Transverse Vibration Response Research Articles

Transverse Vibration Response and Time-Varying Analysis of Axially Moving Beams Based on Choi–Williams Distribution

Cantilever beams with axial extension and contraction functions as time-varying parameter systems have attracted extensive research due to their prevalence in engineering structures. In this paper, the dynamic characteristics of the flat-push bridge mechanism are investigated from the theoretical aspect, firstly, it is simplified into a cantilever beam model with axial motion, and the transverse vibration equations of the cantilever beam are established based on the Euler–Bernoulli beam theory and D’Alembert’s principle, and the transverse displacements of the beam are discretized using the Galerkin truncation method and solved numerically by using the Newmark-[Formula: see text] method for the second-order vibration differential equations with variable coefficients; second-order vibration differential equations were solved numerically by the Newmark-[Formula: see text] method; then the structural examples in the existing literature are verified numerically, and the calculation results are consistent with the literature results, indicating that the transverse vibration equations derived in this paper are solved effectively; then a parametric analysis of the speed of the cantilever beam during axial extension/contraction was done, which showed that the faster the speed of axial motion, the faster the rate of change of the dynamic characteristics of the beam and the more pronounced the vibration; finally, the power signal is decomposed in the time-frequency domain by using the Choi–Williams Distribution (CWD), and the time-frequency characteristics of the system under different speeds are analyzed, and the results show that the use of CWD technique can accurately reflect the system’s transient vibration frequency and vibration energy with the change rule of time and speed, and the axial motion speed of ±0.05[Formula: see text]m/s, the transient frequency of the theoretical prediction and the average relative deviation between the finite element modal frequencies are kept within 5% and the recognition accuracy is high. This analysis provides flexible technical guidance for vibration control in engineering structures.

A study of controlling the transverse vibration of a beam-plate system by utilizing a nonlinear coupling oscillator

In the engineering field, prolonged exposure of complex structures to high-strength vibration environments can lead to various engineering challenges. This underscores the importance of effectively managing the vibration of complex structures. Given the extensive utilization of beams and plates in the construction of intricate structures, this study incorporates a nonlinear coupling oscillator into the beam-plate system and formulates a vibration analysis model for this system. The governing equations of the system are derived theoretically and solved numerically using the Galerkin truncation method. This study focuses on the operational modes of the nonlinear coupling oscillator based on accurate numerical results. Meanwhile, the influence of parameters belonging to the nonlinear coupling oscillator on the transverse vibration responses of the beam-plate system is systemically studied. Upon meticulous examination of the numerical results, the operational states of the nonlinear coupling oscillator encompass the normal vibration suppression mode and the quasi-periodic vibration suppression mode. The alteration in the linear elastic coupling stiffness of the beam-plate system impacts the effectiveness of vibration suppression in the nonlinear coupling oscillator. This influence stems from the fact that changes in the linear elastic coupling stiffness directly affect the nonlinear forces exerted on the beam-plate system within a nonlinear coupling oscillator. Within a feasible range, the nonlinear stiffness and viscous damping can be chosen as the adjustable parameters for the nonlinear coupling oscillator to regulate the vibration of the beam-plate system by adjusting the motion mass of the nonlinear coupling oscillator, which presents a challenge. The appropriate utilization of the nonlinear coupling oscillator demonstrates favorable control effectiveness in managing the transverse vibration of the beam-plate system. The study presented in this work offers a method to simultaneously control the vibration of each component within beam-plate coupling systems.

Vibrational behavior of a 3D printed biomimetic dual‐core composite sandwich beam: An experimental and numerical study

AbstractComposite sandwich structures have been used in various applications like aerospace, automotive, and maritime sectors. The process of identifying the core design and the selection of a prominent core is crucially important in sandwich structures. In this study, biomimetic core development and vibration responses of composite sandwich beams with a dual biomimetic honeycomb core are investigated. The composite face layers are fabricated by the hand lay‐up method, and the fused deposition modeling is used to 3D print the PLA honeycomb cores. Based on ASTM‐E1876 and the alternative dynamic approach, the face layer elastic properties and rigidity modulus of the cores are evaluated, respectively. The numerical simulation is used to predict the sandwich panels' natural frequencies and mode shapes and verified with experimental results. There was an excellent agreement between the calculated and experimental natural frequencies. Due to the presence of the core and enhanced rigidity modulus, the dual lamellar honeycomb core sandwich beam produces the highest natural frequencies among all‐composite sandwich beams, followed by the dual regular honeycomb, single lamellar honeycomb, and single regular honeycomb cores. The geometric parametric studies, including core thickness, length‐to‐breadth ratio, lamination schemes, support conditions, and transverse vibration responses were also analyzed for different sandwich patterns. As a result of this work, thick composite sandwich panels in aeronautical and marine structures can be replaced with dual biomimetic core structures. The study highlights the fact that the dual‐core sandwich beam provided greater modal frequency than the single‐core beam with the same weight proportions.Highlights Pistachio nut shell‐based biomimetic honeycomb core has been developed. Alternative dynamic approach is used to find sandwich‐core shear properties. Lamellar‐infused biomimetic model yields higher shear modulus and stiffness. Dual‐core beam having high flexural stiffness enhances the natural frequency. Various parametric studies were analyzed for different sandwich patterns.

