Cylinder In Terms Research Articles

Bounding the Lagrangian Hofer metric via barcodes

In this paper, we provide an upper bound on the Lagrangian Hofer distance between equators in the cylinder in terms of the barcode of persistent Floer homology. The bound consists of a weighted sum of the lengths of the finite bars and the spectral distance.

Research on the Flow Parameters of Waste Motion in a Rotary Kiln with the Use of the Tracer Method.

The motion of input material in a rotary kiln is an important aspect of its operation. This can be observed especially in the case of the implementation of the hazardous waste incineration process in this device. The values of the flow parameters, mainly the residence time and the degree of mixing, can determine the proper and safe treatment of waste. The relationships that occur in the layer of solid material in a rotary kiln have not been completely recognized. This article presents a research method that involves an experiment on a laboratory stand simulating a rotary kiln in association with a dedicated algorithm. Multi-criteria tests were carried out. The adopted research method was the tracer method. It used a tracer which, subject to the same transport conditions as other material particles, provided information on the characteristic of the motion of tested materials in the rotating cylinder. The application based on the residence time distribution (RTD) algorithm returned information about the characteristics of the motion of the material in the rotary cylinder in terms of residence time distribution and the degree of mixing. This tracer method, together with stimulus impulses on the grate and a dedicated RTD algorithm, was used here as a sensor method to examine the characteristics of material motion on various grate systems. The data obtained as a result of this research may include, among others, the boundary conditions for numerical simulations of processes carried out in a rotary kiln.

The optimization of natural frequency on the cross flow-induced vibration and heat transfer in a circular cylinder with LSTM deep learning model

BackgroundIn this study, the fluid-induced vibrations of a long cylinder placed in the cross flow of a fluid with Reynolds number 325 have been investigated using ANSYS CFX 11. For this purpose, a middle section of the cylinder is considered in two-dimensional geometry and the damping and stiffness of the tube are modeled with appropriate springs and dampers. Since the frequency of the vortex shedding around the cylinder can exert an oscillating force on the cylinder, the effect of the applied force on the drag, lift and vibration path of the cylinder has been investigated. Also, by changing the natural frequency of the structure, different vibration modes and lock-in phenomenon have been investigated. MethodsVarious machine learning approaches have been used for predictive analysis where numerical data are generated to train intelligent algorithms for prediction errors. Different machine learning approaches such as long short-term memory (LSTM), multilayer perceptron (MLP) and support vector regression (SVR) are employed to optimize the prediction of drag and lift coefficient, vibration path of the cylinder and average Nusselt on the cylinder in terms of the natural frequency of the structure. This work proves that machine learning models are capable to predict the complex behavior of fluid flow in systems where flow-induced (FIV) vibration is coupled with heat transfer. FindingsIn the presented results, the Lissajous pattern in the form of number 8 was observed in the lock-in mode and the heat transfer in this mode shows an increase of about 13 percent compared to the fixed cylinder mode

On non-premixed flames of dual porous cylinders in tandem

A porous burner is one of the most efficient combustion devices nowadays due to its recycling features of heat and burning performance. To exploit its advantages for a wide range of external fields, we propose a novel arrangement in terms of tandem porous cylindrical burners and investigate the applicability, specifically on the extension of extinction limits under forced convection. A key parameter is the separation distance (L), presented as a ratio to the cylinder diameter (D). The results of paired cylinders in terms of various experimental and simulation techniques demonstrate superior features of flow pattern, specifically on its stabilization, and thermal interaction achieved by using the tandem array, which led to widened extinction limits at the same total fueling rate. It was found that the extension of the extinction limit reached the maximum near L/D = 1.4. A smaller L/D may discourage entrainment of air into the gap between the cylinders due to inhibition of large vortices, causing the reaction zone to move outward from the gap where the flow is relatively stable. For a larger L/D, the performance degraded due to degeneration of favorable thermal interactions behind the cylinders and excess cold air drawn into the gap by strong vortices.

