Presence Of Cylinder Research Articles

An exact solution of three-dimensional elasticity for sound transmission loss through FG cylinder in presence of subsonic external flow

An exact elasticity solution is presented to study sound transmission loss through functionally graded cylinder in presence of subsonic external flow. This structure cylindrical is excited by an external plane wave with two angles of incidenceψ andγ. The mechanical properties of the functionally graded material are assumed to vary uniformly and continuously with the change of volume fractions of the constituting materials across the thickness of the cylinder according to the power-law distribution. The functionally graded cylinder is approximated by a laminate model, whereas the solution is expected to gradually approach the exact one as the number of layers increases. The governing equations of motion for each layer are derived, based on 3-D elasticity theory. Then, the transfer matrix method is employed, which includes a global transfer matrix that composed as the product of the local transfer matrices by applying continuity of the displacement and stress components at the interfaces of neighboring layers. The transmission loss of the multi-layered functionally graded cylinder are presented for different incidence angles, Mach numbers, thicknesses, radii and distribution functions over a wide frequency range. Comparing the results of present study with those of previous models, particularly for thin shells, leads into good agreements as a result of ignoring the effects of shear and rotation terms on TL. The numerical results of positive Mach number show that TL decreases at the stiffness and coincidence controlled regions with increasing the Mach number but it behaves in opposite manner just in mass-controlled region. In addition, the results indicate that the TL is improved as consequences of decreasing the volume fractions through the thickness of FG cylindrical shells.

Effect of Reynolds Numbers on Flow Past a Square Cylinder in Presence of Multiple Control Cylinders at Various Gap Spacings

In this paper, the numerical investigations for drag reduction and vortex shedding suppression behind a square cylinder are carried out in presence of small control cylinders placed both at upstream and downstream locations of main cylinder. The numerical computations are performed in the ranges of \(80 \le Re \le 200\) and \(0.5 \le g \le 6\), (where Re is the Reynolds number and g is the gap spacing between the control cylinders and main square cylinder, respectively) using a single relaxation time lattice Boltzmann method (SRT-LBM). Firstly, the present code is validated for flow past a single square cylinder at different Reynolds numbers. The effects of Re and g are investigated in terms of vortex shedding frequency, time-history analysis of drag and lift coefficients, energy spectra analysis of lift coefficient, vorticity contours visualization and forces exerted on the cylinder. Three different types of flow patterns are observed at different combinations of Reynolds numbers and gap spacings. The maximum reduction in the mean drag force and root-mean-square value of lift coefficient is found. Furthermore, the applications of SRT-LBM for suppression of vortex shedding and reduction in the drag force are also discussed.

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

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

Special features of the pressure fluctuation field structures in the vicinity of bluff bodies (cylinders)

The fields of turbulent near-wall pressure fluctuations on a surface in a flow are experimentally investigated in the presence of cylinders located in the proximity of the surface. It is shown that the main characteristics of the pressure fluctuation fields can be essentially transformed in the case of nonzero distance (gap) between the cylinder and the surface in a flow, namely, the spectral levels increase over the entire frequency range, a narrow-band frequency maximum is formed, and the spatial distribution of the pressure fluctuation intensity changes. The dependence of the main parameters of the pressure fluctuation fields is presented and a weak influence of the boundary layer thickness is shown.

Stability of MHD Taylor–Couette Flow in a Narrow Gap with Radial Throughflow

An analysis which considers the stability of dissipative, conducting, incompressible flow between two permeable circular cylinders in presence of an axially applied magnetic field is presented. The impact of radial inflow and outflow was investigated on the Taylor–Couette flow in a narrow gap via differential transform method combined with a shooting technique. The semi analytic computations made by differential transformation method are consistent with linear instability predictions. For impermeable cylinders the critical Taylor number at the onset of instability increases with increase in Hartmann number for both conducting and non-conducting walls that establishes the stabilizing influence of the magnetic field. Radial inflow has a stabilizing effect and the stabilization is more for perfectly conducting walls, while a radial outflow destabilizes the system. Also, the critical wave number is independent of radial flow through the cylinders. For non-conducting cylinders, the asymptotes as the Hartmann numbers approaches infinity are obtained for inflow as well as outflow and found that the asymptotes increases for radial inflow and decreases for outflow.

