Axisymmetric Cylinder Research Articles

Splitter-plate proximity-induced transitions in flow-induced vibration of a triangular prism

The effect of a splitter-plate downstream of an elastically mounted equilateral triangular prism on flow-induced vibration is numerically investigated at Reynolds number Re = 100, mass ratio m* = 10, damping ratio ζ = 0.005, cylinder-plate gap G* = 0.3, and various angle of attacks α = 0°–60°. The α = 0° and 60° correspond to vertex and edge of the cylinder facing the free stream. Under the effect of the splitter plate, a single transition from vortex-induced vibration (VIV) to proximity-induced galloping (PIG) in the vibrational response for an axisymmetric circular cylinder is reported, whereas, for the present non-axisymmetric triangular prisms, the varying α exhibits four proximity-induced transitions: VIV to modified VIV at smaller α = 0° and 25°, VIV to PIG at α = 35°, distinct VIV-galloping to combined PIG-galloping at α = 40°, and asymmetric to symmetric-galloping at larger α = 60°. The plate results in more symmetric vibration for high α ≥ 35°, while a reduction is observed for α ≤ 25°. The gap-flow leads to onset (α = 35°) and enhancement (α = 40°) of afterbody re-attachment on the prism, which significantly enhances the galloping instability and vibrational amplitude. A reduction in galloping instability leading to a slight reduction in amplitude is found for α = 60° prism. The study shows that the presence of the splitter-plate downstream influences near-wake structure and far-wake vortex shedding modes, which lead to stabilizing and destabilizing near-wake flow and distinct vibrational characteristics—depending on the angle of attack (α).

Numerical Analysis of Functionally Graded Material (FGM) Axisymmetric Cylinder under Transient Thermal Load and Variable Internal Pressure

Numerical Analysis of Functionally Graded Material (FGM) Axisymmetric Cylinder under Transient Thermal Load and Variable Internal Pressure

Subsonic flows with a contact discontinuity in a finitely long axisymmetric cylinder

This paper concerns the structural stability of subsonic flows with a contact discontinuity in a finitely long axisymmetric cylinder. We establish the existence and uniqueness of axisymmetric subsonic flows with a contact discontinuity by prescribing the horizontal mass flux distribution, the swirl velocity, the entropy and the Bernoulli’s quantity at the entrance and the radial velocity at the exit. It can be formulated as a free boundary problem with the contact discontinuity to be determined simultaneously with the flows. Compared with the two-dimensional case, a new difficulty arises due to the singularity near the axis. An invertible modified Lagrangian transformation is introduced to overcome this difficulty and straighten the contact discontinuity. The key elements in our analysis are to utilize the deformation-curl decomposition introduced in [S. Weng and Z. Xin, A deformation-curl decomposition for three dimensional steady Euler equations, Sci. Sin. Math. 49 (2019) 307–320 (in Chinese): doi:10.1360/N012018-00125] to effectively decouple the hyperbolic and elliptic modes in the steady axisymmetric Euler system and to use the implicit function theorem to locate the contact discontinuity.

Analysis of axisymmetric hollow cylinder under surface loading using variational principle

In this work, a variational principle–based approach has been adopted to analyze one of the classical linear elasticity problem of the axisymmetric cylinder under surface loading. The use of variational principle results in a set of governing partial differential equations with associated boundary conditions. The equations have been solved using the separation of variable approach and the Frobenius method. A general solution has been derived and used to solve two test cases. The proposed solution is capable of meeting all the boundary conditions. The solution has been validated by comparing it with a finite element–based numerical solution and considering a special limiting condition of a solid cylinder, for which results are available in the literature. Further various studies have been carried out to understand the robustness and limitation of the presented solution.

