Horizontal Circular Cylinder Research Articles

Three-dimensional interaction between uniform current and a submerged horizontal cylinder in an ice-covered channel

The problem of interaction of a uniform current with a submerged horizontal circular cylinder in an ice-covered channel is considered. The fluid flow is described by linearized velocity potential theory and the ice sheet is treated as a thin elastic plate. The potential due to a source or the Green function satisfying all boundary conditions apart from that on the body surface is first derived. This can be used to derive the boundary integral equation for a body of arbitrary shape. It can also be used to obtain the solution due to multipoles by differentiating the Green function with its position directly. For a transverse circular cylinder, through distributing multipoles along its centre line, the velocity potential can be written in an infinite series with unknown coefficients, which can be determined from the impermeable condition on a body surface. A major feature here is that different from the free surface problem, or a channel without the ice sheet cover, this problem is fully three-dimensional because of the constraints along the intersection of the ice sheet with the channel wall. It has been also confirmed that there is an infinite number of critical speeds. Whenever the current speed passes a critical value, the force on the body and wave pattern change rapidly, and two more wave components are generated at the far-field. Extensive results are provided for hydroelastic waves and hydrodynamic forces when the ice sheet is under different edge conditions, and the insight of their physical features is discussed.

Study of Liquid Viscosity Effects on Hydrodynamic Forces on an Oscillating Circular Cylinder Underwater Using OpenFOAM®

By neglecting the viscosity of fluid and rotation in flow, the theory of potential flow cannot accurately predict the hydrodynamic forces on the structures under significant viscous effects. In this study, the effects of liquid viscosity on the hydrodynamic forces on a horizontal circular cylinder underwater with a large-amplitude forced oscillation were investigated. The study used a two-dimensional two-phase flow wave tank model based on the viscous fluid theory using the OpenFOAM® package. The numerical calculations were carried out under different types of liquid (i.e., liquid with different viscosities). The liquid viscosity effects are visually shown by comparison of the various frequency components of the hydrodynamic forces on the cylinder, and the magnitude and phase relations of the viscous shear forces and the pressure forces. By analyzing the distribution characteristics of the flow fields around the circular cylinder, the viscous-effect mechanisms are revealed. It is found that the discrepancies of the contributions of viscous shear forces, and the discrepancies of the vortex effects on the phase and magnitude of the pressure forces lead to the obvious differences among the results under different liquid viscosities.

Numerical Investigation at Lower Stagnation Point Flow Over a Horizontal Circular Cylinder of Brinkman-Viscoelastic Fluid

Investigations on the characteristics of fluid flow in manufacturing processes are essential since it will determine the quality of the end products. The flow might be involved whether the Newtonian (viscous) or non-Newtonian fluid moving over the different body depending on the process activities. Since the experimental works sometimes costly and hazardous, the study via mathematical approach is necessary to counter the limitations. Hence, this paper aims to investigate the flow at lower stagnation point over a horizontal circular cylinder on Brinkman Viscoelastic fluid embedded in porous medium. Mathematical model is constructed in terms of partial differential equations with some physical conditions to represent the condition of the problem. An appropriate non-dimensional variable is introduced to transform the model into the solvable system which is in less complexity, and then the system is solved using the Runge-Kutta-Fehlberg method. The numerical solutions for the temperature and velocity profiles as well as skin friction and heat transfer coefficient are computed and presented in graphical and tabular form. The feature of the flow and heat transfer characteristics for various values of mixed convection, Brinkman and viscoelastic parameter are analysed and discussed. This study has found that the incremented Brinkman and viscoelastic parameter have declined the fluid velocity while opposite trend is observed for temperature distribution. The theoretical results produced are relevance to researchers and engineers. It can be used for comparative purposes in data validation or experimentation study.