Effectiveness of Nonuniform Heat Generation (Sink) and Thermal Characterization of a Carreau Fluid Flowing across a Nonlinear Elongating Cylinder: A Numerical Study

During thermal radiation treatments, heat therapies, and examination procedures like scans and X-rays, the cylindrical blood vessels may get stretched; meanwhile, the blood flow through those blood vessels may get affected due to temperature variations around them. To overcome this issue, this work was framed to explore the impact of heat transmission in a Carreau fluid flow (CFF) through a stretching cylinder in terms of the nonlinear stretching rate and irregular heat source/sink. Temperature-dependent thermal conductivity and thermal radiation are taken into consideration in this study. To tranform complicated partial differential equations into ordinary differential equations, appropriate similarity variables are used. For a limited set of instances, the derived series solutions are compared to previously published results. For linear and nonlinear stretching rates, graphs and tables are used to examine the influence of an irregular heat source/sink on fluid movement and heat transfer. The research outcomes demonstrate that the heat source and nonlinear stretching rate cause a disruption in the temperature distribution in the fluid region, which can alter the blood flow through the vessels. In all conditions except for the heat in an internal heat sink, the nonlinear stretching situation improves the velocity and heat profile. Furthermore, with the increase in the values of the Weissenberg number, the temperature profile shows opposing features in a shear-thickening fluid and shear-thinning fluid. For the former n > 1, the blood fluidity gets affected, restricting the free movement of blood. For the latter, n < 1, the phenomenon is reversed. Other industrial applications of this work are wire coating, plastic coverings, paper fabrication, fiber whirling, etc. In all of those processes, the fluid flow is manipulated by thermal conditions.

Light scattering by an infinitely long circular cylinder above a plane interface

An exact analytical method is presented to calculate light scattering by an infinitely long circular cylinder above a plane interface. The transformation relations of rectangular and cylindrical vector wave functions are used to deal with the coupling scattering between the circular cylinder and plane interface. By applying the boundary conditions over the cylindrical surface, the unknown expansion coefficients of the scattered field by the circular cylinder in terms of cylindrical vector wave functions are determined. Mueller matrix elements are computed, and also compared with those measured for a plane wave with normal incidence.

Conserved charges for rational electromagnetic knots

We revisit a newfound construction of rational electromagnetic knots based on the conformal correspondence between Minkowski space and a finite S^3-cylinder. We present here a more direct approach for this conformal correspondence based on Carter–Penrose transformation that avoids a detour to de Sitter space. The Maxwell equations can be analytically solved on the cylinder in terms of S^3 harmonics Y_{j;m,n}, which can then be transformed into Minkowski coordinates using the conformal map. The resultant “knot basis” electromagnetic field configurations have non-trivial topology in that their field lines form closed knots. We consider finite, complex linear combinations of these knot-basis solutions for a fixed spin j and compute all the 15 conserved Noether charges associated with the conformal group. We find that the scalar charges either vanish or are proportional to the energy. For the non-vanishing vector charges, we find a nice geometric structure that facilitates computation of their spherical components as well. We present analytic results for all charges for up to j=1. We demonstrate possible applications of our findings through some known previous results.

Multi-Faceted Surface Effect on Heat Transfer Performance and Flow Dynamics at the Onset of Optimum Nusselt Number

A multi-faceted cylinder of half-circle, flat, and triangle surfaces is investigated numerically in this study. The flow characteristics were observed. Their effects on thermal performance were investigated under various cross-flow conditions and blocking ratios. The multi-faceted cylinder's effectiveness compared to the circular cylinder in terms of a heat exchanger is also presented. The multi-faceted cylinder suffers an average of 0.47% drop in effectiveness relative to the circular cylinder. However, despite producing a higher heat transfer coefficient, the circular cylinder has a lower Nusselt number contributed by a higher Strouhal number. A lower Strouhal number in a multi-faceted cylinder enables it to have a higher Nusselt number in the downstream surface than the circular cylinder. This is due to better fluid contact through flow attachment at the flat surface and the sharp edge. The multi-faceted cylinder's asymmetrical surface also creates higher velocity imbalances in the upper and lower half of the channel, which produced a distinct drag coefficient pattern. The multi-faceted cylinder offers enhanced convective heat transfer compared to the circular cylinder but with relatively higher drag under increasing Reynolds number.

