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Fused deposition modeling (FDM) is an additive manufacturing process that can be used to manufacture three‐dimensional thermoplastic components layer by layer. One disadvantage of FDM is the shrinkage of the components during the manufacturing process. The filament is molten in the nozzle, deposited layer by layer, and cools down again. During solidification, the filament shrinks inhomogeneously in the x/y/z direction, which leads to distortion of the component geometries. Particularly with higher nominal lengths and complex local geometries, there is a need for optimization with regard to dimensional accuracy. The aim of this paper is to counteract this on the software side with global as well as local shrinkage factors. The expected shrinkage within a layer is predicted with an in‐house developed software. The geometric accuracy of the model is verified by experimental investigations on cylindrical test specimens. In these, the so‐called clover effect occurs as a result of the shrinkage. The circular shape of the deposited layer is deformed by the distortion in the x–y plane comparable to a clover. Finally, the results are validated by analyzing a demonstrator in the form of a bracket. [ABSTRACT FROM AUTHOR]

Flow around a circular cylinder is ubiquitous in nature and industrial applications. In marine, coastal and bridge engineering, undesirable vortex-induced vibrations (VIVs) of structural components are common, and the periodic vortex shedding (von K a ´ rmen vortex streets) of the cylinder plays a crucial role in the VIVs. Therefore, it makes sense to consider approaches to suppress vortex shedding and improve the surrounding flow of the cylinder. Two categories of flow control methods, i.e., passive and active strategies, effectively handled this problem. Compared to active control, the passive control method does not require additional energy input to maintain the process and is easier and more cost-effective to implement, making it worth investigating. This selective literature review gives academic frontiers on passive control of flow past a circular cylinder, including splitter plate, groove, screen, rough surfaces, spirals and helical plates, slit passive jets, control rods, porous media coating and vortex generators. Finally, we give a brief outlook on the application of machine deep learning methods in the passive control of flow around a circular cylinder. [ABSTRACT FROM AUTHOR]

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A Zariski open subset of an algebraic variety is called a cylinder if it is isomorphic to the direct product of the affine line and an algebraic variety. We consider the existing condition of relative cylinders with respect to a projective dominant morphism of relative dimension two. Since this consideration is essentially a determination of the existence of cylinders in the generic fiber, we study smooth projective surfaces defined over a perfect field from the point of view of cylinders. In previous work, the existing condition of cylinders in smooth minimal del Pezzo surfaces over a field of characteristic zero is known. In this article, we completely determine the existing condition of cylinders in smooth minimal geometrically rational surfaces over a perfect field. Furthermore, we show that for any birational map between smooth projective surfaces over a perfect field, one contains a cylinder if and only if so does the other. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Babylon Center for Humanities Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mean wake structures of a cube (square cylinder) and circular cylinder of height-to-width aspect ratio 1.0, at a Reynolds number of 1.78 × 104 based on the obstacle width, were investigated experimentally. The boundary-layer thickness was 0.14 of the obstacle height. The study was performed using thermal anemometry and two-dimensional digital particle image velocimetry (DPIV). Streamwise structures observed in the mean wake for both cylinders included well-known tip- and horseshoe (HS)-,vortex pairs as well as additional structures akin to the base vortices. In addition to tip-, base-, and HS-vortices, in the near wake of the cube, two more counter-rotating pairs of streamwise structures, including upper and inboard vortices, were observed. The existence of base vortices formed in the near wake for both obstacles is a unique observation and has not been previously reported for such low-aspect-ratio obstacles in thin boundary-layers. A model of arch-vortex evolution was proposed, in which arch structures were deformed by the external shear-flow to explain the observed base-vortices in the cylinder wake. A weak dominant-frequency of St = f0D/U∞ = 0.114 was observed across the height for the cube, while no discernible spectral peaks were apparent in the wake of the cylinder. Cross-spectral analysis revealed the shedding to be symmetric (in-phase) arch-type for the cylinder and predominantly anti-symmetric (out-of-phase) Karman-type for the cube. The study makes fundamental contributions to the understanding of the flow-field surrounding low-aspect-ratio cylinders. [ABSTRACT FROM AUTHOR]