Effect of fibrous porous material on natural convection heat transfer from a horizontal circular cylinder located in a square enclosure

A numerical simulation study was carried out to investigate a steady two-dimensional laminar natural convective heat transfer from a uniformly heated inner circular cylinder placed inside an air-filled square enclosure with a porous material. The enclosure’s side and upper walls were isothermal, while the bottom wall was adiabatic. All the numerical calculations were performed in the range of Rayleigh numbers between 103 and 107. The material porosity (ε), the solid to fluid thermal conductivity ratio (kr), and Darcy number in the present study were 1.0, 0.5, and 0.01, respectively. The results showed that for Rayleigh numbers that are less than 106, the isotherms are almost parallel inside the three cold walls except for the corners of the adiabatic bottom wall. The rates of vertical velocity are higher than the horizontal velocity, especially at higher Grashof numbers. Also, the use of fibrous porous material with low thermal conductivity relative to the fluid thermal conductivity reduces the values of average Nusselt number, in addition to reducing the horizontal and vertical velocities along the horizontal axis.

Numerical solutions of convective transport on Brinkman-viscoelastic fluid over a bluff body saturated in porous region

Convective is a fundamental mechanism in heat transfer analysis. Convective heat transport refers to the transfer of heat from one stage to another. In order to produce the preferred output, it is critical to understand the properties of fluid flow. In this study, mixed convection flow is considered, which is defined as a situation where the forces of pressure and buoyancy interact. The goal of this endeavor is to scrutinize the numerical solution of Brinkman-viscoelastic fluid for mixed convection transport over a horizontal circular cylinder as one of the bluff body geometry. Using the necessary similarity transformation, the governing equations were converted into a less complicated form and numerically solved using Keller-box procedure. The influence of mixed convection, Brinkman and viscoelastic parameters towards the fluid velocity and temperature together with skin friction and heat transfer coefficient is analyzed and demonstrated in graphs and tables. This study has revealed that the distribution of fluid velocity, skin friction and heat transfer coefficient had strengthened due to rising values of mixed convection parameter and declined by virtue of increasing viscoelastic and Brinkman parameters. The temperature profile, on the other hand, clearly demonstrates the increasing trend as the Brinkman and viscoelastic parameter increase and declines because of mixed convection. The results show that all of the significant parameters in this investigation affluence the fluid flow characteristics. The provided theoretical results will develop a thorough understanding on boundary layer issues and will be used as a reference for future research or validation.

Development and validation of a numerical wave tank based on the Harmonic Polynomial Cell and Immersed Boundary methods to model nonlinear wave-structure interaction

A fully nonlinear potential Numerical Wave Tank (NWT) is developed in two dimensions, using a combination of the Harmonic Polynomial Cell (HPC) method for solving the Laplace problem on the wave potential and the Immersed Boundary Method (IBM) for capturing the free surface motion. This NWT can consider fixed, submerged or wall-sided surface piercing, bodies. To compute the flow around the body and associated pressure field, a novel multi overlapping grid method is implemented. Each grid having its own free surface, a two-way communication is ensured between the problem in the body vicinity and the larger scale wave propagation problem. Pressure field and nonlinear loads on the structure are computed by solving a boundary value problem on the time derivative of the potential. The stability and convergence properties of the solver are studied basing on extensive tests with standing waves of large to extreme wave steepness, up to H/λ=0.2 (H is the crest-to-trough wave height and λ the wavelength). Ranges of optimal time and spatial discretizations are determined and high-order convergence properties are verified, first without using any filter. For cases with either high level of nonlinearity or long simulation duration, the use of mild Savitzky-Golay filters is shown to extend the range of applicability of the model. Then, the NWT is tested against two wave flume experiments, analyzing forces on bodies in various wave conditions. First, nonlinear components of the vertical force acting on a small horizontal circular cylinder with low submergence below the mean water level are shown to be accurately simulated up to the third order in wave steepness. The second case is a dedicated experiment with a floating barge of rectangular cross-section. This very challenging case (body with sharp corners in large waves) allows to examine the behavior of the model in situations at and beyond the limits of its formal application domain. Though effects associated with viscosity and flow separation manifest experimentally, the NWT proves able to capture the main features of the wave-structure interaction and associated loads.

Magnetohydrodynamic Effects in Mixed Convection of Ferrofluid Flow at Lower Stagnation Point on Horizontal Circular Cylinder

In this paper, mixed convection of ferrofluid containing magnetite, Fe3O4 with ferroparticles suspended in water at the lower stagnation point on a horizontal circular cylinder is investigated. The partial differential equation which derived from the transformation of the dimensional governing equation and non-similarity transformation with the consideration of the effect of magnetohydrodynamic (MHD) are solved numerically by using Keller-box method. The influences of an external magnetic field on ferrofluid flow and heat transfer are then discussed. The results showed that the viscosity depends on the ferroparticle volume fraction and ferrofluid temperature. The uniform magnetic field that produced Lorentz force acts as a determiner of the trend of fluid movement and has the tendency to control the cooling rate of the surface.

