Concentric Circular Cylinders Research Articles

Application of Box-Behnken design with RSM to predict the heat transfer performance of thermo-magnetic convection of hybrid nanofluid inside a novel oval-shaped annulus enclosure

The study of flow around a stationary or rotating circular cylinder holds substantial importance in numerous engineering disciplines, including building, bridge, and structural engineering. This knowledge is utilized to manage flow-induced vibrations, implement blowing or suction techniques, control moving surfaces, and develop acoustic thrusters and synthetic jets. The current aims to analyze the numerical and RSM optimization with Box–Behnken design (BBD) for the buoyancy driven convective flow and heat management features of Magneto Fe3O4−MWCNTs/water hybrid nanofluid filled inside a novel oval-shaped annulus enclosure with concentric hot circular cylinder. The water used as base fluid and iron oxide and Multiwall carbon nanotubes as nanoparticles. The finite element method is employed to solve numerically the coupled equations. The RSM optimization with Box–Behnken design (BBD) is applied to optimize the heat transfer rate across different three factors. The stream lines, isotherms and line graphs are design for different flow parameters effect. The results indicated that heat transfer is enhanced by using of hybrid nanofluid. The velocity is reduced via increment in Hartmann number. The local Nusselt number is increases with increment in the values of the Rayleigh number. Furthermore the Heat transfer rate is boosted up with increases the concentration of nanoparticles.

Unsteady Dean flow between concentric circular cylinders in the presence of a uniform axial magnetic field

An analysis is carried out on the unsteady Dean flow of an incompressible electrically conducting viscous fluid between two concentric, stationary permeable circular cylinders in the presence of magnetic field of low intensity. The flow phenomenon is important in view of its biological as well as industrial applications, particularly in polymer industries for designing flows in cylindrical shaped pipes/tubes. The novelty of the study is to analyze the effect of electromagnetic body force which comes into play due to interaction of magnetic field with conducting fluid in flow. The cross flow due to suction/injection, azimuthal pressure gradient, and the Lorentz force (electromagnetic body force) are considered in the momentum transport equation. The mathematical model and the corresponding governing equations are solved in two methods; one is analytical using special function and another one is semi analytical approach, i.e. Laplace transform in conjuction with Riemann–Sum approximation for inversion. The study reveals the effects of magnetic parameter, suction/injection parameter and radii ratio of two concentric cylinders forming annular region. The striking outcomes which fulfills the design requirements are as follows. The applied radial magnetic field resulting electromagnetic body force on the flow, accelerates the circumferential velocity which energizes the industrial setup (flow model) to enhance faster productivity. Moreover, the curves of skin friction at R = λ posses critical points serving as benchmark for engendering flow instability.

Numerical Solution of Natural Convection Problems Using Radial Point Interpolation Meshless (RPIM) Method Combined with Artificial-Compressibility Model

A numerical method is used to solve the thermal analysis of natural convection in enclosures. This paper proposes the use of an implicit artificial-compressibility model in conjunction with the Radial Point Interpolation Meshless (RPIM) method to mimic laminar natural convective heat transport. The technique couples the pressure with the velocity components using an artificial compressibility model. The RPIM is used to discretize the spatial terms of the governing equation. We solve the semi-algebraic system implicitly in backward Euler pseudo-time. The proposed method solves two test problems—natural convection in the annulus of concentric circular cylinders and trapezoidal cavity. Additionally, the results are validated using experimental and numerical data available in the literature. Excellent agreement was seen between the numerical results acquired with the suggested method and those obtained through the standard techniques found in the literature.

