Cylinder Radius Research Articles

Heat transfer in viscous flow over a heated cylinder of nonuniform radius

A heated cylinder of a variable radius and porous surface is moving (stretching and shrinking) with variable velocity in a stagnant fluid. Heat transfer in the flow of viscous fluid from such a cylinder is investigated in this paper. A generalized model is simulated and it presents the diffusion of heat inflow over a cylinder of nonuniform (uniform) diameter, whereas, the porous and variably heated cylinder is stretched (shrunk) with linear and nonlinear (uniform) velocity. The system of nonlinear coupled ordinary differential equations (ODE’s) and boundary conditions (BC’s) is solved numerically for different values of the existing governing parameters. Field quantities, the rate of heat transfer (at the surface of the cylinder), and skin friction are evaluated numerically and the new data is shown in different graphs and tables. For the sake of validity and correctness, the modeled problem and its output are compared with published work in the open literature. Moreover, the uniform, linear and nonlinear nature of injection (suction), stretching (shrinking) velocities, geometry, and surface temperature are explicitly considered and their behavior is frequently demonstrated on the field variables and quantities of physical interest. The validity of the modeled problem is checked, however, we obtained results for both linear and nonlinear (uniform) injection (suction) and stretching (shrinking) velocities. It is confirmed that the nonlinear and nonuniform nature of a cylinder’s surface, injection (suction), stretching (shrinking) velocities, the size of a cylinder, and surface temperature, played a significant role in the variation of all field quantities, skin friction, and the rate of heat transfer.

Self-Aassembly of core-corona colloids under cylindrical confinement: A Monte Carlo study

Hierarchical self-assembly provides a versatile pathway for generating new functional materials. In this work, we show that confining core-corona colloids in a cylindrical cavity leads to an interesting repertoire of self-organized structures, some of which display hierarchical organization. Particle density, corona size, and cylinder radius were varied systematically to elucidate their role in colloidal arrangements. Extensive Monte Carlo simulations were performed to attain structural phase diagrams for the systems studied: complex mesophases are observed for certain model parameters. Among the observed morphologies are helical arrangements: simple and double helices consisting of particle stripes ordered around a cylindrical axis with a pitch dictated by the corona size. We also report the structural analysis of morphologies displaying stratified packing. Length scales of the core-corona particles and confining cylinders studied in this work are comparable to reported experimental systems. Our results offer practicable molecular design principles to obtain specific colloidal nanocrystalline arrangements for targeted applications.

Analysis of convection heat transfer on multiscale rough superhydrophobic and liquid infused surfaces

Multiscale rough superhydrophobic or slippery liquid infused porous surfaces have gained much interest in recent years for their improved transport phenomena properties. While there have been several studies on drag reduction and condensation on non-wetting surfaces, convection heat transfer that is important in many thermal and thermochemical applications has not been addressed systematically. This article utilizes a fractal description of rough surface topographies to develop analytical models for the Nusselt number and the thermal hydraulic factor for fluid flow and heat transfer inside a cylinder with non-wetting surfaces. For air-infused superhydrophobic surfaces, the model considers the dynamic stability of the air/fluid interface in the asperities. Using the analytical formulations and the stability criteria, systematic studies are presented on the effects of the fractal surface parameters, cylinder radius and Reynolds number on the convective heat transfer characteristics, from which surface texture design maps are developed for maximizing the convection heat transfer. It is shown that multiscale non-wetting surfaces are most effective in the range of lower Reynolds number and small cylinder radius for achieving the best convective heat transfer and thermal hydraulic performance. Applying the models to actual non-wetting surface topographies fabricated using electrodeposition and chemical etching, it is shown that contrary to prevailing notion, superhydrophobicity, characterized by the highest contact angles, does not always lead to the maximum convective heat transfer performance, and that under certain fluid flow conditions, hydrophobic surfaces may offer a greater thermal performance.

