Cylinder Structure Research Articles

The effect of end conditions on the body motion and near-wake flow structure of a circular cylinder under vortex-induced vibration

The effect of end conditions on the body motion and near-wake flow structure of a circular cylinder under vortex-induced vibration

Characterization of internal defects in cylindrical components using laser ultrasonic method with a modified SAFT algorithm

The health monitoring of cylindrical elements is particularly important for the safe operation of industrial production, because cylinders bear a lot of support and transmission work. Normal non-destructive evaluation techniques need special designs to suit high curvature surfaces of cylinders. Laser ultrasonic (LU) method can provide a remote and non-destructive inspection solution to solid cylinders due to its flexible adaptability to complex structures and strong penetration depth. However, constrained by the common problems of optical detection systems, the detected ultrasonic signals will suffer low signal-to-noise ratio and bad resolution from poor sample surface quality. Thus, a modified synthetic aperture focusing technique (SAFT) optimized for cylindrical components is proposed to improve the detectability of LU on small and buried defects. Mode conversion wave signals obtained by multiple separate excitations are used in SAFT imaging for the reconstruction of the defects under surface profile correction. To reduce the influence of incident waves such as direct surface acoustic wave, besides common difference method, adjacent wave subtraction algorithm based on cross-correlation is used for signal preprocessing, suppressing the incident waves and exaggerating the mode conversion waves. In numerical simulation, internal defects with diameters from 0.6 to 0.2 mm with various buried depths are visualized and accurately located via the optimized SAFT algorithm using mode conversion waves. For validation, a circumferential scanning system is established in LU experiment and internal defects from 0.8 to 0.4 mm in diameter inside solid cylinders are successfully detected with precise location. The results elucidate the reliability of characterizing the location of small internal buried defects in solid cylinder structures through LU-SAFT imaging.

Investigation on the electro-magneto-thermoviscoelastic response of multilayer rotating hollow cylinder based on two-temperature theory and fractional-order viscoelastic systems

Hollow cylinder structures play a crucial role in scientific experiment and industrial production, and are widely used in various fields, including pipeline transportation of gases and liquids, high-speed engines, porous combustors, and other engineering equipments. As a result, they have garnered considerable academic interest over the years. However, as science and technology progress, studying hollow cylinders under a single physical field is no longer sufficient for real-world applications. Additionally, the classical viscoelastic model has become inadequate in accurately describing complex materials with properties that fall between elasticity and viscosity. Therefore, this article investigates the electro-magneto-thermoviscoelastic coupling behavior of an infinitely long rotating multilayer homogeneous hollow cylindrical conductor. In this study, based on the fractional-order three-phase lag thermoelasticity theory, the fractional-order viscoelastic system and the two-temperature theory are introduced to further increase the accuracy of the model. To solve the corresponding equations, the Laplace transform technique is employed, resulting in solutions with dimensionless physical quantities. Graphs and tables are used to make relevant comparisons and assess the effects of time, material layering properties, different thermoelastic theoretical models, fractional-order parameters and angular velocity on the considered physical quantities. Finally, the numerical results are discussed to reveal the dynamic response of a homogeneous multilayered hollow cylinder under the complex coupling of multiple physical fields.

Passive control of porous media on the aerodynamic forces and wake structures of wall-mounted short circular cylinders

This paper numerically investigates the aerodynamic forces and the three-dimensional wake characteristics of wall-mounted circular cylinders with and without porous media coatings using large eddy simulation at a Reynolds number of 3.2×104. Short cylinders with aspect ratios of 0.5, 1.0, and 3.0 are considered, with one end fixed to a bottom wall in the current work. The study focuses on aerodynamic coefficients, flow characteristics, and wake structures for cylinders both with and without porous coatings. The statistical results indicate that porous media significantly alter flow patterns behind the cylinders, suppress downwash flow from the free end, and reduce velocity fluctuations and turbulent kinetic energy within the wake. The porous coating enhances the leeward side's base pressure, leading to a reduction in drag on the cylinder surface. The analysis of flow structures reveals that the topology of the arch vortex behind solid cylinders is significantly dependent on the aspect ratio, whereas this dependency is negligible for porous cylinders. Porous coatings diminish the intensity of the tip and trailing vortices behind the cylinder. Finally, based on the time-averaged flow field, we proposed two conceptual models of topological correlation for wall-mounted short cylinders, both with and without porous coatings, which contributes to describing the geometric characteristics and interactions of vortex structures.