Theoretical investigation on integrating a torus oscillating body with a concentric perforated cylindrical system

In this paper, the hydrodynamic performance of a hybrid wave energy extraction (HWEE) system consisting of a torus oscillating body (OB) and a concentric perforated cylindrical system was investigated based on the linear potential flow theory. A linear power take-off system is assumed to extract wave power. To solve the diffraction and radiation problems, a theoretical model was proposed using the methods of separation of variables and eigenfunction matching. Through a contrastive study, it was found that the model with an arc-shaped perforated outer cylinder performs better than the model with a partially perforated outer cylinder in terms of effective bandwidth of capture width ratio and the hydrodynamic horizontal forces acting on them. The HWEE system with an arc-shaped perforated outer cylinder was studied particularly and optimized by examining the effect of several main design parameters, including the incident wave angle, the porosity and opening angle of the arc-shaped perforated outer cylinder, as well as the exterior radius and draft of the torus OB. It was also found that the torus OB has no negative effects on the stability of the concentric perforated cylindrical system, at least in terms of the horizontal wave forces acting on the structures.

Residual compressive strength of plain and fiber reinforced concrete after exposure to different heating and cooling regimes

The article investigated the impact of different cooling regimes on the response of both plain and fibre reinforced concrete (FRC) after heating. A total of 256 standard concrete cylinders of normal strength concrete (NSC) and high strength concrete (HSC) were tested in compression after heating at 200 °C, 400 °C, and 600 °C. For each concrete grade, 32 specimens were prepared without fibres while 96 cylinders had fibres (steel, polypropylene (PP) and their hybrid) in the concrete mixture. The cooling regimes adopted for cooling the test specimens were water quenching and natural ambient cooling. Effect of studied parameters was evaluated for tested cylinders in terms of stress-strain characteristics, residual strength, modulus of elasticity, and failure modes. For both NSC and HSC, the reduction in strength increased significantly when the temperature was increased from 400 to 600 °C. At 600 °C, the use of steel fibres caused lower loss in compressive strength, elastic modulus and energy absorption as compared to the use of PP and hybrid fibres. The residual strength of water quenched concrete was more than the air cooled concrete because the heated specimens were kept submerged in water for 24 h, which helped in the rehydration of anhydrous cement products.

Three-dimensional spectral proper orthogonal decomposition analyses of the turbulent flow around a seal-vibrissa-shaped cylinder

The flow around a seal-vibrissa-shaped cylinder (SVSC) is numerically investigated using the large eddy simulation framework at a Reynolds number of 20 000. Compared with a circular cylinder (CC), the wake of the SVSC presents more stable three-dimensional separation, a longer vortex formation length, and a weaker vortex strength. The mean drag and fluctuation of the lift coefficient are 59.5% and 87.7% lower than those of the CC, respectively. Three-dimensional spectral proper orthogonal decomposition (SPOD) is used to investigate the turbulent flow around these two types of cylinders in terms of the spatial modes, mode energy, mode coefficients, and reconstructed flow by a reduced-order modeling. Four typical vortex shedding patterns are first extracted by SPOD for the SVSC, producing crescent-, twist-, branch-, and knot-shaped vortices. A concept model is proposed for the wake dynamics of the SVSC, allowing the formation and transformation of these modes to be elucidated. Detailed analysis of the impact of the flow pattern on the associated forces indicates that the dominant out-phase vortex shedding at the upper and lower saddle planes makes a significant contribution to the reduction in lift fluctuations.

