Vibrational Transfer Research Articles

Flow-induced vibration and heat transfer characteristics of three elliptical cylinders arranged in an isosceles triangle

This study investigates the flow-induced vibration (FIV) and heat transfer behavior of three heated cylinders arranged in an isosceles triangle configuration at a Reynolds number of 100. A dynamic model for the FIV of two-dimensional, elastically supported cylinders was developed using computational fluid dynamics simulations and overset mesh technology. The effects of aspect ratio (AR) and angle of attack (α) were examined by varying α from 30° to 90° and AR from 0.75 to 2.0, with AR = 1.0 corresponding to a circular cross section. To study FIV, the two-degree-of-freedom motion of the cylinders was analyzed across a range of reduced velocities (Ur = 2–12). The results indicate that as α increases, the impact of the upstream cylinder's wake on the downstream cylinders gradually weakens, resulting in lower vibration amplitudes and higher heat transfer rates for the downstream cylinders. Notably, when α reaches 90°, the streamwise amplitude becomes almost negligible. At α = 30° and 45°, the average Nusselt number of the downstream cylinder is generally lower than that of the upstream cylinder. However, when α reaches 60°, the average Nusselt number of the downstream cylinders becomes noticeably higher than that of the upstream cylinder. As the aspect ratio increases, the lock-in region of the cylinders shifts from being concentrated at Ur = 6 and 8 to Ur = 4 and 6, indicating that the increase in aspect ratio raises the vortex shedding frequency.

Modeling and Contribution Analysis of Vibration Transfer Paths for a Dual-Rotor Aeroengine

Modeling and Contribution Analysis of Vibration Transfer Paths for a Dual-Rotor Aeroengine

Vibration source inversion-based fault diagnosis: approach and application

The gear transmission system of industrial equipment is characterized by a highly integrated structure, non-stationary operating conditions, and large loads. Therefore, the attenuation of fault signal characteristics and the complexity of operating conditions in gear transmission systems significantly affect the effectiveness of vibration signal-based fault diagnosis. This paper proposes a unified diagnostic framework based on vibration source inversion for two typical transmission component fault signal phenomena: meshing frequency modulation sidebands and equally spaced fault characteristic frequency interval harmonic clusters. This approach incorporates the vibration transfer path analysis of passive subsystems and identifies bearing dynamic forces, followed by their decomposition, reconstruction, and sensitive frequency band localization. It enables accurate diagnosis of complex gear transmission systems under non-stationary conditions with limited vibration testing. The effectiveness and advantages of this method over existing mainstream signal processing techniques are validated through actual cases of gear and weak bearing fault diagnosis on a complex planetary gear transmission system test bench.

Numerical investigation of the effect of the structure and number of spiral baffles on the vibration and heat transfer coefficient of spiral tubes within spiral tube heat exchangers

In response to the advantages of compactness and high efficiency of spiral elastic tube heat exchanger and its easy-to-vibrate characteristics, this study aims to further improve its heat transfer efficiency by utilizing fluid-induced vibration-enhanced heat transfer technology, so a design scheme of reverse baffle spiral tube heat exchanger (RB-STHE) is proposed to enhance the turbulence characteristics of the shell-side fluid by installing spiral baffles, thus promoting the vibration of the spiral tube. In this study, four new types of the RB-STHE (Model A, B, C, and D) were used as research objects, and the two-way fluid–structure coupling calculation method (using CFX and Transient Structure software) was adopted to systematically investigate the effect of fluid-induced spiral tube vibration on the comprehensive heat transfer coefficient (HTC) of the RB-STHE under different flow velocities and structure schemes, and based on the research data, the objective of no reduction in the comprehensive HTC and savings in the use of materials is taken as the goal, so as to put forward the improved Model C-1. The results show that: although the fluid-induced spiral tube vibration can effectively improve the HTC of the spiral tube, it also increases the pressure drop in the RB-STHE, and the larger the amplitude, the higher the degree of influence; among them, Model C is most affected by the spiral tube vibration, and its HTC and pressure drop are maximally enhanced by 6.33% and 5.85%, respectively. The change in the number of baffles has a significant effect on the comprehensive HTC of the RB-STHE. Compared to the Model D without a spiral baffle, the maximum improvement in the comprehensive HTC of Model C with one spiral baffle installed in the RB-STHE is 14%, while the Model A with four spiral baffles and the Model B with two spiral baffles have a maximum reduction in the comprehensive HTC of 20% and 3%, respectively. In addition, compared to Model C, the structure improved Model C-1 significantly reduces the size of the spiral baffle while effectively maintaining the comprehensive HTC of the RB-STHE, making the structure more reasonable, which provides a reference for heat exchanger design.

