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The paper presents a study of the relationship between the combustion behavior and vibration response of internal combustion (IC) engines fueled with biodiesel based on finite element modelling along with experimental evaluation. An improved finite element (FE) model is established and validated to predict the dynamic responses of cylinder liners with respect to two main sources: combustion shock and piston side thrust. Based on the validated FE model, the response characteristics of the cylinder liner in an IC engine fueled with biodiesel and its causal relationship with excitation sources have been predicted. Due to the lower calorific value of biodiesel, a greater amount of fuel is injected into the combustion chamber to maintain power outputs, which results in a prolonged combustion duration and subsequent higher overall vibration levels, compared with that of diesel. The advanced ignition of biodiesel is the main cause to the compound effect on the coupling of piston side-thrust force, thereby resulting in a nonlinear increase in the root mean square (RMS) of local vibration response close to the combustion top dead center (TDC). These key findings provides insight understandings for not only biodiesel combustion diagnostics but also more accurate diagnostics of fossil diesel based on nonintrusive vibrations. [ABSTRACT FROM AUTHOR]

The aim of this article is to study the exact solution for a free vibration in a thermoelastic hollow cylinder, which is initially undeformed and at uniform temperature. The formulation is applied in the context of two-temperature Green and Naghdi (2TGNIII) theory. Both the inner and outer curved surfaces of the cylinder are considered stress free and isothermal surfaces. The exact analytic solutions are obtained with the use of eigenvalue approach. The dispersion relations for the existence of various types of possible modes of vibrations in the considered hollow cylinder are derived in a compact form. The validation of the roots for the dispersion relation are presented. The numerical results of natural frequency, thermoelastic damping and frequency shift of vibrations have been presented graphically. [ABSTRACT FROM AUTHOR]

In the present paper, fluid force distribution of a long flexible cylinder subject to vortex-induced vibrations is investigated by Generalized Integral Transform Technique (GITT). This method is using experimental response data as input, and then implementing GITT to transfer the governing differential equations to ordinary differential equations. Therefore, the selection of truncation order could be analyzed to avoid the error induced by the high-mode response. Once each mode contribution of fluid force is obtained, the analytical inversion transfer recovers the fluid force. An experiment was carried out in a towing tank and the experimental response was accurately measured and used as input, then GITT was performed to calculate the fluid force distribution of the long flexible cylinder. The comparison between the numerical results from GITT and the experimental results from load cell verified the capability and availability of the proposed method. If one can use this method for lower modes, then one certainly can extend the method for higher modes. Two experimental cases from the literature were evaluated and good agreement was obtained based on the spatio-temporal evolutions of the lift coefficient and the mode numbers. Since this method is easy to implement, it could be an alternative method to investigate fluid force of such slender structures. [ABSTRACT FROM AUTHOR]

Non-contact testing is an important method for the study of the vibrating characteristic of cylindrical resonators. For the vibratory cylinder gyroscope excited by piezo-electric electrodes, mode testing of the cylindrical resonator is difficult. In this paper, a novel vibration testing method for cylindrical resonators is proposed. This method uses a MEMS microphone, which has the characteristics of small size and accurate directivity, to measure the vibration of the cylindrical resonator. A testing system was established, then the system was used to measure the vibration mode of the resonator. The experimental results show that the orientation resolution of the node of the vibration mode is better than 0.1º. This method also has the advantages of low cost and easy operation. It can be used in vibration testing and provide accurate results, which is important for the study of the vibration mode and thermal stability of vibratory cylindrical gyroscopes. [ABSTRACT FROM AUTHOR]