Analytic solution to isotropic axisymmetric cylinder under surface loadings problem through variational principle

Analytic solution to isotropic axisymmetric cylinder under surface loadings problem through variational principle

Analiza elastično-plastičnog naprezanja skupljajućih debelih FGM cilindara

This paper addresses the stress analysis of shrink-fitted thick-walled cylinders made of functionally graded material (FGM). Analytical solutions are provided for the elastic-plastic behavior of shrink-fitted axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory and plasticity laws. Due to the material's functional gradation, mechanical characteristics like Young's modulus, yield stress, and plastic parameters are controlled by a power function along the wall thickness. Considering a plane strain case, elastic-perfectly plastic model and Von Mises yield criterion; theoretical solutions are obtained for both elastic and plastic phases. The radial, hoop, axial, and equivalent Von Mises stresses are obtained for up to 25%, 50%, and 75% of cylinder plasticization for the elastic and plastic zones. Stresses are given in terms of interference and geometrical and mechanical parameters of the assembly. In addition, the interferences to start plastic deformation and the full plastic collapse of the cylinder are discussed. Moreover, the effect of the gradient index on the contact pressure and both the start of yield and plastic collapse pressures are conducted. The analytical results found in the current research are compared with the numerical solutions carried out by Ansys Workbench. Both results show a good agreement.

Water Entry of a Heated Axisymmetric Vertical Cylinder

The computational model that is able to estimate the temperature distribution inside a solid specimen during the film boiling phase of immersion quenching (water entry) process has been presented in this paper. It is based on the prescribed initial temperatures of the solid specimen and the liquid quenchant. In addition, the turbulence effects have to be considered using the assumed turbulence kinetic energy value, i.e., the “frozen turbulence” approach, that remains constant thorough the simulation. The studied material is nickel alloy, Inconel 600, for which extensive experimental data are available. The work has been carried out using ANSYS Fluent computational fluid dynamics software and the methods for solution of Stefan problem by Eulerian two fluid VOF model. A satisfactory agreement between the experimental and the calculated data has been achieved, yielding thereby the computationally obtained data that fit to a great extent the prescribed error band of ±10% during the estimated film boiling phase of the immersion quenching process itself. It was, however, found that the temperature calculated in the center of a specimen fits this error band until reaching somewhere t < 6 s due to low presumed turbulence level in the domain. In addition, the explosion of the vapor phase after the body reaches the free surface of the quenchant has also been successfully tracked using the numerical simulation model proposed herein. The major novelty of the present research lies in the fact that a moving boundary problem has been successfully resolved in conjunction with, to a great extent, basic-principle-based heat and mass transfer in a turbulent flow conjugate heat transfer (CHT) numerical simulation using moderate computational resources.

A similarity approach to the turbulent near-wake of a long slender cylinder with a sharp trailing edge at zero pressure gradient

A high Reynolds number wake flow developing under zero pressure gradient from a long slender axisymmetric cylinder with sharp trail ending is investigated. The main focus is the flow domain immediately behind the trailing edge, where the fully developed upstream turbulent boundary layers separated by the body, unite under no body constraints and the boundary layer identity and characteristics are gradually lost. Similarity solutions for the streamwise mean velocity and centreline velocity are obtained in which the region exhibits the log law of the fully developed boundary layer. A critical assessment of inner near wake characteristic length is done.

Comparative Numerical Analysis for the Error Estimation of the Fluid Flow over an Inclined Axisymmetric Cylinder with a Gyrotactic Microbe

The numerical investigation of bioconvective nanofluid (NF) flow, which involves gyrotactic microbes and heat and mass transmission analysis above an inclined extending axisymmetric cylinder, is presented in this study. The study aims to investigate the bioconvection flow of nanofluid under the influence of heat sources/sinks. Through proper transformation, all partial differential equations are transformed into a non-linear ODE scheme. A new set of variables is presented in the directive to get the first-order convectional equations and then solved numerically using bvp4c MATLAB, embedded in the function. The proposed model is validated after calculating the error estimation and obtaining the residual error. The influence of various factors on the velocity, energy, concentration, and density of motile microorganisms is examined and studied. The analysis describes and addresses all physical measures of concentration such as Skin Friction (SF), Sherwood number, the density of motile microorganisms, and Nusselt number. To validate the present study, a comparison is conducted with previous studies, and excellent correspondence is found. In addition, the ND-Solve approach is utilized to confirm the bvp4c. The mathematical model is confirmed through error analysis. This study provides the platform for industrial applications such as cooling capacity polymers, heat exchange, and chemical production sectors.