Theoretical and experimental study of active vibration control of rotating composite laminated beams using Fx-NLMS algorithm

In the study, an adaptive active vibration control model of rotating composite laminated beam is presented by using the filtered-x normalized least mean square (Fx-NLMS) algorithm, and the experimental study is carried out based on the closed-loop control system. The macro fible composite (MFC) patches is employed to contruct the closed-loop control system of rotating composite laminated beam. By considering peizoelectric coupling effect and the influence of rotating angular velocity, the novel analysis model of vibration transfer function of rotating composite laminated beam with MFC patches is established. The calculation accurancy of the theoretical analysis model is validated by the experimental results. The experimental and simulation studies demonstrate that the low-frequnecy vibration of rotating composite beam is effectively controlled by using the lightweight system. The excellent stability and convergence effect of the closed-loop control system are obtained in the experimental testings. Moreover, the filter orders and learning factor on the active vibration control effect of the rotating composite beam are also stuided and discussed. This work provides a novel appoach for the low-frequency vibration control of the rotating cantilever beams by employing lightweight system.

Flow induced vibration with forced convection of a stationary and oscillating filleted bluff bodies in a staggered position

Flow induced vibration (FIV) and forced convection heat transfer from staggered cylinders are numerically investigated with Re = 150 and Pr = 0.7. Cylinders are arranged in a staggered manner with three different stagger angles (α) = 15°, 30°, and 45°. The upstream cylinder (UC) is kept fixed while the downstream cylinder (DC) is mounted. The cross section of the bluff body is altered by parameter (r*) = 0 (square cylinder), 0.5, 0.75, and 1 (circular cylinder). For every stagger angle and r*, the reduced velocity is varied from 2 to 10. The mass ratio (m*) of the DC is kept at 10 and damping constant set to zero for maximum vibrational amplitude. The incompressible Navier–Stokes equations are coupled with Newton's equation for the mass-damper system of the vibrating cylinder. Flow induced vibration was studied with the help of frequency characteristics, dynamics response of cylinders, and instantaneous phase plots of lift and amplitude. Generally, in the case of square cylinders a delayed response can be observed as compared to other configurations. For α=15°, the DC is fully submerged into the wake of static UC. P + S (P: pair; S: singlet)-type vortices can be observed for r* = 0. For other configurations of filleted cylinders, such as r* = 0.5, 0.75, and 1 at Ur=4, 2 parallel row formation is formed due to negative sign vortices while the other one was a combination of positive and negative vortices in pseudo-P formation. At higher Ur=6 and 8, coalesced and irregular wakes can be noticed. As the stagger angle is increased to higher than 30°, the wake of both cylinders becomes more pronounced. Due to the change in stagger angle, fs (vortex shedding frequency) of UC and DC forces decouples. 2P-type vortex shedding can be observed at Ur=4 for r* = 0.75 and 1. Pairs of vortices are coupled from each cylinder in a row where negative vortices coalesce while losing energy. For lower r* = 0 and 0.5, there is a tendency for three row formation. Further increase in angle pushed the DC completely out of the wake of the UC although vortices from both cylinders are still found to interact and exhibit three row formation and 2P-type vortex shedding. Heat transfer from the DC is highly dependent on the stagger angle. For r* = 1 and 0.5 at Ur=2, the change in Nuavg is 15% and 14.7%, respectively, when the angle changed from 15° to 45°. Heat transfer from any FIV system can be directly influenced by dynamic response, position, shape, and flow topology. The generated results are provide insight for understanding the vibrational modes and heat transfer from two bluff bodies involving fluid–structure interactions.