Free and forced vibration response of a laminated composite sandwich beam with dual honeycomb core: Numerical and experimental study

AbstractFree and forced vibration characteristics of composite sandwich beams with single‐core (SC) and dual‐core (DC) are investigated in this study. The wet hand‐layup technique is followed to make the composite face sheet, and honeycomb cores are 3D printed using the fused filament fabrication method. The natural frequencies of SC and DC sandwich beams were measured using experimental modal tests and validated through a three‐dimensional finite‐element model. Also, parametric studies on the geometry of composite structures are performed to scrutinize the effect of DC sandwich beams with different ply orientations, length‐to‐breadth ratios, core thickness, and core cell wall thickness. In addition, the transverse vibration responses of SC and DC sandwich beams are examined under harmonic force excitations at different end conditions. The study result shows that the sandwich beam's vibration behavior is enhanced by the inclusion of a core.

Investigation on vibration response characteristics and influencing factors of the fuel rods of EPR

First, the theory of wet modal analysis and vibration response analysis are introduced, and the semi-empirical vibration equation is derived in this article. Then, the structural models of the fuel rod of M310 and EPR are introduced, and the fuel rod is simplified to a multi-span continuous simply supported beam model subject to multi-point constraints. The fuel rod is simplified as a simply supported beam, and the springs and dimples are equivalent to elastic constraints. In addition, based on ANSYS-APDL, the wet modal analysis and response analysis of fuel rods are carried out. The modal information and transverse vibration response of the fuel rod of M310 and EPR are compared. In addition, combined with the actual operating conditions of EPR, the effects of different transverse and axial flow velocities on the transverse vibration response are discussed. Finally, different failure conditions are designed to explore the impact of clamping failure on the vibration characteristics of the fuel rod of EPR. The results have shown that compared with the fuel rod of M310, the fuel rod of EPR has a lower natural frequency and larger amplitude; the transverse flow velocity has a greater impact on the transverse vibration response; grid failure would reduce the natural frequency of fuel rods, and different positions of failure have different effects on the different-order natural frequencies of fuel rods.

Dynamic characterization of tapered composite sandwich plate with honeycomb core: Numerical and experimental investigations

In the present study, the numerical and experimental investigations on the dynamic performance of tapered composite sandwich plates with various configurations of a honeycomb core material are presented. The tapered composite sandwich plates are considered with the tapered composite plates as face sheets and honeycomb structure with and without strip reinforcements as core materials. Various tapered composite face sheets are formulated by dropping the plies longitudinally at various locations. Further, the various honeycomb core materials are designed such that stiffeners are reinforced at various locations longitudinally and transversely within the honeycomb patterns to enhance the stiffness and damping properties. Higher order Shear Deformation Theory (HSDT) is used to derive the governing differential equations of motion of the various honeycomb tapered composite sandwich plate and solved numerically. Experimental tests are performed to identify the various mechanical properties of composite face sheets and core materials. Various composite sandwich plates are also fabricated to perform the modal analysis and identify the dynamic properties. The effectiveness of the developed numerical model is demonstrated by comparing the natural frequencies and loss factors identified through experimental tests on the prototype sandwich plates. Various parametric studies are also performed to investigate the effect of strip reinforcement in the honey comb patterns, ply drop off and taper angle of face sheets, aspect ratio of sandwich plates, ply orientation of face sheets and boundary conditions on the free vibration characteristics of the tapered composite sandwich plates. In addition, the transverse vibration responses of tapered composite sandwich plates under harmonic force excitation are examined at different types of the honeycomb core design and the performances are compared with those obtained without the addition of composite strips to demonstrate the effectiveness of strip reinforcement in optimizing the stiffness and damping characteristics of the structures.