Entropy and convection effect on magnetized hybrid nano-liquid flow inside a trapezoidal cavity with zigzagged wall

This work consists of a description of the laminar flow of a nanoliquid in a trapezoidal cavity, In addition to measuring convective exchanges that take place there. The cavity in question is geometrically trapezoidal at right angles containing a hybrid Cu-Al2O3/Water nanofluid. The enclosure with the zigzagged wall is under the action of an external magnetic field and uniform at an angle of inclination γ. The Darcy-Forchheimer model has been used for the permeable domain. The impact due to Hartmann number (0 ≤ Ha ≤ 100), rotation speed (−4000 ≤ ω ≤ 4000), magnetic field inclination angle (0°≤γ ≤90°), Rayleigh number (103 ≤ Ra ≤ 105), cylinder radius (5 × 10−2 ≤ r ≤ 0.2), various N and volumetric fraction (0 ≤ ϕ ≤ 0.08) are investigated. Numerical results in Nusselt's number terms are validated with those in the literature. The obtained findings indicate that the flow of the nanofluid is strongly influenced through the application of a magnetic field, and the thermal performance of the cavity is improved with the augmentation of the Ra and Hartmann numbers. As well as the nanoparticles (NPs) improve heat transport, their rise in the volume fraction augments the total entropy generation with or without the application of the magnetic field and zigzags number (N). However, their contribution to improving heat transfer becomes less convincing with the rise in the Ha.

Study of engine-oil based CNT nanofluid flow on a rotating cylinder with viscous dissipation

An axisymmetric viscous carbon nanotube (CNT) nanofluid flow exterior to a rotating circular cylinder of radius a 0 along with viscous dissipation and magnetohydrodynamic (MHD) is considered here. The two-phased Buongiorno’s model is employed to observe the thermal energy transport in nanofluid with engine-oil as a background fluid and two distinct nanoparticles, i.e., single-walled (SWCNTs) and multi-walled (MWCNTs). The flow is driven because of the torsional motion and stretching of the cylinder along the z-direction, which constitutes the axial pressure gradient. It is seen that in the presence of a magnetic field, the axially dependent swirling motion of the cylinder creates a light transverse flow in the meridional plane, which is the principal cause for the wall jet phenomenon on the axial axis. The function computing the numerical solution is bvp5c, which is available in Matlab®. It is noted that for both SWCNTs/MWCNTs cases, thermal and mass transport coefficients are decreasing function of Prandtl and Schmidt numbers, respectively. However, they are augmented due to the presence of strong Lorentz force. The values for wall stress parameters (WSPs) are determined as a function of a magnetic parameter for 0.01 ≤ Re ≤ 102 (where Re is Reynolds number). It is also perceived that the axial WSP decreases due to an increase in values of Re, but an increase in numerical values of azimuthal WSP and Nusselt number is noticed.

Fluid Flow in Composite Cylindrical Regions

A steady, 2-D, viscous fluid flow past a fixed solid cylinder of radius ‘a’ has been considered where the density is constant for considered fluid. The flow of fluid happens in 3 regions namely fluid, porous and fluid region. The constitutive equations for the flow in porous and fluid regions are Brinkman and Stokes equations respectively. The variation of flow patterns by means of streamlines has been analysed by applying different boundary conditions at the interface of fluid – porous and porous – fluid regions and also on the surface of the solid cylinder assuming that the even velocity far off from the fluid region. The nature of streamlines is observed for the distinct values of porous parameter ‘σ’ and the corresponding flow behaviour is analysed graphically. From the obtained results it is noticed that increase in porous parameter, suppress the fluid flow in porous region consequently the fluid moves away from the solid cylinder.

Effect of combined natural convection and non-gray gas radiation on entropy generation through a cylindrical annulus

The present work is focused on the interaction between natural convection and thermal radiation in a participating medium through a cylindrical annulus. The Ray Tracing method through the quadrature T10 has been adopted in association with the Statistical Narrow Band correlated-k (SNBCK) model to solve the radiative part of the problem. Special attention is given to entropy generation and its dependency on the various governing parameters including the inner cylinder temperature, the outer cylinder radius, emissivities of the annulus walls, and the gas pressure. The results show that radiation remarkably affects the structure of the fluid flow and the temperature distribution, enhancing heat exchanges in the annulus. Moreover, it is found that the volumetric entropy generation due to radiative processes of medium should not be neglected and is comparable to the volumetric entropy generation due to heat conduction. It is also shown that increasing the emissivities of the cylinders intensifies entropy generation due to radiation through walls, but on the other hand doesn’t affect the volumetric entropy generation.