The dynamics of a light sphere in a quickly rotating inclined cylinder filled with liquid under transversal vibrations is experimentally investigated. Due to inertial oscillations of the sphere relative to the cavity, its rotation velocity differs from the cavity one. The intensification of the lagging motion of a sphere and the excitation of the outstripping differential rotation are possible under vibrations. It occurs in the resonant areas where the frequency of vibrations coincides with the fundamental frequency of the system. The position of the sphere in the center of the cylinder could be unstable. Different velocities of the sphere are matched with its various quasistationary positions on the axis of rotating cavity. In tilted rotating cylinder, the axial component of the gravity force appears; however, the light sphere does not float to the upper end wall but gets the stable position at a definite distance fromit. It makes possible to provide a vibrational suspension of the light sphere in filled with liquid cavity rotating around the vertical axis. It is found that in the wide range of the cavity inclination angles the sphere position is determined by the dimensionless velocity of body differential rotation. [ABSTRACT FROM AUTHOR]

In the problem of stability of the Couette flow between unidirectionally rotating cylinders, bifurcation points of codimensions 1, 2, and 3 are calculated. These points are interesting because in their small neighborhood the sequences of fluid flow bifurcations, including the development of chaotic regimes, can be studied analytically by completely correct methods. It is found that at large rotation velocities of both cylinders the pattern of the neutral curves corresponding to bifurcation points of codimension 1 changes and various intersections of two and three neutral curves (bifurcation points of codimensions 2 and 3) appear. [ABSTRACT FROM AUTHOR]

Hollow cylinders used in the industry must be regularly inspected. Elastic guided waves, similar to Lamb modes in a plate, can propagate in the axial direction or around the circumference. They are sensitive to geometrical and mechanical parameters of the cylindrical shell. The objective of this paper is to show that zero group velocity (ZGV) Lamb modes can be used to bring out anisotropy and to measure elastic constants of the material. This study provides experimental and numerical investigations on a Zirconium alloy tube extensively used by the nuclear industry in reactor core components. A non-contact method, based on laser ultrasound techniques and ZGV Lamb modes, demonstrates that the difference observed between axial and circumferential guided waves cannot be explained by an isotropic model. Then, a transverse isotropic model is used for the Zircaloy tube. Four of the five elastic constants are directly extracted from ZGV resonance frequencies. The last one is deduced from the measured dispersion spectra. With this complete set of constants, a good agreement is obtained between theoretical and experimental dispersion curves for both axially and circumferentially propagating guided waves. [ABSTRACT FROM AUTHOR]

What is the effect of interstitial fluid viscosity on granular density segregation in a horizontal rotating cylinder? We conducted experiments in the rolling regime with equal amounts of equal sized high and low density, nearly spherical granular particles saturated with air, water, and water-glycerin mixtures. We held particle density, rotation rate and characteristic length scale constant to highlight differences due purely to the interstitial fluid. Images of the granular flow at an end wall were used to determine radial and axial density segregation rates and patterns. Over a four decade change in viscosity, segregation rates varied by only a factor of two. However, for ratios of lubrication to frictional stresses above one, segregation rates decreased by about 30%, and we observed several notable phenomena in the segregation pattern formation. These were a creeping mode of radial density segregation, a change in shape of the granular bed to kidney shaped from flat, and for cylinders more than half full the typically reported unsheared central portion of the granular bed (often referred to in the literature as a core region) was disrupted by a wavy instability where the rate of disappearance of the core region decreased as the fill level increased. [ABSTRACT FROM AUTHOR]

A new type of flow-induced oscillation is reported for a tethered cylinder confined inside a Hele-Shaw cell (ratio of cylinder diameter to cell aperture, $D/ h= 0. 66$) with its main axis perpendicular to the flow. This instability is studied numerically and experimentally as a function of the Reynolds number $\mathit{Re}$ and of the density ${\rho }_{s} $ of the cylinder. This confinement-induced vibration (CIV) occurs above a critical Reynolds number ${\mathit{Re}}_{c} \ensuremath{\sim} 20$ much lower than for Bénard–Von Kármán vortex shedding behind a fixed cylinder in the same configuration (${\mathit{Re}}_{\mathit{BV K}} = 111$). For low ${\rho }_{s} $ values, CIV persists up to the highest $\mathit{Re}$ value investigated ($\mathit{Re}= 130$). For denser cylinders, these oscillations end abruptly above a second value of $\mathit{Re}$ larger than ${\mathit{Re}}_{c} $ and vortex-induced vibrations (VIV) of lower amplitude appear for $\mathit{Re}\ensuremath{\sim} {\mathit{Re}}_{\mathit{BV K}} $. Close to the first threshold ${\mathit{Re}}_{c} $, the oscillation amplitude variation as $ \mathop{ (\mathit{Re}\ensuremath{-} {\mathit{Re}}_{c} )}\nolimits ^{1/ 2} $ and the lack of hysteresis demonstrate that the process is a supercritical Hopf bifurcation. Using forced oscillations, the transverse position of the cylinder is shown to satisfy a Van der Pol equation. The physical meaning of the stiffness, amplification and total mass coefficients of this equation are discussed from the variations of the pressure field. [ABSTRACT FROM PUBLISHER]

