Round Cylinder Research Articles

Numerical performance of Hall current and Darcy-forchheimer influences on dissipative Newtonian fluid flow over a thinner surface

Present problem concerns may be found in a wide variety of various industries and can takes a shape of round toroid's, cones, cylinders, domes (Axisymmetric shape), and other shapes as well. When it comes to actual applications, they are represented by aerosol cans, submarine pressure hulls, cooling towers, offshore drilling rigs, radomes, nuclear reactors, and other similar objects. The aim of this research is to improve the performance of MHD flow using Darcy-Forchheimer, viscous dissipation, porous and a heat source. The viscous convective permeable flow flowing over a bullet-shaped item is examined. Using similarity transforms, the structure of nonlinear differential equations are converted into dimensionless ODEs. Employing bvp4c shooting technique to decrypt the findings. Influences of physical entities on velocity and temperature were sketched and briefly described. Physical behaviors of skin friction and heat transfer rates are explored. The fluid velocity drops for Eckert number Ec as ε < 1.0, and rises as ε > 1.0, The fluid velocity improves with Darcy-Forchhemier parameter Fr when stretching ratio ε < 1.0 or = 1 or >1.0. The enhancement of fluid temperature is observed with enhanced Ec. A enhance in the Darcy-Forchhemier parameter Fr associated with improvement in skin-friction. In the absence of viscous dissipation, hall current, porous and Dacy-Forchhemier influences, the outcomes are in splendid covenant with those of previous studies.

Comparison of Pressure-based and Skin Friction-based Methods for the Determination of Flow Separation of a Circular Cylinder with Roundness Imperfection

Introduction: A delayed detached eddy simulation in Open FOAM was performed to study flow separation of a circular cylinder with roundness imperfection up to 4% of its diameter at Reynolds numbers of 100, 3900, and 104 in normal flow. Methods: The flow was considered to be Newtonian and incompressible. The separation position was determined independently based on surface pressure distribution and skin friction. Results: Results show that the patterns of these distributions depend on both Reynolds number and roundness imperfection level, and flow separation in an imperfectly round cylinder may be induced by either an adverse pressure gradient or a Gentle Bend (GB) introduced by the roughness. For the separation point determined by the pressure-based method, its accuracy can be affected by the characteristic of pressure distribution near the separation point at low Reynolds numbers, and, thus, its physical validity needs to be verified by flow visualization at high Reynolds numbers. Conclusion: The skin friction-based method can accurately predict separation point for both perfectly and imperfectly round cylinders without additional information. When the roundness imperfection ratio reaches 2% and the Reynolds number reaches 3900, both approaches indicate that the flow separation point converges to the location of GB on the cylinder surface and the two sets of predicted separation points agree well.

A radial basis function partition of unity method for steady flow simulations

A methodology is presented for the numerical solution of nonlinear elliptic systems in unbounded domains, consisting of three elements. First, the problem is posed on a finite domain by means of a proper nonlinear change of variables. The compressed domain is then discretised, regardless of its final shape, via the radial basis function partition of unity method. Finally, the system of nonlinear algebraic collocation equations is solved with the trust-region algorithm, taking advantage of analytically derived Jacobians. We validate the methodology on a benchmark of computational fluid mechanics: the steady viscous flow past a circular cylinder. The resulting flow characteristics compare very well with the literature. Then, we stress-test the methodology on less smooth obstacles—rounded and sharp square cylinders. As expected, in the latter scenario the solution is polluted by spurious oscillations, owing to the presence of boundary singularities.