A Study of Mixed Convection Flow over Stretching Cylinder in Presence of Slip Flow and Thermal Jump Boundary Conditions

The present work focuses on the study of flow and heat transfer in the axisymmetric flow of a viscous incompressible fluid over a permeable vertical stretching cylinder. The flow model is studied for the second order slip flow and first order thermal jump boundary condition. The governing equations of continuity, momentum and energy are transformed into system of non-linear ordinary differential equations and solved numerically. The velocity and temperature distributions are discussed and shown through graphs. The effects of various physical parameters are examined and discussed in detail. The expressions of skin-friction coefficient and Nusselt number at the cylinder are discussed and their variations are presented through tables. It is found that the increase in first and second order slip parameters increases the fluid velocity while temperature distribution is not considerably affected. Further, the increase in thermal jump parameter tends to increase fluid velocity and temperature.

Numerical investigation of magnetohydrodynamic mixed convection over an isothermal circular cylinder in presence of an aligned magnetic field

The influence of magnetic field on the steady, laminar flow of an incompressible and electrically conducting fluid with mixed convection over a circular cylinder subject to uniform surface temperature is analyzed. The governing nonlinear Navier–Stokes equation with buoyancy body force term, coupled with temperature given by energy equation are solved by using a high order finite difference scheme in cylindrical polar coordinates without imposing axis of symmetry and employing quasi-static approximation. Numerical solutions for the flow and temperature fields are obtained for low Re and the effect of magnetic field on the flow structure and heat transfer is discussed. The vortex structure, in the absence of magnetic field, is symmetric in forced convection flows whereas in the mixed convection cases, the symmetry is broken. The applied magnetic field, in turn, opposes the symmetry breaking and tries to restore a nearly symmetric flow about θ=0 line. The total drag coefficient non-monotonically increases with increasing Prandtl number. Heat transfer is analyzed by computing the surface and mean Nusselt numbers and the behavior of local Nusselt number is explained. The mean Nusselt number monotonically increases with Ri and Pr whereas it exhibits non-monotonic behavior with applied magnetic field strength.

Stagnation point flow and heat transfer behavior of Cu–water nanofluid towards horizontal and exponentially stretching/shrinking cylinders

In this study we analyzed the stagnation point flow and heat transfer behavior of Cu–water nanofluid towards horizontal and exponentially permeable stretching/shrinking cylinders in presence of suction/injection, heat source and shape of nanoparticles. The governing boundary layer equations are transformed to nonlinear ordinary differential equations using similarity transformation which are then solved numerically using bvp4c Matlab package. The influence of non-dimensional governing parameters on the flow field and heat transfer characteristics are discussed and presented through graphs and tables. The study indicates that the solutions for the horizontal and exponential cylinders are non-unique and shape of nanoparticles also influences the rate of heat transfer. Comparisons of the present results with existed studies are presented. Present study has an excellent agreement with the existed studies under some special conditions.

MHD Flow, Heat and Mass Transfer due to Axially Moving Cylinder in Presence of Thermal Diffusion, Radiation and Chemical Reactions in a Binary Fluid Mixture

the present paper we have studied the effects of magnetic field, thermal diffusion, thermal radiation and chemical reaction on velocity, temperature and concentration fields about an axially moving isothermal semi infinite solid vertical cylinder in two dimensional incompressible viscous binary fluid mixtures. The governing equations of continuity, momentum, energy and concentration are transformed into non similar boundary layer equations and are solved by using a regular perturbation method together with Matlab's built in solver bvp4c. Numerical solutions for axial velocity component, temperature and concentration of the rarer and lighter component of the binary fluid mixture are obtained on the basis of boundary layer approximation and presented graphically for axial curvature parameter, magnetic field parameter, thermal diffusion parameter, radiation parameter and chemical reaction parameter. It has been found that these parameters affect considerably the flow characteristics. The problem under consideration reduces to the flat plate case when the curvature parameter is absent. Keywordscylinder, magnetic field, thermal diffusion, radiation, chemical reaction, binary fluid mixture, MATLAB-bvp4c.

