Cylinder Model Research Articles

Comparison of composite cylinder damage under different working conditions

Abstract The finite element model of the carbon fiber all-wound aluminum cylinder was created to analyze the damage caused by high pressure, and the progression of damage as pressure increased was examined. The damage initially occurs in the transitional area between the cylinder end and cylinder body before progressing to the winding layer of the cylinder. The failure characteristics of the circumferential wound layer contrast with those of the spiral wound layer.

Dynamic modeling and vibration characteristics analysis of cylinder with local defects in axial piston pump

The piston/cylinder pair suffers from excessive wear during the operation of axial piston pumps, and the local defects usually occur in the brass bush in the cylinder bore. Generally, the wear of cylinder is the main source of failure that affects the reliability of axial piston pumps. Thus, it is necessary to conduct an in-depth study on the vibration generated by the cylinder with local defects. Considering the effect of defect dimension, a novel time-varying displacement excitation model of the axial piston pump cylinder defect is proposed and establishes a 13 degrees of freedom lumped parameter dynamic model for cylinder fault. Then, investigating the effects of length and depth of the defect on the spectral amplitude and exploring the fault characteristic frequency of cylinder. Lastly, the model was validated on a test rig. The results demonstrate that the constructed model can predict the vibration caused by a locally defective cylinder with a frequency domain error of 0.69% and the fault characteristic frequency of cylinder is the same as its rotational frequency. Moreover, the defect length will influence the amplitude and duration of the cylinder-defect pulse waveform. The fault excitation amplitudes increase with the increase of defect depths.

Modeling of Blockage and Wake Effect: Comparison with Field data

We apply engineering approaches for estimating the induction zone in front of a wind turbine and escalating to the global blockage at wind farm and cluster of farms scale as well accounting for wind farm wake. The methods include the vortex cylinder model and the self-similar model for blockage, and Jensen and Eddy-viscosity models for the wake estimation. To calibrate each model, Reynold Average Navier-Stokes with Actuator disc simulations are employed. Every model’s efficacy is assessed in comparison to the validation data of an operated wind farm in Scotland with more than 100 turbines of 10 MW each. We also examine the widely used process within the wind industry for transferring the application of calibrated wake and blockage models from one wind farm. According to our simulation analysis, blockage causes sideways acceleration and upstream slowdown. This also result in a gradient in the power produced by each turbine on the farm, which, if not properly accounted for, appears to be a wake model constraint. Furthermore, the response of different turbine type in another environment is not effectively predicted by the blockage and wake model, which is based on a particular turbine type and environment.

A simple method for mechanical analysis of pressurized functionally graded material thick-walled cylinder

The complex function method is employed to establish a mechanical model for pressurized thick-wall cylinders made of functionally graded materials (FGM). This model is applicable to all radial varying modes of material properties, including both continuous and discontinuous variations in Young’s modulus and Poisson’s ratio. The main concept behind this mechanical model involves dividing the thick-walled cylinder into concentric thin cylinders, each equipped with a pair of analytical functions representing stress functions. By imposing continuity conditions between adjacent thin cylinders and considering the stress boundary conditions of the entire structure, all unknown forms of analytical functions can be determined. Subsequently, by establishing the correspondence relationship between these analytical functions and stress or displacement, it becomes possible to solve for the stress or displacement at any radial position within the thick-walled cylinder. Through comparison and verification against the numerical simulation results, it can demonstrate that as long as the differential scale is sufficiently small, high accuracy can be achieved in the final result. In other words, solutions obtained for multi-layered hollow cylinder converge toward those obtained for continuously graded thick-walled cylinder. Notably, by starting from the level of stress function and avoiding complex differential and integral equations, a linear equation system can provide information on stress and displacement distributions along the radial direction. Therefore, compared to other solving methods available, this proposed approach offers simplicity and applicability.