Three-Dimensional Mixed Convection in a Rectangular Enclosure Containing a Circular Cylinder

This study carried out a three-dimensional, unsteady, numerical simulation to investigate the effects of the cylinder radius, Reynolds number, three-dimensionality and unsteadiness on the mixed convection in a rectangular enclosure containing a cold circular cylinder. The variations in the cylinder radius in the range of 0.1 to 0.3 times the length of the enclosure and the Reynolds number in the range of 100 to 1000 were considered. The flow and thermal structures reached three different regimes depending on the radius of cold cylinder and Reynolds number. The patterns in the flow and thermal fields were categorized into three regimes: steady two-dimensional convection, steady three-dimensional convection, and unsteady three-dimensional convection. The temperature distribution, vortical structure, and Nusselt number for a heated bottom wall were extensively analyzed. The transition of flow regime, flow instability and the heat transfer performances were influenced by the presence of cylinder. In addition, the three-dimensional flow characteristics were quantified using orthogonal enstrophy, and the unsteady characteristics were investigated by carrying out the frequency analysis of Nusselt number. As the three-dimensionality in flow and thermal fields increases and the flow regime changes to the three-dimensional unsteady convection regime, the difference in the results of two and three-dimensional simulations also increases.

Study of mixed convection in two layers of saturated porous medium and nanofluid with rotating circular cylinder

In this study, a numerical investigation of mixed convective heat transfer in a square enclosure partitioned in two layers with a rotating circular cylinder at the middle of the cavity has been carried out. The experiments are performed with Al2O3–water nanofluid (upper layer) and superposed porous medium (lower layer). The upper and lower horizontal walls are assumed to be insulated, while the left and right walls are kept at high and low temperature respectively. Galerkin finite element method has been used to solve the dimensionless governing equations. This study is focused to investigate the effect of Darcy number (10−2≤ Da ≤10−5), Rayleigh number (103≤ Ra≤106), dimensionless angular rotational velocity (−6000≤ W ≤ 6000), solid volume fraction (0≤ ɸ ≤0.06), and the radius of the inner circular cylinder (R = 0.1, 0.2 and 0.3) on the heat transfer, fluid flow, and the physical characteristics thermal of the thermal fields. The results show that the intensity of the flow, steep temperature gradient, and the average Nusselt number (Nu) increase with increasing the value of Darcy number, Rayleigh number, and solid volume fractions at any cylinder radius. Moreover, the recirculation and isotherm distribution lines of the fluid at low Darcy numbers are high when the cylinder rotates counter-clockwise compering with clockwise. The findings also revealed that when W = 0, the maximum Nu is at R = 0.1 and decreases as the cylinder radius increases. Moreover, at high Darcy number, the highest local Nusselt number is found at the porous layer region in case of clockwise rotation while at the nanofluid layer region in case of anti-clockwise rotation.

Evaluation of effective area of air piston gauge with limitations in piston–cylinder dimension measurements

The air piston gauge (APG) has been established at the National Physical Laboratory, India (NPLI) for Pascal realization since 2002. The APG at NPLI has been considered a transfer pressure standard because it has been calibrated against the primary pressure standard, i.e. ultrasonic interferometer manometer. As per existing international protocol, the APG establishment as a primary standard, the effective area (A e) of piston–cylinder (p–c) assembly and masses must be directly traceable to SI units. We have calculated A e and associated uncertainty of p–c assembly using the theory of rarefaction gas dynamics, which is based on dimension measurements. The value of A e is obtained for varying temperatures and radii of piston and cylinder in their respective uncertainty limits. The variation of the cylinder's inner radius within its uncertainty limit of 0.7 µm includes the expected effective area, i.e. 3.356 775 (5) cm2. The effective area’s expected values are obtained for the cylinder’s radius of 10.338 00 (2) mm, which is approximately 0.65 µm away from the value obtained from dimensional measurements and well within the uncertainty limit. Therefore, to get the effective area of 3.356 775 (5) cm2, the uncertainty of the cylinder’s radius should be at least one order less (similar to piston’s radius) than that of the present value. The precision in dimension measurement of the cylinder's internal radius is the critical parameter for effective area calculation of p–c assembly.