Static stress analysis of carbon nano-tube reinforced composite (CNTRC) cylinder under non-axisymmetric thermo-mechanical loads and uniform electro-magnetic fields

Static stresses analysis of carbon nano-tube reinforced composite (CNTRC) cylinder made of poly-vinylidene fluoride (PVDF) is investigated in this study. Non-axisymmetric thermo-mechanical loads are applied on cylinder in presence of uniform longitudinal magnetic field and radial electric field. The surrounded elastic medium is modeled by Pasternak foundation because of its advantages to the Winkler type. Distribution of radial, circumferential and effective stresses, temperature field and electric displacements in CNTRC cylinder are determined based on Mori–Tanaka theory. The detailed parametric study is conducted, focusing on the remarkable effects of magnetic field intensity, elastic medium, angle orientation and volume fraction of carbon nano-tubes (CNTs) on distribution of effective stress. Results demonstrated that fatigue life of CNTRC cylinder will be significantly dependent on magnetic intensity, angle orientation and volume fraction of CNTs. Results of this research can be used for optimum design of thick-walled cylinders under multi-physical fields.

Numerical study on flow and aerodynamic characteristics: Square cylinder and eddy-promoting rectangular cylinder in tandem near wall

Numerically simulated results are presented for shear flow past a square cylinder (of height a) near a wall (at a gap height 0.5a) in presence of eddy promoting rectangular cylinders (of fixed height a with different widths b⩽a) to gain a better insight into the dependency of aerodynamic characteristics of both the cylinders on the parameters: spacing distance between the cylinders S (=D/a:0.5⩽S⩽20) and aspect ratio r (=b/a:0.1⩽r⩽1.0). The value of Reynolds number Re is kept as Re=100 and 200. The governing unsteady Navier–Stokes equations are solved numerically based on the finite volume method on a staggered grid system using QUICK scheme. The resulting equations are then solved by an implicit, time-marching, pressure correction-based SIMPLE algorithm. The influence of numerical parameters on the validated code used in this study is demonstrated here. The strong dependency of vortex shedding (from both the cylinders) on aspect ratio r and spacing distance S are explored and, hence, a region of finite area in the Sr-plane is proposed in order to generate the unsteadiness in the steady flow of the downstream cylinder. An attempt is made to identify the different flow regimes depending on the flow patterns of the downstream cylinder, associated with the geometrical parameters (S and r). Owing to the differences in the basic shedding frequency of the square (downstream) cylinder from that of the rectangular cylinder (promoter) of different widths, the major issue of appearing multiple peaks in the spectrum of fluctuating lift coefficient of the downstream cylinder is addressed. The thrust force observed on the downstream cylinder in presence of the thinner promoter at closely spaced arrangement is justified presenting the surface pressure distribution. Finally, the present numerical results at large spacing distances are certified with some previous numerical and experimental findings.

Axial drive to nonlinear flow between rotating cylinders

Stability of pseudoplastic rotational flow between cylinders in presence of an independent axial component is investigated. The fluid is assumed to follow the Carreau model and mixed boundary conditions are imposed. The conservation of mass and momentum equations give rise to a four-dimensional low-order dynamical system, including additional nonlinear terms in the velocity components originated from the shear-dependent viscosity. In absence of the axial flow, as the pseudoplasticity effects increases, the purely-azimuthal base flow loses its stability to the vortex structure at a lower critical Taylor number. Emergence of the vortices corresponds to the onset of a supercritical bifurcation also present in the flow of a linear fluid. However, unlike the Newtonian case, pseudoplastic Taylor vortices lose their stability as the Taylor number reaches a second critical number corresponding to the onset of a Hopf bifurcation. Existence of an axial flow induced by a pressure gradient appears to further advance each critical point on the bifurcation diagram. In continuation, complete flow field together with viscosity maps is analyzed for different flow scenarios. Through evaluation of the Lyapunov exponent, flow stability and temporal behavior of the system for cases with and without axial flow are brought to attention.

