**Commenced**in January 2007

**Frequency:**Monthly

**Edition:**International

**Paper Count:**2776

# Search results for: flow around square cylinders.

##### 2776 Numerical Simulations of Cross-Flow around Four Square Cylinders in an In-Line Rectangular Configuration

**Authors:**
Shams Ul Islam,
Chao Ying Zhou,
Farooq Ahmad

**Abstract:**

**Keywords:**
Four square cylinders,
Lattice Boltzmann method,
rectangular configuration,
spacing ratios,
vortex shedding.

##### 2775 Flow around Two Cam Shaped Cylinders in Tandem Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Hamidreza Bayat

**Abstract:**

In this paper flow around two cam shaped cylinders had been studied numerically. The equivalent diameter of cylinders is 27.6 mm. The space between center to center of two cam shaped cylinders is define as longitudinal pitch ratio and it varies in range of
2

**Keywords:**
Cam shaped,
tandem cylinders,
numerical,
drag
coefficient.

##### 2774 Numerical Analysis of Laminar Flow around Square Cylinders with EHD Phenomenon

**Authors:**
M. Salmanpour,
O. Nourani Zonouz

**Abstract:**

In this research, a numerical simulation of an Electrohydrodynamic (EHD) actuator’s effects on the flow around a square cylinder by using a finite volume method has been investigated. This is one of the newest ways for controlling the fluid flows. Two plate electrodes are flush-mounted on the surface of the cylinder and one wire electrode is placed on the line with zero angle of attack relative to the stagnation point and excited with DC power supply. The discharge produces an electric force and changes the local momentum behaviors in the fluid layers. For this purpose, after selecting proper domain and boundary conditions, the electric field relating to the problem has been analyzed and then the results in the form of electrical body force have been entered in the governing equations of fluid field (Navier-Stokes equations). The effect of ionic wind resulted from the Electrohydrodynamic actuator, on the velocity, pressure and the wake behind cylinder has been considered. According to the results, it is observed that the fluid flow accelerates in the nearest wall of the frontal half of the cylinder and the pressure difference between frontal and hinder cylinder is increased.

**Keywords:**
CFD,
corona discharge,
electro hydrodynamics,
flow around square cylinders.

##### 2773 Numerical Simulation of Turbulent Flow around Two Cam Shaped Cylinders in Tandem Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Meghdad Ebrahimi Sabet

**Abstract:**

In this paper, the 2-D unsteady viscous flow around two cam shaped cylinders in tandem arrangement is numerically simulated in order to study the characteristics of the flow in turbulent regimes. The investigation covers the effects of high subcritical and supercritical Reynolds numbers and L/D ratio on total drag coefficient. The equivalent diameter of cylinders is 27.6 mm The space between center to center of two cam shaped cylinders is define as longitudinal pitch ratio and it varies in range of 1.5< L/D<6. Reynolds number base on equivalent circular cylinder varies in range of 27×103< Re <166×103 Results show that drag coefficient of both cylinders depends on pitch ratio. However, drag coefficient of downstream cylinder is more dependent on the pitch ratio.

**Keywords:**
Cam shaped,
tandem,
numerical,
drag coefficient,
turbulent.

##### 2772 Numerical Simulation of Flow Past an Infinite Row of Equispaced Square Cylinders Using the Multi- Relaxation-Time Lattice Boltzmann Method

**Authors:**
S. Ul. Islam,
H. Rahman,
W. S. Abbasi,
N. Rathore

**Abstract:**

**Keywords:**
Blockage ratio,
Multi-relaxation-time lattice
Boltzmann method,
Square cylinder,
Vortex formation.

##### 2771 Experimental Investigations of a Modified Taylor-Couette Flow

**Authors:**
A. Esmael,
A. El Shrif

**Abstract:**

In this study the instability problem of a modified Taylor-Couette flow between two vertical coaxial cylinders of radius R1, R2 is considered. The modification is based on the wavy shape of the inner cylinder surface, where inner cylinders with different surface amplitude and wavelength are used. The study aims to discover the effect of the inner surface geometry on the instability phenomenon that undergoes Taylor-Couette flow. The study reveals that the transition processes depends strongly on the amplitude and wavelength of the inner cylinder surface and resulting in flow instabilities that are strongly different from that encountered in the case of the classical Taylor-Couette flow.