Task-Driven Path Planning for Unmanned Aerial Vehicle-Based Bridge Inspection in Wind Fields

Using unmanned aerial vehicles (UAVs) for bridge inspection is becoming increasingly popular due to its ability to improve efficiency and ensure the safety of monitoring personnel. Compared to traditional manual monitoring methods, UAV inspections are a safer and more efficient alternative. This paper examines the impact of meteorological conditions on UAV-based bridge monitoring during specific tasks, with the aim of enhancing the safety of the UAV’s costly components. The wake vortex behind a bridge structure can vary over time due to airflow, which can have a direct impact on the safety of UAV flights. To assess this impact, numerical analysis is conducted based on monitoring requirements specific to different tasks, taking into account wind speed, wind direction, and air temperature. In order to optimize UAV trajectory, it is important to consider the wake vortex intensity and its associated influence region, which can pose a potential danger to UAV flight. Additionally, the analysis should take into account the aerodynamic effects of different types of bridge columns on the wake vortex. An optimization algorithm was utilized to optimize the trajectory of a UAV during bridge inspections within the safe region affected by wind fields. This resulted in the determination of an effective and safe flight path. The study reveals that varying wind speeds have an impact on the safe flight zone of UAVs, even if they are below the operational requirements. Therefore, when monitoring bridges using UAVs, it is important to take into account the influence of meteorological conditions. Furthermore, it was observed that the flight path of UAVs during square cylinder column monitoring is longer and more time-consuming than round cylinder column monitoring. Determining an effective UAV inspection path is crucial for completing bridge monitoring tasks in windy conditions, establishing bridge inspection standards, and developing the Intelligent Bridge Inspection System (IBIS).

Hearing the shape of ancient noncollapsed flows in R4$\mathbb {R}^{4}$

AbstractWe consider ancient noncollapsed mean curvature flows in whose tangent flow at is a bubble‐sheet. We carry out a fine spectral analysis for the bubble‐sheet function u that measures the deviation of the renormalized flow from the round cylinder and prove that for we have the fine asymptotics , where is a symmetric 2 × 2‐matrix whose eigenvalues are quantized to be either 0 or . This naturally breaks up the classification problem for general ancient noncollapsed flows in into three cases depending on the rank of Q. In the case , generalizing a prior result of Choi, Hershkovits and the second author, we prove that the flow is either a round shrinking cylinder or 2d‐bowl. In the case , under the additional assumption that the flow either splits off a line or is self‐similarly translating, as a consequence of recent work by Angenent, Brendle, Choi, Daskalopoulos, Hershkovits, Sesum and the second author we show that the flow must be 2d‐oval or belongs to the one‐parameter family of 3d oval‐bowls constructed by Hoffman‐Ilmanen‐Martin‐White, respectively. Finally, in the case we show that the flow is compact and SO(2)‐symmetric and for has the same sharp asymptotics as the O(2) × O(2)‐symmetric ancient ovals constructed by Hershkovits and the second author. The full classification problem will be addressed in subsequent papers based on the results of the present paper.

Effect of contact angle on spreading of refrigerant mixture over the vertical cylinder

The paper presents 3D numerical modeling of spreading dynamics of R21 (mol. fraction: 0.9) and R114 refrigerant mixture film. We considered an outer flow along a round vertical cylinder at Reynolds numbers of 50 and 104 and contact angles of 10°, 30°, 50°, 70° and 90°. The simulation was performed in OpenFOAM software on the basis of the volume of fluid (VOF) method. Main simulated results are presented in the form of velocity fields of liquid that allow evaluating both wetting dynamics and local characteristics of the liquid film. We obtained that the contact angle has a key effect on the wetted area due to the change of liquid spreading modes over the cylinder. At that, we distinguished the following flow modes: the continuous film, the stable jet mode, the cascade jet mode, the mode of the massive jet, the jet-droplet mode and the drying mode. These modes are similar ones for horizontal tubes. In some flow modes over the vertical cylinder we demonstrated the existence of the noticeable transversal velocity at the wetting front, that leads to moving of jets sources, and the back liquid flow between jets, directed against gravity.