Abstract: Recently, energy storage systems are one of necessity in smart microgrid systems. Electro-mechanical batteries have important advantages compared with chemical batteries. More efficiency and life time, lower weight and volume can be mentioned. The vibration of an elastic, thick, hollow and finite length cylinder when subjected to the constant angular velocity is studied in this paper. Based on the technique of variables separation and utilizing the finite circular cylinders solution, a general solution is developed to analyze the vibration of rotating cylinders. Convergence of the method is determined to calculate the natural frequencies of various geometrical configurations. It is shown that the results obtained from the present semi-analytical method are in good agreement with those obtained using the previously semi-analytical methods for zero angular velocity. [Copyright &y& Elsevier]

The electromechanical properties of thin tangentially polarized, stripe-electroded piezoceramic elements are considered. Theoretical analysis is made based on a piecewise linear approximation of the actual nonuniform electric field in the volume of the stripe-electroded cylinder design. Analytical expressions are derived for the electromechanical properties (including the effective coupling coefficient) of the tangentially polarized elements as a function of the geometry and electrode configuration (i.e., electrode width and spacing). The properties of stripe-electroded cylinders are calculated and compared with the ideal case of a uniform circumferential electric field, which may be realized in practice with segmented cylinders comprised of 33-polarized bar elements. The reasons for the reduction in the effective coupling coefficient of tangentially polarized stripe-electroded cylinders compared to the ideal coupling coefficient k33 achievable with the segmented cylinder designs are discussed. The results of calculations of the electromechanical properties are in good agreement with experimentally obtained data on a variety of samples. [ABSTRACT FROM AUTHOR]

We consider an axisymmetric problem of free longitudinal vibrations of hollow piezoelectric cylinders for some types of boundary conditions on the end faces. The piezoceramic material is polarized in the radial direction. The side faces of a cylinder are covered with short-circuited thin electrodes. The method of solution of the problem is based on the combination of the spline collocation method along the longitudinal coordinate and the step-by-step search method along the radial coordinate. We present results of a numerical analysis of a cylinder of PZT 4 ceramic in a wide range of changes in the geometric parameters of the cylinder. [ABSTRACT FROM AUTHOR]

The article presents a paper which examines the noise types of master cylinder and vacuum booster, acoustic signature, and the acoustic treatment impact. The paper used Heim 480 multi-channel data acquisition system together with a digitally programmable controlled hydraulic applying mechanism. It also mentions that the paper developed a direction that will optimise acoustic treatment characteristics, which could reduce the quantity of filters and cost when followed.