Numerical simulation of combined effects of a vertical magnetic field and thermal radiation on natural convection of non-Newtonian fluids confined between circular and square concentric cylinders

BackgroundThis study addresses magnetohydrodynamic (MHD) natural convection involving non-Newtonian fluids. Focusing on the annular region between concentric circular and square cylinders, the research examines the impact of a vertical magnetic field and thermal radiation. MethodsThe Multiple Relaxation Time Lattice Boltzmann Method (MRT-LBM) is employed to simulate momentum and energy interactions in non-Newtonian fluid. Control parameters like Rayleigh number, Hartmann number, Radiation parameter, aspect ratio, square cylinder subdivision, and power-law index are systematically varied, while maintaining a constant Prandtl number. Significant findingsUsing shear-thinning fluid (n < 1) significantly improves cooling, particularly in conjunction with radiation effect. Correlations for the mean Nusselt number are established, offering insights. Results emphasize the substantial influence of parameters like Ra, Rd, and AR. High values of the latter promote the flow intensity and heat evacuation. For n < 1, increasing Ra from 103 to 5 × 104 results in a substantial increase in the heat transfer rate reaching 65 %. For shear-thickening fluid, the heat transfer rate is reduced by 25.31 % at Ra = 5 × 104 when Ha is increased from 0 to 50 in the absence of radiation. In addition, radiation enhances the heat transfer rate by 71.41 % by incrementing Rd from 0 to 0.8 for Ha = 0. The most pronounced effect of the radiation parameter is observed in the cases of Newtonian and shear-thickening fluids. Conversely, Ha and n act by reduction effects on the outputs of the problem. The attenuating effect of the magnetic field is more pronounced in the case of shear-thinning fluids. The plot of mean Nusselt number vs. AR shows an hysteresis phenomenon due to the existence of multiple steady solutions in a range of this parameter. In the latter range of AR, heat transfer induced by multicellular flow is higher than that induced by bicellular one. Heat transfer is somewhat enhanced by the RC configuration, compared to SC one.

A nonlinear instability theory for a wave system inducing transition in spiral Poiseuille flow

This paper is on the transition scenario of the class of spiral Poiseuille flows that results from the onset, propagation and evolution of disturbances according to mechanisms of Tollmien-Schlichting, and Taylor, acting simultaneously. The problem is approached from the fundamental point of view of following the growth of initially infinitesimally small disturbances into their nonlinear stage when the effect of Reynolds stresses makes itself felt. To this end a set of Generalised Nonlinear Orr–Sommerfeld, Squire and Continuity Equations is set up that enables accounting for effects of growth of initially infinitesimally small disturbances into nonlinearities through a rational iteration scheme. The present proposal closely follows the method put forth for this pupose in 1971 by Stuart and Stewartson in their seminal papers on the influence of nonlinear effects during transition in the bench-mark flows of the class of spiral Poiseuille flows; which are the plane-walled channel flow and the flow in the gap between concentric circular cylinders (Taylor instability).The basic feature of the proposed method is the introduction of an Amplitude Parameter and of a slow/long- scale variable through which the effects of growing disturbances are accounted for within the framework of a rational iteration scheme. It is shown that the effect of amplified disturbances is capturable, as in the bench-mark flows, by a Ginzburg–Landau type differential equation for an Amplitude Function in terms of suitably defined slow/long-scale variables. However, the coefficients in this equation are numbers that depend upon the flow parameters of the spiral Poiseuille flow, which are a suitably defined Reynolds Number, the Swirl Number, and the geometric parameter of transverse curvature inherent in the flow geometry. The Ginzburg–Landau equation derived hints at the drastic changes in flow pattern that the spiral Poiseuille flow in transition may undergo, as its Swirl Number is taken from very small to very large values.