**Keywords:**
Hydrodynamic Instability,
Modified Taylor-Couette
Flow,
Turbulence,
Taylor vortices.

##### 2770 Numerical Investigation of Non-Newtonians Fluids Flows between Two Rotating Cylinders Using Lattice Boltzmann Method

**Authors:**
S. Khali,
R. Nebbali,
K. Bouhadef

**Abstract:**

A numerical investigation is performed for non Newtonian fluids flow between two concentric cylinders. The D2Q9 lattice Boltzmann model developed from the Bhatangar-Gross-Krook (LBGK) approximation is used to obtain the flow field for fluids obeying to the power-law model. The inner and outer cylinders rotate in the same and the opposite direction while the end walls are maintained at rest. The combined effects of the Reynolds number (Re) of the inner and outer cylinders, the radius ratio (η) as well as the power-law index (n) on the flow characteristics are analyzed for an annular space of a finite aspect ratio (Γ). Two flow modes are obtained: a primary mode (laminar stable regime) and a secondary mode (laminar unstable regime). The so obtained flow structures are different from one mode to another. The transition critical Reynolds number Re_{c} from the primary to the secondary mode is analyzed for the co-courant and counter-courant flows. This critical value increases as n increases. The prediction of the swirling flow of non Newtonians fluids in axisymmetric geometries is shown in the present work.

**Keywords:**
Taylor-Couette flows,
non Newtonian fluid,
Lattice Boltzmann method.

##### 2769 Numerical Simulations of Shear Driven Square and Triangular Cavity by Using Lattice Boltzmann Scheme

**Authors:**
A. M. Fudhail,
N. A. C. Sidik,
M. Z. M. Rody,
H. M. Zahir,
M.T. Musthafah

**Abstract:**

In this paper, fluid flow patterns of steady incompressible flow inside shear driven cavity are studied. The numerical simulations are conducted by using lattice Boltzmann method (LBM) for different Reynolds numbers. In order to simulate the flow, derivation of macroscopic hydrodynamics equations from the continuous Boltzmann equation need to be performed. Then, the numerical results of shear-driven flow inside square and triangular cavity are compared with results found in literature review. Present study found that flow patterns are affected by the geometry of the cavity and the Reynolds numbers used.

**Keywords:**
Lattice Boltzmann method,
shear driven cavity,
square cavity,
triangular cavity.

##### 2768 Effect of Hartmann Number on Free Convective Flow in a Square Cavity with Different Positions of Heated Square Block

**Authors:**
Abdul Halim Bhuiyan,
M. A. Alim,
Md. Nasir Uddin

**Abstract:**

This paper is concerned with the effect of Hartmann number on the free convective flow in a square cavity with different positions of heated square block. The two-dimensional Physical and mathematical model have been developed, and mathematical model includes the system of governing mass, momentum and energy equations are solved by the finite element method. The calculations have been computed for Prandtl number Pr = 0.71, the Rayleigh number *Ra* = 1000 and the different values of Hartmann number. The results are illustrated with the streamlines, isotherms, velocity and temperature fields as well as local Nusselt number.

**Keywords:**
Finite element method,
free convection,
Hartmann number,
square cavity.

##### 2767 Effect of Reynolds Number on Flow past a Square Cylinder in Presence of Upstream and Downstream Flat Plate at Small Gap Spacing

**Authors:**
Shams-ul-Islam,
Raheela Manzoor,
Zhou Chao Ying

**Abstract:**

**Keywords:**
Detached flat plates,
drag and lift coefficients,
Reynolds numbers,
square cylinder,
Strouhal number.

##### 2766 Heat Transfer from Two Cam Shaped Cylinders in Side-by-Side Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Hamidreza Bayat

**Abstract:**

**Keywords:**
Cam shaped,
side-by-side cylinders,
numerical,
heat
Transfer.

##### 2765 Stress Analysis of Laminated Cylinders Subject to the Thermomechanical Loads

**Authors:**
Ş. Aksoy,
A. Kurşun,
E. Çetin,
M. R. Haboğlu

**Abstract:**

In this study, thermo elastic stress analysis is performed on a cylinder made of laminated isotropic materials under thermomechanical loads. Laminated cylinders have many applications such as aerospace, automotive and nuclear plant in the industry. These cylinders generally performed under thermomechanical loads. Stress and displacement distribution of the laminated cylinders are determined using by analytical method both thermal and mechanical loads. Based on the results, materials combination plays an important role on the stresses distribution along the radius. Variation of the stresses and displacements along the radius are presented as graphs. Calculations program are prepared using MATLAB® by authors.