In this study, we investigate the dynamics of a freely rising and falling cylinder. This is, in essence, a vortex-induced vibration (VIV) system comprising both transverse (Y) and streamwise (X) degrees-of-freedom (d.o.f.), but with zero spring stiffness and zero damping. This problem represents a limiting case among studies in VIV, and is an extension of recent research of elastically mounted bodies having very low spring stiffness, as well as bodies with very low mass and damping. We find that if the mass ratio (where m* = cylinder mass/displaced fluid mass) is greater than a critical value, m*crit = 0.545, the body falls or rises with a rectilinear trajectory. As the mass ratio is reduced below m*crit = 0.545, the cylinder suddenly begins to vibrate vigorously and periodically, with a 2P mode of vortex formation, as reported in the preliminary study of Horowitz & Williamson (J. Fluids Struct. vol. 22, 2006, pp. 837–843). The similarity in critical mass between freely rising and elastically mounted bodies is unexpected, as it is known that the addition of streamwise vibration can markedly affect the response and vortex formation in elastically mounted systems, which would be expected to modify the critical mass. However, we show in this paper that the similarity in vortex formation mode (2P) between the freely rising body and the elastically mounted counterpart is consistent with a comparable phase of vortex dynamics, strength of vortices, amplitudes and frequencies of motion and effective added mass (CEA). All of these similarities result in comparable values of critical mass. The principal fact that the 2P mode is observed for the freely rising body is an interesting and consistent result; based on the previous VIV measurements, this is the only mode out of the known set {2S, 2P, 2T} to yield negative effective added mass (CEA < 0), which is a condition for vibration of a freely rising body. In this paper, we deduce that there exists only one possible two degree-of-freedom elastically mounted cylinder system, which can be used to predict the dynamics of freely rising bodies. Because of the symmetry of the vortex wake, this system is one for which the natural frequencies are fNX = 2fNY. Although this seems clear in retrospect, previous attempts to predict critical mass did not take this into account. Implementing such an elastic system, we are able to predict vibration amplitudes and critical mass (m*crit = 0.57) for a freely rising cylinder in reasonable agreement with direct measurements for such a rising body, and even to predict the Lissajous figures representing the streamwise–transverse vibrations for a rising body with very small mass ratios (down to m* = 0.06), unobtainable from our direct measurements. [ABSTRACT FROM AUTHOR]

The problem of free vibrations of a solid cylinder with different boundary conditions is solved using the three-dimensional theory of elasticity and a numerical analytic approach. The spline-approximation and collocation methods are used to reduce the partial differential equations of elasticity to systems of ordinary differential equations of high order with respect to the radial coordinate. These equations are solved by stable numerical discrete orthogonalization and incremental search. Calculated results are presented for transversely isotropic and inhomogeneous materials of the cylinder and for several types of boundary conditions at its ends [ABSTRACT FROM AUTHOR]

The mechanism of wake-induced vibrations (WIV) of a pair of cylinders in a tandem arrangement is investigated by experiments. A typical WIV response is characterized by a build-up of amplitude persisting to high reduced velocities; this is different from a typical vortex-induced vibration (VIV) response, which occurs in a limited resonance range. We suggest that WIV of the downstream cylinder is excited by the unsteady vortex–structure interactions between the body and the upstream wake. Coherent vortices interfering with the downstream cylinder induce fluctuations in the fluid force that are not synchronized with the motion. A favourable phase lag between the displacement and the fluid force guarantees that a positive energy transfer from the flow to the structure sustains the oscillations. If the unsteady vortices are removed from the wake of the upstream body then WIV will not be excited. An experiment performed in a steady shear flow turned out to be central to the understanding of the origin of the fluid forces acting on the downstream cylinder. [ABSTRACT FROM AUTHOR]

We petform direct numerical simulations of the flow past a circular cylinder undergoing a one-degree-of-freedom transverse oscillation. The displacement follows a sine function raised to an arbitrary integer power ranging from 1 to 8. When the displacement power is above 2, we have multifrequency oscillation, and the number of Fourier components in the oscillation increases with the power but they are either odd or even multiples of the input (argument) frequency of the displacement function. We study the responses of the nondimensional lift and drag under these different oscillation profiles and the transfer of nondimensional mechanical energy due to the oscillation, and their trends as the power (hence the number of Fourier components in the oscillation) increases. For odd powers, the energy is transferred to the cylinder; whereas for even powers, it is transferred to the flow. A unity power (harmonic oscillation) corresponds to the maximum energy transfer to the cylinder, which can explain the occurrence of this profile in the case when the cylinder is free to oscillate due to the vortex-induced vibration (VIV) phenomenon. The lift exhibits a mean value only with even powers above 2. The results show that the lift is driven to a large extent by the acceleration of the oscillation rather than its velocity. This should be considered when modeling the fluid-structure coupling in reduced-order VIV models. [ABSTRACT FROM AUTHOR]