One-dimensional longitudinal space charge calculation based on integrated green function approach

For fast longitudinal electron beam dynamics study or optimization in an x-ray free electron laser (FEL) linear accelerator, the one-dimensional longitudinal space charge (1D LSC) impedance, assuming a round cylinder beam with uniform transverse distribution is extensively used in both analytical analysis and numerical simulation. In this paper, instead of employing the impedance model in the frequency domain, we directly calculate the longitudinal electric field by convolving the longitudinal beam density with the slice green function, i.e., the longitudinal electric field generated by a slice beam. For high-energy electron beam, the slice green function rapidly diminishes to zero within a distance significantly smaller than the bunch length. In order to resolve the sharp variation, we report on a fast and high-precision method by applying the integrated green function (IGF) approach to compute the 1D LSC field numerically with few grid points, therefore, providing us with an alternative approach to the impedance model.

Calculation of the Electrostatic Field of a Circular Cylinder with a Slot by the Wiener–Hopf Method

The paper presents an exact solution to the internal boundary value problem of the field distribution in an electrostatic lens formed by two identical semi-infinite coaxially located round cylinders separated by a slit of finite width and located inside an infinite outer cylinder. The problem is reduced to a system of singular Wiener–Hopf integral equations, which is further solved by the Wiener–Hopf method using factorized Bessel functions. Solutions to the problem for each region inside the infinite outer cylinder are presented as exponentially converging series in terms of eigenfunctions and eigenvalues. Using the obtained formulas, a numerical calculation of the axial distribution of the potential of a two-electrode lens was made for various values of the radii of the outer and inner cylinders.

CFD Simulation of Aerodynamics Truck Using Cylinder as Drag Reduction Device

Reducing drag is an excellent approach to improving truck efficiency and saving fuel. The addition of the cylinder could be an alternative for drag reduction devices like the windshield that has a similar function to enhance the truck’s aerodynamic performance. A numerical analysis was performed using Ansys Fluent CFD software to estimate the influence of the cylinder on the truck's drag force. The study was conducted by comparing truck without additional cylinder above the truck’s head, truck with windshield, and truck with cylinder variations, which round, type-I, and type-D cylinders. In the simulation, the analysis was carried out at a velocity of 30 m/s using the k-epsilon turbulence model. A grid independence test was conducted to minimize errors and optimize iteration time. The simulation results showed that using round, I-type, and D-type cylinders as an alternative to the windshield reduced the truck's drag coefficient, with the D-type cylinder achieving the highest reduction in drag coefficient, which is 0.72. Modifications in the design of the drag reduction cylinder can lower fuel consumption indirectly by 6.95 % using a D-type cylinder.

Research on the External Fluid Flow of a Round Cylinder with CFD

Fluid mechanics is a frequently applied discipline, and technology advancements have substantially improved how engineers’ approach and solve issues, and one of them is CFD. The purpose of the study was to evaluate how closely CFD adheres to accepted engineering principles. Selected CFD conducts computations to compare the magnitude and direction of drag coefficient changes under conditions of rising Reynolds number by simulating conditions in a wind tunnel to gather data on the object's reaction to fluid velocity. Within this range, the drag coefficient decreases with increasing Reynolds number. The simulated Reynolds number and drag coefficient do have a consistent relationship with the facts.

Assessment of Diamond Rotary Instruments Advertised for Cutting 3Y-TZP Restorations. A Scanning Electron Microscope Analysis

Aim: To examine the cutting efficiency and amount of material removed from crown-cutting diamond burs from a different manufacturer on zirconia using an electric handpiece. Material and Methods: The performance of super coarse diamond bur round-end from five different manufacturers that were commercially advertised as zirconium crown cutters were assessed. The five manufacturers and their respective diamond bur models tested were super coarse Group 1: Dimond bur, Group 2: Zirconia Diamond Bur, Round End Cylinder, Meisinger, Group 3: 4ZR Zirconia Cutter Diamond Crown Removal Bur, Group 4: Brasseler Dental Diamond Bur, Group 5: Expanded SS White® Lineup of Zirconia Cutting Diamonds. The qualitative assessment of diamond burs (before zirconia cutting) and (after zirconia cutting) was assessed using a scanning electron microscope. The mean cutting distance and material removed for each group were calculated and analyzed using one-way ANOVA. Results: The highest cutting efficiency was found in group 2 and the lowest efficiency was observed in group 5. Post-SEM images of rotary zirconia cutting instruments in groups (Post G1-G5) demonstrate pullout, wear, chipping, and loss of the diamond grains in general. Conclusion: Zirconia Diamond Bur (G2) was found to be suitable. Whereas, (G5) Expanded SS White® Lineup of Zirconia Cutting Great White®Z Diamonds is less effective.