A novel weight index-based uniform partition technique of multi-dimensional probability space for structural uncertainty quantification

Accurately and efficiently achieving the uncertainty quantification of engineering structures is a challenging issue. The direct probability integral method (DPIM) provides an effective pathway to address this issue. However, the key partition technique via Voronoi cell of DPIM requires a prohibitive computational burden for multi-dimensional probability space. Moreover, due to the distributed nonuniformity of representative points, the accuracy of DPIM with the partition technique via Voronoi cell (DPIM-Voronoi) for obtaining the response probability density function (PDF) of structures with multi-dimensional probability space still needs to be improved. To this end, a novel weight index-based uniform partition technique is proposed in this study. This technique can generate uniformly distributed representative points and calculate their assigned probabilities using the weight indexes of representative regions. This feature ensures that the representative points can fill the probability space in a highly uniform manner, and avoid the resource-consuming calculation process of assigned probability by Monte Carlo simulation in the original partition technique via Voronoi cell. Based on the proposed technique, DPIM with a Weight index-based Uniform partition technique (DPIM-WU) is developed. Compared to DPIM-Voronoi, the advantages of DPIM-WU include: (1) improving the computational accuracy of response PDF for structures with multi-dimensional probability space, especially in the tail region, leading to improved accuracy of the dynamic reliability; (2) remarkably reducing the computational cost, with minimal computer memory required for the partition process of multi-dimensional probability space; (3) enhancing the robustness to the number of representative points. These advantages are verified through the stochastic response and dynamic reliability analyses of four typical examples, including the 5-story buildings, dry friction system, cylinder structure, and adjacent buildings with pounding motion. Notably, in the stochastic pounding response analysis of adjacent buildings, a stochastic P-bifurcation occurs as the coefficient of variation of the structural parameters decreases.

Optimization of ball mill cylinder structure based on response surface optimization module and multi-objective genetic algorithm

Optimization of ball mill cylinder structure based on response surface optimization module and multi-objective genetic algorithm

Active feedback control on acoustic radiation of metastructure shell with low-frequency and broadband characteristics

Due to the tunable characteristics of elastic waves, the vibroacoustic coupling behavior of a mechanical metastructure is a hot topic of underwater vehicles. In this work, a metastructure shell with active feedback control is presented and fabricated. The dynamic effective density and sound pressure level are derived to find the influences of acceleration and displacement feedback control. Different from a single cylinder, a double cylinder structure has both in-phase and anti-phase modes. Numerical results are obtained by Fourier transform and harmonic series expansion. With the introduction of an active feedback control system, the reduction of acoustic radiation shows low-frequency and broadband characteristics. In addition, finite element simulation is applied to support numerical results and present vibroacoustic characteristics. Finally, an experiment is performed in the anechoic chamber to illustrate the quiet metastructure shell, which can be applied to new designs of underwater vehicles.

The effect of permeability on the flow structure of porous square cylinders

This study experimentally investigates the wake structure of a porous square cylinder in terms of permeability over two decades of $Da$ (i.e. $2.4 \times 10^{-5} < Da < 2.9 \times 10^{-3}$ ). The porous cylinder, featuring a simple cubic lattice structure, was fabricated using an additive manufacturing technique. This unique method, combined with a periodic and scalable lattice structure, effectively isolates permeability from porosity, making it suitable for an in-depth parametric study. The key parameter, permeability, was directly estimated by measuring the pressure drop and superficial velocity for each porous case in an open-loop pipe flow system. The downstream flow fields were obtained using standard planar particle image velocimetry measurements in an open-loop wind tunnel. Based on the experimental data, structural modifications in the near wake were examined in relation to permeability, leading to the identification of four distinct flow regimes depending on $Da$ . Additionally, the downstream flow adjustment length ( $L_i$ ) was assessed by introducing a permeability-based source term into the momentum equation, facilitating the development of an analytical model for $L_i$ . The present experimental data support this analytical model, and our results further confirmed that $L_i$ plays a crucial role as a characteristic length scale in the near wake.