Hydrodynamic Forces on a Submerged Circular Cylinder in Two-layer Fluid with an Ice-cover

We consider problems based on linear water wave theory concerning the interaction of wave with horizontal circular cylinder submerged in two-layer ocean consisting of a upper layer of finite depth bounded above by an ice-cover and below by an infinite layer of fluid of greater density, the ice-cover being modelled as an elastic plate of very small thickness. Using the method of multipoles, we formulate the problems of hydrodynamic forces on a submerged cylinder in either the upper or the lower layer. The vertical and horizontal forces on the circular cylinder are obtained and depicted graphically against the wave number for various values of flexural rigidity of ice-cover to show the effect of the presence of ice-cover on these quantities. Also when the flexural rigidity and surface density of the ice-cover are taken to be zero, the ice-cover tends to a free-surface. Then all the forces are the same as in the case of two-layer fluid with free surface.

Mixed convection flow of Brinkman fluid with convective boundary condition at lower stagnation point of horizontal circular cylinder

Convective heat transfer occurs when heat is transferred from one level to another upon the motion of fluid. Understanding on the characteristics of fluid flow is essential since it will produce the desired output of the product. therefore, this paper examines the mixed convection flow at lower stagnation point of horizontal circular cylinder on Brinkman fluid saturated in porous region with convective boundary condition. The influence of Brinkman, mixed convection and conjugate parameter on the flow field are studied. To reduce the complexity of the equations, a suitable similarity transformation is used. The numerical results of governing equations are obtained via bvp4c tools in Matlab. The effect of mixed convection, Brinkman and conjugate parameter on the temperature and velocity profile, skin friction coefficient together with Nusselt number are analysed and portrayed in graph and table form. The velocity profile increased with improving mixed convection and conjugate value, but decreased with increasing Brinkman factor. It is also discovered that the temperature decrease when the mixed convection parameter increase. This theoretical results will benefit the researchers, particularly in the manufacturing industry, in validating experimental study data.

Augmentation of Natural Convection Heat Transfer from Horizontal Circular Cylinder by Means of Helical-Coil-Turns.(Dept.M)

Augmentation of steady natural convection heat transfer from horizontal cylinder were studied experimentally. The test section consisted of a brass circular cylinder, of 301 mm length and diameters of 21.5/ 12.2 mm, heated with a constant heat flux supplied by an electrical resistive heater made of nickel-chrome wire coil. The experimental data have been obtained when the test cylinder is covered with eight type of helical-wire-coils wounded around it as well as when the cylinder is bare. The number of helix per meter length (NC) varied from 178 to 835 and the number of turns of each helical-coil per meter length (Nt) Varied from 50 to 196 at cylinder-to-helix diameters ratio (D/d) of 4.22. The tests were conducted in aim in the range of Rayleigh number of 2000 to 52000 and Prandtl number of nearly The results of heat transfer coefficient are rep resented in the relation of average Nusselt number versus Rayleigh number. The relations indicate that (Nu) is a significant function of (Ra), (Ne) and (Nt). The augmentation of heat transfer in case of use the helical-wire-coils varied from 5 to 106 % compared with the bare cylinder.

Influence of boundary layer thickness and gap ratios on three-dimensional flow characteristics around a circular cylinder in proximity to a bottom plane