Снижение колебаний массы бумаги в бумагоделательной машине

The subject of the research is a paper for sanitary-hygienic purposes. The objects of the study are a pulper infeed system and a round grid perforated forming device. The purposes of the work are to identify sources and reduce fluctuations of 1 m2 of pulp for sanitaryhygienic paper, which decrease the structural irregularities of the paper web in longitudinal and transverse directions. The methodology of the study is to investigate the flow pulsation of the pulp, the fluctuations of the pulp web at the Yankee cylinder (without crepe), to verify the tensile strength of the paper web in longitudinal and transverse directions for identification of a correlation between the pulsation, the vibration of the pulp and the strength of the paper web. The trials were made during the production of sanitary-hygienic paper with the mass 17–18 g/m2 at a steady working speed of the machine 5 m/s. Pulsations of paper pulp in the low-frequency spectrum of 0.14–1.35 Hz prevail in the mass-intake device. The rectangular paper samples 432×230 mm2 were created for examination of structural irregularities of the paper web. The length 432 mm was taken in the longitudinal direction of paper movement in the machine. It was equal to 0.125 mm in the circumference of the round grid screen cylinder. The width of the paper web in the commodity bobbin was 230 mm. The samples were made from a single sheet of paper sequentially without intermediate cuts at 5 m/s speed of the machine. It was determined that the frequencies of fluctuations of the masses of sanitary paper samples coincide by 86 % with the pulsation frequencies of the pulp and depend on other factors by 14 %. The major frequency was 1.45 Hz. The amplitude of the deviation of the mass at this frequency from the arithmetic mean was 0.026 g. The tensile strength of the paper web in the machine direction was 5.6 times greater than in the transverse direction. It was caused by unregulated rotation frequency of the holey roll and clogging of its holes. The significant change of speed of the pulp flow on the short cylindrical part of the vacuum chambers initiated synchronically low frequency pulsation of the pulp and fluctuations of masses of the paper samples, therefor, the paper web in the machine. The irregularities of the structure of the paper web create the frequent paper breaks and reduced quality of the commodity products.

Numerical investigation of two-dimensional unsteady flow and heat transfer from rounded equilateral isothermal triangular cylinders in cross flow

Numerical investigation of two-dimensional unsteady flow and heat transfer from rounded equilateral isothermal triangular cylinders in cross flow

Coupled Simulation of Fluid Flow and Vibro-Acoustic Processes in the Channel with a Circular Cylinder

Vibro-acoustic processes are an interacting set of pulsations of the working fluid and vibrations of mechanical structural elements. The simulation of vibro-acoustic processes in a long pipe with an elastic round cylinder is considered. The mathematical model is developed in a coupled formulation, when not only pressure pulsations cause pipe vibrations, but also vibrations of the mechanical subsystem affect sound wave propagation in the working fluid. The influence of vortex formation processes in the channel on the system dynamics is taken into account. The fluid flow is found using delayed detached eddy simulation. The flow regimes around a single round cylinder corresponding to various Reynolds numbers are investigated to validate the computational algorithm. The distributions of the flow quantities and vibro-acoustic behavior of the system are discussed.