Urban Wind Harvesting Using Flow-Induced Vibrations

The growing global interest in sustainable energy has paved the way to the rapid development of large-scale wind farms, consisting of dozens to hundreds of wind turbines. Although these large wind farms can generate enormous amount of power, they are also costly and require large areas of land or water, and thus are not suitable for urban environments. Smaller urban wind turbines have been developed for urban environments, but there are significant challenges to their widespread deployment. One of these challenges are their urban wind flows as they are strongly affected by complex building structures, producing highly turbulent flows. Any urban wind turbine would need to be designed to function efficiently and safely under these flow conditions; however, these unpredictable and turbulent winds can induce undesirable vibrations and cause early failures. Recently, bladeless wind turbines are gaining interest due to their reduced costs compared with conventional wind turbines such as the vertical-axis wind turbine and horizontal-axis wind turbine. These bladeless turbines convert flow wind energy into vibration energy, then converts the vibration energy into electricity. This paper examines the effects of force-induced vibrations on a cantilever beam system through wind tunnel experimentation. When fluid flows around a bluff body, periodic shedding of vortices may occur under the right conditions. The vortex shedding process creates an asymmetric pressure distribution on the body which causes the body to oscillate, known as vortex-induced vibrations. The purpose of the paper is to understand the factors affecting flow-induced vibrations and to improve wind energy harvesting from these vibrations. The first part of the paper focuses on wind tunnel experiments, by utilizing a cantilever beam configuration, conceptualized by previous research. Then, the experimental model was tested in different configurations, to determine the best setup for maximizing vibrations induced on the model. The long-term goal of the project was utilizing the model to optimize the system to improve efficiency of wind energy harvesting. The experimental results showed that the presence of an upstream cylinder will significantly improve the amplitude of vibration for energy harvesting, furthermore, the experiments showed that spacing in different directions also affect the amplitude of the vibrations. A two tandem cylinder system was used in this work, including a fixed rigid upstream cylinder and a downstream cylinder supported by a cantilever beam. Various configurations of these two cylinders in terms of spanwise and streamwise separation distances were studied and their maximum and root mean square displacements are reported for different wind speeds. Results showed that the presence of an upstream cylinder will significantly improve the amplitude of vibrations. This work verified that a wind energy harvester needs to consider the effects of wind speed and separation configuration of the cylinders in order to maximize the harvester’s performance in urban environments. KEYWORDS: Sustainable Energy; Energy Harvesting; Urban Environments; Bladeless Wind Turbines; Flow-Induced Vibrations; Cantilever Beam System; Wind Tunnel; Wake

Linear instability of concentric annular flow: Effect of Prandtl number and gap between cylinders

The stability of non-isothermal Poiseuille flow in a coaxial annular domain is studied using normal mode analysis. The stably stratified flow (i.e., when buoyant force is in the direction of forced flow) is induced due to external pressure gradient and maintenance of linear variation of the temperature of the inner cylinder. We have emphasized the impact of the gap between cylinders in terms of curvature parameter (C) and Prandtl number (Pr) on the instability of the flow under axisymmetric as well as non-axisymmetric disturbances. In general, it has been found that the flow of low Pr fluids under axisymmetric disturbance is more stable in comparison with the flow under non-axisymmetric disturbance. When the gap between cylinders is relatively small (i.e. C is large), the flow under non-axisymmetric is most stable for the fluids having high Pr. It is known that the Newtonian pipe flow is linearly stable for all values of Reynolds number (Re). However, in the present study, we have seen the instability of the pipe flow with a thin rod placed at the center even for a very small value of heat source intensity (in terms of Rayleigh number) at Re=2000. Here the disturbance velocity is concentrated in the vicinity of the inner wall and instability is due to transfer of kinetic energy from the basic flow through Reynold’s stress. Depending on the value of controlling parameters, three types of instability: thermal-shear, interactive, thermal-buoyant have been observed. In general, for a fixed value of Pr, the type of instability is not affected by C and Re. The non-isothermal Poiseuille flow of low Pr (including mercury and gases) is governed by thermal-shear instability and the same of high Pr (including liquid and oil) is governed by thermal-buoyant instability.

Criterion of stability of hydraulic cylinder and method of increasing its reliability under longitudinal-transverse loads

Currently, in most cases, the study of the operability of hydraulic cylinders in terms of their bearing capacity is carried out by means of assessing the longitudinal stability of a compressed rod with the variable cross section. In this case, the inclination of the rod in space is not taken into account. However, during operation, as a rule, a hydraulic cylinder inclined in space due to longitudinal-transverse loading is deformed in the vertical longitudinal plane with the appearance of a full-scale deflection. So, the limit value of the longitudinal compressive force is less than the limit compressive force of a stable rod, which implies that a rod having an initial curvature is more susceptible to bending, appearance of residual deformations in its elements and has less reliability than a straight, vertically arranged one. As the guide elements of the hydraulic cylinder wear out, its total deformation increases, which leads to an increase in longitudinal-transverse loads. With regard to long-stroke hydraulic cylinders, a special danger is their immediate stop in space when the working equipment of the machine meets an insurmountable obstacle. The purpose of the study is a scientifically based description of the areas of functioning of the hydraulic cylinder in the conditions of longitudinal-transverse bending or stability, as well as the boundaries separating them