Three-dimensional flow characteristics around a horizontal circular cylinder near a plane boundary are investigated using a Direct Numerical Simulation (DNS) at the Reynolds number of 350. The cylinder has a gap-to-diameter ratio G/D = 0.2, 0.6 and 1.0, with a boundary layer thickness-to-diameter ratio δ/D = 0, 0.7 and 1.6. The hydrodynamic forces, pressure distributions, vortex shedding patterns, wake transitions and flow three-dimensionality features are presented and discussed. The hydrodynamic forces and pressure distributions are strongly dependent on G/D and δ/D. The mean drag coefficient decreases with increasing δ/D, whereas the mean lift coefficient increases with decreasing G/D. The pressure coefficient distribution around the cylinder changes from being asymmetric to symmetric as G/D is increased from 0.2 to 1.0, resulting in a development from the suppressed state to the fully developed state of the vortex shedding. As for the vortex dynamics, the strength and size of primary vortices decrease with increasing δ/D. The crossing trajectories exhibiting an inversion on the position of clockwise and counterclockwise vortices can only be observed in the wake when G/D is greater than a critical value below which the vortex shedding is completely suppressed, and when the cylinder is partially immersed into the boundary layer (G/D < δ/D < G/D + 1). An intrinsic switching between the single- and dual-frequency modes of the drag coefficient is found to be related to a complex interaction between the boundary layer and the near-wake vortex shedding. For a specific G/D, the flow three-dimensionality represented by the spanwise kinetic energy is found to decrease with increasing δ/D. For a specific δ/D, the spanwise kinetic energy shows a non-monotonic trend with the variation of G/D.

Free Convection Boundary Layer Flow over a Horizontal Circular Cylinder in Al2O3-Ag/Water Hybrid Nanofluid with Viscous Dissipation

In this paper, the mathematical model of free convection boundary layer flow of horizontal circular cylinder immersed in Ag/Water nanofluid and Al2O3-Ag/Water hybrid nanofluid are considered. The governing non-linear partial differential equations are first transformed to a more convenient way before being solved numerically using the Keller-box method. The numerical values for the reduced Nusselt number and the reduced skin friction coefficient are obtained and illustrated graphically as well as temperature profiles and velocity profiles. Effects of the Prandtl number, Eckert number and nanoparticle volume fraction are analyzed and discussed. It is found that the Nusselt number for Al2O3-Ag/Water hybrid nanofluid is comparable with Ag/Water nanofluid with a reduction in skin friction coefficient. The preliminary results reports here are important as a reference in exploring the potential of hybrid nanofluid to reduce the production cost compared to the used of metal nanofluid.

Analysis of the Physical Behavior of the Periodic Mixed-Convection Flow around a Nonconducting Horizontal Circular Cylinder Embedded in a Porous Medium

An oscillatory mixed-convection fluid flow mechanism across a nonconducting horizontal circular cylinder embedded in a porous medium has been computed. For this purpose, a model in the form of partial differential equations is formulated, and then, the governing equations of the dimensionless model are transformed into the primitive form for integration by using primitive variable formulation. The impact of emerging parameters such as porous medium parameter Ω , Richardson number λ , magnetic force parameter ξ , and Prandtl number Pr on skin friction, heat transfer, and current density is interpreted graphically. It is demonstrated that accurate numerical results can be obtained by the present method by treating nonoscillating and oscillating parts of coupled partial differential equations simultaneously. In this study, it is well established that the transient convective heat transfer, skin friction, and current density depend on amplitude and phase angle. One of the objects of the present study is to predict the mechanism of heat and fluid flow around different angles of a nonconducting horizontal circular cylinder embedded in a porous medium.

Computation of non-similar solution for magnetic pseudoplastic nanofluid flow over a circular cylinder with variable thermophysical properties and radiative flux