MATHEMATICAL MODELING OF THE HEAT TRANSFER PROCESS IN THE SYSTEM OF MULTILAYER CYLINDRICAL SOLID BODIES CONSIDERING INTERNAL SOURCES OF HEAT

The article is devoted to the application of the direct method to the study of heat transfer processes in the "continuous cylinder inside a multilayer cylindrical shell" system. To solve the initial problem, an auxiliary problem is posed with a “remote” cylinder of sufficiently small radius. The solution is based on the reduction method, the concept of quasiderivatives, the Fourier scheme using the modified eigenfunctions method. The solution to the original problem was obtained by following the radius of the remote cylinder to zero.

Strong coupling between in-plane photonic modes and out-of-plane plasmonic modes in 2D metal–dielectric–metal nanocylinder arrays

Arrays of metal–dielectric–metal (MDM) multilayer nanostructure can support various kinds of plasmonic modes including in-plane (IP) localized/delocalized surface plasmons or lattice resonances, photonic waves, as well as out-of-plane (OP) plasmon modes. Hybridization between different modes offers rich physics such as lasing, sub- and super-radiant modes, and efficient light absorption. While interplays between different sets of in-plane modes have been intensively investigated, the interaction between in-plane and out-of-plane modes is rarely explored. Here, we propose a MDM nanostructure with 2D nanocylinder array and study in detail the strong coupling between the in-plane photonic modes at the dielectric layer and the out-of-plane plasmon modes excited at the cylinder sidewalls. We demonstrate the strong coupling between the localized second-order IP mode and the first-order OP mode with a Rabi splitting up to 250 meV in the near-infrared region. A new IP mode arising from the radiative field can induce another kind of strong coupling with OP modes as the cylinder radius is larger than 98 nm. The underlying physics within this plasmon–photon system is quantitatively revealed by the coupled oscillator model and calculated E-field distribution. The proposed MDM system provides a good platform for investigating multimode coupling and nano-optics devices.

Determination of the conditions of laminar/turbulent flow transition using pressure compensation method in the case of Ga75In25 alloy stirred by RMF

The effect of melt-flow on the microstructure has been investigated by performing several unidirectional solidification experiments where the melt was flown in a rotating magnetic field. It is a well-known fact that the angular frequency of the melt cylinder always differs from the angular frequency of the magnetic field. However, it proves to be very difficult to determine during the experiments. In our present study, the magnetic Taylor number and the Reynolds number were determined as a function of the radius of melt cylinder, the magnetic induction, and the angular frequency of magnetic field using the real angular frequency defined by the so-called pressure-compensation method developed earlier in the case of Ga75In25 alloy. The simulations developed for performing similar experiments can be checked as well as the different experiments can be compared correctly by using the obtained measurement results. By knowing the critical Reynolds number belonging to the laminar/turbulent flow transition, the value of critical magnetic induction belonging to the transition was determined as a function of the radius of the melt cylinder.

Analysis of SH wave in hollow piezo-composite cylinder with coupled imperfect interface condition

Present study primarily focuses on interpreting the propagation pattern of Shear horizontal (SH) wave in a piezo-composite layered cylinder. The structure consists of three concentric cylinders composed of hollow fiber-reinforced (FR) cylinder enclosed within piezomagnetic (PM) cylinder along the curved surface area which is similarly superimposed by a piezoelectric (PE) cylinder. The overall system is believed to be pre-stressed in a circumferential direction. The common boundary between each of the cylinder is demonstrated as imperfectly bonded. At the interface of PM and PE media, mechanical, electrical, magnetic and inter-coupled types of imperfections are assumed. Dispersion relations have been obtained for both the electrically open magnetically short (EOMS) and electrically short magnetically open (ESMO) circuit condition. Dispersion curves have been plotted to unravel the peculiarities of parameters like the radius of the hollow cylinder, thickness of FR and PM cylinder, thickness ratio of PM and PE cylinder, initial stress parameters, helical angle of the reinforcement. The influence of different interface parameters on the phase velocity of the wave has been studied and marked distinctly. For a detailed study, two successive modes have been plotted. Present study may help in improving the performance of piezo-composite cylindrical surface acoustic wave (SAW) sensors.

