Pipe Resonance Research Articles

A quarter wave infrasonic noise generator

The far-field prediction of infrasonic noise, e.g. from large emitters such as wind turbines, requires precise measurement of the sources. A method to determine the source power based on near-field holography techniques are currently under development in our group. However, tuning the method requires a calibrated infrasound source. In this work, we present the concept of a traceable loudspeaker driven infrasound source using the quarter wave resonator principle in a pipe. The power emitted by the source is measured in situ based on the two-port theory. The infrasonic frequencies can be tuned by adjusting the length of the resonator pipe. Results of the free-field measurements at multiple points at varying distances away from the source are presented. The results suggest that the infrasonic source can be used as a calibrated reference for method development and validation.

Attenuation properties of a meta-pipe: Analytical, experimental, and numerical prediction

Flexural vibration characteristics of a meta-pipe are investigated in this paper. Initially, the metamaterial piping system consisting of a homogeneous pipe and periodic flexible supports is designed. Subsequently, the dispersion relationship which is a function of the wavenumber and the frequency is derived employing the transfer matrix method and Bloch’s theorem. The designed system reveals a zero-frequency stopband and a wide passband in the examined frequency range, which are verified by both experimental and numerical results. To enhance the performance of this system, it is essential to effectively control the obtained passband. For this, a single-degree-of-freedom localized resonator is designed, which is subsequently installed at the center of each unit-cell of the pipe. The dispersion properties of this system are first evaluated analytically and then validated using experimental and numerical methods. Finally, the effect of pipe system parameters and resonator properties on the stopband characteristics is studied in depth. It was observed that the stopband properties can be effectively tuned by appropriately designing the piping system and resonators. The results presented in this study offer valuable insights into the propagation characteristics of flexural waves and the strategies devised for controlling vibrations in pipes.

Numerical analysis of the tread grooves' acoustic resonances for the investigation of tyre noise

Abstract Tyre/road noise is one of the major sources of noise pollution in urban areas. This phenomenon can be described as the combined effect of several generation and amplification mechanisms. Acoustic resonances due to the tread grooves at the footprint region, also known as pipe resonances, are particularly important since they can generate high noise levels if they combine with harmonic generation mechanisms. This paper deals with a numerical investigation of this phenomenon and describes modelling approaches that might be used to estimate the frequencies and the mode shapes of these resonances.

An inerter-based concept of locally resonant fluid-conveying pipe

Preventing damage or failure caused by vibrations in periodic fluid-conveying pipes needs appropriate mitigation strategies. This paper proposes a novel concept of locally resonant fluid-conveying pipe resting on periodically spaced inerter-based resonant supports, each including an inerter and linear springs. On adopting a Timoshenko beam model for the pipe, two types of inerter-based resonant supports are investigated, differing by the arrangement of the internal components, i.e., inerter and springs. For both types, elastic wave dispersion analyses of the infinite pipe demonstrate the existence of two low-frequency band gaps in the frequency response. The second band gap, caused by local resonance, exhibits better attenuation over a relevant part of its frequency range; its lower/upper edge frequencies and amplitude may be suitably changed depending on the parameters of the inerter-based resonant supports, and very considerable amplitudes can be obtained thanks to the large inertia effects warranted by the grounded inerter. The influence on the band gaps of key parameters such as fluid velocity and ratio of fluid mass to total pipe mass is assessed. Moreover, the effect of damping is considered, assuming a Kelvin–Voigt viscoelastic behavior for the pipe material and including viscous dashpots in parallel with the springs within the inerter-based resonant supports. An original exact dynamic-stiffness method is formulated for computational purposes, targeting wave dispersion analysis of the infinite pipe as well as frequency-domain analysis of the finite pipe. In particular, the main novelty is the derivation of the exact dynamic-stiffness matrix and exact load vector of the unit cell of the Timoshenko pipe with Kelvin–Voigt viscoelastic behavior. Remarkably, the transmittance of the finite pipe confirms the predictions from wave dispersion analysis of the infinite pipe and substantiates the effectiveness of the proposed concept of locally resonant fluid-conveying pipe.

