Numerical Vibration Analysis Research Articles

Numerical analysis of flow-induced vibrations and heat transfer in a triangular arrangement of circular cylinders

This numerical study explores the flow characteristics and heat transfer performance of three isothermal circular cylinders arranged in a triangular configuration at angles of attack of 45° and 60°. The impact of one-degree-of-freedom (1DOF) flow-induced vibrations (FIV) in the cross-flow direction on forced convective heat transfer is analyzed using ANSYS FLUENT, considering reduced velocities from 4 to 8 at a constant Reynolds number of 100. Comparative simulations are conducted for both stationary and vibrating cylinders. Results indicate that, when stationary, the cylinders at a 45° angle exhibit lower heat transfer rates compared to those at 60°, with a 2.66% reduction in overall heat transfer. The study also examines the nuanced effects of 1DOF FIV in the cross-flow direction on heat transfer: while the upstream cylinder generally experiences increased heat transfer during vibrations, the downstream cylinders often show reduced rates. Specifically, at a 45° angle, the most significant reduction in heat transfer from downstream cylinders, nearly 9.99%, occurs at reduced velocities of 5 and 6. For the stationary tube bundle at 45°, the average Nusselt number is 11.77, but it decreases by approximately 5.21% at a reduced velocity of 5 under vibration. Conversely, at a 60° angle, the average Nusselt number generally increases at higher reduced velocities, except at Ur = 4, where it drops by 2.89% from the stationary state. These findings highlight the complex interplay between 1DOF vibration and heat transfer in triangular cylinder arrangements.

Numerical analysis of molecular vibration under Lennard-Jones potential

Numerical analysis of molecular vibration under Lennard-Jones potential

Numerical analysis of vortex-induced vibration of deepwater drilling riser based on Van der Pol wake oscillator model

Coupled equations of the dynamic model and the Van der Pol wake oscillator model are solved by the central finite difference method for the deepwater drilling riser. The vortex-induced vibration (VIV) response and fatigue life of the riser are calculated and the model validation is performed by comparing with the published experimental and simulation results. The effects of the top tension, current flow velocity, flow velocity profile, internal flow velocity as well as the installation of buoyancy modules on the VIV are discussed. Dynamic response and fatigue life of the riser under In-Line (IL) and Cross-Flow (CF) VIV are preliminarily analyzed. The results show that the VIV of the riser has multiple modes and exhibits a mixed behavior of standing waves and traveling waves. With the increase of top tension and flow velocity profile coefficient, the order of the VIV dominant mode and the peak values of the root mean square (RMS) of VIV displacement decrease, and the fatigue life of the riser is extended. With the increase of current flow velocity, the order of the VIV dominant mode increases and the riser fatigue life decreases. The effect of internal flow velocity on the riser VIV is neglectable. The installation of buoyancy modules can improve the riser stress state and extend the fatigue life. Compared with the CF VIV model, the calculated minimum fatigue life of the riser is extended under the IL and CF coupled VIV model due to the decrease of bending moment and the changing position of fatigue weak point.

Numerical analysis of fractional nonlinear vibrations of a restrained cantilever beam with an intermediate lumped mass

This paper focuses on the numerical investigation of the fractional nonlinear oscillator for a restrained cantilever beam with an intermediate lumped mass. A numerical approach based upon the fractional complex transformation and the global residue harmonic balance method (FCT-GRHBM) is suggested for approximately solving this fractional oscillation system of fifth-order nonlinearity. The approximated fractional periodic solutions and frequencies are provided by FCT-GRHBM, which are not touched in the existing literature. Numerical results and sensitive analysis with respect to different parameters are shown to confirm its efficiency.

Numerical Analysis of Structural Vibrations in Masts—A Practical Study Applied to a 28-Meter Tugboat

This article investigates the vibration analysis of the mast on the bridge top of a 28 m tugboat, in the quasi-static regime. The study aims to determine the natural frequencies using an equivalent dynamic model of the mast and considers the accelerations of different degrees of freedom of the vessel. Practical design and reinforcement strategies for the local bridge top structure are proposed, utilizing numerical and analytical tools. The investigation explores various alternatives to optimize the structural arrangement. By analyzing the modal behavior, insights are provided for efficient design and reinforcement. The results contribute to understanding the mast’s vibration characteristics, offering guidance for similar structures. This study employs numerical and analytical methods, enhancing the optimization of the mast’s behavior. It determines natural frequencies, proposes practical design strategies, and explores alternatives for structural optimization. The findings provide insights for shipbuilding and mast design applications in other vessels and industries such as radar mast, compass deck, and guyed mast.