A cantilever thin rotating circular cylindrical shell is investigated in this paper. The precession factor of vibrating shape is obtained by an energy approach, with damping and geometric nonlinearity considered. Donnell's shallow-shell theory is used, the non-linear equations of motion are discretized by Galerkin method, in which geometric nonlinearity and precession of vibrating shape are taken into account. The non-linear mode equations are studied by using Runge-Kutta method and harmonic balance method, and the stability of analytical solutions is studied. The results show that geometric nonlinearity does not influence the precession factor of vibrating shape but causes multi-value and leap characteristics. [ABSTRACT FROM AUTHOR]

This paper presents the research results of the connected fields of different physical nature that appear in the arch cylindrical lattice. This lattice is made of the thin wall cylindrical piesoceramical transformations with locally responding acoustic screens in the inner cavity and without them. The fields appear at the interaction between lattices and flat acoustic waves and depend on the parameters of transformations, lattices and waves. Finally, we determine the regularities of influence of this interaction on the specificity of acoustic, mechanical and electric fields formation by the lattice transformations. [ABSTRACT FROM AUTHOR]

Based on the linear theories of thin cylindrical shells and viscoelastic materials, the governing equation generally describing vibration of a sandwich circular cylindrical shell with partially constrained layer damping treatment under harmonic excitation, which can be written in a matrix differential equation of first order, is derived by considering the energy dissipation due to the shear deformation of the viscoelastic layer and the interaction between all layers. After that a semi-analytical and semi-numerical method for solving this governing equation is presented by means of the extended homogeneous capacity precision integration approach. Its essential difference from the recent works on transfer matrix method is that the state vector in governing equation is composed of the twelve displacements and internal forces of the sandwich shell rather than of the displacements and their derivatives. As a result, the present method can be applied to solve the dynamic problems of the kind of sandwich shell with various boundary conditions and partially constrained layer damping. Numerical examples show that the proposed approach is very effective and reliable, compared with the existing analytical solutions. Furthermore, the effects of PCLD coverage percents and locations on FRF are then discussed. [ABSTRACT FROM AUTHOR]

A perturbation-based approach is used to formulate the governing equations for wave propagation at high frequencies in infinite in vacuo and fluid-filled elliptical cylindrical shells. The in vacuo equations thus formulated have the form of a perturbation over the corresponding equations for the circular cylindrical shell. Here, eccentricity of the cross-section is assumed to be small and used as the perturbation parameter. Next, the coupled equations for the fluid-filled elliptical shell are obtained as a perturbation over the in vacuo shell equations (by using a single fluid-loading parameter μ). Asymptotic arguments are used to neglect various terms in the derivation, and a compact form of the non-dimensional governing equations is found. Presenting the governing equations in this form is the main contribution of this work. Due to the eccentricity, all spatial quantities need to be represented in terms of a harmonic series instead of a single harmonic term. Using symmetry and asymptotic arguments, the nature of the harmonic series is obtained. Using the harmonic series expansion, the dispersion relation is formulated for both the in vacuo and the fluid-filled cases. The in vacuo dispersion equation is solved using the regular perturbation method, while the transcendental coupled dispersion equation is solved numerically. [ABSTRACT FROM AUTHOR]