Decreasing production and rising prices of cars, especially those with electric drive, lead to longer use of cars with internal combustion engines. It can be assumed that in the future, more and more cars powered by such engines with high mileage and therefore high wear will be used. Engine wear leads to reduced efficiency and increased emissions. This paper analyzes the impact of wear of the piston–rings–cylinder system components on energy losses associated with gas leakage from the combustion chamber and friction of the rings against the cylinder liner in a car spark-ignition engine. A ring pack model was used for the analyses. The input data for the simulation were gained in measurements made on the engine test stand and measurements of the wear of the engine components used in the car. The energy losses associated with blow-by in an unworn engine ranged from 1.5% of the indicated work at high load to almost 5% at low load. In the engine after 300,000 km, these losses increased to 2.5% and 7.5%, respectively. Ring friction losses in an unworn engine ranged from 1.5% at high load to 9% at low load. The effect of wear on these losses was smaller. They increased by only 0.1% at high load and 1% at low load. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A vertex subset S of a graph G is said to 2-dominate the graph if each vertex not in S has at least two neighbors in it. As usual, the associated parameter is the minimum cardinal of a 2-dominating set, which is called the 2-domination number of the graph G. We present both lower and upper bounds of the 2-domination number of cylinders, which are the Cartesian products of a path and a cycle. These bounds allow us to compute the exact value of the 2-domination number of cylinders where the path is arbitrary, and the order of the cycle is n ≡ 0 (mod 3) and as large as desired. In the case of the lower bound, we adapt the technique of the wasted domination to this parameter and we use the so-called tropical matrix product to obtain the desired bound. Moreover, we provide a regular patterned construction of a minimum 2-dominating set in the cylinders having the mentioned cycle order. [ABSTRACT FROM AUTHOR]

Stability and heat transfer efficiency of the Rayleigh–Bénard-convective system (RBCS) in a vertically vibrated very-shallow cylinder are investigated in the paper for two conventional nanoliquid media, i.e., water-aluminum and water-AA7075 nanoliquids. Using a normal mode solution involving zeroth- and first-order Bessel functions, linear stability analysis is performed. The influence of added aluminum and AA7075 nanoparticles, and sinusoidal waveform of vertical vibration on the onset in a RBCS is reported by obtaining analytical expressions for the marginal and the correction Rayleigh numbers. A minimum number of eigenfunctions is used to arrive at the modified, non-autonomous Lorenz model which is then projected into a Stuart–Landau equation using the method of multiscales. The solution of the Stuart–Landau equation is used to compute the time-averaged Nusselt number. The study reveals that the presence of nanoparticles in water is to destabilize the system and opposite is the influence of vertical vibration. For large frequency of periodic vibrations, its influence on the onset of convection is negligible. Further, the influence of nanoparticles in a baseliquid is to enhance heat transport and this can be used as a remedy for recovering the loss of heat due to a vertical vibration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The bolt-shotcrete support of roadway is generally calculated by beam model, but the mechanical state of bolt-shotcrete support on the curved side of the roadway is obviously different from that on the straight side. The force of the shotcrete layer is analyzed in order to reasonably determine the bolt-shotcrete support parameters of the curved side of the roadway. The bolt-shotcrete support structure is simplified as a mechanical model of coupling between a fixed-end beam and a cylinder. This study undertakes a stress analysis of a shotcrete layer in order to find the mechanical mechanism of bolt-shotcrete support in a circular roadway (or the arc part of the roadway), and reasonably determine the parameters of bolt-shotcrete support. The bolt-shotcrete supporting structure is simplified as a mechanical model of the coupling between a fixed-end beam and a cylinder. The mechanical model for the influence of shotcrete layer thickness, shotcrete strength, bolt spacing and bolt length on the self-supporting capacity of the surrounding rock is established in combination with the Mohr-Coulomb strength theory. The influential law of the parameters of bolt-shotcrete support and the self-supporting capacity of the surrounding rock is determined. The results show the existence of a linear relationship between the strength of the shotcrete and the self-supporting capacity of the surrounding rock. A quadratic function relationship between the thickness of shotcrete and the self-supporting capacity of the surrounding rock is found. The results also show a cubic function relationship between the spacing and length of the bolt and the self-supporting capacity of the surrounding rock. The research results have a certain guiding significance for the determination of bolt-shotcrete support parameters on the curved side of roadway.

The article analyzes the materials from which the piston is made for internal combustion engines. For automobile and tractor engines, in particular, eutectoid mixtures of the AL25 type and eutectoid mixtures containing copper, nickel, magnesium and manganese are used. The chemical composition of aluminum alloys is given. Pistons for high-speed, forced diesel, medium-speed engines are made of gray or malleable cast iron (SCh24-44, SCh28-48, SC32-53), as well as alloyed with additives of vanadium, chromium, titanium, copper (RF45-5). Heat-resistant steels of the 20Kh3VMF type are used for combined pistons. Research work is being carried out on pistons made of titanium and carbon fiber. Pistons with automatic adjustment of the degree of compression can limit the thermal and mechanical stress of the parts of the cylinder-piston group, boost the engine at an average effective pressure of 1.5-2 times, improve starting quality, provide the ability to use different brands of fuel. A combined piston with copper-fluoroplastic inserts is available for internal combustion engines, compressors, pumps and other reciprocating machines. Inserts made of copper-fluoroplastic composition provide the application of a thin film of copper on the friction surface throughout the life of the engine, which significantly accelerates running, reduces burrs and abrasions, increases wear resistance and durability of CNG parts. The main disadvantages and advantages of the performance characteristics of pistons made of different materials. The analysis of designs of pistons is made. The main requirements for the design of pistons are: simplicity of design, and if possible to ensure symmetry about the axis of the cylinder, minimum weight, maximum strength and rigidity, wear resistance of the material, efficient heat dissipation (cooling); minimum cost of production. The main defects of the piston are: the height of the first groove, the diameter of the hole under the piston pin, the diameter of the skirt

