presented and discussed for the range of these conditions: Re = 10 to 40, Ri = 0 to 2 at fixed value of Prandtl number of Pr = 1 and at fixed geometrical configuration. In order to analyze the effect of thermal buoyancy on fluid flow and heat transfer characteristics the main results are illustrated in terms of streamline and isotherm contours. The total drag coefficient as well as average Nusselt number of each cylinder are also computed to determine exactly the effect of buoyancy strength on hydrodynamic force and heat transfer evacuation of each cylinder.

Abstract: This work deals with the effect of thermal buoyancy on momentum and heat transfer characteristics of confined square cylinder submerged in Non Newtonian shear-thinning fluids. In two-dimension, the governing equations are solved by using the commercial code ANSYS-CFX. The effects of thermal buoyancy and power-law index, n, on the non-dimensional Drag coefficient and Nusselt number are studied for the conditions: Ri = 0 to 1, n = 0.3 to 0.9, Re = 40, Pr = 1 and blockage ratio β = 1/4. The detailed flow and temperature field are presented in terms of streamlines and isotherm contours. It is found that for all values of Richardson number increase in the power-law index increases the total drag coefficient and decreases the non-dimensional Nusselt number.

Abstract: According to the problem that the thickness change of the square cylinder as energy-absorption component affect energy-absorption characteristics of the square cylinder, this paper researches that the thickness of the square cylinder for energy-absorption component of the square cylinders influence through theoretical analysis and using numerical calculation method. The theoretical part in this paper analyze local deformation of the square cylinder theoretical model as a result of axial compression ,and in the numerical simulation part this paper simulate the dynamic response of the thin wall square cylinder model structure , thereby research the thickness change of the square cylinder influence on energy-absorption characteristics of the square cylinder. At last, the change curve of the force-deformation is drawn with the change curve of force-peak load, and it is obtained law that the thickness of the square cylinder influence on energy-absorption characteristics the square cylinder and optimum thickness.

Abstract: Many studies related with characteristics of fluid flow acrossing in a bluff body have been conducted. The aim of this research paper was to reduce pressure drop occuring in narrow channels, in which there was a circular cylindrical configuration with square cylinder as disturbance body. Another goal of this research was to reduce the drag force occuring in circular cylinder. Experimentally research of flow characteristics of the wind tunnel had a narrow channel a square cross-section, with implemenred of Reynolds number based on the hydraulic diameter from 5.21x10⁴ to 1.56x10⁵. Wind tunnel that was used had a 125x125mm cross-sectional area and the blockage ratio 26.4% and 36.4%. Specimen was in the form of circular cylinder and square cylinder as disturbance body. Variation of angle position was the inlet disturbance body with α = 20⁰, 30⁰, 40⁰, 50⁰ and 60⁰, respectively. The results was obtained from this study was Reynolds Number value was directly linear with pressure drop there, it was marked by increasing of Reynolds number, the value was also increasing pressure drop. Additional information was obtained by adding inlet disturbance body shaped of square cylinder on the upstream side of the circular cylinder that could reduce pressure drop in the duct and reduce drag happening on a circular cylinder. The position of the optimum angle to reduce pressure drop and drag force was found on the inlet disturbance body with angle α = 30⁰.

Abstract: In this paper the ability of the Lattice Boltzmann Method (LBM) is investigated for simulating acoustic problems, especially for the propagation of acoustic waves in a wall bounded region. To treat the wall boundary conditions, a non-equilibrium extrapolation scheme for the LBM is adopted. LBM is next applied to simulate the complex aerodynamic noise generated from a square cylinder. In order to efficiently suppress the disturbances at the computational boundaries, the improved absorbing boundary condition (IABC) is developed in this paper. To validate the flow and acoustic solution of a square cylinder, comparisons between the present LBM and the previous studies are carried out. It is demonstrated that the LBM can efficiently simulate the noise generated from a square cylinder.

Abstract: A compact finite differences method is used to calculate two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow through a row of cylinders with square cross-sections is calculated and used as a validation study. The computed average drag coefficient and Strouhal number are compared to data available in the literature, showing a good agreement between the results. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown and various flow regimes identified. Different inlet boundary conditions are compared. The drag coefficient is larger when a uniform inlet velocity is prescribed and the variability between cylinders is lower.

Abstract: Laminar natural heat transfer in the horizontal channel with a heated square cylinder has been studied by using lattice Boltzmann method. Air and water are applied as fluid flow and the walls of channel are adiabatic. Lattice Boltzmann method (LBM) as one of stochastic methods has been used to study the hydrodynamic and thermal behaviours of water and air, with Prantle number 7.01 and 0.71, respectively. Velocity and temperature profiles are achieved near each surface of the square. The results show relation between Prantle number and symmetric degree of streamlines and isotherms profile

Abstract: This paper is centred on a compact finite differences method for the calculation of two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow past a cylinder with square cross-section inside a plane channel is calculated. The computed average drag coefficient and Strouhal number are compared to data available in the literature. The agreement between the results is good. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown. The work presented in this paper illustrates the potential of the immersed boundary method in general and of this implementation in particular to simulate the flow through porous matrices.

Abstract: Over the past decade, a lot of attention has been paid to plasma actuators because they are useful tools for flow control. Previous successes with plasma actuators include drag and noise reductions from a circular cylinder, one of representative bluff bodies, mainly through separation delay. However, to the best of authors’ knowledge, no attempt has been made to examine its capability to control square cylinder wake with fixed separation points. The purpose of this study is to numerically investigate whether or not the square cylinder wake can be controlled by means of plasma actuators. In particular, a linear plasma synthetic jet actuator is adopted and attached to the rear side of the cylinder. In this study, we use an immersed boundary method combined with an empirical plasma model for plasma-based flow control. The present method is second order accurate in time and space. Results show that the wake behind the square cylinder can be controlled effectively when the plasma-induced force is strong enough. With the plasma actuator on, the mean drag is reduced and the Karman vortex shedding is alleviated because the induced jet increases the base pressure and prevents the separating shear layers from interacting with each other.

Abstract: In this paper, the flow characteristics and heat transfer over two equal square cylinders which are placed in tandem arrangement, are investigated numerically. The simulations are performed for a Reynolds number range varying from 1 to 200 and spacing between the cylinders is five widths of the cylinders. The calculations are carried out on a finite volume code for both steady and unsteady incompressible laminar flow in the two dimensional regime. In this study, the instantaneous and mean streamlines and isotherm patterns for different Reynolds numbers are presented. In addition, the effect of Reynolds number on the flow patterns around the cylinders are in detail presented. In addition, the quantities such as pressure and viscous drag coefficients and pressure coefficients are presented.