Vortex collision against static and spinning round cylinders: A lattice Boltzmann study

In this paper, the flow physics generated by the collision of a vortex dipole that moves against a spinning round cylinder is investigated numerically. Fluid dynamics is predicted by a combined central-moments-based lattice Boltzmann-immersed boundary method. First, the model is validated against well established consolidated benchmark problems, showing very high accuracy properties. Then, results from a comprehensive numerical campaign are presented. A wide set of values of the Reynolds number (Re) is investigated, ranging from 10 to 1000. The cylinder is forced to spin around its centre with different angular velocities, which are obtained by varying the spinning number (Sp) between 0 (corresponding to the static case) and 0.75. The generation of secondary vortices as a consequence of the impact is elucidated and linked to the time evolution of the kinetic energy, enstrophy and hydrodynamic forces. Interestingly, we find that the flow physics changes drastically when Re≥250, independently from the value of Sp. Through a closer look at the vorticity field, we find that the impact creates two primary–secondary structures and a second impingement takes place when Re≥250. Interestingly, the normalised drag force (Cd) is found to constantly fluctuates around a mean value. Oscillations are due to the vorticity created by the rotation of the cylinder and are more emphasised as Sp grows. Specifically, Cd can achieve marked negative values as a consequence of the velocity field created by the cylinder during its rotation.

Magneto-optical double zero-index media and their electromagnetic properties in the bulk

Double-zero-index media (DZIM) with zero permittivity and permeability are one important class in zero-refractive index photonics. Here, we extended the concept of DZIM and proposed a more general type, i.e., the magneto-optical DZIM (MODZIM), of which the permittivity and the determinant of the Hermitian permeability tensor are simultaneously zero. By formulating the Maxwell’s equations in the basis of complex-valued axes and using some mathematical principles, we studied the electromagnetic (EM) properties in the bulk of the MODZIM with different boundaries and impurities. Inside the MODZIM which is infinite along in the out-of-plane direction, it is shown that the scalar (out-of-plane) field is not uniform in general, in contrast to traditional DZIM where the scalar field is always uniform in the bulk. Nevertheless, for a normal incidence, the uniform scalar field inside the MODZIM can be achieved by optimizing the boundary conditions and doping some types of impurities, such as resonant round cylinders and arbitrary shaped media with a zero permeability. As long as the scalar field is uniform, the propagation of the EM wave inside the MODZIM can be analyzed with closed-form expressions. Our work will extend the study of zero-refractive-index photonics and provide deeper understanding of wave dynamics in the bulk of MODZIM.

Numerical Modeling of Interactions between Solitary Waves and Floating Breakwaters

In the current numerical work, a 2D wave tank has been planned to explain the shared impacts among three different solitary waves and three different floating breakwaters by applying Reynolds-Averaged Navier-Stokes models and the volume of fluid method. Three dissimilar floating breakwaters (i.e., square breakwater, circular breakwater, and modified breakwater) were chosen. A total of eighteen cases were investigated, including three different floating breakwaters, a solitary wave (SW) with three different wave heights, and two different densities of floating breakwaters. We achieved the production of a solitary wave by moving a wave paddle (WP) and the motion of floating breakwater in two various directions by applying two different codes as user-defined functions. The dynamic mesh technique has been employed for re-forming mesh during the motion of the wave paddle and the floating breakwater. The numerical calculations have been confirmed by some numerical, analytical, and experimental case studies. First, the generation of a SW using the WP movement and the free motion of a heaving round cylinder on the free surface of motionless water were modeled and validated. Additionally, the effects of various parameters, including floating breakwater shape, floating breakwater density, and solitary wave height, on the hydrodynamic performances of the floating breakwater, the floating breakwater’s motions, and the free-surface elevation were considered under various conditions.