Numerical simulation and experimental study of the dynamic characteristics of a gas turbine rotor system with beam sea and head sea excitation

Vibration analysis is crucial for studying rotor dynamics. The gas turbine rotor system is subjected to complex alternating loads during navigation, resulting in vibrations transmitted to the bearings that alter the system’s dynamic characteristics. Based on the similarity law of the wave resistance test, a hull model was established. Beam sea and head sea tests were conducted in the towing pool to measure the acceleration response at the key positions. A finite element model of the turbine rotor system was established, and the test data were imported into the model after wavelet noise reduction and resampling to calculate the vibration response at the front and rear bearing points. The vibration responses transmitted to different locations and directions caused by beam sea and head sea conditions were analyzed. A comparison and analysis were conducted on the acceleration responses in various locations and directions under beam sea or head sea conditions. The equivalent von Mises stress distribution of the gas turbine rotor system under beam sea and head sea loads was obtained. The vibration transfer model was verified for accuracy and can be used to quickly analyze the vibration response of bearings under wave load transfer. This study provides a theoretical basis and reference for enhancing the stability of the gas turbine rotor system.

Dynamic behaviors of multiphase vortex-induced vibration for hydropower energy conversion

To satisfy the growing electricity demand, continuous and stable hydropower conversion is particularly critical in tidal power station operation. In the above industrial application, multiphase vortices will be formed, and they suck air and floating items into the flow tube, thus causing irregular pulsation that affects turbine performance. Due to nonlinear characteristics of gas-liquid coupling transfer, dynamic modeling and transition behavior of the multiphase vortex-induced vibration have improtant difficulties. This paper conducts a fluid-structure mechanic optimization model with the dynamic mesh technology to investigate multiphase vortex-induced vibration (MVIV) dynamic behaviors and reveal the internal relation between displacement responses and multiphase flow states. The fluid-induced vibration sensing platform is developed to validate MVIV transition behaviors, and a wavelet packet signal analyzing approach is adopted to acquire energy-spectrum distribution regularities of the vibration distortion state. Results show that the presented optimization modelling strategy can well obtain the MVIV transition behaviors and energy transfer mechanism. The flow flux can control the Ekman transfer intensity, and vibration energy waves take on various frequency components at the critical penetration state. Moreover, impulse energy components and structure evolution properties of high-frequency bands can be utilized to recognize the MVIV distortion peak. It can supply theoretical guidance and technology support for hydropower conversion.

Entropy generation in newtonian vs non-newtonian nanofluid flow under vibration

Numerical investigation into the effects of vibration on heat transfer and entropy generation in Newtonian and Non-Newtonian nanofluid flows through pipes reveals enhanced heat transfer via intensified fluid agitation and improved particle dispersion. Thermal entropy generation analysis shows reduced irreversibility in vibrated flow, indicating improved flow mixing. Vibration enhances heat transfer by intensifying fluid agitation and promoting particle dispersion near the wall, resulting in a significantly more uniform temperature distribution along the pipe, approximately 100 times more than steady-state flow. This study underscores vibration’s potential to optimize heat transfer and reduce entropy generation in nanofluid systems, emphasizing velocity and rheological impacts. Comparison of vibrated flow to steady-state flow for Newtonian and non-Newtonian fluids reveals significant improvements under vibration, particularly at lower Reynolds numbers where non-Newtonian fluids exhibit pronounced effects. Future research directions include exploring thermal radiation’s impact on entropy generation, analyzing different nanofluid compositions, and investigating varied boundary conditions and geometries to advance understanding in this field. This study provides valuable insights into the complex interplay among vibration, fluid dynamics, and heat transfer in nanofluid flows. Its findings have practical implications for optimizing thermal management systems in diverse engineering applications.

Distinct vibrational motions promote disparate excited-state decay pathways in cofacial perylenediimide dimers.