This study represents a numerical analysis of stress and strain in the functionally graded material (FGM) hollow cylinder subjected to two different temperature profiles and inhomogeneity parameter. The thermo-mechanical properties of a cylinder are assumed to vary continuously as power law function along the radial coordinate of a cylinder. Based on equilibrium equation, Hooke's law, stress-strain relationship in the cylinders, and other theories from mechanics second order differential equation is obtained that represents the thermoelastic field in hollow FGM cylinder. To find a numerical solution of governing differential equation, the finite element method (FEM) with standard discretization approach is used. The analysis of numerical results reveals that stress and strain in the FGM cylinder are significantly depend upon variation made in temperature profile and inhomogeneity parameter n. The results show good agreement with results available in the literature. It is shown that thermoelastic characteristics of the FGM cylinder are controlled by controlling the value of the above discussed parameters. Moreover, these results are very useful in various fields of engineering and science as FGM cylinders have a wide range of applications in these fields.

Free vibrations of a reinforced cylindrical shell filled with liquid are investigated. The case of an orthotropic shell is considered when the cord filament is placed symmetrically with respect to the meridian of the shell. The motion of a fluid is potential and is described by a wave equation. The fluid moves without separation from the walls of the cylinders. The fluid pressure is taken into account in the equations of motion of the shells, and the velocities of the fluid and the shell are equalized at the boundaries. Representing a solution in a harmonic form reduces to a system of transcendental equations. Comparison of the solutions of the problems without a liquid and with a liquid shows the dependence of the frequency of the system without a liquid at the frequency of the system with the liquid. An inverse method is proposed for solving the equation. The inverse method for solving the problem has made it possible to construct a more accurate frequency spectrum of free oscillations of the system. For some values of the system parameters, the natural frequencies of the cylinder are determined.

The creep and plastic flow of cylindrical pressurized vessel with rigid casing was considered. To combine creep and plastic deformations the vessel was heated and subjected to the high inner pressure. The semi-analytical solution for plain strain problem of a thick-walled cylinder with rigid casing in the frame of small strain theory was obtained in this paper. This solution consists of analytical formula for displacement distribution with asking values of pressure and irreversible strains (plastic and creep) and a numerical solution for irreversible strain values. The Norton power law and advanced Mises condition for viscoplasticity, associated with flow rules have been used to describe creep and plastic behavior of medium. Four stages of the deformation process were considered: pressure increasing, pressure fixed on maximum value for a long time, pressure decreasing and relaxing stage with zero pressure. Two cases of maximum pressure values of 200 MPa and 320 MPa were studied. An additional case of elastoplastic deformation was considered to investigate the influence of creep on the deformational process. It has been observed that creep has a significant influence on stress and strain evolution in medium, especially on stages with maximum and zero pressure. Also, because of the creep plastic flow evolves slower and stoppes earlier on the loading stage. In the unloading stage, the plastic flow starts earlier and affects greater area due to greater irreversible strains. Creep leads to sufficient stress relaxation and stresses for two pressure cases get similar values at the end of the stage with maximum pressure value. At the end of the relaxing stage besides stresses displacement and deformation also became similar for the two cases.

Sediment transport modeling for flows with cylinders is very challenging owing to the complicated flow–cylinder–sediment interactions, especially under the combined wave-current flows. In this paper, an improved formulation for incipient sediment suspension considering the effect of cylinder density (i.e., solid volume fraction) is employed to simulate the bottom sediment flux in the flow with cylinders. The proposed model is calibrated and validated using laboratory measurements under unidirectional and combined wave-current flows in previous studies. It is proved that the effects of cylinders on sediment suspension can be accounted for through a modified critical Shields number, and the proposed model is capable of simulating sediment suspension under both unidirectional and combined wave–current flows reasonably well with the average the coefficients of determination and model skills greater than 0.8 and 0.64.