Investigation on vibration characteristics of rock based on circular plate and cylinder model: dimension, geometric shape and boundary condition

Abstract The declaration on the “natural frequency of rock” exists in many engineering areas, and it has caused many misunderstandings. Different from the mass-spring model usually used, the circular plate model and cylinder model are respectively established to clarify the relationship between the vibration characteristics (including natural frequency and vibration mode) and their influencing factors of rock by modal analysis. The effect of dimension, geometric shape, and boundary condition on the vibration characteristics of rock with plate structure is investigated, in which the semi-analytical solutions agree well with the simulation results. By using the cylinder model based upon the Lamé-Navier Eq., the effect of such influencing factors on the vibration characteristics of the block rock sample is further studied and verified by numerical simulation and experimental results. The results suggest that the natural frequency of “rock” (including the experimental rock sample) is strongly dependent on the dimension, geometric shape, and boundary condition. The resonance frequency observed in the excitation experiment is not only closely associated with the natural frequency of a specific order, but also dependent on the dominance of the particular vibration mode. These findings contribute to a better understanding of the rock-breaking mechanism under dynamic loads with a certain excitation frequency.

Bond strength between ductile carbon/glass hybrid fibers-reinforced polymer bar and concrete through plate-type bond samples

The ductile carbon/glass hybrid fibers-reinforced polymer (C/G-HFRP) bar with excellent corrosion resistance is considered as an outstanding alternative to steel bar in structural concrete. The bond strength of C/G-HFRP bar to concrete plays a dominant contribution to fully realize the prominent properties of C/G-HFRP bar-reinforced concrete structures. In this work, the bond strength between ductile C/G-HFRP bar and concrete was investigated through a plate-type bond sample under direct pullout load. The effects of C/G-HFRP bar diameter, rib pitch, carbon/glass ratio, embedment length, concrete strength, cover thickness, bar type and sample type on the bond strength of C/G-HFRP bar to concrete were considered. The experiment outcomes revealed that the bond strength between C/G-HFRP bar and concrete by plate-type bond samples was 32.4 % lower than that by cube-type ones, resulting from that the influence of reaction frame on the crack propagation of concrete was eliminated during the loading procedure of plate-type bond samples. Also, the bond strength of C/G-HFRP bars to concrete increased with the tensile modulus, while the bond strength between C/G-HFRP bar and concrete was 48.5 % lower than that between steel bar and concrete. The failure mode of bond samples was controlled by the cover thickness of concrete when the compressive strength of concrete was not more than 55 MPa. Furthermore, the bond strength of sample was associated with the failure modes of test samples. The bond strength was decided by the mechanical properties of concrete when the bond sample happened splitting failure, while it was decided by the shear-resistant strength of flange ribs for C/G-HFRP bar when the failure mode of bond sample belonged to pull-out failure. Finally, the bond strength of C/G-HFRP bar to concrete was calculated by the thick-walled cylinder model.

Simulation-Driven Universal Surrogates of Coupled Mechanical Systems: Real-Time Simulation of a Forestry Crane

Abstract Preparing simulation-driven surrogates for a coupled mechanical system can be challenging because the associated mechanical and actuator dynamics demand high-fidelity numerical solutions. Proposed here is a universal hydraulic surrogate (UHS), which can provide solutions to high-fidelity mechanical systems with a universal actuator in a surrogate-assisted monolithic approach. The UHS acts as an alternative to the standard lumped fluid theory by eliminating the hydraulic pressures differential equations. A surrogate-assisted universal actuator uses an approximated model to define hydraulic force in high-fidelity mechanical systems. The approximated force model was developed through training against the dynamics of a one-dimensional (1D) hydraulic cylinder and spring-damper. A covariance matrix adaption evolutionary strategy (CMA-ES) was used as an optimization algorithm to minimize differences between the standard dynamics and UHS approaches at the position and velocity levels. The robustness of resulting UHS was validated to predict the behaviors of the simple four-bar mechanism and the forestry crane. The focus was on numerical accuracy and computational efficiency. The maximum percent normalized root mean square error (PN-RMSE) between the states of the approximated force model and lumped fluid theory were approximately 2.04% and 6.95%, respectively. The proposed method was approximately 52 times faster than the standard lumped fluid theory method. By providing accurate predictions outside the training data, the simulation-driven UHS promises better computational performance leading to real-time simulation solutions for the coupled mechanical systems. The UHS can be applied in simulation, optimization, control, state and parameter estimation, and Artificial Intelligence (AI) implementations for coupled mechanical systems.