A complex interplay of structural, electronic, and vibrational degrees of freedom underpins the fate of molecular excited states. Organic assemblies exhibit a myriad of excited-state decay processes, such as symmetry-breaking charge separation (SB-CS), excimer (EX) formation, singlet fission, and energy transfer. Recent studies of cofacial and slip-stacked perylene-3,4:9,10-bis(dicarboximide) (PDI) multimers demonstrate that slight variations in core substituents and H- or J-type aggregation can determine whether the system follows an SB-CS pathway or an EX one. However, questions regarding the relative importance of structural properties and molecular vibrations in driving the excited-state dynamics remain. Here, we use a combination of two-dimensional electronic spectroscopy, femtosecond stimulated Raman spectroscopy, and quantum chemistry computations to compare the photophysics of two PDI dimers. The dimer with 1,7-bis(pyrrolidin-1'-yl) substituents (5PDI2) undergoes ultrafast SB-CS from a photoexcited mixed state, while the dimer with bis-1,7-(3',5'-di-t-butylphenoxy) substituents (PPDI2) rapidly forms an EX state. Examination of their quantum beating features reveals that SB-CS in 5PDI2 is driven by the collective vibronic coupling of two or more excited-state vibrations. In contrast, we observe signatures of low-frequency vibrational coherence transfer during EX formation by PPDI2, which aligns with several previous studies. We conclude that key electronic and structural differences between 5PDI2 and PPDI2 determine their markedly different photophysics.

Vibration Transfer in Spatially Separated Thin-Film Graphene Resonators

Vibration Transfer in Spatially Separated Thin-Film Graphene Resonators

Bandgap Calculation and Experimental Analysis of Piezoelectric Phononic Crystals Based on Partial Differential Equations.

Focusing on the bending wave characteristic of plate-shell structures, this paper derives the complex band curve of piezoelectric phononic crystal based on the equilibrium differential equation in the plane stress state using COMSOL PDE 6.2. To ascertain the computational model's accuracy, the computed complex band curve is then cross-validated against real band curves obtained through coupling simulations. Utilizing this model, this paper investigates the impact of structural and electrical parameters on the bandgap range and the attenuation coefficient in the bandgap. Results indicate that the larger surface areas of the piezoelectric sheet correspond to lower center bands in the bandgap, while increased thickness widens the attenuation coefficient range with increased peak values. Furthermore, the influence of inductance on the bandgap conforms to the variation law of the electrical LC resonance frequency, and increased resistance widens the attenuation coefficient range albeit with decreased peak values. The incorporation of negative capacitance significantly expands the low-frequency bandgap range. Visualized through vibration transfer simulations, the vibration-damping ability of the piezoelectric phononic crystal is demonstrated. Experimentally, this paper finds that two propagation modes of bending waves (symmetric and anti-symmetric) result in variable voltage amplitudes, and the average vibration of the system decreases by 4-5 dB within the range of 1710-1990 Hz. The comparison between experimental and model-generated data confirms the accuracy of the attenuation coefficient calculation model. This convergence between experimental and computational results emphasizes the validity and usefulness of the proposed model, and this paper provides theoretical support for the application of piezoelectric phononic crystals in the field of plate-shell vibration reduction.

Peculiarities of reducing the broadband transfer of vibration and working medium pulsation through vibration-isolating junctions of pipelines with liquid by constructive and active methods

Peculiarities of reducing the broadband transfer of vibration and working medium pulsation through vibration-isolating junctions of pipelines with liquid by constructive and active methods

Reconstructed source method for underwater noise prediction of a stiffened cylindrical shell

The absence of excitation characteristic parameters significantly hinders the efficacy and precision of underwater noise predictions, especially under multiple excitations. Addressing this issue, a novel noise prediction reconstructed source method has been proposed for the noise analysis of a stiffened cylindrical shell. This method diverts attention from the actual sources and reconstructs the source utilizing the shell's vibrational response and transfer functions. The structural vibration response induced by the reconstructed source remains congruent with the actual behavior. The issue of non-unique solutions inherent in the reconstructed source is resolved through the application of the least squares principle. With the reconstructed sources and the stability of the transfer functions, underwater noise prediction becomes readily attainable. The method has been substantiated via an experiment from a stiffened cylindrical shell. The results indicate that the noise predictions derived from the reconstructed source method exhibit excellent agreement with experimental data, the overall level error of noise prediction is up to 0.7 dB. Furthermore, in comparison to the BEM, this method significantly enhances the efficiency under identical computational settings, with the prediction duration constituting a mere 1% of that required by the BEM.