We investigate numerically vortex-induced vibrations (VIV) of two identical two-dimensional elastically mounted cylinders in tandem in the proximity?wake interference regime at Reynolds number Re= 200 for systems having both one (transverse vibrations) and two (transverse and in-line) degrees of freedom (1-DOF and 2-DOF, respectively). For the 1-DOF system the computed results are in good qualitative agreement with available experiments at higher Reynolds numbers. Similar to these experiments our simulations reveal: (1) larger amplitudes of motion and a wider lock-in region for the tandem arrangement when compared with an isolated cylinder; (2) that at low reduced velocities the vibration amplitude of the front cylinder exceeds that of the rear cylinder; and (3) that above a threshold reduced velocity, large-amplitude VIV are excited for the rear cylinder with amplitudes significantly larger than those of the front cylinder. By analysing the simulated flow patterns we identify the VIV excitation mechanisms that lead to such complex responses and elucidate the near-wake vorticity dynamics and vortex-shedding modes excited in each case. We show that at low reduced velocities vortex shedding provides the initial excitation mechanism, which gives rise to a vertical separation between the two cylinders. When this vertical separation exceeds one cylinder diameter, however, a significant portion of the incoming flow is able to pass through the gap between the two cylinders and the gap-flow mechanism starts to dominate the VIV dynamics. The gap flow is able to periodically force either the top or the bottom shear layer of the front cylinder into the gap region, setting off a series of very complex vortex-to-vortex and vortex-to-cylinder interactions, which induces pressure gradients that result in a large oscillatory force in phase with the vortex shedding and lead to the experimentally observed larger vibration amplitudes. When the vortex shedding is the dominant mechanism the front cylinder vibration amplitude is larger than that of the rear cylinder. The reversing of this trend above a threshold reduced velocity is associated with the onset of the gap flow. The important role of the gap flow is further illustrated via a series of simulations for the 2-DOF system. We show that when the gap-flow mechanism is triggered, the 2-DOF system can develop and sustain large VIV amplitudes comparable to those observed in the corresponding (same reduced velocity) 1-DOF system. For sufficiently high reduced velocities, however, the two cylinders in the 2-DOF system approach each other, thus significantly reducing the size of the gap region. In such cases the gap flow is entirely eliminated, and the two cylinders vibrate together as a single body with vibration amplitudes up to 50% lower than the amplitudes of the corresponding 1-DOF in which the gap flow is active. Three-dimensional simulations are also carried out to examine the adequacy of two-dimensional simulations for describing the dynamic response of the tandem system at Re= 200. It is shown that even though the wake transitions to a weakly three-dimensional state when the gap flow is active, the three-dimensional modes are too weak to affect the dynamic response of the system, which is found to be identical to that obtained from the two-dimensional computations. [ABSTRACT FROM AUTHOR]

Analysis of electromechanical transducers employing axially symmetric vibrations of piezoelectric ceramic thin-walled tubes of arbitrary aspect ratio is presented based on application of the energy method [B. S. Aronov, J. Acoust. Soc. Am. 117, 210-220 (2005)]. The suggestion made by Giebe and Blechshmidt [Ann. Physik, Ser. 5 18, 417-485 (1933)] regarding representation of a tube vibration as a coupled vibration of two partial systems is used to choose the assumed modes of the piezoceramic tube vibration, and the energy of the flexural deformations accompanying the extensional vibration of a tube is also taken into consideration. The Lagrange type equations describing the transducer vibrations are derived, and the equivalent electromechanical circuit is introduced that conveniently represents the solution. The resonance frequencies, effective coupling coefficients, and velocity distributions for differently poled piezoceramic tubes as functions of their height-to-diameter aspect ratio are calculated. The validity of the equivalent circuit is extended to the case that a piezoceramic tube is mechanically and acoustically loaded on the ends and acoustically loaded on its outer surface. The results of calculations are in good agreement with the results of experimental investigations. [ABSTRACT FROM AUTHOR]

The propagation of torsional waves in a prestressed compound (bi-layered) hollow circular cylinder is in vestigated within the frame work of a piecewise homogeneous body model, with the use of a three-dimensional linerized theory of elastic waves in initially stressed bodies. The elasticity relations for components of the compound cylinder are obtained from the Murnaghan potential. Numerical investigations are performed for bronze and steel. According to the results obtained, the effect of variations in the geometric (the ratio between the thickness of the cylinder and its inner radius) and mechanical parameters on the dispersion curves are analyzed. [ABSTRACT FROM AUTHOR]