A new cone species, Cylinder feliciae, is described from the Saleh Gulf (Teluk Saleh) of Sumbawa, Nusa Tenggara Islands (Lesser Sunda Islands), Indonesia. The new species is morphologically similar to Cylinder gloriamaris (Chemnitz, 1777) from the southwestern Pacific and represents a geographically-isolated relict of a once widespread molluscan fauna that extended all along the coast of the Middle Pleistocene Sundaland Peninsula. [ABSTRACT FROM AUTHOR]

Numerical and experimental methods are used to investigate the aerodynamic characteristics of a laboratory model in the form of a cylinder with an active rotating element (deflector) that can be used as a working blade of a wind turbine. Numerical simulation was based on solving the Reynolds-averaged Navier–Stokes equations for the realizable () turbulence model using the Ansys Fluent software. Experimental studies were performed using a laboratory model with a cylinder 205 mm long and 50 mm in diameter and a deflector 100 mm in diameter, which was produced based on the results of the numerical simulation. A comparative analysis of the numerical and experimental aerodynamic characteristics of the model was carried out and the aerodynamic features of the airflow around the test model were identified. [ABSTRACT FROM AUTHOR]

This study analyzes the influence of crankshaft angular velocity on the working processes, integral characteristics, and coolant movement dynamics of a reciprocating hybrid energy machine with two suction valves. Based on a numerical experiment conducted using a previously developed mathematical model, the coolant consumption in the studied reciprocating hybrid energy machine decreases with an increase in crankshaft rotational speed. In addition, the maximum values of the supply coefficient and indicator efficiency are noted in the range of 700–900 min-1. Furthermore, the amount of relative energy utilized to organize the forced downward flow of the liquid decreases with an increase in crankshaft rotational speed. [ABSTRACT FROM AUTHOR]

The paper analyzes the effect of injection pressure at constant suction pressure on fluid motion dynamics, operating processes, and integral characteristics of a high-efficiency reciprocating hybrid positive displacement energy machine with two suction valves. As a result of a numerical experiment conducted using a previously developed mathematical model, it was established that the maximum value of the relative coolant flow rate is achieved at an injection pressure of 0.4 MPa and is approximately 120 kg/kg. The gas supply through the leaks of suction valve 2 to intensify the downward movement of the liquid causes the relative gas consumption and relative energy losses, which increase with increasing injection pressure. The maximum value of the indicator adiabatic efficiency is achieved at an injection pressure of 0.5 MPa, while the supply coefficient decreases steadily with increase in injection pressure. [ABSTRACT FROM AUTHOR]

The electro-hydraulic plastic deforming method belongs to non-conventional plastic deforming techniques class. The shape of the discharging chamber and of the energy concentrators influences workpiece machining, along with the other parameters of the equipment (electrical pulses, electrodes, space between electrodes, pressure wave transmission medium, way to propagate the pressure wave). The paper proposes a comparative analysis of the geometric parameters of the discharging chambers and of their effects on the technological processing. [ABSTRACT FROM AUTHOR]

The flow and heat characteristics of an unsteady, laminar biomagnetic fluid, namely blood containing Fe3O4 magnetic particles, under the influence of thermal radiation and a magnetic dipole over a cylinder with controlled boundary conditions using a group theory method are investigated in the present study. The mathematical formulation of the problem is constructed with the aid of biomagnetic fluid dynamics (BFD) which combines principles of ferrohydrodynamics (FHD) and magnetohydrodynamics (MHD). It is assumed that blood exhibits polarization as well as electrical conductivity. Additionally, the shape of the magnetic particles, namely cylindrical and spherical, is also considered. Moreover, in this model, a group theoretical transformation, namely a two-parameter group technique, is applied. By applying this group transformation, the governing system of partial differential equations (PDEs) along with applicable boundary conditions are reduced to one independent variable and, consequently, converted into a system of ordinary differential equations (ODEs) with suitable boundary conditions. An efficient numerical technique is applied to solve the resultant ODEs and this technique is based on three essential features, namely (i) a common finite differences method with central differencing, (ii) tridiagonal matrix manipulation and (iii) an iterative procedure. The flow and heat characteristics of blood-Fe3O4 are found to be dependent on some physical parameters such as the particle volume fraction, the ferromagnetic interaction parameter, the magnetic field parameter, and the thermal radiation parameter. An ample parametric study is accomplished to narrate the influences of such physical parameters on velocity, temperature distributions as well as the coefficient of skin friction and rate of heat transfer. From the numerical results, it is deduced that the fluid velocity is enhanced for the ferromagnetic number and the temperature profile is decreased as the ferromagnetic number is gradually increased. It is also obtained that for the cylindrical shape of magnetic particles, the fluid temperature is more enhanced than that of the spherical shape. Both the skin friction coefficient and the local Nusselt number are increased for increasing values of the ferromagnetic interaction parameter, where the heat transfer rate of blood-Fe3O4 is significantly increased by approximately 33.2% compared to that of pure blood, whereas the coefficient of skin friction is reduced by approximately 6.82%. [ABSTRACT FROM AUTHOR]