**Keywords:**
Isotropic materials,
laminated cylinders,
thermoelastic stress,
thermomechanical load.

##### 2764 Phase-Averaged Analysis of Three-Dimensional Vorticity in the Wake of Two Yawed Side-By-Side Circular Cylinders

**Authors:**
T. Zhou,
S. F. Mohd. Razali,
Y. Zhou,
H. Wang,
L. Cheng

**Abstract:**

Thewake flow behind two yawed side-by-sidecircular cylinders is investigated using athree-dimensional vorticity probe. Four yaw angles (α), namely, 0°, 15°, 30° and 45° and twocylinder spacing ratios T* of 1.7 and 3.0 were tested. For T* = 3.0, there exist two vortex streets and the cylinders behave as independent and isolated ones. The maximum contour value of the coherent streamwise vorticity ~* ωx is only about 10% of that of the spanwise vorticity ~* ωz . With the increase of α, ~* ωx increases whereas ~* ωz decreases. At α = 45°, ~* ωx is about 67% of ~* ωz .For T* = 1.7, only a single peak is detected in the energy spectrum. The spanwise vorticity contours have an organized pattern only at α = 0°. The maximum coherent vorticity contours of ~* ω x and ~* ωz for T* = 1.7 are about 30% and 7% of those for T* = 3.0.The independence principle (IP)in terms of Strouhal numbers is applicable in both wakes when α< 40°.

**Keywords:**
Circular cylinder wake,
vorticity,
vortex shedding.

##### 2763 Convective Heat Transfer of Viscoelastic Flow in a Curved Duct

**Authors:**
M. Norouzi,
M. H. Kayhani,
M. R. H. Nobari,
M. Karimi Demneh

**Abstract:**

**Keywords:**
Viscoelastic,
fluid flow,
heat convection,
CEF
model,
curved duct,
square cross section.

##### 2762 Triggering Supersonic Boundary-Layer Instability by Small-Scale Vortex Shedding

**Authors:**
Guohua Tu,
Zhi Fu,
Zhiwei Hu,
Neil D Sandham,
Jianqiang Chen

**Abstract:**

Tripping of boundary-layers from laminar to turbulent flow, which may be necessary in specific practical applications, requires high amplitude disturbances to be introduced into the boundary layers without large drag penalties. As a possible improvement on fixed trip devices, a technique based on vortex shedding for enhancing supersonic flow transition is demonstrated in the present paper for a Mach 1.5 boundary layer. The compressible Navier-Stokes equations are solved directly using a high-order (fifth-order in space and third-order in time) finite difference method for small-scale cylinders suspended transversely near the wall. For cylinders with proper diameter and mount location, asymmetry vortices shed within the boundary layer are capable of tripping laminar-turbulent transition. Full three-dimensional simulations showed that transition was enhanced. A parametric study of the size and mounting location of the cylinder is carried out to identify the most effective setup. It is also found that the vortex shedding can be suppressed by some factors such as wall effect.

**Keywords:**
Boundary layer instability,
boundary layer transition,
vortex shedding,
supersonic flows,
flow control.

##### 2761 Numerical Study of Liquefied Petroleum Gas Laminar Flow in Cylindrical Elliptic Pipes

**Authors:**
Olumuyiwa A. Lasode,
Tajudeen O. Popoola,
B. V. S. S. S. Prasad

**Abstract:**

Fluid flow in cylinders of elliptic cross-section was investigated. Fluid used is Liquefied petroleum gas (LPG). LPG found in Nigeria contains majorly butane with percentages of propane. Commercial available code FLUENT which uses finite volume method was used to solve fluid flow governing equations. There has been little attention paid to fluid flow in cylindrical elliptic pipes. The present work aims to predict the LPG gas flow in cylindrical pipes of elliptic cross-section. Results of flow parameters of velocity and pressure distributions are presented. Results show that the pressure drop in elliptic pipes is higher than circular pipe of the same cross-sectional area. This is an important result as the pressure drop is related to the pump power needed to drive the flow. Results show that the velocity increases towards centre of the pipe as the flow moves downstream, and also increases towards the outlet of the pipe.

**Keywords:**
Elliptic Pipes,
Liquefied Petroleum Gas,
Numerical Study,
Pressure Drop.

##### 2760 Force Statistics and Wake Structure Mechanism of Flow around a Square Cylinder at Low Reynolds Numbers

**Authors:**
Shams-Ul-Islam,
Waqas Sarwar Abbasi,
Hamid Rahman

**Abstract:**

Numerical investigation of flow around a square cylinder are presented using the multi-relaxation-time lattice Boltzmann methods at different Reynolds numbers. A detail analysis are given in terms of time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualizations, streamlines and phase diagrams. A number of physical quantities mean drag coefficient, drag coefficient, Strouhal number and root-mean-square values of drag and lift coefficients are calculated and compared with the well resolved experimental data and numerical results available in open literature. The Reynolds numbers affected the physical quantities.