A Numerical Analysis of the Non-Uniform Layered Ground Vibration Caused by a Moving Railway Load Using an Efficient Frequency–Wave-Number Method

The ground vibration caused by the operation of high-speed trains has become a key challenge in the development of high-speed railways. In order to study the train-induced ground vibration affected by geotechnical heterogeneity, an efficient frequency–wave-number method coupled with the random variable theory model is proposed to quickly obtain the numerical results without losing accuracy. The track is regarded as a composite Euler–Bernoulli beam resting on the layered ground, and the spatial heterogeneity of the ground soil is considered. The ground dynamic characteristics of an elastic, layered, non-uniform foundation are investigated, and numerical results at three typical train speeds are reported based on the developed Fortran computer programs. The results show that as the soil homogeneity coefficient increases, the peak acceleration continuously decreases in the transonic case, while it gradually increases in the supersonic case, and the ground acceleration spectrum at a far distance obviously decreases; the maximum acceleration occurs at the track edge, and a local rebound in vibration attenuation occurs in the supersonic case.

Finite element numerical analysis of structural vibration of a certain pump station

Abstract In the process of pump station operation, the vibration of factory structure caused by hydraulic or mechanical factors will seriously threaten the ordinary operation of pump station; reduce the efficiency of units; shorten the service lifespan of equipment, and even lead to failure of units. In this paper, ANSYS software and modal analysis method are applied to simulate the vibration effect on pump station under natural vibration, unit vibration excitation and hydraulic excitation. The intrinsic vibration features of pump station structure under diverse boundary conditions, different working conditions and distinct external excitation sources are studied. According to the results of modal and harmonic response analysis, it can be concluded that: 1. A cross relationship has been found existing between pump station structure and unit excitation of speed frequency. 2. In addition to the upper part of the pump station fragile structure, the vibration of the pier is more noteworthy. 3. The vibration amplitude of the whole pump station along vertical direction is larger than that in other directions while the deformation following the unit axis and flow direction presents a strong tendency. 4. In general, the influence of hydraulic load on the structural force of pump station is relatively small.

Vibration response of ultra-shallow floor beam composite floors

This paper examines the vibration response of the steel–concrete composite ultra-shallow floor beam (USFB) flooring system, which incorporates asymmetric steel perforated beams to accommodate the concrete floor slab within the depth of the flanges while allowing reinforcement and/or service ducts to pass through the web openings. This is a lightweight flooring system that can accommodate long spans, thus becoming susceptible to floor vibrations due to external resonant dynamic loads. To investigate the influence of slab thickness and boundary conditions on the natural frequencies of the USFB flooring system, parametric studies are conducted using a finite-element model and five floor spans. The model was first validated against an experimental test conducted by the authors. Emphasis is placed on the fundamental frequency to predict the possibility of resonance of this complex flooring system with typical human-induced dynamic loads in building structures. To further facilitate the practical numerical modelling and vibration analysis of buildings with USFB floors in standard commercial structural software, an analytical method of deriving equivalent isotropic plate properties is developed and its accuracy is numerically verified with regard to detailed Abaqus models.

Numerical Analysis of Flow-Induced Transverse Vibration of a Cylinder with Cubic Non-Linear Stiffness at High Reynolds Numbers

Numerical calculations were performed to study the vortex-induced vibration (VIV) of a circular cylinder, which was elastically supported by springs of linear and cubic terms. These simulations were conducted at high Reynolds numbers ranging from 4200 to 42,000. To simulate the cylinder’s motion and the associated aerodynamic forces, Computational Fluid Dynamics were employed in conjunction with dynamic mesh capabilities. The numerical method was initially verified by testing it with various grid resolutions and time steps, and subsequently, it was validated using experimental data. The response of cubic nonlinearities was investigated using insights gained from a conventional linear vortex-induced vibration (VIV) system. This 2D study revealed that both the amplitude and frequency of vibrations are contingent on the flow velocity. The highest output was achieved within the frequency lock-in region, where internal resonance occurs. In the case of a hardening spring, the beating response was observed from the lower end of the initial branch to the upper end of the initial branch. The response displacement amplitude obtained for the linear spring case was 27 mm, whereas in the cubic nonlinear case, the value was 31.8 mm. More importantly, the results indicate that the inclusion of nonlinear springs can substantially extend the range of wind velocities in which significant energy extraction through vortex-induced vibration (VIV) is achievable.