Transverse vibration responses of the in-plane-wise functionally graded piezoelectric composite plates

Aided by the scaled boundary finite element method (SBFEM), analytical precise integration solutions to the transverse free vibration responses of functionally graded piezoelectric composite plates are provided for the first time. Distributions of the functionally graded piezoelectric materials follow arbitrary mathematical formulae as concerns the in-plane unidirectional or bidirectional coordinates. The vibration behaviors of piezoelectric composite plates with various geometrical shapes, multifarious boundary constraints and any number of laminae can be explored by the introduced technique. Additionally, the shear correction factors and assumptions on the changing patterns of mechanical and electrical variables are not needed to be offered in the employed methodology. The proposed approach regards only four quantities containing three elastic displacement components and the electric potential as the primary unknowns, which can be denoted as an analytical matrix exponent in terms of the thickness coordinate. Only two-dimensional high-order spectral elements are adopted to discretize the in-plane surface of the plate with less nodes and degree of freedoms, which promotes to lowering the calculative expense and advancing the computational efficiency. The introduced scaled boundary coordinate system and the dual vector technology are helpful to simplify the basic partial differential equations of piezoelectric materials into the first order ordinary differential SBFEM governing equation, from which the highly accurate global stiffness matrix are constructed by dine of the precise integration technique (PIT). With the aid of the kinetic energy scheme and compatibility conditions between neighboring layers, the whole mass matrix for the laminated piezoelectric plates can be built. According to solving the eigenvalue equation, the precise integration solutions to free vibration frequencies can be acquired. Finally, numerical experiments are afforded to elucidate the high precision and fast convergence of the present method. Moreover, the effect of different boundary constraints, gradation parameters and aspect ratios on the transverse vibration responses of in-plane-wise functionally graded piezoelectric composite plates is revealed.

Study on frequency domain response characteristics of straight pipe conveying fluid

In this paper, a transfer matrix method (TMM) for solving the frequency domain response of the straight pipe conveying fluid is established based on 14-equation model by Laplace transformation. The reliability of the method is verified by the frequency domain response results of fluid velocity and structural axial stress in the pipe under free boundary conditions. Then, based on the transfer matrix method, the influence of boundary conditions and fluid density on the frequency domain response characteristics of pipeline vibration is analyzed. The numerical results show that the boundary conditions have a significant effect on the amplitude of the vibration response of the pipeline, but the amplitude changes little under the fixed and simply supported boundary conditions. The vibration frequency is inversely proportional to the density, while the axial vibration response amplitude increases with the increase of fluid density, and the change of density has little effect on the transverse vibration response.

Vision-based transverse vibration displacement measurement of hoisting vertical ropes in mine hoists

At present, there is no appropriate way to measure the transverse vibration response of moving hoisting vertical rope in hoist. Therefore, a vision-based measurement method combining the digital image correlation (DIC) and digital image processing (DIP) algorithms is proposed in this paper. In this method, a reference line perpendicular to the vertical ropes is added in image sequence by DIP algorithm to form some virtual cross targets, which makes the improved DIC algorithm with adaptive template updating (ATU) rule can track the moving hoisting vertical rope without any labels. Then for distinguishing all ropes in the measuring area, a displacement threshold is set to locate the current measured rope and exclude the other ropes. The transverse vibration displacements of the hoisting vertical rope in an actual mine hoist was measured in three background situations, verifying the feasibility of the proposed method. Moreover, in a laboratory artificial vibration test, the measurement results from the proposed vision method and a laser displacement sensor yielded a very good agreement. The two experimental results indicate that it is fairly reasonable and effective to measure the transverse vibration displacements of hoisting vertical ropes.

Transverse Vibration of Geared-Rotor Integrated With Active Magnetic Bearings in Identification of Multiple Faults

Abstract This paper presents a novel concept of the modeling, active control of transverse vibration responses, and identification of fault parameters in a geared-rotor system integrated with active magnetic bearings (AMBs). The sources of error in gears while in the operation are the gear mesh deformation, transmission error, and runout, resulting in dynamic forces, excessive vibration, and noise. To avoid any undesirable effect on the gear-pair and other supporting structures, it is essential to investigate these forced vibrations in time and frequency domain. Hence, an approach to monitor and control the transverse vibration of mating gears is presented with the help of AMBs. The AMBs are capable of suppressing the vibration of the system (transients as well as steady-state) by controlled electromagnetic forces considering the rotor vibrational displacement with a closed-loop feedback system. A mathematical model has been developed with geared rotor faults, like the mesh deformation, gear run-out, and asymmetric transmission error. The transmission error has been modeled as the sum of mean and varying components of error in two orthogonal transverse directions. Based on the mathematical model, an identification algorithm has been developed. Considering full spectrum analysis of the rotor vibration and AMB current information, estimation of system parameters, i.e., the equivalent mesh stiffness, mesh damping, gear runouts, the mean and varying transmission error magnitude and phase angles, and the current and displacement constants of AMBs has been performed. Gaussian noise in responses and modeling errors in mathematical models have been added to test the robustness of the proposed algorithm to comply with the experimental settings.