Investigation of Wind-Loads Acting on Low-Aspect-Ratio Cylindrical Structures Based on a Wind Tunnel Test

The low-aspect-ratio cylindrical structures represented by oil tanks is a kind of wind sensitive structure, which is prone to buckling under wind-loads. A wind tunnel test was conducted to investigate the properties of wind-loads acting on smooth cylinders with an aspect ratio AR = 0.323 and 0.875, respectively. Some parameters, such as Reynolds number (Re) and turbulence intensity, were taken into account. The results reveal that low-aspect-ratio cylinders have a Re effect, and the effect rises with AR. AR is the main factor affecting the value of the base pressure coefficient and positive pressure range, and the former increases with AR, while the latter decreases with AR. Moreover, due to the influence of the free end and turbulence, which may suppress vortex shedding, the power spectrum of the lift coefficient essentially shows broad spectral peaks with Re and turbulence. Increasing the incoming turbulence made the flow round cylinders at a higher Re state, that is, the supercritical regime is reached at a smaller Re. When turbulence is greater than 4.0%, turbulence and Re have little effect on the mean base force coefficient of low-aspect-ratio cylinders.

Exploration and Identification of the Entomopathogenic Fungus Metarhizium anisopliae in Corn Plants in Sebandung Village, Sukorejo, Pasuruan

Metarhizium anisopliae is a biological control agent (BCA) that have been developed to control plant pest in this disruption era. These fungi penetrate the insect body through its skin between the head and the thoraxs also in between the joint. The purpose of this research is to identify the characteristic of the fungi M. Anisopliae from the exploration in sebandung village, sub-district Sukorejo, district Pasuruan. Data analysis is done by using descriptive data. Step of the research involves (1) sample gathering from the soil in the cornfield that has been predicted to have BCA biodiversity, after that determined 5 sampling points diagonally, each sample contains 100 gr of soil from the depth of 10 -20 cm, (2) fungi baiting by using a mealworm (Tenebrio Molitor) as a bait, (3) M. Anisopliae isolate using PDA (Potato Dextrose Agar), (4) identification is conducted by macroscopic and microscopic. The identification result shows that the isolate has a white mycelium that forms into a mossy green spore, fine texture, easily spread, and insulated mycelium, straight conidiophore, hyalin, and branching, single-cell conidia, hyalin, round cylinder type, also white to the mossy green colony. Parasitism test results show that T.molitor larvae develop a hard body, have a murky color, covered in white hyphea till it transforms into moosy green spore with a fine texture and easily spread, the spore is the final form of the fungi propagule existence in the host as a survival phase in extreme condition.

Ancient asymptotically cylindrical flows and applications

In this paper, we prove the mean-convex neighborhood conjecture for neck singularities of the mean curvature flow in $${\mathbb {R}}^{n+1}$$ for all $$n\ge 3$$ : we show that if a mean curvature flow $$\{M_t\}$$ in $${\mathbb {R}}^{n+1}$$ has an $$S^{n-1}\times {\mathbb {R}}$$ singularity at $$(x_0,t_0)$$ , then there exists an $$\varepsilon =\varepsilon (x_0,t_0)>0$$ such that $$M_t\cap B(x_0,\varepsilon )$$ is mean-convex for all $$t\in (t_0-\varepsilon ^2,t_0+\varepsilon ^2)$$ . As in the case $$n=2$$ , which was resolved by the first three authors in Choi et al. (Acta Math, 2018), the existence of such a mean-convex neighborhood follows from classifying a certain class of ancient Brakke flows that arise as potential blowup limits near a neck singularity. Specifically, we prove that any ancient unit-regular integral Brakke flow with a cylindrical blowdown must be either a round shrinking cylinder, a translating bowl soliton, or an ancient oval. In particular, combined with a prior result of the last two authors (Hershkovits and White in Commun Pure Appl Math 73(3):558–580, 2020), we obtain uniqueness of mean curvature flow through neck singularities. The main difficulty in addressing the higher dimensional case is in promoting the spectral analysis on the cylinder to global geometric properties of the solution. Most crucially, due to the potential wide variety of self-shrinking flows with entropy lower than the cylinder when $$n\ge 3$$ , smoothness does not follow from the spectral analysis by soft arguments. This precludes the use of the classical moving plane method to derive symmetry. To overcome this, we introduce a novel variant of the moving plane method, which we call “moving plane method without assuming smoothness”—where smoothness and symmetry are established in tandem.