Performance degradation model and life prediction method of spool pair caused by erosion wear

The erosion of solid particles in the fluid causes the wear of the metering edge of the spool pair, resulting in a decrease in system performance. This paper aims to develop a general method to evaluate performance degradation and life prediction of spool pairs induced by erosion. Considering the diversity of influencing factors and the complexity of operating conditions, traditional numerical calculation methods will consume huge computational costs. It is difficult to qualitatively and quantitatively analyze the evolution of metering edge by numerical calculation. The erosion prediction model (EPM) constructed by machine learning methods can be used to predict the wear profile discretized in time and space. Combined with the mathematical model of the valve-controlled cylinder, a performance degradation model (PDM) that can simulate real-time working conditions is established. Through the data exchange and iterative update between EPM and PDM, a complete digital platform for the calculation of slide valve durability is constructed. After comparing with the experimental results, it can be concluded that the proposed method can realize the performance degradation evaluation and life prediction of the spool pair caused by erosion wear under continuous working conditions.

Validation of the added mass effect in the narrow gaps of nuclear reactor pressure vessels

Nuclear reactor pressure vessels (RPVs) must be robust to external environmental excitations such as seismic loads. Precise numerical models that predict the dynamic responses to external loads are crucial for evaluating the safety of RPVs. Notably, in RPVs submerged in reactor coolant, it is necessary to examine the added mass effect of the fluid via fluid-structure interaction (FSI) analysis, employing either an analytical approach or a numerical analysis. The present study focuses on modeling and analyzing the added mass effect in the narrow gaps associated with the dense structural layout in the reactor. In this context, this paper validates analytical and numerical models that accurately describe the added mass effect for two cases: (i) simple concentric cylinders with a narrow gap filled with fluid and (ii) a complex small-scale RPV with narrow gaps also filled with fluid. Initially, the analytical model, employing Lagrange's equation of motion and velocity potential, and the numerical model, utilizing FE modeling in acoustic FSI through ANSYS, were validated through experimental modal testing for the added mass effect in the narrow gap between simple concentric cylinders. The analytical model for the concentric cylinders indicates that the added mass diverges to infinity as the gap approaches zero, which should be examined carefully. Through experiments for the concentric cylinders, the analytical and FEM-based added mass effects were validated with a natural frequency error of 3 %. Subsequently, based on the results for the concentric cylinders, a complex numerical model of the small-scale reactor with complex boundary conditions was developed and cross-validated through corresponding experimental modal testing of the small-scale RPV. The added mass model for the narrow gaps in the RPV was validated by substantial agreement of eight representative modes, as demonstrated by a 5 % natural frequency error.

A comprehensive numerical study of the effects of surface roughness on a finite-length cylinder with an aspect ratio of 1.5 for Reynolds numbers ranging from 3.9 × 103 to 4.8 × 105