Investigation of bone fracture diagnosis system using transverse vibration response.

In this study, a new diagnostic system is developed to easily identify bone fractures in non-medical environments. It is difficult to determine the extent of cracks, fractures, and the healing process inside humans owing to the differences among people and limitations of state-of-the-art medical devices. Thus, various medical techniques, such as X-ray, computed tomography, or fork tuning systems have been developed, and more advanced technologies are emerging in the medical engineering field. In hazardous circumstances, medical devices to detect bone fracture are not available or cannot be easily applied. Thus, there is a need for the rapid detection of bone fractures without medical devices. To this end, this study analyzes the transverse vibration responses of bones because bone fractures cause different mechanical vibration reactions. By comparing the transverse vibration responses of both healthy and fractured bones, the modal assurance criterion can be calculated and applied to detect the existence of bone fractures. The transverse vibration responses at low and high frequencies are different and exhibit different modal assurance criteria depending on whether or not they are abnormal. Then, the virtual spectrogram of the differences between the signals from non-fractured and fractured bones is calculated. With the help of the present criterion with transverse vibration data, this difference can be analyzed quantitatively and effectively. To validate the proposed system, experiments with artificial specimens, animal legs, and a cadaver are performed.

Assessment on dynamic characterization of the cylindrical laminated composite shallow shell panel through experimental and numerical approach

In the present study, the dynamic characterization of the glass fiber-reinforced polymer (GFRP)-laminated composite cylindrical open shallow shell panels is explored with the experimental and numerical approach. In the finite element modeling (FEM), the governing equilibrium equation of the cylindrical shell panel is developed with higher-order shear deformation theory by considering the nine-noded rectangular elements. The convergence and validation study of the present FEM is accomplished with the available literature. The cylindrical laminated composite shallow shell panels are fabricated with a curvature radius of 0.8 m, and the experimentation on the free vibration investigation is performed with various boundary conditions; then, the experimental outcomes are compared with the present FEM to verify the effectiveness. The detailed parametric investigation is executed to explore the impact of curvature radius (R), boundary conditions, thickness ratio, aspect ratio (L/B), and stacking sequence on the structural response of the cylindrical laminated composite shallow shell panel. Transverse vibration response of the GFRP cylindrical laminated composite shallow shell panel is also performed with the various curvature ratios at clamped at all end conditions.

An Analytical Procedure to Predict Transverse Vibration Response of Jack-Up Riser under the Random Wave Load

Marine riser is a key equipment in offshore drilling operation, and failure of the riser can lead to drilling moratorium; in severe cases, it may cause oil and gas leaks. In this paper, the time-dependent boundary conditions of the riser and the randomness of wave load are considered to improve the calculation efficiency and accuracy of the dynamic response of the jack-up riser. Based on the Euler–Bernoulli beam theory, an analytical method to determine the response of the jack-up riser subjected to the random wave load was established by the Mindlin–Goodman method in the frequency domain, and an experiment was carried out to verify it. The research shows that transverse dynamic response is the main component of the transverse response of the riser, and the method proposed is feasible to calculate the transverse response of the riser.

The Fairing Arrangement for Vortex Induced Vibration Suppression Effect in Soliton Current

Qi, X.; Zhang, D.; Guo, H., and Chen, Y., 2020. The fairing arrangement for vortex induced vibration suppression effect in soliton current. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 293–298. Coconut Creek (Florida), ISSN 0749-0208.For oil and gas industry, the riser is an important device connecting the subsea wellhead platform and the production system. Due to its slender nature, it is easily affected by the vortex-induced vibration of the ocean current, which poses a potential danger to the safety of the entire system. Soliton current is a special environmental factor to be considered during riser operation. A faring system have been development and do some test to verify its performance in the previous literature. In this paper, based on the obvious effect for the fairing system to reduce the vortex induced vibration, it has been simulated for the different arrangement for a riser that running under the soliton current. Then it is indicated that cover 57% of the whole length of riser is a cost-effective arrangement suggestion. This arrangement could reduce the transverse Vortex-induced vibration (VIV) response obviously. The maximum ratios of RMS Amplitude divided by External Diameter (A/D) and stress was reduced to 20% compared to the bare one.