Experimental Investigations on the Wake‐Induced Vibration of an Electromagnetic Energy‐Harvesting System

The wake energy of an electromagnetic harvesting device is derived from the phenomena of wake‐induced vibration (WIV). Experiments were conducted to determine the effects of the Reynolds number, the resistance of the circuit, and the distance between two concentric circular cylinders on the wake energy of the flow. The mechanism of the diaphragm energy harvester (DEH) consists of a single and tandem circular cylinders, which were examined separately. An elastic diaphragm with a magnet was also mounted in the wake of the cylinders. The Reynolds number varies between 2000 and 5000. The converter transforms the wake energy of the flow into electricity due to the vibration of the cylinder in a magnetic field. This research fills a critical gap in the literature by investigating the energy performance of a DEH under the wake‐induced vibration of two fixed circular bluff bodies, demonstrating for the first time the feasibility of capturing vortex energy through the wake in the presence of a diaphragm. This unique approach distinguishes our work in the field of electromagnetic energy‐harvesting devices, showcasing the potential for practical applications in renewable energy generation. The test results indicate that increasing the Reynolds number enhances the converter’s power output. Additionally, it has been observed that two critical distances are significant for the output voltage: the gap between the tandem cylinders (L∗) and the distance between the edge of the diaphragm and the center of the cylinder (X∗). The voltage output of tandem cylinders suggests that an optimal cylinder spacing falls within the range of 4 ≤ L∗ &lt; 5.

Experimental Investigation of The Influence of Modifying the Inner Tube Outer Surface on Free Convection in A Concentrated Double Pipe

ABSTRACT Convection across circular concentric gaps between cylinders is crucial in industrial applications, including electronic cooling, heat exchangers, and solar collectors. The effect of longitudinal and annular grooves on the outside surface of the inside tube on natural convective heat transmission in enclosure concentric circular annulus is experimentally investigated in the present work. Twin pairs of circular aluminum cylinders with the same radius ratio, length, and surface area were examined. Each one consists of two concentric circular cylinders. To maintain a steady heat flux, the inside cylinder of each pair has an electrical heater connected. The results indicate that the increases in the Nusselt number of around 25%, 43%, 67%, 123%, 142%, 157%, and 172% are seen for groove depths of 0.05 cm, 0.10 cm, 0.15 cm, 0.20 cm, 0.25 cm, 0.3 cm, 0.35 cm, and 0.4 cm. In addition, increasing the depth of the longitudinal groove raises the Nusselt number by roughly 33%, 51%, 79%, 99%, 136%, 153%, 173%, and 184%. The longitudinal grooves with a depth of 4.0 mm enable a 38% increase in free convection over prior research. An annular groove of 4.0 mm depth increases free convection by 36%. Furthermore, a further advancement over earlier research is attributable to the extensive surface contact area of the inner cylinder made possible by longitudinal or annular grooves.

Thermal Lattice Boltzmann Flux Solver for Natural Convection of Nanofluid in a Square Enclosure.

In the present study, mathematical modeling was performed to simulate natural convection of a nanofluid in a square enclosure using the thermal lattice Boltzmann flux solver (TLBFS). Firstly, natural convection in a square enclosure, filled with pure fluid (air and water), was investigated to validate the accuracy and performance of the method. Then, influences of the Rayleigh number, of nanoparticle volume fraction on streamlines, isotherms and average Nusselt number were studied. The numerical results illustrated that heat transfer was enhanced with the augmentation of Rayleigh number and nanoparticle volume fraction. There was a linear relationship between the average Nusselt number and solid volume fraction. and there was an exponential relationship between the average Nusselt number and Ra. In view of the Cartesian grid used by the immersed boundary method and lattice model, the immersed boundary method was chosen to treat the no-slip boundary condition of the flow field, and the Dirichlet boundary condition of the temperature field, to facilitate natural convection around a bluff body in a square enclosure. The presented numerical algorithm and code implementation were validated by means of numerical examples of natural convection between a concentric circular cylinder and a square enclosure at different aspect ratios. Numerical simulations were conducted for natural convection around a cylinder and square in an enclosure. The results illustrated that nanoparticles enhance heat transfer in higher Rayleigh number, and the heat transfer of the inner cylinder is stronger than that of the square at the same perimeter.