Study of Flow Behaviour in Vertical Centrifugal Casting

In centrifugal casting processes, flow of fluid layers determines the quality of the cast. However flow visualization is not possible, as mould and molten metal are opaque in nature. Therefore many research workers have resorted to understand the flow visualization process by carrying out simulation studies. Literature survey indicates that earlier investigators have studied the melt flow in horizontal centrifugal casting process by conducting cold modeling experiment using horizontal transparent mould and fluids of different viscosity. However it appears that there is no published information available in the area of influence of various parameters in the case of vertical centrifugal casting process. Therefore in this research work the cold modeling experimentation on fluids of different viscosity like water, Glycerin and SAE 90 rotated in a transparent mould at a constant room temperature had been conducted with an objective of understanding the influence of rotational speed and aspect ratio on flow patterns of different fluids subjected to vertical axis rotation. Later the flow behavior had been studied by numerical simulation through Ansys fluent software. Further for the purpose of comparison, casts of paraffin wax at different rotational speeds had been obtained and the trend of variation of the lift with the variation of rotational speed had been compared with the trend predicted using cold modeling studies and using Ansys software. From cold modeling studies it can be concluded that of the dimensional accuracy of fluid cylinder in terms of lift had been increased with increase in viscosity. The possibility of formation of complete fluid cylinder increases with increase in rotational speed and mould diameter. Howvere, at aspect ratio of 1.0 the formation of complete fluid cylinder had not been obtained.The trend of result observed in CFD study was found to be similar to the trend of results observed in cold modeling study. The study of actual paraffin cast confirmed the result obtained in cold modeling and CFD.

Bifurcation and instability of annular Poiseuille flow in the presence of stable thermal stratification: Dependence on curvature parameter

The bifurcation and instability of nonisothermal annular Poiseuille flow (NAPF) of air as well as water is studied. We have emphasized the impact of a gap between cylinders in terms of curvature parameter (C) for axisymmetric as well as nonaxisymmetric disturbances. The results from the linear stability analysis reveal that the first azimuthal mode acts as a least stable mode of the NAPF of air for relatively small values of C. In this situation, even though for some values of C, the NAPF has supercritical bifurcation, but the same flow may experience subcritical bifurcation under zero azimuthal mode. It has also been observed that for relatively larger values of the Reynolds number (Re) and lower values of C, the NAPF under axisymmetric disturbance always exhibits subcritical bifurcation. However, for small values of Re, the NAPF exhibits only supercritical bifurcation. The finite amplitude analysis predicts only supercritical bifurcation of NAPF of water. The influence of nonlinear interaction of different harmonics on the amplitude profile as well as kinetic energy spectrum is investigated. The amplitude profile possesses a jump in the vicinity of a point where the type of bifurcation is changed. In the subcritical regime, the induced shear production due to modification of the gradient production acts as a main destabilizing factor balanced by the gradient production of kinetic energy.

Combined Effects of Fluid Yield Stress and Geometrical Arrangement on Natural Convection in a Square Duct From Two Differentially Heated Horizontal Cylinders

Abstract Laminar natural convection in Bingham plastic fluids has been investigated from two differentially heated cylinders arranged either one above the other or along the diagonal of the square enclosure. The coupled momentum and energy equations have been solved to elucidate the effect of Rayleigh number (104–106), Prandtl number (10–100), Bingham number (0.01 to Bnmax), and the gap between the two cylinders in terms of the geometric parameters (0 to −0.25 for vertical alignment and 0.15 to 0.35 for diagonal alignment) on the detailed structure of the flow field and the overall heat transfer characteristics of the system. New extensive results are visualized in terms of streamlines, isotherm contours, and variation of the local Nusselt number along various surfaces. Additional insights are developed by examining the shear-rate contours and the yield surfaces delineating the fluid-like and solid-like regions in the flow domain. At high values of the Bingham number, the average Nusselt number reaches its asymptotic value corresponding to the conduction limit. The increasing Rayleigh number promotes fluid-like behavior which promotes heat transfer. The augmentation in heat transfer depends on the volume of fluid participating in the buoyancy-induced flow. For the vertical arrangement, the average Nusselt number (for the heated cylinder) decreases a little as these are moved slightly away from the center of the enclosure, followed by an increase as the two cylinders approach one of the sidewalls; this is so even in the conduction limit. In contrast, when the two cylinders are arranged along the diagonal, the Nusselt number progressively decreases as the gap between the two cylinders increases. Finally, predictive correlations have been developed for the average Nusselt number and the limiting Bingham number thereby enabling their estimation in a new application.