A comprehensive and systematic, computational investigation is presented on the effect of wall roughness on the supersonic flow over a circular cylinder with a Reynolds number of 500. Flow simulations are conducted using ANSYS Fluent. Wall roughness is modeled by a perturbation of the cylinder geometry with harmonic modes of varying amplitude and frequency. Validated smooth cylinder flow simulations for a range of Mach and Reynolds numbers with slip and no-slip wall serve as a reference. Roughness is shown to increase the effective diameter of the cylinder and the drag by displacing the outer flow along the peaks of the roughness elements. For lower frequencies, this effect is less pronounced than for higher roughness frequencies. While for smooth cylinders the vorticity is mostly generated by viscous shear forces, for rough cylinder the baroclinic vorticity generation is shown to be dominant and shown to determine the topology of the recirculating region. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rated pressure of common hydraulic pumps varies depending on their principle and geometric displacement but generally doesn't significantly exceed 400bar threshold. While this is perfectly adequate for most industrial and off-highway applications, there are applications requiring very high force that cannot be achieved by the linear actuator supplied with common pump pressure due to the space constraints placed upon the actuator. Increasing the pressure by means of pressure amplification resolves this problem. This presentation deals with principle, design considerations, applications, and benefits of hydraulic cartridge pressure amplifiers integrated directly into the hydraulic linear actuators and developed by PistonPower. The resulting linear actuator with integrated pressure amplifier thus features higher power density compared to the conventional hydraulic linear actuators. [ABSTRACT FROM AUTHOR]

Building information models (BIM) in the civil industry are very popular nowadays. The basic information of these models is the 3D geometric model of a building structure. The most applied methodology to model the existing buildings is by generating 3D geometric information from point clouds provided by laser scanners. The fundamental principle of this methodology is the recognition of structures shaped in basic geometric primitives, e.g., planes, spheres, and cylinders. The basic premise of the efficiency of this methodology is the automation of detection, since manual segmentation of a point cloud can be challenging, time-consuming, and, therefore, inefficient. This paper presents a novel algorithm for the automated segmentation of geometric shapes in point clouds without needing pre-segmentation. With the designed algorithm, structures formed in three types of basic geometrical primitive can be identified and segmented: planar (e.g., walls, floors, ceilings), spherical (e.g., laser scanner reference targets), and cylindrical (e.g., columns, pillars, piping). The RANSAC paradigm partially inspires the proposed algorithm; however, various modifications must be made. The algorithm was tested on several point clouds and was compared with the standard RANSAC algorithm; this part is described in the last section of the paper. One of the tests was performed on a double cylinder-shaped test object, the parameters (radius and height) of this object were available with high accuracy (0.1 mm), and the differences between the known and estimated parameters were below 0.5 mm in each case, indicating the correctness of the proposed algorithm. Also, a comparison with the standard RANSAC algorithm was performed, where the algorithm proposed showed better results than the standard RANSAC algorithm. The segmentation quality was, on average, increased from 50% to 100%. [ABSTRACT FROM AUTHOR]

The generation of noise by the flow of a compressible viscous gas over a circular cylinder as a result of the formation of vortices in it and the separation of them from the surface of the cylinder was considered. The sound field of this flow was calculated using the method of simulation of large vortices, and its acoustic characteristics were determined using the method of acoustic analogy based on the solution of the Ffowcs Williams–Hawkings equation. On the basis of the direct numerical simulation data on the indicated flow, its regimes at diff erent Reynolds numbers were investigated. The results of calculation of the acoustic characteristics of this flow within the framework of the two- and three-dimensional approaches to the solution of the Ffowcs Williams–Hawkings equation were compared. A good agreement has been obtained between the calculated gasdynamic and acoustic characteristics of a gas flow over a circular cylinder and the corresponding experimental and calculation data available in the literature. [ABSTRACT FROM AUTHOR]

A mathematical model of working processes of a positive displacement piston hybrid power machine with a gas cap and two suction valves is proposed, in which, due to the effect of surface forces on the coolant, its movement in the jacket space is intensified, which improves the cooling of the compressed gas and, as a result, increases the efficiency and delivery rate. The mathematical model is based on general equations of energy, mass and motion conservation, as well as the equations of state for compressed gas and coolant, and includes the calculation of thermodynamic parameters in the chambers of variable and constant volume, taking into account the motion dynamics of self-acting valves, and the calculation of gas and fluid motion in connecting pipelines. The mathematical model can be used for analyzing the influence of the main operational and geometric parameters on the working processes and integral characteristics of the machine under study. [ABSTRACT FROM AUTHOR]