Impact of Fusion Temperature on Hydrothermal Features of Flow within an Annulus Loaded with Nanoencapsulated Phase Change Materials (NEPCMs) during Natural Convection Process

A new type of nanofluids is nanoencapsulated phase change materials (NEPCMs), where nanoparticles are made of a shell and a core. In the current study, characteristics of free convection flow, entropy generation, and heat transfer of NEPCMs in an enclosure are investigated. The enclosure is an annulus between concentric horizontal circular and square cylinders with a porous medium. The governing equations (i.e., continuity, energy, and momentum) are written in the nondimensional form and then numerically solved by the control volume finite element method (CVFEM). The results of the validation are in good agreement with those of the literature. The effects of decision variables on the entropy generation number and the average Nusselt number are investigated. The outcomes discovered that there is a maximum for Nu ave and a minimum for N gen at θ f = 0.4 for each value of the Stefan number. Also, Nu ave and ECOP increase by 8.8% and 24.8%, respectively, while N gen decreases by 12.8% when ϕ increases from 0 (pure fluid) to 0.05 at θ f = 0.4 .

Study on the helicoidal flow through cylindrical annuli with prescribed shear stresses

In this article, we presented an analysis of the helical flow, for evaluating the incompressible Maxwell fluid indwelling between the two circular regions created by infinitely long concentric circular cylinders. Time-depended longitudinal and torsional shear stresses are implemented around the periphery of the inner circular cylinder to set the fluid in motion, while keeping the outer one inert. Exact analytic solution of the mathematical model in form of partial differential equations(PDE) is obained by performing the integral transform. We also retrieved the analogous solution of fluid, encompassing same properties as of Newtonian fluid in form of our general solutions. To end up with, we presented different graphs, showing the sway of appropriate parameters affecting the shear stresses and velocity components. In addition, we also presented graphs for comparison of Newtonian and Maxwell fluids. To end up with, the significance of appropriate parameters on the components of shear stresses and velocities, as well as motion for Newtonian and Maxwell fluids are analyzed and discussed via graphs.

DİK KONSANTRİK SİLİNDİRLER ARASINDAKİ AL2O3-ETİLEN GLİKOL VE SU KARIŞIM BAZLI NANOAKIŞKANLARIN DOĞAL KONVEKSİYONU

Natural convection of ethylene glycol (EG) and water mixture based Al2O3 nanofluids between vertical concentric circular cylinders heated from the inner wall and cooled from the outer wall was investigated numerically in this study. The computations were carried for the Rayleigh numbers of 104, 105, 106, and 107, nanoparticle volume fractions of 0%, 4% and 8%, ethylene glycol (EG) to water volume ratios of 0:100 %, 50:50%, and 100:0%, the radius ratios of 2, 3 and 4, and aspect ratios of 0.5, 1, and 2. The Brinkman model was used to predict the viscosity and the Yu and Choi model for the thermal conductivity of nanofluid. The results show that the average Nusselt number shows a considerable increase with an increase in the Rayleigh number and radius ratio. The results also show that the average Nusselt number shows a medium increase with increasing nanoparticle volume fraction and a slight increase with increasing volume ratios of EG to water. Furthermore, the results show that the average Nusselt number experiences first an increase then a decrease with an increase in the aspect ratio except for the low Ra numbers. Finally, the average Nusselt number experiences a slight increase with the aspect ratio for the low Rayleigh numbers.

Transient behaviors of mixed convection in a square enclosure with an inner impulsively rotating circular cylinder