This paper describes the first noncontact elastic vibration measurements of an object in a high gamma radiation field. Using a laser-coupled resonant ultrasound technique, the vibration modes of an Inconel hollow capped cylinder were measured as the gamma radiation field was increased to 104 Gy/h. This measurement technique allowed shifts in the resonant frequency of the sample's vibration modes to be tracked over a 170-h period. The vibration mode frequencies changed in a manner consistent with the temperature dependence of the elastic stiffness coefficients of the material. These results demonstrate the efficacy of the laser approach for real-time resonant ultrasound measurements in this severely hostile nuclear environment. [ABSTRACT FROM AUTHOR]

The viscous flow inside a closed rotating cylinder of gas subject to periodic axial compression is investigated numerically. The numerical method is based on a spectral Galerkin expansion of the velocity field, assuming axisymmetry of the flow. If the forcing amplitude is weak and the angular forcing frequency is less than twice the rotation rate, inertial waves emanate from the corners, forming conical oscillatory jets which undergo reflections at the walls. Their thickness is O(E1/3), or O(E1/4) for particular forcing frequencies, where E is the Ekman number. For larger forcing amplitudes, the conical pattern breaks down. When the forcing frequency is resonant with a low-order inertial mode, the flow can undergo two types of parametric instabilities: a mode-triad resonance, and a subharmonic instability. The combination of both these mechanisms provides a possible route to quasiperiodicity of the flow. [ABSTRACT FROM AUTHOR]

The laminar unsteady periodic flow motion found in the wake of a rotationally oscillating circular cylinder is investigated numerically at a Reynolds number of 855 over a wide range of oscillation amplitude and frequency ratio. The governing Navier–Stokes equations are integrated to determine the flow field structure for large values of the time using an accurate spectral-finite difference method, but with the boundary vorticity calculated using global vorticity conditions rather than local finite-difference approximations. The lock-on phenomenon has been predicted and its effect on the flow hydrodynamics has been determined. The numerical scheme is verified by applying it to the special case of a steadily rotating cylinder (no forced oscillations) and good qualitative agreements are found. [ABSTRACT FROM AUTHOR]

Wavelets and local discriminant bases (LDB) selection algorithm is applied to vibration signals in a single-cylinder spark ignition engine for feature extraction and fault classification. LDB selects a complete orthogonal basis from a wavelet packet library of bases, which best discriminates the given classes, based on their time-frequency energy maps. An appropriate normalization method in both data and wavelet coefficient domains, and a neural network classifier during the identification phase are used to enhance the classification. By applying LDB to a real-world machine data the accuracy of the algorithm in machine fault diagnosis and classification is shown. [ABSTRACT FROM AUTHOR]

An analyticalnumerical technique, for the solution of the two-dimensional electromagnetic plane-wave scattering by a finite set of perfectly conducting circular cylinders buried in a dielectric half-space, is presented. The problem is solved for both the near- and the far-field regions, for TM and TE polarizations. The diffracted field is represented in terms of a superposition of cylindrical waves and use is made of the plane-wive spectrum to take into account the reflection and transmission of such waves by the interface. The validity of the approach is confirmed by comparisons with results available in the literature, with very good agreement. The multiple interactions between two buried cylinders have been studied by considering both the induced currents and the scattered field diagrams. Applications of the method to objects of arbitrary cross-section simulated by a suitable configuration of circular cylinders are shown. [ABSTRACT FROM AUTHOR]

A modal theory is developed for investigating the acoustic scattering by elastic cylinders of arbitrary cross section immersed in a fluid. Numerical results are presented for a plane wave incidence normal to the axis of an elliptical cylinder but arbitrary with respect to the noncircular cross section. Experimental results are obtained for an aluminum elliptical cylinder with the use of an impulse method. Comparisons between theoretical and experimental data are performed in the broad frequency range 8.5 ≤ ka ≤ 30 (k is the wave number in the fluid and a the major axis radius of the elliptic cylinder!. The experimental observations are in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

The axisymmetric wave equation is solved for the problem of torsional elastic waves scattered by a spherical cavity located symmetrically in an infinitely long circular cylinder. Using Fourier transforms, the problem is reduced to the solution of an infinite system of simultaneous equations, which is suitable for the numerical solution. The numerical results on the transmission and reflection coefficients are shown for various values of sphere radius and frequency. Equation of energy conservation is utilized to check the numerical procedure. [ABSTRACT FROM AUTHOR]