Transverse nonlinear vibration of the eccentric rotor in a 12/8 switched reluctance motor

PurposeTo investigate transverse vibration of the eccentric rotor in a 12/8 poles switched reluctance motor (SRM), a transverse analytical vibration model is built by finite element method (FEM) under the interaction of radial magnetic resultant and vibration displacement. External forces, including radial magnetic resultant and centrifugal force, are also derived in detail, according to the variation of airgap and current and other intermediate parameters with rotation angle.Design/methodology/approachThe transverse vibration response of the eccentric rotor including radial magnetic resultant and vibration displacement is solved by Newmark-β method, after inputting the currents of three phase windings under angle position control strategy. The basic characteristics of radial magnetic resultant and vibration displacement are reflected in time and frequency domain.FindingsThe magnetic resultant vector of the eccentric rotor presents multi-petals star geometric shape. The frequency distribution of magnetic resultant relates to rotation speed, current waveform and the least common multiple of the stator and rotor teeth. However, the frequency distribution of the vibration displacement also relates closely to the first-order critical whirl speed of the rotor. When the rotor is running at certain speeds, it will display superharmonic resonance and show abundant displacement locus.Originality/valueBy using this analytical model and solving process proposed in this paper, the nonlinear coupled vibration response of the eccentric rotor in SRM can be analyzed and discussed rapidly; only the stator’s winding currents obtained by experiment or electromagnetic simulation is needed as input.

Ground Vibration Test and Dynamic Response of Horseshoe-shaped Pipeline During Tunnel Blasting Excavation in Pebbly Sandy Soil

In order to ensure the safety of horseshoe-shaped pipeline during tunnel blasting excavation, the vibration test and dynamic response of horseshoe-shaped pipeline were investigated. The velocity and frequency of tunnel blasting vibration were analyzed. Sodev's empirical formula was used for regression analysis of the velocity of blasting vibration. 3D numerical model of a horseshoe-shaped pipelines was established with ALE algorithm using ANSYS/LS-DYNA. The propagation law of a blasting seismic wave was analyzed, and the transverse and longitudinal vibration response characteristics of pipelines under tunnel blasting vibration were studied. The velocity of the pipeline increases gradually and the frequency tends to decrease with the decrease of the distance away from the explosion source center under the same charge. The principal frequency of vibration in the Z direction is mainly distributed from 50 to 80 Hz, which is difficult to generate resonance with the pipelines. The maximum relative error between the simulated and measured velocity of X, Y and Z directions was 8.2%. It was reliable to study the dynamic response of pipelines under blasting vibration based on this numerical model. The blasting seismic wave first reached the bottom of the pipeline right above the explosive. Subsequently, seismic waves propagated along the transverse and the longitudinal axes of the pipeline, and the pressure on the pipeline increased gradually. And when it attenuated completely in the soil, the pipeline stopped its response. The peak value of tensile stress of each element of the vault is the largest. However, the velocity of the bottom plate and the arch roof of pipeline are the largest. The peak values of velocity and tensile stress exist in 0 to 4 m away from the explosion source, and gradually decrease as the distance away from the explosion source increases.

Vibration analysis of the multi-walled carbon nanotube reinforced doubly curved laminated composite shallow shell panels: An experimental and numerical study

In this study, free and forced vibration analysis of the multi-walled carbon nanotube reinforced doubly curved laminated composite shallow shell panels has been performed. The governing differential equation of motion of the doubly curved laminated composite shallow shell panel is formulated using higher order shear deformation theory with the Lagrangian approach. In a finite element formulation , the mathematical model is derived with a nine-node quadrilateral element considering seven degrees of freedom at each node. The efficiency of the present finite element model (FEM) is demonstrated and compared by validating the results with the available literature, and it is also compared with the experimental measurements of the cylindrical laminated composite shell panel with and without multi-walled carbon nanotube reinforcement. Material properties of the laminated composite structure with and without multi-walled carbon nanotube reinforcements are evaluated through the impulse excitation vibration test in accordance with the ASTM E1876-15. The influence of multi-walled carbon nanotube on the stiffness and structural integrity of the curved laminated composite shallow shell panels is also studied in terms of natural frequencies. Parametric analysis for the multi-walled carbon nanotube reinforced doubly curved laminated composite shallow panel is performed to study the influence of radius of curvature, shell geometry, thickness ratio, aspect ratio, stacking sequence, and the boundary conditions on structural performance. The forced vibration behavior of the curved composite shallow shell panel is studied with the different geometry configuration, and the influence of multi-walled carbon nanotube in the transverse vibration response is also studied. It has been concluded that the rigidity and structural performance of the doubly curved laminated composite shell panels are enhanced with the reinforcement of multi-walled carbon nanotube.