The aerodynamic performance of the flow around a cylinder with two free ends, which is also referred to as a finite-length cylinder, continues to be a subject of rigorous academic inquiry. However, limited research has been conducted on finite-length cylinders with rough surfaces. To evaluate the impact of relative roughness on the aerodynamic performance of a finite-length cylinder, we performed numerical simulations on a cylinder model with an aspect ratio of 1.5 with various relative roughness values. These simulations covered a range of Reynolds numbers from 3.9 × 103 to 4.8 × 105. The results indicated that both the relative roughness and Reynolds number could affect the aerodynamic characteristics of the cylinder by altering the flow pattern around the cylinder. As the Reynolds number increased, the four spiral eddies behind the finite-length cylinder gradually lost their symmetry in the axial direction and eventually transformed into a pair of recirculating eddies. Moreover, when the Reynolds number was constant at 2.0 × 104, an increase in the surface roughness of the cylinder triggered the same phenomenon. Additionally, the mechanism by which the surface roughness affected the aerodynamic coefficient of a finite-length cylinder in the current Reynolds number range was revealed. This influence was mainly attributed to the impact of pressure on the backside of the cylinder.

Aerodynamics Behavior in High Speed Sports Jersey Fabrics with Different Roughness

Enhancing aerodynamic performance holds paramount importance in high-speed sports, leading to a growing interest in garments that can positively impact aerodynamic efficiency. Wind tunnel experimentation has played a pivotal role in assessing aerodynamic properties, employing both cylinder and leg models within a closed return circuit tunnel setup. Utilizing a plastic cylinder model, researchers evaluated the aerodynamic properties of various knitted samples, with dummy cylinders introduced to minimize 3D flow effects and ensure adherence to the infinite length hypothesis. By employing the foot and knee as additional dummy components, efforts were made to further mitigate 3D flow effects. These wind tunnel tests encompassed nine knitted single jersey fabrics, predominantly composed of 100% polyester, subjected to speeds ranging from 20 to 80 km/h to simulate real-world sporting conditions. The findings revealed a significant correlation between fabric manufacturing, indicated by the cover factor, and fabric roughness, with discernible impacts on aerodynamic parameters. Notably, consistent aerodynamic behaviors were observed across fabric tests conducted on both the cylinder and leg models, underscoring the reliability of the experimental setup.

Experimental study of dynamic pressure and wave load on variform vertical cylinders under extreme waves

Extreme waves pose a significant threat to the proliferating marine structures, however, the impact on the vertical cylinder with different cross-sectional shapes remains inadequately evaluated. Herein, we carried out a physical experiment, comprising 45 scenarios generated by three water depths, three wave paddle velocities, and five vertical cylinder models, to measure the extreme wave-induced pressure and load on this type of structure. The wave load and dynamic pressure distribution in time and spatial domains under the influence of cross-sectional shapes and wave conditions have been fully discussed. The experimental results indicate that: 1) As the position turns from front to back side, the circumferential pressure of five models initially decreases and then increases. 2) The maximum differential pressure between the front and back side decreases with increased water depth and decreased velocity, and occurs earlier than the peak pressure on the front side. 3) The chamfered cross-section (round and right triangle) can significantly reduce the wave load compared to the rectangular section, and the circular section suffers the lowest force logically. The dynamic pressure and wave load in this experiment can serve to establish a more sophisticated load model and provide valuable insights for marine structural design and disaster prevention.

A mathematical model of tissue axial and radial diffusion in the microvasculature for intravascular microscopy and phosphorescence quenching data

This study aims to extend earlier Krogh Cylinder Models of an oxygen profile by considering axial diffusion and analytically solving Fick's Law Partial Differential Equation with novel boundary conditions via the separation of variables. We next prospectively collected a total of 20 animals, which were randomly assigned to receive either fresh or two-week-old stored red blood cell (RBC) transfusions and PQM oxygen data were measured acutely (90 min) or chronically (24 h). Transfusion effects were evaluated in vivo using intravital microscopy of the dorsal skinfold window chamber in Golden Syrian Hamsters. Hamsters were initially hemorrhaged by 50% of total blood volume and resuscitated 1-h post hemorrhage. PQM data were subsequently collected and fit the derived 2D Krogh cylinder model. Systemic hemodynamics (mean arterial pressure, heart rate) were similar in both pre and post-transfusion with either stored or fresh cells. Transfusion with stored cells was found to impair axial and radial oxygen gradients as quantified by our model and consistent with previous studies. Specifically, we observed a statistically significant decrease in the arteriolar tissue radial oxygen gradient after transfusion with stored RBCs at 24 h compared with fresh RBCs (0.33 ± 0.17 mmHg μ m-1 vs, 0.14 ± 0.12 mmHg μ m-1; p = 0.0280). We also observed a deficit in the arteriolar tissue oxygen gradient (0.03 ± 0.01 mmHg μ m-1 fresh vs. 0.018 ± 0.007 mmHg μ m-1 stored; p = 0.0185). We successfully derived and validated an analytical 2D Krogh cylinder model in an animal model of microhemodynamic oxygen diffusion aberration secondary to storage lesions.