Numerical Analysis of Unsteady Vibrations of a Plate Resting on an Elastic Isotropic Half-Space

The paper is devoted to the numerical solution of the problem of vibrations of an infinite elastic plate resting on an elastic isotropic half-space using the analytical method based on the ray method with its numerical realization via the Maplesoft package. Unsteady oscillations are caused by the action of instantaneous loads on the plate, resulting in the appearance of two plane wave surfaces of strong discontinuity in the elastic half-space, behind the fronts of which, up to the contact boundary, the solution is constructed using ray series. The unknown functions entering the coefficients of the ray series and the equation of plate motion are determined from the boundary conditions of the contact interaction between the plate and the half-space. Previously, the approximate solution of this problem was obtained analytically without using mathematical packages, and the dynamic deflection of the plate involving only the first three terms of the ray series was written down. In this work, a two-layer medium with different properties was investigated using an algorithm developed to solve contact dynamic problems related to the occurrence and propagation of strong and weak discontinuity surfaces.

Experimental and numerical investigation of free vibration behaviours of sandwich syntactic foams

The studies on the development of new composite materials that are lighter and have high strength and rigidity are increasing with the developing technology in recent years. Among these new technological materials, syntactic foams are polymer structures fabricated by dispersing low-density hollow particles (microballoons-MB) in a matrix material. Because of its advantages, syntactic foams are widely used in the automobile, marina, and aerospace industries, and it is very important to investigate the vibration behaviour in the design process. There are limited studies in the literature on the numerical and experimental free vibration analysis of syntactic foams. In this study, the vibration characteristics of sandwich syntactic foams were numerically and experimentally investigated. First, the differential equations of the sandwich syntactic foam beams were derived according to higher-order shear deformation theory (HSDT). Numerical analysis was carried out using the finite element method written in MATLAB. Then, to prove the accuracy of the present numerical model, the natural frequencies are compared with the experimental results. Then, the present numerical model was validated by comparing it with the experimental results. Since the numerical model was validated, the effects of varying the MB volume fractions and MB density on the vibration behaviour of the sandwich syntactic foams were investigated. Thus, according to the authors’ knowledge, the HSDT-based FEM and experimental method were used for the first time to study the vibration analysis of sandwich syntactic foams. The authors aimed to contribute in this regard.

Numerical analysis and test of vibration and interference characteristics of dual U-tube Coriolis flowmeter

The Coriolis flowmeter is a resonant instrument that can be easily affected by environmental vibration interference factors. Therefore, it is necessary to study the vibration characteristics of the Coriolis flowmeter, as well as the on-site environmental interference vibrations. In this paper, a full-scale numerical model of the flowmeter, including the support pipe and flange, was established, and the vibration characteristics of the Dual U-Tube Coriolis flowmeter were analyzed using structural dynamics and fluid-structure coupling calculation methods. The first to sixth natural frequencies and vibration modes were obtained. A mass flowmeter of the same model was selected from the oil transportation station, and vibration analysis and testing were carried out on the Dual U-Tube Coriolis flowmeter. The driving frequency of the Coriolis mass flowmeter and the frequency of external interference vibration signals during the distribution process were obtained through Fast Fourier transform, which verified the correctness of the numerical calculation model. It was found that the natural frequency of the Coriolis flowmeter varies with the installation conditions, and it was pointed out that external vibration signals can interfere with the operation of the Coriolis flowmeter during field operations. This work in this paper has significant reference value for the actual field installation and noise reduction of the Coriolis mass flowmeter.

Numerical analysis of reverse wake-induced vibration at low Reynolds number

Reverse wake-induced vibration (RWIV) of two tandem cylinders with the downstream one fixed is numerically studied in this paper; Reynolds number is set as 150 (Re = 150). The effect of different spacing ratios (α) ranging from 3 to 6 with a gap of 0.5 is simulated to investigate the vibration characteristics of RWIV, where the spacing ratio (α) is defined as the nondimensional ratio of the center-to-center separation between the cylinders. As the spacing ratio increases from 3 to 6, RWIV shows a transition from galloping to vortex-induced vibration (VIV), which is also a reverse phenomenon compared to wake-induced vibration (WIV). As to the wake mode, two different types of vortex motion (2S - 2P - 2S and 2S - 2P) are observed within the given range of spacing ratio. Empirical modal decomposition is also applied to further analyze the vibration characteristics of galloping and VIV in RWIV. When the system shows galloping, the number of decomposed modes is larger with the increasing reduced velocity, and different vibration modes show evident mutual anisotropy. In addition, the vortex line diagram is used to analyze the wake vortex characteristics of the RWIV and to supplement the above findings.