Role of fluid phase in compression of nonlinear elastic fluid-saturated porous medium

This paper is about the role of the fluid in supporting the overall compressive stress applied to nonlinear elastic fluid-saturated porous material. The case of large deformation and compressible hyperelastic matrix material is considered. Due to complexity of the problem, a simple model of the porous medium consisting of an assemblage of fluid-filled cylinders is studied in more detail. The procedure for computing the stress partitioning between the solid phase of the cylinder and the fluid in withstanding the overall stress consists of two steps. In the first step, the radial stress σ of given magnitude is applied to outer radius of the fluid-filled cylinder and the radial displacement is determined. In the second step, the displacement of the outer surface of the cylinder is equal to that of the first step but the cavity of the cylinder is empty. The radial stress acting on the outer boundary of the cylinder in the second step is defined as an effective stress in the solid skeleton of the porous medium, σsk. For the given overall stress σ and the computed value of the effective stress σsk, the effective stress supported by the fluid Peff is computed as the difference σ−σsk. Each of the two steps requires a solution to a boundary value problem which is solved numerically with the help of Python bvp solver.

Investigation of the coupling efficiency between graded index photonic crystal-based flat lenses and various types of waveguides

The importance of transmission, guiding and delivery of electromagnetic waves to the targeted part of a photonic circuit, leads to design couplers with high coupling efficiency. In the present work, we apply two types of photonic crystal-based flat lenses for designing the couplers. The lenses are made of annular $${\text{ ZrO }}_{{2}}$$ rods with a triangular structure embedded in air. To design the lenses, the outer radius of the annular cylinders is kept constant while the inner radius follows two linear and parabolic functions. At the next step, the lenses are placed along a slot waveguide, conventional photonic crystal waveguide and funnel-form photonic crystal waveguide, separately, for creating coupled structures. The incident light is focussed by the graded index flat lenses and transmits through the waveguides. In the following, we study the coupling efficiency of all mentioned structures, using finite-difference time-domain and plane wave expansion methods. The results reveal that the coupled funnel-form waveguide with the linear lens gives the highest coupling efficiency, which is $$7.49\,\text{ dB }$$ and shows great improvement compared to the previous works.

Gradient Damage Analysis of a Cylinder Under Torsion: Bifurcation and Size Effects

In this work, an elastic-damage evolution analysis is carried out for a cylinder under torsion made of a material obeying a gradient damage model with softening. Both semi-analytical and asymptotic approaches are developed to analyze the elastic, axisymmetric and bifurcation stages. We show the existence of a fundamental branch where the damage field is asymmetric and localized within a finite thickness from the boundary. By minimizing a generalized Rayleigh quotient, the bifurcation time and modes are obtained as a function of the length scale epsilon =ell /R involving a material internal length and the cylinder radius. We will then focus on these size effects by assuming that epsilon is a small parameter in an asymptotic setting. After justification, specific spatial and temporal rescaled variables are introduced for the boundary layer problem. It is shown that the axisymmetric damage evolution and the bifurcation are governed by two universal functions independent of the length scale. The simulation results obtained by the semi-analytical approach are formally justified by the asymptotic methods.