Heuristic Incremental Theory of Diffraction for a Wedge with Impedance Surfaces

This paper proposes a novel incremental theory of diffraction (ITD) formulation to calculate the fringe field from a wedge characterized by impedance surfaces and arbitrary exterior angles. The ITD formula was originally based on the Fourier transform pair relationship between the solution for the canonical wedge problem and incremental field contribution. However, this procedure can be utilized to report the ITD formula only for planar and half-planar impedance surfaces. Therefore, this paper develops a heuristic ITD formula by conceptually deriving the incremental diffracted field contribution from the uniform theory of diffraction coefficient and inferring the physical optics edge-diffracted field contribution from the terms related to the incidence shadow and reflection shadow boundaries. The proposed formula is applied to simple triangular impedance cylinder and disk models with impedance surfaces, and the results are compared with those of the method-of-moment and VIRAF’s ITD solver to show that is performs similar to the former and better than the latter.

A new model for predicting the axial compression capacity of reinforced concrete cylinders strengthened with CFRP

Numerous scholars have identified the shortcomings of imprecise terminology and substantial computational inaccuracies in the current models for predicting the axial compression capacity of CFRPstrengthened reinforced concrete (RC) cylinders. To improve the prediction accuracy of the axial compressive capacity model for CFRP-strengthened RC cylinders, the present axial compressive capacity model for CFRP-strengthened RC cylinders was scrutinized and evaluated. Drawing on Mander’s constraint theory and the concrete triaxial strength model, a novel axial compressive capacity model for CFRP-strengthened RC cylinders was proposed. This study collected 116 experimental data on the axial compression of CFRP-strengthened RC cylinders and analyzed the accuracy of various models using the data. The findings indicate that the model proposed in this study outperforms other models in predicting axial compression capacity and demonstrates high prediction accuracy. Furthermore, an analysis is conducted on the variation law of the model’s predicted value with respect to the design parameters. The proposed model in this study identifies concrete strength, stirrup spacing, and elastic modulus of CFRP as the primary factors that influence the axial compression capacity of CFRP-strengthened RC cylinders.

Numerical simulation of leakage jet flame hazard of high-pressure hydrogen storage bottle in open space

The jet fire is a common type of fire accident in high-pressure hydrogen storage bottles. It is crucial to conduct research on the thermal radiation hazards resulting from on-board hydrogen storage bottle leaks, leading to jet fires within 35 MPa. Additionally, accurately and swiftly calculating the characteristic parameters of hydrogen jet flames, such as flame geometry and radiation heat flow, is of utmost importance. To study the jet fire hazard caused by high-pressure hydrogen storage cylinder leaks, a simplified model of the hydrogen storage cylinder was established using FLUENT software for numerical simulation analysis. The study analyzed the impact patterns of high-pressure hydrogen leakage jet flames under different scenarios, including leakage aperture, leakage pressure and ambient wind speed. The results demonstrate a positive correlation between the leakage aperture and pressure with the size of the jet flame and the extent of thermal radiation damage. The larger the leakage aperture and pressure, the larger the hydrogen jet flame size. The higher the peak value of the flame thermal radiation, the greater the hazard range. Additionally, the temperature of the stable axis of the jet flame rises with increasing leakage aperture. As the leakage pressure rises, the thermal radiation of the flame also increases. Conversely, as the ambient wind speed increases, the flame length, the burn radius, and the thermal radiation range decreases, but the high-temperature heat range expands. The empirical formula between flame length and leakage pressure and leakage aperture under different environmental wind speeds is obtained by data fitting, which can be used as a priori prediction of flame length under wind speed conditions.