Effects of pressure ratio allocation on the flow characteristics in a five-stage ionic liquid compressor

Ionic liquid compressors are a new type of hydrogen compressor technology with significant advantages when applied to high-pressure hydrogen refueling stations, where multi-stage compression is an ideal solution. The utilization of a liquid piston introduces complex two-phase flow phenomena within the cylinders, and understanding the characteristics of two-phase flow is crucial for the thermodynamic performance of the compressor. For the multi-stage compressors, pressure ratio allocation has a significant influence on the structural design and energy conversion efficiency of the compressor, however, there is a lack of relevant research in the existing studies. In this paper, the compression cylinder structures of a five-stage ionic liquid compressor under three pressure ratio allocation strategies are designed, and then the two-phase flow characteristics inside the cylinder are numerically investigated. Based on the analysis of the two-phase flow pattern in the cylinder, the minimum initial liquid heights in each stage that ensure the solid piston is not exposed are determined, and the escape characteristics of ionic liquid and the energy efficiency of the ionic liquid compressor were then analyzed. Under the same total pressure ratio and flow rate, when the consumption cost of ionic liquid was considered as a secondary factor, the strategy of equal pressure ratio allocated for five stages was recommended as the compressor efficiency was higher with better heat transfer performance.

Insights into reaction–diffusion behaviors of acetylene selective hydrogenation on pellet catalysts

AbstractIn this work, a particle‐resolved computational fluid dynamics model of the acetylene hydrogenation process is developed to investigate the effects of catalyst particle structures on the reaction–diffusion behaviors aiming to improve selectivity toward target ethylene. The effects of packing structures on mass and heat transfer are explored by employing particles with varying shapes, wall thicknesses, and external diameters. The simulation results reveal that decreasing diffusion paths and elevating reactor bed temperature will enhance ethylene selectivity, and cylinder and Raschig ring packing structures exhibit the lowest and highest ethylene selectivity of 35.6% and 48.9% at 70% of acetylene conversion, respectively. Reducing wall thicknesses of Raschig ring particles facilitates the diffusion of generated ethylene from the interior zone of catalysts but concurrently inhibits the conversion of acetylene to ethylene. The Raschig ring catalyst particle with 1.9 mm of wall thickness and 3.5 mm of external diameter is finally revealed to exhibit the highest ethylene selectivity.

Characterizing vibrations and associated wake structures of tandem square cylinders at different angles of incidence

Finite element computations were conducted to investigate the transverse vibrations of three identical tandem square cylinders and the associated wake patterns at a Reynolds number Re = 150. The reduced velocities ranged from U*=3 to 20, and the angles of incidence were set at α=0°, 22.5°, and 45°. The streamwise gaps for these three α were Lx=5H, 3.8H, and 3.5H, respectively, where H represents the projected dimension of the cylinder normal to the freestream. The mass ratio of the cylinders was fixed at m*=2, and damping was neglected to allow the cylinders to attain maximum amplitudes. In the presence of primary vortices being shed from all three cylinders, the upstream cylinder at α=22.5° and 45° exhibits three distinct vibration regimes: initial excitation and upper and lower response regions. On the other hand, due to interaction with the upstream vortices, the two downstream cylinders display four response regions. In the case of α=0°, the dynamic response of the upstream cylinder appears in only two regimes, but with a higher peak amplitude compared to α=22.5° and 45°. Vibration and shedding frequencies closely synchronize with the natural frequency of the spring-mass system in the second regime, leading to high amplitude oscillations for the most upstream cylinder with α=22.5° and 45°. The third response regime for the two downstream cylinders is associated with the lock-in phenomenon. In α=0° and 22.5° configurations, the shedding mode is 2S in all response regimes, while at α=45°, the shedding mode shifts to P + S during the second regime. Up to the second regime, lift and vortex forces are in-phase with the cylinder's oscillation for α=0° and 22.5°, but they go out of phase beyond that. In the case of α=45°, although lift remains in-phase with the displacement in the second regime, the vortex force is found to be out of phase. This study is expected to enhance the understanding of fluid–structure interaction phenomena involved in multiple structures and can aid in the design of stable structures in civil engineering, offshore engineering, and development of energy harvesting devices.

Crack-tip constraint analysis of cylinder structure with axial penetrating crack at outside surface

Crack-tip constraint analysis of cylinder structure with axial penetrating crack at outside surface

Hydraulic characterization and start-up of a novel circulating flow bio-carriers

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier.