PurposeGenerally, in computational thermofluid dynamics, the thermophysical properties of fluids (e.g. viscosity and thermal conductivity) are considered as constant. However, in many applications, the variability of these properties plays a significant role in modifying transport characteristics while the temperature difference in the boundary layer is notable. These include drag reduction in heavy oil transport systems, petroleum purification and coating manufacturing. The purpose of this study is to develop, a comprehensive mathematical model, motivated by the last of these applications, to explore the impact of variable viscosity and variable thermal conductivity characteristics in magnetohydrodynamic non-Newtonian nanofluid enrobing boundary layer flow over a horizontal circular cylinder in the presence of cross-diffusion (Soret and Dufour effects) and appreciable thermal radiative heat transfer under a static radial magnetic field.Design/methodology/approachThe Williamson pseudoplastic model is deployed for rheology of the nanofluid. Buongiorno’s two-component model is used for nanoscale effects. The dimensionless nonlinear partial differential equations have been solved by using an implicit finite difference Keller box scheme. Extensive validation with earlier studies in the absence of nanoscale and variable property effects is included.FindingsThe influence of notable parameters such as Weissenberg number, variable viscosity, variable thermal conductivity, Soret and Dufour numbers on heat, mass and momentum characteristics are scrutinized and visualized via graphs and tables.Research limitations/implicationsBuongiorno (two-phase) nanofluid model is used to express the momentum, energy and concentration equations with the following assumptions. The laminar, steady, incompressible, free convective flow of Williamson nanofluid is considered. The body force is implemented in the momentum equation. The induced magnetic field strength is smaller than the external magnetic field and hence it is neglected. The Soret and Dufour effects are taken into consideration.Practical implicationsThe variable viscosity and thermal conductivity are considered to investigate the fluid characteristic of Williamson nanofluid because of viscosity and thermal conductivity have a prime role in many industries such as petroleum refinement, food and beverages, petrochemical, coating manufacturing, power and environment.Social implicationsThis fluid model displays exact rheological characteristics of bio-fluids and industrial fluids, for instance, blood, polymer melts/solutions, nail polish, paint, ketchup and whipped cream.Originality/valueThe outcomes disclose that the Williamson nanofluid velocity declines by enhancing the Lorentz hydromagnetic force in the radial direction. Thermal and nanoparticle concentration boundary layer thickness is enhanced with greater streamwise coordinate values. An increase in Dufour number or a decrease in Soret number slightly enhances the nanofluid temperature and thickens the thermal boundary layer. Flow deceleration is induced with greater viscosity parameter. Nanofluid temperature is elevated with greater Weissenberg number and thermophoresis nanoscale parameter.

Flow of Jeffrey Fluid over a Horizontal Circular Cylinder with Suspended Nanoparticles and Viscous Dissipation Effect: Buongiorno Model

Mathematical model of Jeffrey fluid describes the property of viscoelastic that clarifies the two components of relaxation and retardation times. Nevertheless, the poor thermal performance of Jeffrey fluid has been a key issue facing the public. This issue can be accomplished by the use of nanofluid that has superior thermal performance than the conventional fluids. A better cooling rate in industry is in fact not appropriate to attain by the thermal conductivity of the conventional fluids. On that account, the present study aims to delve into the impact of viscous dissipation and suspended nanoparticles on mixed convection flow of Jeffrey fluid from a horizontal circular cylinder. A concise enlightenment on the separation of boundary layer flow is included and discussed starting from the lower stagnation point flow up to the separation point only. The non-dimensional and non-similarity transformation variables are implemented to transform the dimensional nonlinear partial differential equations (PDEs) into two nonlinear PDEs, and then tackled numerically through the Keller-box method. Representation of tabular and graphical results are executed for velocity and temperature profiles as well as the reduced skin friction coefficient, Nusselt number and Sherwood number to investigate the physical insight of emerging parameters. It was found that the incremented ratio of relaxation to retardation, Deborah number and Eckert number have delayed the boundary layer separation up to 120o

Heat Transfer Improvement in MHD Natural Convection Flow of Graphite Oxide/Carbon Nanotubes-Methanol Based Casson Nanofluids Past a Horizontal Circular Cylinder

This numerical investigation intends to present the impact of nanoparticles volume fraction, Casson, and magnetic force on natural convection in the boundary layer region of a horizontal cylinder in a Casson nanofluid under constant heat flux boundary conditions. Methanol is considered as a host Casson fluid. Graphite oxide (GO), single and multiple walls carbon nanotubes (SWCNTs and MWCNTs) nanoparticles have been incorporated to support the heat transfer performances of the host fluid. The Keller box technique is employed to solve the transformed governing equations. Our numerical findings were in an excellent agreement with the preceding literature. Graphical results of the effect of the relevant parameters on some physical quantities related to examine the behavior of Casson nanofluid flow were obtained, and they confirmed that an augmentation in Casson parameter results in a decline in local skin friction, velocity, or temperature, as well as leading to an increment in local Nusselt number. Furthermore, MWCNTs are the most efficient in improving the rate of heat transfer and velocity, and they possess the lowest temperature.