This work numerically investigated the unsteady mixed convective heat transfer between a square enclosure and an inner concentric circular cylinder maintained at different temperatures. The cylinder undergoes a transition of motion whose physics is significant for engineering applications such as cooling of rotating shaft and lubricating of journal bearing. It keeps stationary at first and steady-state natural convective flow is achieved, then impulsively rotates at a constant angular velocity and the flow arrives at a new final steady-state. Although the mixed convective heat transfer for rotating cylinder configurations are analyzed in a number of works, the transient behaviors of the thermal and flow characteristics from the onset of cylinder rotation to the final steady-state are not investigated, which restrains the thorough understandings on the relevant flow physics and mechanisms. The present work performs the first numerical investigation on the targeted physical problem. The objective is to explore the transient characteristics of the mixed convective heat transfer, and to identify the effects of cylinder rotation and rotation speed (tangential velocity at cylinder surface, V0) on the flow and heat transfer behaviors. The results are presented and analyzed by the temporal variations and spatial distributions of the thermal field, mean heat transfer rate, local heat transfer rate and velocity/temperature in certain regions where the flow is significantly affected. Our numerical results for the first time identify two flow regimes depending on the tangential velocity: mixed buoyancy-shear stress dominated flow for V0 ≤ 1.0 where the effect of natural convection is pronounced and the flow is driven by both buoyancy and shear stress from the cylinder surface, and shear stress dominated flow for V0 ≥ 2.0 where the flow is almost entirely driven by rotating cylinder and heat transfer is realized by conduction. The transient behaviors of the thermal and flow quantities are characterized and categorized based on the two regimes.

A coupled Volume Penalization-Thermal Lattice Boltzmann method for thermal flows

In this article, a coupled Volume Penalization-Thermal Lattice Boltzmann method is proposed to solve the thermal flow problem. The temperature Dirichlet boundary condition of the temperature field is ensured by introducing an external thermal penalization heat source term into the energy equation. Coupled with the Lattice Boltzmann-Volume Penalization method, which is used to simulated athermal flow past obstacles, the thermal flow problem can be solved. Besides, performing the Volume Penalization-Thermal Lattice Boltzmann method on a certain point, only the variables of this point are needed, which means the present method can be conducted parallelly. To verify the present method, the heat transfer between two concentric circular cylinders experiment is carried out firstly, in which the accuracy of the present method is also studied. Then natural convection between two concentric circular cylinders and between a cold square outer and a hot cylinder inner is performed to verify the present method further. To validate the ability of the method to solve the forced convection and mixed convection, the flows past a heated circular cylinder and the mixed convection of a heated rotating cylinder in a square enclosure are conducted. Good agreements between the present results and those in the previous literatures are achieved.

Numerical simulation of thermal flow of power-law fluids using lattice Boltzmann method on non-orthogonal grids

In this study, a lattice Boltzmann model is proposed to investigate thermal flow of power-law fluids in irregular geometries. Non-orthogonal grids on the physical plane are adopted to accurately depict curved boundaries. With respect to power-law fluid, the evolutions of particle distribution functions for velocity and temperature fields on the computational plane are derived on the basis of the generalized form of interpolation-supplemented lattice Boltzmann method and the rheological equation. For forced convection, the double-distribution-function method is used to predict the temperature field. The coupled lattice BGK model is employed to consider the conditions under which the velocity and temperature fields are strongly coupled, such as natural convection. The adiabatic boundary and symmetry boundary in body-fitted coordinates are specifically prescribed. Numerical procedure is further validated by modeling a series of cases including forced convection over a stationary heated circular cylinder and natural convection in cavities and an annulus between concentric circular cylinders, respectively. Good agreements with available data in the literature are achieved. The numerical results demonstrate that the effect of rheological and thermodynamic properties of power-law fluid on the heat transfer performance and flow field in complex geometries can be suitably captured by present thermal lattice Boltzmann method on non-orthogonal grids.

Solving natural convection heat transfer in turbulent flow by extending the meshless local Petrov–Galerkin method

This study extends the conventional meshless local Petrov–Galerkin method to enable the meshless technique to solve natural convection heat transfer in turbulent regimes. To do so, the Navier–Stokes and energy equations are expressed in terms of the stream function and vorticity formulation and are incorporated with the Spalart–Allmaras model which governs the turbulent viscosity. In this developed meshless numerical work, the fluid variables are approximated using the moving least squares interpolation, and the weighting function is given a unity value for the weak form of the governing equations. The proposed meshless technique is then applied to solve three conventional test cases of, the natural convection heat transfer in a square cavity, the natural convection heat transfer between two concentric cylinders of square outer and circular inner walls, and the natural convection heat transfer through a fluid bounded between two concentric circular cylinders. All the three test cases are solved for 0.71 Prandtl and different turbulent Rayleigh numbers. Based on the proposed extended method results and comparing them with those of the conventional numerical and experimental methods, the proposed technique shows to be amenable and accurate to solve turbulent natural convection heat transfer problems.