**Keywords:**
Code validation,
Force statistics,
Multi-relaxation-time lattice Boltzmann method,
Reynolds numbers,
Square cylinder.

##### 2759 Analysis of Wave Propagation in Two-dimensional Phononic Crystals with Hollow Cylinders

**Authors:**
Zi-Gui Huang,
Tsung-Tsong Wu

**Abstract:**

**Keywords:**
Phononic crystals,
Band gap,
SAW,
BAW.

##### 2758 Simulation of Natural Convection in Concentric Annuli between an Outer Inclined Square Enclosure and an Inner Horizontal Cylinder

**Authors:**
Sattar Al-Jabair,
Laith J. Habeeb

**Abstract:**

**Keywords:**
natural convection,
concentric annulus,
square
inclined enclosure

##### 2757 Magnetohydrodynamic Free Convection in a Square Cavity Heated from Below and Cooled from Other Walls

**Authors:**
S. Jani,
M. Mahmoodi,
M. Amini

**Abstract:**

Magnetohydrodynamic free convection fluid flow and heat transfer in a square cavity filled with an electric conductive fluid with Prandtl number of 0.7 has been investigated numerically. The horizontal bottom wall of the cavity was kept at Th while the side and the top walls of the cavity were maintained at a constant temperature Tc with Th>Tc. The governing equations written in terms of the primitive variables were solved numerically using the finite volume method while the SIMPLER algorithm was used to couple the velocity and pressure fields. Using the developed code, a parametric study was performed, and the effects of the Rayleigh number and the Hartman number on the fluid flow and heat transfer inside the cavity were investigated. The obtained results showed that temperature distribution and flow pattern inside the cavity depended on both strength of the magnetic field and Rayleigh number. For all cases two counter rotating eddies were formed inside the cavity. The magnetic field decreased the intensity of free convection and flow velocity. Also it was found that for higher Rayleigh numbers a relatively stronger magnetic field was needed to decrease the heat transfer through free convection.

**Keywords:**
Free Convection,
Magnetic Field,
Square Cavity,
Numerical Simulation.

##### 2756 Mechanical and Thermal Stresses in Functionally Graded Cylinders

**Authors:**
A. Kurşun,
E. Kara,
E. Çetin,
Ş. Aksoy,
A. Kesimli

**Abstract:**

In this study, thermal elastic stress distribution occurred on long hollow cylinders made of functionally graded material (FGM) was analytically defined under thermal, mechanical and thermo mechanical loads. In closed form solutions for elastic stresses and displacements are obtained analytically by using the infinitesimal deformation theory of elasticity. It was assumed that elasticity modulus, thermal expansion coefficient and density of cylinder materials could change in terms of an exponential function as for that Poisson’s ratio was constant. A gradient parameter n is chosen between - 1 and 1. When n equals to zero, the disc becomes isotropic. Circumferential, radial and longitudinal stresses in the FGMs cylinders are depicted in the figures. As a result, the gradient parameters have great effects on the stress systems of FGMs cylinders.

**Keywords:**
Functionally graded materials,
hollow cylinder,
thermoelasticity,
thermomechanical load.

##### 2755 Heat Transfer from Two Cam Shaped Cylinders in Tandem Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Hamidreza Bayat

**Abstract:**

Heat transfer from two cam shape cylinder in tandem arrangement had been studied numerically. The distance between the centers of cylinders (L) is allowed to vary to change the longitudinal pitch ratio (L/Deq). The equivalent diameter of the cylinder (Deq) is 27.6 mm and longitudinal pitch ratio varies in range 2<L/Deq<6. The Reynolds number based on equivalent circular cylinder are within 50< Reeq <300. Results show that Nusselt number of second cylinder increases about 5 to 33 times when longitudinal pitch ratio increases from 2 to 6.