Acoustic radiation from a cylindrical source undergoing angularly periodic and axially-dependent harmonic surface vibrations while eccentrically suspended within a fluid cylinder, which is submerged in an infinite fluid medium, is analyzed in an exact manner. This configuration, which is a realistic idealization of a cylindrical liquid-filled acoustic lens with focal point inside the lens when used as a sound projector, is of practical importance with applications in underwater and biomedical ultrasonics. The formulation utilizes the appropriate wave-field expansions along with the pertinent translational addition theorem to develop an infinite series solution. The analytical results are illustrated with a numerical example in which the basic acoustic quantities, such as the modal acoustic radiation impedance load on the source, on-axis pressure magnitude, radiated far-field pressure directivity patterns, and the radiation intensity distribution are evaluated for representative values of the parameters characterizing the system. Numerical results clearly illustrate that, in addition to source frequency and surface velocity distribution, its position (eccentricity) can be of great significance in sound radiation. [ABSTRACT FROM AUTHOR]

The sound field in the region of a deep shadow behind an impedance cylinder is analyzed for the case of plane wave diffraction by the cylinder surface. The main part of the field is represented by a cylindrical wave that has a complex index determined from the boundary conditions and decays with the angular coordinate. An expression for the amplitude of this wave is determined by extracting it from the total field formed in the shadow region. It is demonstrated that this wave approximates more closely the total field behind the cylinder, as compared to the least damped wave in the field representation obtained on the basis of the Watson transform. A way to improve the sound barriers is indicated. [ABSTRACT FROM AUTHOR]

Develops a three-dimensional method of analysis for the free vibration frequencies of hollow circular cylinders of elastic material. Based upon local coordinates attached to the center of cylindrical wall; Assumption for the three displacement components of a Fourier series in the circumferential direction and algebraic polynomials in the radials and axial directions.

The paper reports on an experimental and a theoretical investigation into the vibration of three ring-stiffened circular cylinders under external water pressure. The theoretical analysis was via the finite element method, where both the structure and the surrounding water were modelled using finite elements. Comparison between experiment and theory was good, and showed that the resonant frequencies decreased with increasing external pressure. The results also showed that there was a possibility of a form of dynamic buckling, when the vibration eigenmodes became of similar form to the static buckling eigenmodes. [ABSTRACT FROM AUTHOR]

The scattering problem is analyzed in the case where an electromagnetic wave is incident on a perfectly conducting rectangular cylinder located near the conducting plane. Since it Is difficult to solve this problem directly as the boundary value problem, the problem is replaced with that of scattering by two conducting rectangular cylinders by means of the method of electrical image. The analysis is based on the point matching method and the amount of computation is reduced by reducing the number of simultaneous equations derived from the boundary conditions into one-half by using the symetry of the electromagnetic field. As the numerical examples, the near field and the scattering patterns are presented which have not been reported often. Numerical results are compared for the perfectly conducting circular cylinder located near the conducting plane with those of the rectangular cylinder. To confirm the theory, a model experiment is conducted at microwave frequencies so that reliability of the theory is tested. [ABSTRACT FROM AUTHOR]

Orthotropic laminated structures have attracted much interest in many applications because of their desirable properties such as improved thermal and mechanical properties, high strength to weight ratio, and high stiffness to weight ratio. In this paper, an improved version of the differential quadrature method, called the generalized differential quadrature (GDQ) method, is used for the first time to study the vibration of antisymmetric angle-ply laminated cylindrical panels with boundary conditions other than the simply supported type on its four edges. The GDQ method has shown computational advantages over the existing differential quadrature methods in that there is no restriction on the number of grid points in the approximation and the weighting coefficients are determined using a recurrence relation. The GDQ method has shown superb accuracy, efficiency and convenience, and great potential in solving the differential equations of structural problems. The present analysis is formulated using Donnell's shell theory and is validated by comparing results with those in the literature. [ABSTRACT FROM AUTHOR]