Hydromagnetic solid–liquid pulsatile flow through concentric cylinders in a porous medium

The current research is reported about the hydromagnetic solid–liquid flow in an annulus between two concentric circular cylinders embedded in a porous media. The impact of joule heating is also accounted for. Unlike the usually applied constant pressure gradient, the pulsatile pressure gradient is employed. The flow problem is first modeled and then tackled by Runge–Kutta–Fehlberg fourth–fifth-order (RKF45) numerical scheme along with shooting algorithm. The impacts of emerging parameters namely magnetic field parameter and porosity parameter on velocity and temperature distributions are displayed through graphs and briefly addressed.

Analytical study on a submerged tubular wave energy converter

Abstract A submerged tubular wave energy converter, whose main structure is an upright concentric circular cylinder, is proposed. The turbine is installed near the bottom of the internal tunnel for the survivability consideration. The analytical solution for the wave diffraction problem of the structure is derived based on the linear potential flow theory. The oscillatory mass flow rate in the tunnel is particularly investigated for it can be used to assess the feasibility of the converter that utilises the vertically oscillatory water flow. The effect of the submerged tubular structure in a wave field is to guide the vertically oscillatory motion, the magnitude of which, otherwise, diminishes exponentially with depth, down to the deeper water. That greatly increases the available kinetic energy for the turbine installed in the deep water. Effects of the parameters of the tubular structure on the efficiency of the device are also discussed.

English

English

An iterative source correction based immersed boundary-lattice Boltzmann method for thermal flow simulations

Temperature jump at the boundary occurs when the conventional immersed boundary-lattice Boltzmann (IB-LB) method is applied to simulating the near boundary flows with heat transfer. To remedy this problem, an iterative correction is proposed to modify the heat source term in the IB-LB method. The source term in the LB equation is treated by Cheng’s scheme, in which the heat source at the next timestep is taken as unknowns and iteratively corrected until the resulting boundary temperature matches its desired value. Typical verification cases, including the two-dimensional (2D) heat transfer between two horizontal plates, the natural convection between two concentric circular cylinders, and 2D sedimentation of a single particle with heat convection are simulated to analyze the accuracy of the method. It is shown that the boundary temperature jump can be effectively removed for a certain range of LB relaxation time τ, while the first-order spatial convergence of the IB method is still maintained. Also, a theoretical analysis is conducted based on the case of heat transfer between two plates. It is shown that the proposed method outperforms the widely-used direct source method in treating the Dirichlet boundary conditions when τ is smaller than 1.624. To further demonstrate its capability for resolving complicated fluid-structure interaction problems, a three-dimensional sedimentation of a single particle in a vertical channel is analyzed. We find that the thermal convection may fundamentally affect the way the particle interacts with the surrounding fluid.

Buoyancy-induced flow, heat, and mass transfer in a porous annulus

ABSTRACTThis paper reports on double-diffusive natural convection heat transfer in a porous annulus between concentric horizontal circular and square cylinders. A pressure-based segregated finite volume method is used to solve the problem numerically. The diffusion fluxes are discretized using the MIND fully implicit scheme. Furthermore, a modified pressure correction equation is derived that implicitly accounts for the nonorthogonal diffusion terms, which are usually neglected in the standard SIMPLE algorithm. Results indicate that convection effects increase with an increase in Rayleigh number, Darcy number, porosity, and enclosure aspect ratio. Further, at low Darcy values, porosity has no effect on the flow, temperature, and concentration fields.