Exploring heat transfer augmentation and entropy generation in nanofluid flow induced by vibration: Influence of velocity and rheological properties

This study numerically investigates the heat transfer and entropy generation of nanofluid flow under mechanical vibration, employing approved formulations to model the nanofluid density, specific heat, viscosity, and conductivity. Specifically, the impact of vibration on laminar forced convection thermal flow of both pure water and Al2O3-water nanofluid within a pipe is explored using CFD. Various Reynolds numbers are examined under constant heat flux conditions, with nanofluid properties determined using established correlations. Results indicate that applying Al2O3 nanofluid slurry instead of pure water at low Reynolds numbers reduces entropy generation, proving advantageous. Vibration enhances heat transfer by intensifying fluid agitation and promoting particle dispersion near the wall, resulting in a significantly more uniform temperature distribution along the pipe, approximately 100 times more than steady-state flow. Analysis reveals vibration’s effectiveness in reducing irreversibility, especially at lower Reynolds numbers, with substantial enhancements in heat transfer coefficients, up to approximately fivefold compared to steady-state flow, particularly for nanofluid flows. Optimal conditions for maximizing heat transfer enhancement emphasize nanoparticle size and concentration. Mechanical vibration with different frequencies produces significant improvements in heat transfer compared to amplitude variations, primarily influenced by the Reynolds number. Overall, this study offers valuable insights into the intricate relationship between vibration, fluid dynamics, and heat transfer in nanofluid flows, with practical implications for optimizing thermal management systems across various engineering applications.

Vibration Characteristics and Mesoscopic State Evolution of Ballasted Track During Dynamic Stabilizing Operation

Dynamic stabilization of large machines is necessary procedures before the commencement of operations railway lines that are newly built. However, limited or no studies have been carried out to reveal the operational mechanism from the vibration transfer characteristics of ballasted track subjected to excitation by stabilizing machines. The focus of this study is to solve this shortcoming. First, a typical new railway line was selected to test the dynamic response of the ballasted track during stabilizing operation, and then a stabilizing machine-ballasted track model was established with the help of the DEM-MBD coupling method. And the biaxial vibration accelerometers were inserted at various locations in the ballast bed to monitor the evolution of the vibration level on real-time basis. The influence of the stabilizing operation process on the vibration transmission and attenuation characteristics of sleeper and ballast bed was explored using wavelet analysis and Fast Fourier Transform method. The vibration absorption capacity and energy dissipation characteristics of the ballasted track under various stabilizing frequencies were analyzed. At the same time, the contact state and movement posture of ballast particles during the stabilizing operation were explored. Results showed that the vertical vibration attenuation rate of the slope toe of the ballast bed after the first stabilizing machine pass is 92.32%, while the vertical vibration attenuation rate of the second stabilizing machine is reduced by 3.14%. The second stabilizing machine can cause a large lateral movement of the ballast at the bottom of the sleeper. Under the excitation of 25[Formula: see text]Hz stabilizing frequency, it was observed that, the vibration absorption capacity of the ballast bed at the bottom of the sleeper is high, the vibration level at the ballast bed slope is low, and the stability is better. This is the optimal frequency for the stable operation of the new railway. This study can provide theoretical support for the establishment of the internal correlation mechanism between the vibration characteristics of stabilizing machines and the mechanical state of the ballast bed.

Vibration transfer from underground train to multi-story building: Modelling and validation with in-situ test data

Excessive underground train-induced vibration becomes a serious environmental problem in cities. To investigate the vibration transfer from an underground train to a building nearby, an explicit-integration time-domain, three-dimensional finite element model is developed. The underground train, track, tunnel, soil layers and a typical multi-story building nearby are all fully coupled in this model. The complex geometries involving the track components and the building are all modelled in detail, which makes the simulation of vibration transfer more realistic from the underground train to the building. The model is validated with in-situ tests data and good agreements have been achieved between the numerical results and the experimental results both in time domain and frequency domain. The proposed model is applied to investigate the vibration transfer along the floors in the building and the influences of the soil stiffness on the vibration characteristics of the track-tunnel-soil-building system. It is found that the building vibration induced by an underground train is dominant at the frequency determined by the P2 resonance and influenced by the vibration modes of the building. The vertical vibration in the building decreases in a fluctuant pattern from the foundation to the top floor due to loss of high frequency contents and local modes. The vibration levels in different rooms at a same floor can be different due to the different local stiffness. A room with larger space thus smaller local stiffness usually has higher vibration level. Softer soil layers make the tunnel lining and the building have more low frequency vibration. The influence of the soil stiffness on the amplification scale along the floors of the building is found to be nonlinear and frequency-dependent, which needs to be further investigated.