Lower Stagnation Point Flow of Convectively Heated Horizontal Circular Cylinder in Jeffrey Nanofluid with Suction/Injection

Lower stagnation point flow of Jeffrey nanofluid from a horizontal circular cylinder is addressed under the influences of suction/injection, mixed convection and convective boundary conditions. Copper (Cu) is taken as the nanoparticles while Carboxymethyl cellulose (CMC) water is taken as the base fluid. The transformed boundary layer equations through the non-dimensional variables and non-similarity transformation variables are subsequently tackled by means of the Runge-Kutta Fehlberg method (RKF 45). The impact of dimensionless parameters such as the suction/injection, nanoparticles volume fraction and Deborah number are graphically presented and discussed in detail. The outcomes reveal that the velocity and temperature profiles are both augmented with rising values of nanoparticles volume fraction. Velocity profile escalates as suction/injection parameter rises but declines as Deborah number upsurges. Temperature profile reduces when suction/injection parameter enlarges and augments when Deborah number increases.

Flow around a near-bed horizontal circular cylinder mounted on a vertical wall

Flow around a near-bed horizontal circular cylinder mounted on a vertical side wall is simulated numerically in this study. The purpose of the study is to investigate the flow characteristics around the junction area between the cylinder and two plane boundaries. The effects of gap to diameter ratio (G/D = ∞, 0.5 & 0.2), Reynolds number based on the diameter (ReD = 1250, 2500 & 5000) and the length to diameter (aspect) ratio (L/D = 10, 20 & 40) are investigated. It is found that the three-dimensional flow structures formed in the junction area between the vertical wall and the cylinder are strongly affected by the gap ratio. Highly three-dimensional flow structures (i.e. oscillations of horseshoe vortices) are observed in the influence of gap ratio and Reynolds number. The end effect induced by the vertical wall is limited within 0.7D in the spanwise direction, 0.5D upstream and 3D downstream of the cylinder. The extent of the end effect is not sensitive to the gap ratio, Reynolds number or the aspect ratio.

Hydrodynamic Forces on a Submerged Horizontal Circular Cylinder in Uniform Finite Depth Ice Covered Water

Hydrodynamic forces on a submerged cylinder in uniform finite depth ice-covered water is formulated by using the method of multipoles, the ice-cover being modelled as an elastic plate of very small thickness. The forces (vertical and horizontal) are obtained analytically as well as numerically and depicted graphically for various values of flexural rigidity of the ice-cover to show the effect of its presence. When the flexural rigidity and surface density of the ice-cover are taken to be zero, then the curves for the forces almost coincide with the curves for the case of uniform finite depth water with free surface.

Trapped flexural waves supported by a pair of identical cylinders in a two-layer fluid

Existence of trapped waves in ocean shows the presence of discrete wave frequencies in the continuous spectrum. In the present work, we compute those trapped mode frequencies due to a pair of identical horizontal circular cylinders submerged in one of the layers of a two-layer fluid with a thin ice-cover at the upper layer and an infinite depth for the lower layer. Theory is developed for multiple cylinders but numerical computation is carried out only for a pair of cylinders. Due to a thin ice-cover replacing the free surface, a fifth-order boundary condition is to be considered in the upper layer that makes the problem complex and challenging but more practical. Considering linear water wave theory, the boundary value problem is developed through modified Helmholtz equation and associated conditions. Subsequently, applying multipole expansion method, an infinite system of homogeneous linear equations with complex coefficients is obtained and solved. By fixing the geometrical parameters and density ratio, the trapped mode frequencies are computed numerically by tracing the zeros of the determinant generated from the truncated system of the above mentioned equations. In the first instance, the cylinders are placed in the lower layer and the variation of trapped modes is examined by varying different parameters such as upper layer depth, submergence depth, ice-cover thickness etc. In the second instance, the same conditions and configurations are considered in the upper layer and existence of trapped modes is looked into in a similar manner. For the considered parameter values, the number of trapped modes enclosed in the continuous spectrum decreases corresponding to an increase in the flexural rigidity of the ice-cover. The trapped mode frequency decreases when either the the upper layer depth or the submergence depth increases. Further, corresponding to a small change in the separation parameter, embedded trapped modes are observed to cease to exist for the free surface and also for a very thin ice-cover. Our findings are supported by graphs depicting various modes. Further, comparison of present result with an established result shows excellent agreement.