Thermosolutal convection of a nanofluid in ∧-shaped cavity saturated by a porous medium

Purpose The purpose of this study is to simulate the thermo-solutal convection resulting from a circular cylinder hanging in a rod inside a ∧-shaped cavity. Design/methodology/approach The two dimensional ∧-shaped cavity is filled by Al2O3-water nanofluid and saturated by three different levels of heterogeneous porous media. An incompressible smoothed particle hydrodynamics (ISPH) method is adopted to solve the governing equations of the present problem. The present simulations have been performed for the alteration of buoyancy ratio (−2≤N≤2), radius of a circular cylinder (0.05≤Rc≤0.3), a height of a rod (0.1≤Lh≤0.4), Darcy parameter (10−3≤Da≤10−5), Lewis number (1≤Le≤40), solid volume fraction (0≤ϕ≤0.06), porous levels (0≤η1=η2≤1.5)and various boundary-wall conditions. Findings The performed numerical simulations indicated the importance of embedded shapes on the distributions of temperature, concentration and velocity fields inside ∧-shaped cavity. Increasing buoyancy ratio parameter enhances thermo-solutal convection and nanofluid velocity. Adiabatic conditions of the vertical-walls of ∧-shaped cavity augment the distributions of the temperature and concentration. Regardless the Darcy parameter, a homogeneous porous medium gives the lowest values of a nanofluid velocity. Originality/value ISPH method is used to simulate thermo-solutal convection of a nanofluid inside a novel ∧-shaped cavity containing a novel embedded shape and heterogeneous porous media.

Double-diffusive convection of a rotating circular cylinder in a porous cavity suspended by nano-encapsulated phase change materials

The main objective of this study is to simulate the suspension of a nano-encapsulated phase change material (NEPCM) during the double-diffusive convection flow inside a compound cavity. A novel cavity shape is formed from a central circular cylinder mounted with two rectangular shapes. An incompressible smoothed particle hydrodynamics (ISPH) method is used to solve the governing equations of the present physical problem. A heat capacity of the core-shell layers assisted the phase changes of the encapsulated nanoparticles. The main findings of the performed simulations showed that a fusion temperature controls both location and intensity of a phase change zone inside a cavity. Regardless of the impacts of a buoyancy ratio parameter on the flow speed, the melting-solidification zones are not changing under the variations in a buoyancy ratio parameter. An increase in a radius of a circular cylinder enhances the double diffusive convection and it reduces the intensity of a phase change zone. In addition, the increase in the radius of the circular cylinder powers the average Nusselt and Sherwood numbers. Increasing nanoparticles concentration enhances a phase change zone.

Identification of potential targets for kimberlite exploration using satellite imagery and map combination approach in the Lesotho Kimberlite Province

This study presents the use of satellite data and map combination approach for kimberlite exploration to identify follow-up exploration targets. The study area falls in the Lesotho Kimberlite Province, which hosts diamondiferous kimberlite pipes such as Letseng and Kao in Lesotho, and Monastery and Jagersfontein in South Africa. This study focusses on processing and integration of evidential map layers (geomorphic features, linear structures and kimberlite indicator minerals) that have known correlation with kimberlite occurrence. The evidential map layers were acquired from satellite platforms such as ASTER and SRTM DEM. These layers were integrated to identify favourable sites for detailed follow-up exploration by subdividing the area into high, moderate and low prospective regions based on the number of controlling evidences operating in each sub-region. A follow-up sampling and ground magnetic survey were carried out at one of the high prospective zones to validate the results of the present approach. Kimberlite indicator minerals such as garnet, diopside, ilmenite and chromite were recovered from the collected sample. Several garnets show adhering materials known as kelyphite rims, which are typical surface features of peridotitic garnets having close relationship with diamondiferous kimberlite. Keating correlation coefficient, which uses a simple pattern recognition to locate magnetic anomalies that resemble the response of modelled kimberlite pipes, was applied to ground magnetic data. We used a series of reference kimberlite models composed of homogeneous vertical cylinders of various radius ranging from 50 to 200 m and depth varying from 50 to 500 m. The correlation coefficients between analytical signal grid of modelled kimberlite pipe and observed magnetic data were computed. Following this approach, kimberlite model with correlation coefficients exceeding 80% was selected. By matching the response of modelled kimberlite pipe with the magnetic anomalies, four pipe-like targets were located. The target(s) may be a potential source of the recovered kimberlite indicator minerals since the morphology of these minerals suggest a proximal kimberlitic source.