Analytical Modeling of Shrink-Fitted FGM Thick-Walled Cylinder

One off the most powerful assembly technique is the shrink-fitting process.It is found in many fields such us mechanics, petroleum, military industries as well as in nuclear power plants etc. This article developed an analytical formulation of shrink-fitted Functionally Graded Material axisymmetric thick-walled cylinder based on the linear plane elasticity theory. The stresses and displacement fields in the thick cylindrical shells are calculated using the laws of linear elasticity. The resulting displacements and stresses are analyzed, and particularly the residual contact pressure and her relationship with the interference values. The results show that the variation of the FGM material composition has a clear effect on the fit pressure in the intersection area of the two fitted cylinders. The value of this pressure affects the distribution of radial and tangential stresses in the FGM cylinder walls. Subsequently, we highlighted the influence of the interference value, on the residual contact pressure which increases with the increase of the interference value. The stresses are modeled for a case study using MATLAB software. keywords. shrink-fit, FGM, Interference, residual stress, Elasticity.

Hyperbolic Conduction and Radiation Heat Transfer in Axisymmetric Cylinders with Variable Properties

This work investigates the combined mode of hyperbolic heat conduction and radiation transfer in a one-dimensional axisymmetric cylinder filled with absorbing, emitting, and scattering media. The volumetric radiation is investigated thanks to the semianalytic solution of the matrix formulation of the spherical harmonics equations PN. The governing hyperbolic energy equation is solved using the finite volume method (FVM) with Roe’s correction of interface fluxes in order to enhance the performances of the method, and the lattice Boltzmann method (LBM) has been designed for comparisons. The effects of the parameters such as constant and spatial-dependent scattering albedos, temperature-dependent thermal conductivity, heat-generated sources, extinction, and the conduction–radiation parameter on both the temperature and heat flux distributions for steady and transient states within the medium are examined. The results of the present work are in excellent agreement with those available in the literature. The PN−FVM results are also compared to those obtained with the PN−LBM combination, and excellent agreement is obtained. These results show that the mentioned parameters have a significant effect on both the temperature profiles and the hyperbolic sharp wave front. This study also shows that the proposed layered approach is an efficient, fast, and accurate solution method for radiative analysis in inhomogeneous media, whereas the Roe’s correction of interface fluxes in the FVM is suitable to accommodate a thermal wave front in non-Fourier analysis.

Buckling and fracture analysis of thick and long composite cylinders with cutouts under axial Compression: An experimental and numerical campaign

This article reports on the manufacturing, experimental testing, and finite element analysis of very thick and long carbon-fiber-reinforced polymers (CFRP) tubes under uniaxial compression (radius-to-thickness ratio ∼ 10 and length-to-radius ratio ∼ 21). Herein, long and hollow axisymmetric composite cylinders were produced through bladder molding. The CFRP tubes have two oppositely located cutouts in the middle of the structures. Three test specimens with different cutout diameters (5, 10, and 15 mm) were experimentally tested until failure. The experimental testing campaign was supported by digital image correlation, acoustic emission, and infrared thermographic measurements to investigate the damage propagation and failure analysis. The CFRP tubes failed at the cutout location due to fiber fracture. Linear static and geometrically non-linear analyses were performed using ABAQUS to analyze the CFPR tubes under axial compression. In general, numerical and experimental results are in good agreement if the maximum stress or Hashin criteria are applied.