A direct multimode method for the reduction of vibration induced oscillations on force signals during “pseudo-rigid” water impact experiments

A new experimental method is proposed to improve the force measurements during water impact experiments (e.g. water entry or wave impact tests) carried out with “pseudo-rigid” mock-ups. Despite the efforts of making the mock-up as stiff as possible, the impulsive nature of water impact loads may induce a transient response of the mock-up with a broad frequency content and a perturbation of the force measurements. Using the principles of momentum conservation, it can be shown that the load cell signal is the sum of the hydrodynamic forcing term and of an additional inertial term directly related to the vibrations of the structure. In the present paper, we suggest to estimate the inertial term using several accelerometers which record the response of the structure at different locations. Assuming that the structure response can be approximated by a set of natural modes, we show that it is possible to estimate the inertial term by a linear combination of the acceleration signals. The coefficients of the linear combination may be identified a priori by performing hammer tests, but in certain cases they can also be identified a posteriori using a segment of the signal time series. The performance of the method is demonstrated by considering two experimental test cases of increasing complexity. The first test case is a hydrofoil of constant section impacting water at constant speed which exhibits two-dimensional beam-like vibrations. The second test case is a segmented model of a vertical cylinder impacted by a breaking wave whose segments exhibit three-dimensional vibrations. The proposed method is efficient, conceptually simple and very simple to implement from a signal processing point of view, which makes it promising not only for water impact problems but also for other unstationary fluid–structure interaction problems.

Aerodynamic model comparison for an X-shaped vertical-axis wind turbine

Abstract. This article presents a comparison study of different aerodynamic models for an X-shaped vertical-axis wind turbine and offers insight into the 3D aerodynamics of this rotor at fixed pitch offsets. The study compares six different numerical models: a double-multiple streamtube (DMS) model, a 2D actuator cylinder (2DAC) model, an inviscid free vortex wake model (from CACTUS), a free vortex wake model with turbulent vorticity (from QBlade), a blade-resolved unsteady Reynolds-averaged Navier–Stokes (URANS) model, and a lattice Boltzmann method (from PowerFLOW). All models, except URANS and PowerFLOW use the same blade element characteristics other than the number of blade elements. This comparison covers the present rotor configuration for several tip-speed ratios and fixed blade pitch offsets without unsteady corrections, except for the URANS and PowerFLOW which cover a single case. The results show that DMS and 2DAC models are inaccurate – especially at highly loaded conditions, are unable to predict the downwind blade vortex interaction, and do not capture the vertical/axial induction this rotor exhibits. The vortex models are consistent with each other, and the differences when compared against the URANS and PowerFLOW mostly arise due to the unsteady and flow curvature effects. Furthermore, the influence of vertical induction is very prominent for this rotor, and this effect becomes more significant with fixed pitch offsets where the flow at the blade root is considerably altered.

Research on Dual Fuel Combustion Characteristics of PFI Natural Gas +DI Gasoline in Large Cylinder Diameter Engine

A 3D simulation model of a single cylinder of a natural gas engine was established. PFI natural gas DI gasoline was used to control the time matching between injection and ignition, so that gasoline could form a small active stratified area near the spark plug. The combustion characteristics under different matching conditions were studied, and finally compared with pure natural gas. It is found that gasoline can be used in large cylinder diameter natural gas engine in a small range, which can accelerate the combustion of natural gas fuel, shorten the time used by CA0-CA5 by 77.6%, shorten the time used by CA5-CA90 by 26.5%, and increase the indicated thermal efficiency of natural gas engine by 1.4%.

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.