Numerical analysis of thin cylindrical shell vibrations with a weak nonlinearity

Numerical analysis of thin cylindrical shell vibrations with a weak nonlinearity

Improved criteria for evaluating impact targets in regulative drop tests of dangerous goods packagings

AbstractFor dangerous goods packagings, drop testing onto an essential unyielding target can be used to assess the mechanical resistance to impact loads. Adopted regulations like Agreement concerning the International Carriage of Dangerous Goods by Road (ADR)/Regulation concerning the International Carriage of Dangerous Goods by Rail (RID) require that the impact surface provided shall be integral with a mass at least 50 times than that of the heaviest package to be tested. The problem is that many manufacturers do not possess impact targets that satisfy the required 50 times mass ratio for regulative drop tests during series production. The objective of this work is to verify existing and define improved criteria for impact target structures based on systematic investigations. Previous evidence highlights the relevance of other parameters in addition to the mass ratio. Therefore, in this research, a variation of drop test parameters was carried out experimentally. Furthermore, numerical vibration analysis was applied to investigate the deformability of the impact surface. The results conclude that the mass ratio of 1:50 cannot be defined as a decisive criterion. In order to determine the influence of further drop test parameters, the research findings were used to validate a parametric model that assesses impact target deflection. An approximation quality of over 90% was achieved. As a result, new evaluation criteria are proposed. First, a method for identifying critical impact target designs is provided. Second, a new comprehensive formula compares the approximated maximum deflection of a real impact target to the respective theoretical threshold derived from a worst‐case assumption. In practice, this leads to great advantages in the evaluation of already installed impact targets for dangerous goods packagings.

Numerical and experimental analysis of stable, unstable, and limit cycle spiral vibrations

In rotating machinery, non-uniform temperature distribution or hot spots on the rotor surface can induce spiral vibrations. In this paper, a novel experimental apparatus is used to analyze the influence of a hot spot on the dynamic behavior of a flexible rotor supported by oil journal bearings. The hot spot is generated using an induction system with controlled amplitude and phase shift with respect to the vibration vector. Hence, it was possible to mimic phenomena like the Morton effect or the Newkirk effect. Different types of spiral vibrations were experimentally reproduced: stable, unstable and limit cycle. In the latter case, the vibration vector describes a closed loop when plotted in a polar plot. Therefore, the present work isolates the phenomenon of spiral vibrations from the complexity of the physics behind the generation of hot spot whether this source is the viscous shearing, rotor rubbing, or eddy current losses in magnetic bearings.Moreover, a theoretical model is derived to gain insight on the mechanisms driving spiral vibrations especially the role that the phase shift between the hot spot and the vibration vector plays in the stability of the system. Theoretical and experimental stability maps obtained for sub-synchronous and super-synchronous angular speeds are in excellent agreement. Additionally, the notion of thermal period, i.e., the period that govern the oscillation of the vibration vector is introduced. A concept never addressed before. It was found that this thermal period depends not only on the thermal inertia of the rotor, but also on the amplitude and phase shift of the hot spot, the distance to the critical speed and the damping ratio.

Experimental and Numerical Analysis of Triply Coupled Vibration of Thin-Walled Beam with Arbitrary Closed Cross-Section

In this paper, a numerical experimental study about coupled vibration and natural frequency of thin-walled beams with an arbitrary closed cross-section is presented. A new thin-walled beam dynamic transfer matrix method, named TDTMM, is presented in the frequency domain for the thin-walled beam, which expands the advantages of the general dynamic transfer matrix method (GDTMM). The theory takes into account the influence of warping effect, that is, both the bimoment B and the rate of twist ϕ(x) of the beam are considered, and the TDTMM is derived by solving the governing differential equations of motion for coupled bending and torsional vibration of the thin-walled beam. Finally, two numerical examples and one experimental example are given and compared with the GDTMM and the finite element method (FEM) results to validate the developed theory.

Numerical analysis and experimental research of vibration and noise characteristics of oil-immersed power transformers

Oil-immersed power transformers play a prominent role in power grid system, and its vibration and noise influence the operation of the power grid. In this paper, an electromagnetic–mechanical-acoustic coupled three-dimensional finite element method of oil-immersed transformer is established. On this basis, according to a noise and vibration experiment of product-level oil-immersed power transformer, it not only proves the effectiveness of the calculation model, but also explores the influences of the radiating grilles and input voltage on the vibration and noise characteristics of the oil immersion transformer quantitatively. Research shows that the main frequency components of transformer vibration and noise focus on 100 Hz and its higher and integer multiple frequencies. The errors of total vibration acceleration level and overall sound pressure levels between the simulation results and test results do not exceed 3 dB, which verify the effectiveness of the numerical method.

Numerical analysis of impact vibration based on a bifurcation diagram with two varying control parameters

Numerical analysis of impact vibration based on a bifurcation diagram with two varying control parameters

Numerical Analysis of Flow-Induced Vibration and Noise Generation in a Variable Cross-Section Channel

Numerical Analysis of Flow-Induced Vibration and Noise Generation in a Variable Cross-Section Channel