Research on the Sealing Mechanism of Split-Liner High-Pressure Hydrogen Storage Cylinders

Hydrogen storage is a crucial factor that limits the development of hydrogen energy. This paper proposes using a split liner for the inner structure of a hydrogen storage cylinder. A self-tightening seal is employed to address the sealing problem between the head and the barrel. The feasibility of this structure is demonstrated through hydraulic pressure experiments. The influence laws of the O-ring compression rate, the distance from the straight edge section of the head to the sealing groove, and the thickness of the head on the sealing performance of gas cylinders in this sealing structure are revealed using finite elements analysis. The results show that when the gas cylinder is subjected to medium internal pressure, the maximum contact stress on the O-ring extrusion deformation sealing surface is greater than the medium pressure. There is sufficient contact width, that is, the arc length of the part where the stress on the O-ring contact surface is greater than the medium pressure, so that it can form a good sealing condition. At the same time, increasing the compression ratio of the O-ring and the head’s thickness will help improve the sealing performance, and reducing the distance from the straight edge section of the head to the sealing groove will also improve the sealing performance.

Attention-ResNet-AR-LSTM: An intelligent method for PCCP deformation prediction via structure monitoring based on distributed fiber optics

The prestressed concrete cylinder pipeline (PCCP) is extensively employed in long water diversion projects due to its commendable performance and cost-effectiveness. Nonetheless, the continuous application of load on the prestressed steel wire during the production phase can amplify the creep deformation in both the concrete and steel cylinder of the PCCP. This phenomenon may potentially lead to the development of cracks at the socket end of the PCCP, posing a significant risk to the safe operational integrity of the pipeline. In this study, the strain development prediction model of PCCP concrete and steel cylinder is constructed through the integration of ResNet, AR, and LSTM modules, and the attention mechanism is also applied. Based on the prototype test of PCCP structure monitoring, the strain values of steel cylinder and inner concrete were recorded by pre-set distributed fiber optic sensors on the 1st, 3rd, 5th, 7th, 9th, 11th, 13th, 15th, 17th, and 20th day after the production of PCCP. Then an Attention-ResNet-AR-LSTM model is constructed to predict the strain development of PCCP steel cylinder and concrete based on monitoring data on the 20th day using the data of 1st to 11th days. For steel cylinder and concrete structures, the R2 of the proposed models is above 98%, indicating that the proposed models can capture the strain changes of different structures well. Compared with other deep models and machine learning models, the proposed model also shows a significant predictive ability. This model introduces a novel approach to forecast strain evolution during the manufacturing of PCCP.

Influence of gap thickness on aerodynamic forces and flow structures of circular cylinders under passive-suction-jet control

A parametric study of the passive-suction-jet control scheme was experimentally performed for the cylinder model. The dependence of the control effectiveness on the gap thickness was determined for a cylinder model controlled by passive-suction-jet pipes at Reynolds number (Re) values ranging from 20,000 to 60,000. The fluid forces and flow structure were measured on a cylinder model without any control and used to evaluate the control effectiveness. Proper orthogonal decomposition (POD) analysis, phase average, and triple decomposition were applied to the flow fields to explore the control mechanism. The results show that the pipe control was most effective when the gap thickness was 0.075D. Too large or too small a gap thickness was not beneficial for controlling the resistance level, and the fluctuating lift was reduced to a tiny level as the thickness increased to 0.075D. The steady jets ejected from the leeward slots rolled up into several small-scale standing vortices. These vortices modified the streamline topology of the model, developing a new saddle point in the wake. Moreover, the roll-up of the separated shear layers was restrained by the pipe, which inhibited the vortex formation and shedding processes and the unsteady forces exerted on the model.

Data-driven identification and pressure fields prediction for parallel twin cylinders based on POD and DMD method

The mode analysis of parallel twin cylinders is conducted in this paper using two data-driven methods: proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). First, a high-fidelity computational fluid dynamics (CFD) model of parallel twin cylinders is established, and numerical simulations of the model are carried out. Subsequently, the fundamental principles of the POD and DMD algorithms are systematically introduced. Utilizing snapshots obtained from the high-fidelity CFD model, the POD and DMD methods are employed to extract the dominant flow structures. Furthermore, a comparison between the two data-driven methods is conducted by analyzing modal frequencies, pressure distribution, and the reconstruction errors of pressure fields. Finally, the pressure fields of non-sample points are predicted based on the POD–backpropagation neural network (BPNN) surrogate model and the DMD method, and the predicted results are compared with the CFD simulation results. It found that (i) the DMD method is capable of extracting the main coherent structures of the pressure fields, directly obtaining flow modes and their corresponding frequencies, and assessing the stability of flow modes; (ii) the DMD method can capture the main flow features of the pressure fields in both spatial and temporal dimensions, while the POD method is primarily efficient at capturing the spatial features of the pressure fields; (iii) in contrast to the frequency-ranked DMD method, the energy-ranked POD method can reconstruct the pressure fields using a smaller number of modes, indicating that the POD method has an advantage in terms of mode reduction; (iv) in contrast to the energy-ranked POD method, the frequency-ranked DMD method has a wider applicability to the range of flow types and has more advantages in stability analysis of complex dynamic systems; (v) the predicted pressure fields around the cylinder using the first five-order POD modes or DMD modes closely align with CFD calculation results. Additionally, the evolution of pressure fields predicted by the POD–BPNN surrogate model with the first five-order POD modes or the DMD method with the first 200-order DMD modes significantly agrees with CFD simulation results; (vi) the combined use of the POD–BPNN surrogate model and DMD methods allows efficient interpolation and extrapolation of samples, delivering exceptional predictive performance. This study offers insight into the coherent structures in parallel twin cylinders.