Numerical investigation on transverse vibration responses of non-uniform composite plates

In this study, the numerical investigation on the traverse vibration responses of the non-uniform composite plates is performed using a finite element method. The First-order shear deformation theory (FSDT) is used to formulate the governing differential equations of motion of various non-uniform composite plates. The material damping effects are included in the formulation by including material properties as a complex elastic modulus in terms of storage modulus and loss modulus. The dynamic response of various non-uniform configurations under harmonic forced excitation is studied and the design guidelines are provided to identify the suitable non-uniform composite configurations.

Transverse nonlinear vibration modeling and response of eccentric rotor in a switched reluctance motor

In order to investigate the transverse vibration of eccentric rotor in a 12/8 switched reluctance motor (SRM), a whole nonlinear coupled vibration equation of eccentric rotor is built with finite element method (FEM). Based on single tooth radial force and the key parameters variation with rotor position, an analytical formula of magnetic resultant taking into account of the rotor’s vibration displacement is deduced in detail, which is applied onto the intermediate node of eccentric rotor in form of concentrated force. Once the windings currents obtained either by experiments or numerical simulations is input, the vibration response can be solved numerically by Newmark-[Formula: see text] method. Six phase windings currents under angle position control (APC) strategy are chosen as an example and the vibration response are discussed to reflect intrinsic vibration characteristics. From radical resultant vector and its amplitude spectrum, it is proved that the magnetic resultant vector presents multi-petals star shape. The frequency components in magnetic resultant are [Formula: see text], [Formula: see text], and [Formula: see text], [Formula: see text], related to rotational speed, current waveform and minimum common multiple of stator and rotor teeth. However, from displacement locus and its amplitude spectrum, the frequency component of the rotor vibration displacement is also related to the critical whirl speed of the rotor. Transverse superharmonic resonance of eccentric rotor appears at some particular rotational speed and result in a larger rotor vibration. If the rotor runs at the superharmonic speed of 1/19 of first-order critical whirl speed, the maximum vibration displacement radius of the eccentric rotor reaches almost four times that of the rated speed. The vibration locus at these particular speed show rich diversity.

Stationary and flow-induced vibration of two elliptic cylinders in tandem by immersed boundary-MRT lattice Boltzmann flux solver

Numerical method, combining immersed boundary method and multi-relaxation-time lattice Boltzmann flux solver, is used to carry out flow-structure interaction problems in this paper. Without dynamic mesh technique and body fitted grid re-generation, the flow-structure interaction problems can be solved by Cartesian mesh in order to simplify calculation process and save computation time. The accuracy and rationality of this method are verified by comparison of force coefficients, vibration amplitudes and flow characteristics with previous numerical results. Numerical simulations of two stationary and flow-induced vibration elliptical cylinders in tandem are carried out in laminar flow. For two stationary elliptical cylinders, the existing of downstream elliptical cylinder effectively prevents the unsteady characteristic of upstream wake at small gap spacing. With the increase of aspect ratio, the critical gap augments. After reaching the critical gap, the upstream force coefficients decrease and the downstream ones increase as aspect ratio increasing. Flow characteristic presents three regimes, including steady flow, shear layer attachment and 2S shedding vortex and 2S or C(2S) shedding vortex. For two flow-induced vibration elliptical cylinders, in comparison with stationary simulations, upstream transverse vibration responses are strengthened and downstream ones are strengthened at larger gap spacing and aspect ratio. The in-line vibration responses are both weaken, especially for downstream bluff body. Flow characteristic show different flow-regimes: (a) shear layer attachment for upstream and 2S shedding vortex for downstream; (b) 2S shedding vortex for upstream and C(2S) shedding vortex for downstream; (c) 2S shedding vortex for upstream and vortex pair presenting in the downstream wake. Greater L/D and AR, the effects of upstream wakes on downstream elliptical cylinder are more intense.