The isometric path cover (partition) problem of a graph consists of finding a minimum set of isometric paths which cover (partition) the vertex set of the graph. The isometric path cover (partition) number of a graph is the cardinality of a minimum isometric path cover (partition). We prove that the isometric path partition problem and the isometric k-path partition problem for k 3 are NP-complete on general graphs. Fisher and Fitzpatrick in [The isometric number of a graph, J. Combin. Math. Combin. Comput. 38 (2001) 97–110] have shown that the isometric path cover number of the (r × r)-dimensional grid is ⌈2r/3 ⌉. We show that the isometric path cover (partition) number of the (r × s)-dimensional grid is s when r s(s − 1). We establish that the isometric path cover (partition) number of the (r × r)-dimensional torus is r when r is even and is either r or r + 1 when r is odd. Then, we demonstrate that the isometric path cover (partition) number of an r-dimensional Benes network is 2r. In addition, we provide partial solutions for the isometric path cover (partition) problems for cylinder and multi-dimensional grids. We apply two di erent techniques to achieve these results.

The electro-hydraulic plastic deforming method belongs to non-conventional plastic deforming techniques class. The shape of the discharging chamber and of the energy concentrators influences workpiece machining, along with the other parameters of the equipment (electrical pulses, electrodes, space between electrodes, pressure wave transmission medium, way to propagate the pressure wave). The paper proposes a comparative analysis of the geometric parameters of the discharging chambers and of their effects on the technological processing.

The paper deals with assessments of ability of the three RANS turbulence models (k-ω SST, k-ε RNG and one of the differential RSM formulations) to predict local and integral characteristics of the statistically 3D Rayleigh – Bénard liquid-metal convection with a key role of large-scale circulation (LSC). URANS-based calculations at the Rayleigh number of 106 and the Prandtl number of 0.025 have been performed for a bottom heated cylindrical container with equal diameter to height, using computational grids of varied cell sizes. The case of the slightly tilted container was considered where the LSC azimuth position being fixed. The suitability of the used turbulence models was evaluated by comparing the obtained results with the direct numerical simulation data obtained earlier for the same conditions.

The article is devoted to the study and development of a mathematical model of the process of electrification of textile materials in the system "man - clothing - environment" in hot climatic conditions. The phenomenon of static electrification, which occurs in the processes of manufacturing textile materials and products from them, as well as during the operation of finished products, leads to a decrease in the quality of products, causes inconvenience in work, and when an electric discharge occurs, it poses a threat to human life. Such interactions of elements in the "person - clothing - environment" system such as friction, compression, tension, shear increase the contact area of two media, and depending on the rate of these processes, they enhance or weaken metabolic processes, which contributes to an increase in the maximum static charge generated on contacting surfaces. temperature values for special clothing of limited length at the nodal points. At the same time, the number of nodal points is 1601, the number of connected elements is 800. In the area of temperature distribution along the length of the garment, in four different versions, it was found that in the I – version , in the II – version , in the III – version , in the IV – version , in the V – version , in the VI - version, the length of the clothes in this area increased by 10% compared to the length of the clothes in the II – version.

• This paper focuses on the boundary layer and entropy production of Casson nanofluids under cylindrical stretching motion in the case of nanoparticle aggregation. • The results show that increasing the volume fraction of nanoparticles from 1% to 3% increases the heat transfer efficiency by 2.72% in the absence of aggregation and by 12.42% in the presence of nanoparticle aggregation. It is also found that the presence of aggregation of nanoparticles significantly increased the heat transfer capacity and frictional resistance of Casson nanofluids compared to the absence of aggregation. • The heat transfer capacity and frictional resistance of Casson nanofluid were significantly improved in the presence of nanoparticle aggregation compared to the absence of nanoparticle aggregation. This paper focuses on the heat transfer and entropy production of the Casson nanofluid under cylindrical stretching motion in the case of nanoparticle aggregation. Calculations derived from the BVP4C numerical solution were utilized in the study to verify the accuracy of the calculations in comparison with previous results. The results showed that when the nanoparticle volume fraction was increased from 1% to 3%, the heat transfer efficiency improved by 2.72% in the absence of nanoparticle aggregation, while the heat transfer efficiency improved by 12.42% in the existence of nanoparticle aggregation. It is also found that the existence of aggregation of nanoparticles significantly increased the heat transfer capacity and flow resistance of the Casson nanofluid compared to the absence of aggregation. The results of this study can provide important theoretical support for applications in thermal management of stretched cylinders, biomedical drilling, and other fields. [ABSTRACT FROM AUTHOR]