Lightweighting Study of Rotary Kiln Cylinder Structure Based on Response Surface

To achieve the lightweight design of the rotary kiln cylinder, reduce its manufacturing costs, and improve its mechanical properties, the maximum stress and deformation were determined through a static and thermal structural analysis of the rotary kiln equipment. Employing the Box-Behnken response surface method, an optimization of the rotary kiln cylinder structure was performed, with the aim of minimizing the cylinder mass and deformation, while considering constraints such as cylinder thickness and yield strength. A multi-objective optimization mathematical model was established, and three sets of Pareto solutions were obtained using a multi-objective genetic algorithm. The optimized design of thickness structure was determined for the stall section, transition section, and cylinder section of the rotary kiln. The finite element method was utilized to simulate the optimized solutions and verify their validity and accuracy. The results showed that the rotary kiln cylinder mass was reduced by 13.8%, and the maximum deformation under static structural conditions was reduced by 4.6%, while maintaining the strength requirement of the structural stiffness. The relevant geometric parameters of the optimal solution were verified by finite element numerical tests, and the optimized cylinder mass, maximum stress and deformation under static structural conditions, and maximum deformation and stress under thermal structural coupling were in good agreement with the numerical test results, with a deviation of less than 2%. Additionally, this study realized the lightweight design of the rotary kiln cylinder and provided useful references for the thickness design of the rotary kiln cylinder.

Mehaničko modeliranje termomehaničkih procesa

The problem of stress in perforated thin-walled cylinders due to mechanical and thermal load was analyzed for cases where the load of the system varies both along the cylinder circumference and axially. Starting from the solution and considerations for a smooth thin-walled cylinder, the concept was expanded and the distribution of deformations caused by thermal loads on the cylinder and the resulting stresses in the structure of the thin-walled perforated cylinder was observed for a specific form of perforation. The cylindrical perforated burner is one of the main elements of premixed condensing boiler for home heating systems. The quality of combustion, and thus the heat load on the outer sheath of the burner, largely depends on the layout, shape and dimensions of the perforation. This paper presents the mechanical modeling of thermomechanical processes of a cylindrical gas burner with premixing for a triangular layout or the so-called checkerboard shape of perforation.

Analysis on mechanism of material removal rate and surface flow machining process

A novel finishing technique called abrasive flow machining (AFM) uses abrasive particles as the instrument for material removal. The term "self-deformable stone" refers to the abrasive particle-containing carrier medium, and AFM is commonly known as "no-tool" precision finishing procedure. AFM involves passing a semi-solid polymer-based medium through the work piece at a specific pressure while adding abrasive particles in a specific amount. The three main parts of the AFM are the machine, the medium, and the tooling or fixture. The machine is made up of a media cylinder, hydraulic cylinder, control system, and frame structure. A typical AFM method uses extrusion pressures ranging from 15 bars to 110–210 bars. Tooling and fixtures serve the purpose of positioning the workpiece and giving instructions to the media as they go over the finished product. A carrier, some additives, and an abrasive powder make up the medium. Since the finite volume approach deals with fluid flow, it can be used to represent the flow of media. For the modelling and simulation in this work, the ANSYS 15 software package's FLUID FLOW FLUENT was utilised. Together with the fixtures, 2D model of a cylindrical workpiece and 3D model of 4 rotating dies have been created. Using the available experimental data, the two models have been validated. For varying volume fractions and media speeds, the most influential flow output characteristics, such as velocity, strain rate, and dynamic pressure have all been examined. The granular and non-granular flows were both simulated using the 3D model. The impact of various abrasive particles with varying volume fraction and diameter on the Skin friction coefficient and granular pressure, two flow output characteristics that have been researched. The outputs' flow analysis provides a forecast for the effectiveness of material removal.