Numerical investigation of MHD effects on Al2O3–water nanofluid flow and heat transfer in a semi-annulus enclosure using LBM

In this study, free convection heat transfer in a concentric annulus between a cold square and heated elliptic cylinders in presence of magnetic field is investigated. The square and elliptic cylinders are maintained at uniform temperatures and it is assumed that the walls are insulating magnetic field. Lattice Boltzmann method is applied to solve the governing equations. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The numerical investigation is carried out for different governing parameters namely; the Hartmann number, Rayleigh number and nanoparticle volume fraction. Also a correlation of Nusselt number corresponding to active parameters is presented. The results reveal that average Nusselt number is an increasing function of nanoparticle volume fraction and Rayleigh number, while it is a decreasing function of Hartmann number. Moreover it can be found that the enhancement in heat transfer increases as Hartmann number increases but it decreases with increase of Rayleigh number.

NANOFLUID FLOW ON A VERTICAL CYLINDER UNDER THE EFFECT OF MAGNETOHYDRODYNAMICS

The present work is a numerical investigation of the effect of laminar natural convection flow of nano fluid taking Cu nano particles and the water as based fluid on a vertical cylinder in presence of magnetohydrodynamics. The governing equations which used are continuity, momentum and energy equations. These equations are transformed to dimensionless equations using vorticity-stream function method and the resulting nonlinear system of partial differential equations are then solved numerically using finite difference approximation. A thermal boundary condition of a constant wall temperature is considered. A computer program was built to calculate the rate of heat transfer in terms of average Nusselt number, velocity distribution as well as temperature distribution for magnetohydrodynamics range of and the volume fraction . Numerical solution have been considered for a fluid Prandtl number fixed at (Pr = 6.2), Rayleigh number . The results show that Nu increase with increasing Ral and M and increased with the particle volume fraction up to φ = 0.15 then decreased due to viscosity and agglomeration effect. The effect of Rayleigh number and magnetohydrodynamics on the rate of heat transfer is concluded by a correlation equation.

Magnetic field effects on natural convection around a horizontal circular cylinder inside a square enclosure filled with nanofluid

In this study, natural convection in a concentric annulus between a cold outer square and heated inner circular cylinders in presence of static radial magnetic field is investigated numerically using the lattice Boltzmann method. The inner and outer cylinders are maintained at constant uniform temperatures and it is assumed that all walls are insulating the magnetic field. The numerical investigation is carried out for different governing parameters namely; the Hartmann number, nanoparticles volume fraction and Rayleigh number. The effective thermal conductivity and viscosity of nanofluids are calculated using the Maxwell–Garnetts (MG) and Brinkman models, respectively. Also, the multi-distribution-function (MDF) model is used for simulating the effect of uniform magnetic field. The results reveal that the average Nusselt number is an increasing function of nanoparticle volume fraction as well as the Rayleigh number, while it is a decreasing function of the Hartmann number.

MAGNETO HYDRODYNAMIC NATURAL CONVECTION FLOW ON A VERTICAL CYLINDER WITH A PRESENCE OF HEAT GENERATION AND RADIATION

The present work investigates the effect of magneto – hydrodynamic (MHD) laminar natural convection flow on a vertical cylinder in presence of heat generation and radiation. The governing equations which used are Continuity, Momentum and Energy equations. These equations are transformed to dimensionless equations using Vorticity-Stream Function method and the resulting nonlinear systemof partial differential equations are then solved numerically using finite difference approximation. A thermal boundary condition of a constant wall temperature is considered. A computer program (Fortran 90) was built to calculate the rate of heat transfer in terms of local Nusselt number, total mean Nusselt number, velocity distribution as well as temperature distribution for a selection of parameters setsconsisting of dimensionless heat generation parameter (0.0 ≤ Q ≤ 2.0), conduction – radiation parameter (0.0 ≤ N ≤ 10.0), and the dimensionless magneto hydrodynamic parameter (0.0 ≤ M ≤ 1.0). Numerical solution have been considered for a fluid Prandtl number fixed at (Pr=0.7), Rayleigh number (102 ≤ ≤ 105 ) l Ra . The results are shown reasonable representation to the relation between Nusselt number and Rayleigh number with other parameters (M, N and Q). Generally, Nu increase with increasing Ra, M, N and Q separately. When the MHD, N, and Q effect added to the heat transfer mechanism, the heat transfer rate increased and this effect increased with increasing in Ra, MHD, N, and Q. The effect of magneto hydrodynamic, heat generation and heat radiation on the rate of heat transfer is concluded by correlationequations. The results are found to be in good agreement compared with the results of other researchers.