• Magnus force on cylinder or sphere in a shear-thinning fluid is investigated. • Magnus force reduces compared with that in a Newtonian fluid. • Shear viscosity sensitive functions are introduced to analyze this force reduction. • A relationship is proposed to quantify Magnus force reduction for small Re. This study aims to investigate the impact of fluid shear-thinning on the Magnus forces acting on a rotating cylinder or a sphere immersed in an unbounded flow using direct numerical simulation. The Carreau model is employed to represent the shear-thinning fluid, with the considered Reynolds number (Re) ranging from 0.01 to 100, Carreau number (Cu) from 0 to 100, power-law index (n) from 0.1 to 1, and viscosity ratio (β) from 0.001 to 0.5. The rotation rate (α) is fixed at 6. A characteristic Reynolds number, Re c , based on a viscosity evaluated at the characteristic shear rate, γ ˙ α = α U ∞ / 2 a , is introduced. It is found that, at a constant Re c , compared to that in a Newtonian fluid, the Magnus force exerted on the rotating cylinder or sphere in the shear-thinning fluid is reduced. This reduction results from the difference in viscosity distribution between the upper and lower sides of the cylinder or sphere. Furthermore, our analysis demonstrates that the logarithmic reduction in the Magnus force coefficient can be expressed as a linear combination of the logarithm of the strain rate difference and the logarithm of the shear strain rate sensitive function at two limit states, Cu →0 or Cu →∞. This work may be helpful to deepen the understanding of complex rheological behavior encountered in swirling flow hydrodynamics. [ABSTRACT FROM AUTHOR]

The objective of this research is to analyze vortex structures, lift, and drag coefficients, generated by a variety of obstacles in the context of a 2D laminar flow, comparing the results between the different cases. To that aim, numerical simulations using the Smoothed Particle Hydrodynamics (SPH) method have been carried out. The resulting data presented herein constitute a comprehensive study of the flow around obstacle problem in 2D using SPH. The influence of the geometry on vortex formation has been studied at the Reynolds number Re = 100. The results show a strong agreement with the values in the literature for cylinders and squares. This is a crucial stage for the validation of the methodology before expansion to various geometries, e.g. square-cylinder combinations, piggybacks, and horizontal spoiler configurations. Notably, this study introduces a novel horizontal spoiler configuration, as opposed to the conventional vertical orientation found in the literature. To the best of the authors' knowledge, this configuration is presented here for the first time. Among single shapes, the cylinder with a spoiler exhibits the highest value for the drag coefficient, being 34% greater when compared to the single cylinder configuration. In addition, regarding configurations with a pair of side-by-side obstacles, the results indicate a notable increase in the drag coefficient for the case of a larger cylinder coupled with a smaller cylinder at the smallest gap amongst the ones tested. Having a look at the lift coefficient, the results for the different shapes oscillate considerably compared to the case of a single cylinder used as a reference. The maximum increase is obtained for the cylinder with spoiler (122%) and the piggyback at the minimum distance tested (135%), suggesting that objects in close proximity (or joined together) highly influence lift inception. Conversely, the greatest reduction in lift oscillations is found for the both the piggyback (58%) and the cylinder with a square (52%) when the gap between the two objects increases. In terms of the Strouhal number, the highest value is observed for the case of a single cylinder. For the other shapes tested, the Strouhal number is reduced from 11% to 63%. Therefore, the study allows to analyze the influence of different shapes on lift and drag forces, vortex shedding frequencies, and the relation amongst them, helping to understanding interference effects and shape influence, thus offering relevant insights to various engineering applications. The SPH method is validated using two of the geometries considered. In addition, a verification analysis is carried out in the case of the single cylinder considering lift and drag coefficients as well as Strouhal number. These studies (validation and verification) constitute a comprehensive convergence analysis – customary in CFD applications – for the proposed numerical scheme, confirming the accuracy of the SPH results for this particular problem. The simulations were carried out using the AQUAgpuSPH software, developed at Universidad Politécnica de Madrid (UPM). • Vortex formation and forces from various obstacle shapes are studied with SPH. • Verification and validation studies are done for cylinder and square single shapes. • A novel spoiler with the highest drag coefficient among tested shapes is introduced. [ABSTRACT FROM AUTHOR]