Analysis of Vibration Characteristics of Tractor–Rotary Cultivator Combination Based on Time Domain and Frequency Domain

A good planting bed is a prerequisite for improving planting quality, while complex ground excitation often leads to machine bouncing and operation vibration, which then affects the operation effect. In order to improve the quality of rotary tillage operations, it is necessary to study the effects of various vibration excitations on the unit during tractor rotary tillage operations and analyze the vibration interaction relationship among the tractor, the three-point suspension mechanism, and the rotary tiller. For this purpose, multiple three-way acceleration sensors were installed at different positions on the rotary tiller unit of a Lexing LS1004 tractor(Lexing Agricultural Equipment Co. Ltd., Qingdao, China) to collect vibration data at different operating speeds and conduct vibration characteristic analysis between different components. The test results showed that when the unit moved forward at 2.1 km/h, 3.6 km/h, and 4.5 km/h, respectively, the vibration acceleration of the tractor, the three-point suspension mechanism, and the rotary tiller increased with the increase in speed, and there was indeed interaction between them. The vertical acceleration change during the test in the three-point suspension mechanism was the most significant (5.914 m/s2) and was related to the increase in the speed of the vehicle and the vibration transfer of the rotary tiller. Meanwhile, the vertical vibration acceleration of the tractor’s symmetrical structure was not similar, suggesting the existence of structural assembly problems. From the perspective of frequency domain analysis, the resonant frequency at the cab of the tractor was reduced in a vertical vibration environment, with relatively low frequencies (0~80 Hz) and small magnitudes, which might be beneficial to the driver’s health. The rotary tillage group resonated around 350 Hz, and this characteristic can be used to appropriately increase the vibration of the rotary tiller to reduce resistance. The tractor cab resonated around 280 Hz, which must be avoided during field operations to ensure driver health and reduce machine wear. The research results can provide a reference for reducing vibration and resistance during tractor rotary tillage operations, as well as optimizing and improving the structure of rotary tillers and tractors.

Characterization of elastic wave propagation in high-speed railway tracks considering temperature effects

This study establishes a three-dimensional infinite-length periodic ballasted track model, considering the effect of coupling between bending and torsion and the impact of sleeper width. The GPWE method is employed to investigate the energy bandgap structure of the track. The results show three vertical bending wave bandgaps below 1500 Hz: 0–109 Hz, 110–167 Hz, and 1081–1126 Hz. The node responses from a hammer impact experiment are used in the WSM to calculate the frequency dispersion curves, which confirms the validity of this model. The model is then utilized to analyze the influence of rail temperature forces and temperature-dependent fastener stiffness on the vibration transmission characteristics of the track within a temperature range of −35°C to 25°C. As temperature increases, the starting and cutoff frequency values and the width of bandgaps both decrease nonlinearly and later stabilize, with the width of the Bragg bandgap showing a significant reduction of 83%. The vibration attenuation rate in the bandgap gradually increases and finally stabilizes, especially above 15°C, while the vibration transfer characteristics are not significantly affected by temperature.

Exploring the Feasibility of Estimating Intraocular Pressure Using Vibrational Response of the Eye: A Methodological Approach.

This study addresses the limitations of current tonometry techniques by exploring vibroacoustic properties for estimating intraocular pressure (IOP), a key diagnostic parameter for monitoring glaucoma-a significant risk factor for vision loss. Utilizing vivo porcine eyeballs, we investigated the relationship between IOP and the nonlinear vibration transfer function ratio (NVTFR). Through applying varying vibration levels and analyzing responses with transfer function analysis and univariate regression, we identified a strong negative correlation between NVTFR and IOP, evidenced by a Pearson correlation coefficient of -0.8111 and significant results from generalized linear model (GLM) regression (p-value < 0.001). These findings indicate the potential of NVTFR as a vital indicator of IOP changes. Our study highlights the feasibility of using vibroacoustic properties, specifically NVTFR, to measure IOP. While further refinement is necessary for in vivo application, this approach opens new possibilities for non-invasive and patient-friendly IOP monitoring, potentially enhancing ophthalmology diagnostic techniques and providing a foundation for future research and development in this critical area.