Finite element analysis of natural heat transfer from an isothermal array of cylinders in presence of vertical oscillations

A numerical simulation is performed to study the effects of vertical vibrations on natural convection heat transfer in an array of isothermal circular cylinders. Governing equations consist of continuity, momentum and energy equations were solved numerically by finite element method and Arbitrary Lagrangian–Eulerian kinematics description. The results showed that vertical oscillations of cylinders do not necessarily results in increment of average Nusselt number of each cylinder.

Separation of species of a binary fluid mixture confined between two concentric rotating circular cylinders in presence of a strong radial magnetic field

The effect of a radial magnetic field on separation of a binary mixture of incompressible viscous thermally and electrically conducting fluids confined between two concentric rotating circular cylinders with different angular velocity is examined. The equations governing the motion, temperature and concentration in cylindrical polar coordinate are solved analytically. The solution obtained in closed form for concentration distribution is plotted against the radial distances from the surface of the inner circular cylinder for various values of non-dimensional parameters. It is found that the non-dimensional parameters viz. the Hartmann number, thermal diffusion number, baro diffusion number, rotational Reynolds number, the product of Prandtl number and Eckert number, magnetic Prandtl number and the ratio of the angular velocities of inner and outer cylinders affects the species separation of rarer and lighter component significantly. The problem discussed here derives its application in the basic fluid dynamics separation processes to separate the rarer component of the different isotopes of heavier molecules where electromagnetic method of separation does not work.

Natural convection flow from an isothermal horizontal circular cylinder in presence of heat generation

Natural convection laminar boundary layer flow from a horizontal circular cylinder with a uniform surface temperature at presence of heat generation has been investigated. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear systems of partial differential equations are solved numerically applying two distinct methods namely (i) implicit finite difference method together with the Keller box scheme and (ii) series solution technique. The results of the surface shear stress in terms of the local skin friction and the surface rate of heat transfer in terms of the local Nusselt number for a selection of the heat generation parameter γ (= 0.0, 0.2, 0.5, 0.8, 1.0) are obtained and presented in both tabular and graphical formats. Without effect of the internal heat generation inside the fluid domain for which we take γ = 0.0, the present numerical results show an excellent agreement with those of Merkin [J.H. Merkin, Free convection boundary layer on an isothermal horizontal circular cylinders, in: ASME/AIChE, Heat Transfer Conference, St. Louis, MO, August 9–11, 1976]. The effects of γ on the fluid velocity, temperature distribution, streamlines and isotherms are examined.

Vortex shedding from a square cylinder in presence of a moving wall

AbstractA numerical study on the flow past a square cylinder placed parallel to a wall, which is moving at the speed of the far field has been made. Flow has been investigated in the laminar Reynolds number (based on the cylinder length) range. We have studied the flow field for different values of the cylinder to wall separation length. The governing unsteady Navier–Stokes equations are discretized through the finite volume method on a staggered grid system. A SIMPLE type of algorithm has been used to compute the discretized equations iteratively. A shear layer of negative vortex generates along the surface of the wall, which influences the vortex shedding behind the cylinder. The flow‐field is distinct from the flow in presence of a stationary wall. An alternate vortex shedding occurs for all values of gap height in the unsteady regime of the flow. The strong positive vortex pushes the negative vortex upwards in the wake. The gap flow in the undersurface of the cylinder is strong and the velocity profile overshoots. The cylinder experiences a downward force for certain values of the Reynolds number and gap height. The drag and lift are higher at lower values of the Reynolds number. Copyright © 2005 John Wiley & Sons, Ltd.