Numerical and experimental methodologies to investigate the damage progression inside the axisymmetric composite cylinders with cutouts under torsion

Torsional performance and damage progression inside the long and hollow axisymmetric composite cylinders with different cutouts sizes are investigated via experimental and numerical methods. Acoustic emission, Digital image correlation, and Infrared thermography are deployed to investigate failure propagation. Four acoustic sensors adhere to different locations, and the frequency-based analysis is performed for the damage classification. The cumulative energy data of each sensor is correlated with the nearby strain gauge data to identify the cause of failure. Among all the classified failure types, the predominant failure is matrix cracking which is caused by shear stresses. The percentage of each failure type varies at different locations of the cylinder, and global failure is caused by the simultaneous occurrence of these failure events. Thermography analysis measures the temperature change due to the failure and provides the imprints of the failure initiated by certain damage activities. The thermograms reveal the damage propagation around the cutout and post-global failure postmortem. A material degradation-based progressive damage analysis is performed through Ansys APDL using Hashin failure criteria. The reliability of the performed study is exhibited by comparing the full-field displacement maps and torque-rotation curves of the experimental and numerical analysis.

Fluid End Blocks: Numerical Analysis of Autofrettage and Reautofrettage Based Upon a True Material Model

AbstractFluid end blocks (FEBs) are the most important components of hydraulic fracturing pumps. A potential important application of the hydraulic autofrettage process (HAP) is to strengthen the fatigue-prone FEBs. This creates a favorable compressive residual stress field near to the critical surface locations within the component and serves to increase its pressure-bearing capacity and/or improve lifetime. This requires a fundamental understanding and modeling of the complex mechanics of the HAP in order to accurately predict such residual stresses. The key outstanding modeling issue is the complex material behavior, dominated by the Bauschinger effect and associated with reversed yielding. This effect differs throughout the FEB. It has been modeled for plane axisymmetric cylinders but has not previously been incorporated into FEB analyses. In this paper, a newly developed finite element analysis (FEA)-based user programable function (UPF), featuring true material constitutive behavior, i.e., replicating an existing Bauschinger-effect characterization (BEC), is adopted to accurately simulate the HAP and quantitatively investigate the stress–strain evolution and residual stress fields throughout the FEB. This simulation is then compared with FEA modeling by a traditional bilinear kinematic hardening material model to indicate the importance of the accuracy of the material constitutive model in determining appropriate residual stresses and strains. An autofrettage pressure of 500 MPa generally achieves net compressive hoop stresses at each of four critical crossbore location. Finally, a prospective re-autofrettage sequence is described; approximate modeling suggests an improvement that might permit operation at higher working pressure.

Stress wave propagation analysis of 2D-FGM axisymmetric finite hollow thick cylinder

In this paper, a numerical axisymmetric elastic stress wave propagation analysis of the 2D-FGM hollow thick finite cylinder has been performed. The new accurate material distribution model based on Mori-Tanaka scheme and third-order transition function for 2D-FGMs has been implemented in the graded finite element method with higher-order quadrilateral elements. A non-uniform impulsive pressure has been applied on the one-third of the top inner cylinder wall. Consequently, different wave velocities and reflections from the boundaries have been observed due to the graded distribution of material along with two directions. Moreover, the effects of two-dimensional material property distributions on the stress wave propagations and displacements through the cylindrical wall at different locations have been studied systematically. Normalized effective stresses based on von-Mises criteria has been performed in comparison with the internal impulsive pressure amplitude to provide a measure of the cylinder wall response to the mechanical impact loading, the effective stresses are nearly 2.5 times the internal pressure loading amplitude, closed to the impact location. According to the results, 2D material property gradations has effected the stresses significantly. Alternatively, desired stress values can be achieved through optimal design and appropriate choice of property distribution.