Investigation on vortex-induced vibration of twin rectangular 5:1 cylinders through wind tunnel tests and POD analysis

This paper investigates the vortex-induced vibration (VIV) performance of twin rectangular cylinders with an aspect ratio of 5. A series of wind tunnel dynamic tests and pressure measurements were carried out. Proper orthogonal decomposition (POD) technique was applied to the fluctuating wind pressure field around the cylinders at wind velocities corresponding to the maximum VIV amplitudes. The experimental results show the downstream cylinder has larger VIV responses than the upstream one for most cases. The gap distance has a critical impact on the aerodynamic behavior of twin rectangular cylinders in terms of VIV responses, mean and fluctuating pressure distribution and aerostatic coefficients. POD analysis indicates the first mode is dominant to the VIVs of the downstream cylinder, while the second mode is closely related to the VIVs of the upstream one. The fluctuating lift and moment coefficient time-histories reconstructed with the first two modes agree well with the results from the original data.

Laser-induced nanostructures on titanium surfaces ensure osseointegration of implants in rabbit femora

The lifetime of orthopedic prostheses is determined i.a. by the quality of their osseous fixation. Numerous surface modification techniques have been developed to improve the ingrowth of implants into the surrounding bone. These strategies aim at an increase of surface area to allow for an enhanced osseointegration, i.e. a functional connection between bone and implant. In the present study, a laser-based nanostructuring technique has been able to generate real nanostructures with cavities between 20–30 nm on cylindrical titanium alumina vanadium (TiAl6V4) alloy implants either coated with titanium niobium nitride (TiNbN) or titanium plasma spray (TPS) which were implanted into rabbit femora. In general, all implants appeared to be osseointegrated and well anchored in the bone. There were no differences in the pull-out forces applied to the untreated in comparison to the laser-irradiated implants. On the TPS cylinders obvious abrasive marks were left following the process of im- and explantation. However, the laser-induced nanostructures seemed to be resistant to damage. TPS-coated implants appeared to be more tightly anchored in the bone than TiNbN-coated cylinders in terms of bone-to-implant contact (BIC). There also were no differences in the bone / tissue volume ratio when comparing untreated to laser-irradiated implants. Taken together, nanostructured titanium surfaces are biocompatible and ensure a bony ingrowth. Nonetheless, the presence of nanostructures apparently has no further influence on the fixation of the implants in rabbit femora. Consequently, the optimal surface roughness as well the size and pattern of micro- and nanostructures of implants still requires further investigation.

Laser-Induced Nanostructures on Titanium Surfaces Ensure Osseointegration of Implants in Rabbit Femora

The lifetime of orthopedic prostheses is determined i.a. by the quality of their osseous fixation. Numerous surface modification techniques have been developed to improve the ingrowth of implants into the surrounding bone. These strategies aim at an increase of surface area to allow for an enhanced osseointegration, i.e. a functional connection between bone and implant. In the present study, a laser-based nanostructuring technique has been able to generate real nanostructures with cavities between 20-30 nm on cylindrical titanium alumina vanadium (TiAl6V4) alloy implants either coated with titanium niobium nitride (TiNbN) or titanium plasma spray (TPS) which were implanted into rabbit femora. In general, all implants appeared to be osseointegrated and well anchored in the bone. There were no differences in the pull-out forces applied to the untreated in comparison to the laser-irradiated implants. On the TPS cylinders obvious abrasive marks were left following the process of im- and explantation. However, the laser-induced nanostructures seemed to be resistant to damage. TPS-coated implants appeared to be more tightly anchored in the bone than TiNbN-coated cylinders in terms of bone-to-implant contact (BIC). There also were no differences in the bone / tissue volume ratio when comparing untreated to laser-irradiated implants. Taken together, nanostructured titanium surfaces are biocompatible and ensure a bony ingrowth. Nonetheless, the presence of nanostructures apparently has no further influence on the fixation of the implants in rabbit femora. Consequently, the optimal surface roughness as well the size and pattern of micro- and nanostructures of implants still requires further investigation.