**Keywords:**
Cam Shaped,
tandem Cylinders,
Numerical,
Heat
Transfer.

##### 2754 Experimental and Numerical Study of The Shock-Accelerated Elliptic Heavy Gas Cylinders

**Authors:**
Jing S. Bai,
Li Y. Zou,
Tao Wang,
Kun Liu,
Wen B. Huang,
Jin H. Liu,
Ping Li,
Duo W. Tan,
CangL. Liu

**Abstract:**

**Keywords:**
About four key words or phrases in alphabeticalorder,
separated by commas.

##### 2753 Electromagnetic Imaging of Inhomogeneous Dielectric Cylinders Buried in a Slab Mediumby TE Wave Illumination

**Authors:**
Chung-Hsin Huang,
Chien-Ching Chiu,
Chun Jen Lin

**Abstract:**

**Keywords:**
Slab Medium,
Unrelated Illumination Method,
TEWave Illumination,
Inhomogeneous Cylinders.

##### 2752 Numerical Simulations of Electronic Cooling with In-Line and Staggered Pin Fin Heat Sinks

**Authors:**
Yue-Tzu Yang,
Hsiang-Wen Tang,
Jian-Zhang Yin,
Chao-Han Wu

**Abstract:**

Three-dimensional incompressible turbulent fluid flow and heat transfer of pin fin heat sinks using air as a cooling fluid are numerically studied in this study. Two different kinds of pin fins are compared in the thermal performance, including circular and square cross sections, both are in-line and staggered arrangements. The turbulent governing equations are solved using a control-volume- based finite-difference method. Subsequently, numerical computations are performed with the realizable *k - ԑ* turbulence for the parameters studied, the fin height* H*, fin diameter* D*, and Reynolds number (Re) in the range of 7 ≤ *H* ≤ 10*, *0.75 ≤ *D* ≤ 2, 2000 ≤ Re ≤ 126000 respectively. The numerical results are validated with available experimental data in the literature and good agreement has been found. It indicates that circular pin fins are streamlined in comparing with the square pin fins, the pressure drop is small than that of square pin fins, and heat transfer is not as good as the square pin fins. The thermal performance of the staggered pin fins is better than that of in-line pin fins because the staggered arrangements produce large disturbance. Both in-line and staggered arrangements show the same behavior for thermal resistance, pressure drop, and the entropy generation.

**Keywords:**
Pin-fin,
heat sinks,
simulations,
turbulent flow.

##### 2751 Grid Independence Study of Flow Past a Square Cylinder Using the Multi-Relaxation-Time Lattice Boltzmann Method

**Authors:**
Shams-Ul-Islam,
Hamid Rahman,
Waqas Sarwar Abbasi

**Abstract:**

Numerical calculations of flow around a square cylinder are presented using the multi-relaxation-time lattice Boltzmann method at Reynolds number 150. The effects of upstream locations, downstream locations and blockage are investigated systematically. A detail analysis are given in terms of time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualizations and phase diagrams. A number of physical quantities mean drag coefficient, drag coefficient, Strouhal number and root-mean-square values of drag and lift coefficients are calculated and compared with the well resolved experimental data and numerical results available in open literature. The results had shown that the upstream, downstream and height of the computational domain are at least 7.5, 37.5 and 12 diameters of the cylinder, respectively.

**Keywords:**
Grid independence,
Multi-relaxation-time lattice Boltzmann method,
Physical quantities,
Square cylinder,
Vorticity contours visualizations.

##### 2750 Vortex-Shedding Suppression in Mixed Convective Flow past a Heated Square Cylinder

**Abstract:**

**Keywords:**
bluff body,
buoyancy,
free-stream orientation,
vortex-shedding.

##### 2749 Flow Characteristics of Pulp Liquid in Straight Ducts

**Authors:**
M. Sumida

**Abstract:**

**Keywords:**
Fiber Concentration,
Flow Characteristic,
Pulp Liquid,
Straight Duct.

##### 2748 Reconstruction of the Most Energetic Modes in a Fully Developed Turbulent Channel Flow with Density Variation

**Authors:**
Elteyeb Eljack,
Takashi Ohta

**Abstract:**

Proper orthogonal decomposition (POD) is used to reconstruct spatio-temporal data of a fully developed turbulent channel flow with density variation at Reynolds number of 150, based on the friction velocity and the channel half-width, and Prandtl number of 0.71. To apply POD to the fully developed turbulent channel flow with density variation, the flow field (velocities, density, and temperature) is scaled by the corresponding root mean square values (rms) so that the flow field becomes dimensionless. A five-vector POD problem is solved numerically. The reconstructed second-order moments of velocity, temperature, and density from POD eigenfunctions compare favorably to the original Direct Numerical Simulation (DNS) data.

**Keywords:**
Pattern Recognition,
POD,
Coherent Structures,
Low dimensional modelling.

##### 2747 Vortex Shedding on Combined Bodies at Incidence to a Uniform Air Stream

**Authors:**
T. Yavuz,
Y. E. Akansu,
M. Sarıoglu,
M. Ozmert

**Abstract:**

**Keywords:**
Bluff body,
vortex shedding,
flow separation,
flow reattachment