Unsteadiness in hypersonic leading-edge separation

Hypersonic leading-edge separation is studied toward understanding the varying shock-related unsteadiness with freestream Reynolds number (\(1.66 \times 10^5 \le \text{Re}_D \le 5.85 \times 10^5\)) in the newly constructed hypersonic Ludwieg tunnel (HLT) at a freestream design Mach number of \(M_\infty =6.0\). An axisymmetric flat-face cylinder of base body diameter \(D=35\) mm is fitted with axial protrusions of different fineness (\(d/D=0.1,0.2,0.26,0.34\) at \(L/D=1.4\)) and slenderness (\(L/D=0.7,1,1.4,1.9\) at \(d/D=0.2\)) ratio to induce a wide range of leading-edge separation intensities. Qualitative and quantitative assessments are made using schlieren imaging, planar laser Rayleigh scattering, and unsteady pressure measurements. A well-known to-and-fro shock motion called pulsation and a flapping shock-shear layer oscillation is observed as \(\text{Re}_D\) changes. A shorter protrusion length (\(L/D=0.7\)), associated with pulsation, produces a pressure loading four orders higher than the cases with longer protrusion lengths associated with flapping. There exists a critical separation length (\(L/D \ge 1.4\)) beyond which the separated shear layer trips to turbulence and introduces fluctuations in the recirculation region as \(\text{Re}_D\) increases. The intensity of the separated turbulent shear layer is dampened by an order of magnitude, provided the reattachment angle is shallow by increasing the fineness ratio to \(d/D \ge 0.34\). There also exists a set of critical geometrical parameters (\(L/D=1, d/D=0.2\)) for which the unsteady modes (pulsation and flapping) switch between themselves during successive runs, probably due to upstream fluctuations. From the modal analysis of the Rayleigh scattering images, the first four dominant modes that drive flapping are identified as translatory flapping, sinuous flapping, and large and small-scale shedding.

Analytical and numerical analysis of functionally graded (FGM) axisymmetric cylinders under thermo-mechanical loadings

This study examines the thermo-mechanical behavior of FGM hollow cylinders subjected to mechanical loading and steady thermal stresses. The distribution of temperature, displacement, and stresses on the cylinder's inside and outside surfaces is considered a function of radius. The analytic solution of the displacement and stress distributions was obtained by solving Navier's second-order differential equation using the integral and differential transform method, derived from the mechanical equilibrium and heat equations. Moreover, numerical models were built using the finite element method with USDFLD and the finite difference method to test the accuracy of the analytical solution. The analytical formulation and numerical simulation predictions have a high level of agreement, indicating that the model is accurate. The effect of inhomogeneity in the FGM thick cylinder was addressed in this study by selecting a non-dimensional parameter β=[−2,2]that may be assigned any value influencing the stresses in the cylinder. It is concluded that by altering the valueβ, the properties of FGM can be altered to achieve the lowest stress levels. It is also shown that the effect of various Boundary Conditions (B.Cs) is significant in stress fields. This present work also observed that the significance of thermal B.C. is more dominant than fixed pressure B.Cs.

A robust stability criterion on the time-conformable fractional heat equation in a axisymmetric cylinder

A robust stability criterion on the time-conformable fractional heat equation in a axisymmetric cylinder

Stability of nonswirl axisymmetric solutions to the Navier–Stokes equations

The existence of global regular axisymmetric solutions to the Navier–Stokes equations without swirl and in a finite axisymmetric cylinder is proved. The solutions are such that norms bounded with respect to time are controlled by the same constant for all . Assuming that the initial velocity and the external force are sufficiently close to the initial velocity and the external force of a nonswirl axisymmetric solutions, we prove existence of global regular axisymmetric solutions which remain close to the nonswirl axisymmetric solution for all time. In this sense, we have stability of nonswirl axisymmetric solutions. However, to prove this, we need a smallness condition on the angular component of vorticity of the external force for the nonswirl solution.

Analytical and Numerical Analysis of Functionally Graded (Fgm) Axisymmetric Cylinders Under Thermo-Mechanical Loadings

Analytical and Numerical Analysis of Functionally Graded (Fgm) Axisymmetric Cylinders Under Thermo-Mechanical Loadings