The aerodynamic impact of surface roughness and trips on a circular cylinder was investigated. Surface roughness was caused by textile sleeves of seven distinct fabrics varying in roughness. These sleeves were configured with one or two seams strategically positioned to influence the flow dynamics over a Reynolds number range of 4 × 1 0 4 ⩽ Re ⩽ 1. 3 × 1 0 5 . Measurements of the aerodynamic drag, lift, unsteady flow, and mean flow field were made. It is shown that seam(s) can reduce cylinder drag across the Reynolds number range. The parameters influencing this reduction include the number, position, configuration of seams, and fabric roughness. For a single seam, drag reduction of up to 45% and an increase in vortex shedding frequency were observed, relative to a smooth cylinder. In the case of fabrics with two symmetrical seams about the cylinder stagnation point, a significant reduction in the critical Reynolds number occurred, accompanied by approximately 35% drag reduction across a broad range of Reynolds numbers. Furthermore, an increase in freestream turbulence intensity caused a considerable reduction in both the critical Reynolds number and drag. These variations in the forces acting on the cylinder were related to the behavior of shear layers and wake. [ABSTRACT FROM AUTHOR]

This paper discusses an investigation on the wake interaction of a pitching NACA0012 airfoil placed downstream of a circular cylinder, which serves as a simple model for blades in atmospheric turbulence. The study examines the mean velocity, turbulence intensity, and high-order moments of the wake, and applies power spectral density to the streamwise velocity data captured by a hot-wire anemometer. Two parameters of the amplitude of pitching motion(α 0) and reduced frequency(k) were assessed at Reynolds number R e c = 10 5. The study shows a significant change in time-averaged flow characteristics profiles compared to a single cylinder and single pitching airfoil. The results also reveal that the dominant frequency for a single cylinder is f = 90.72 H z (Strouhal number of 0.193). Additionally, the frequency of eddies with the highest energy in the wake is the same as the pitching frequencies of the airfoil, indicating that most of the energy exchanged between the flow and the pitching airfoil occurs in pitching frequencies. Finally, the findings suggest that an increase in the angle of attack from zero to 5° increases the energy content in lower frequencies. • Analysis of the wake of cylinder-pitching airfoil was performed. • Amplitude of pitching oscillation and reduced frequency were assessed. • Time-average characteristics and power spectral density of wake were investigated. • PSD shows the highest energy level in the frequency of the pitching airfoil. [ABSTRACT FROM AUTHOR]

• Experimental study of slot synthetic jet impingement on circular cylinder. • Thermal behavior of slot synthetic jet is analyzed under various operating parameters. • SJ was found to perform better in the constrained environment. • Thermal behavior differs on cylindrical surfaces, showing unique traits. The present study aimed to comprehensively investigate the thermal behavior of a slot synthetic jet (SJ) interacting with a circular cylinder in both free and constrained environments through experimental analysis. By traversing the cylinder along the jet centerline across a range of non-dimensional distances (H/w = 5-50), spanning from the near-field to the fully developed region, the research aimed to elucidate the factors governing heat transfer performance. Key parameters such as Reynolds number, jet-cylinder separation distance, and excitation frequency were scrutinized to understand their influence on thermal performance. The SJ was found to perform better in the constrained environment, attributed to relatively higher flow fluctuations developed by the complex interaction of the vortex with the sidewall boundary layer and the cylinder. Almost 12% higher average heat transfer was observed in the case of the constrained environment over the range of parameters employed in the current work. Moreover, a strong dependence of heat transfer on the jet cylinder separation distance was also found. In contrast to the SJ impinging on flat target surfaces where the maximum heat transfer was attained in the intermediate field, at H/w = 14 to 18, for SJ impingement on the circular cylinder, however, this was consistently achieved in the near field, i.e., H/w = 5. Also, the thermal performance as a function of the flow Reynolds number was comparable to the uniform flow case when the Reynolds number was based on the approach flow velocity (i.e., local velocity based on the cylinder location) instead of the velocity at the slot exit. [ABSTRACT FROM AUTHOR]

• Experimentally investigated how the flow structure influences heat transfer. • Flow structures were captured clearly to interpret variation of Nusselt number. • Five mechanisms of flow affecting heat transfer were identified. • Similar heat transfer mechanisms were found at lower and higher Reynolds numbers. • Staggered cylinder arrangements enhance heat transfer better than tandem ones. Two cylinders in staggered and tandem configurations were experimentally investigated to understand how the flow structure influences heat transfer. The results indicate the heat transfer of downstream cylinder exhibits more variability than that of the upstream cylinder as the stagger angle changes. The heat transfer characteristics for each flow pattern and the mechanisms governing heat transfer for the cylindrical array were clarified. Additionally, the significant effects of flow motion on the local Nusselt number of the cylinder surfaces resulting from varying stagger angles were elucidated. The overall Nusselt number in a staggered array system increases with the stagger angle, whereas in a tandem array system, it increases with the distance ratio. Notably, staggered cylinder arrangements exhibited a more pronounced enhancement in heat transfer compared to the tandem arrangement. [ABSTRACT FROM AUTHOR]