Resonators in free reed instruments: Good, bad, and unusual effects

Western free reed instruments such as the accordion and the harmonica do not typically use pipe resonators. Yet even without pipes there are two sorts of resonators employed. In the case of mouth blown instruments, free-reed or not, the resonances of the players vocal tract are quite significant. Less often recognized as resonators are the reed chambers necessary to provide a secure mounting for the reed and to properly direct the airstream. The acoustical properties of these may or may not be beneficial. Because of their different reed construction, the Asian free-reed mouth organs require pipe resonators in to function. This paper will present examples of ways in which reed chamber and pipe resonances can enhance or interfere with tone production, as well as some interesting special effects produced by intentional mismatches between reed and resonator.

Nonlinear dynamics of a circular curved cantilevered pipe conveying pulsating fluid based on the geometrically exact model

Due to the novel applications of flexible pipes conveying fluid in the field of soft robotics and biomedicine, the investigations on the mechanical responses of the pipes have attracted considerable attention. The fluid-structure interaction (FSI) between the pipe with a curved shape and the time-varying internal fluid flow brings a great challenge to the revelation of the dynamical behaviors of flexible pipes, especially when the pipe is highly flexible and usually undergoes large deformations. In this work, the geometrically exact model (GEM) for a curved cantilevered pipe conveying pulsating fluid is developed based on the extended Hamilton’s principle. The stability of the curved pipe with three different subtended angles is examined with the consideration of steady fluid flow. Specific attention is concentrated on the large-deformation resonance of circular pipes conveying pulsating fluid, which is often encountered in practical engineering. By constructing bifurcation diagrams, oscillating shapes, phase portraits, time traces, and Poincare maps, the dynamic responses of the curved pipe under various system parameters are revealed. The mean flow velocity of the pulsating fluid is chosen to be either subcritical or supercritical. The numerical results show that the curved pipe conveying pulsating fluid can exhibit rich dynamical behaviors, including periodic and quasi-periodic motions. It is also found that the preferred instability type of a cantilevered curved pipe conveying steady fluid is mainly in the flutter of the second mode. For a moderate value of the mass ratio, however, a third-mode flutter may occur, which is quite different from that of a straight pipe system.

Numerical study on the effect of intermediate pressure pulsation on COP in the vapor injection cycle

The vapor injection cycle with flash tank and two stage compressor is known as an efficient cycle. It is known that the intermediate pressure is a key factor for COP improvement and pressure change during the injection process could reduce the COP. However, the effect of the pulsating intermediate pressure of a two-stage compressor on COP is not clear. In a previous study, the authors experimentally showed that COP varied with injection pipe length. There seemed to be a correlation between COP and the resonance phenomenon caused by pressure pulsation in the injection pipe. However, the mechanism of COP improvement is not well understood. In this study, a one-dimensional simulation model was developed to clarify the mechanism and was verified with the experimental results. The simulation results show that resonance in the injection pipe does not increase the injection mass flow rate into the suction pipe. On the contrary, backflow occurs in the injection pipe and the backflow ratio is minimum in the resonant condition. Due to the high temperature of the backflow coming from the discharge pipe, the saturated vapor from the flash tank is easily heated, causing heat loss and lower COP. It was found that COP can be improved by using resonance to suppress the backflow.

CFD analysis of thermal fluid dynamic parameters inside an organ pipe: influence of air temperature variations

Organ pipes represent a fluid-dynamic challenge since the time of Bernoulli and Reynolds. A complete and reliable description of the fluid behaviour at the basement of the resonator named the “mouth” of the pipe is still absent. In the context of the design of an air-heating system for the attenuation of the inconsistencies between sounding frequencies of organ pipes, computing efforts were carried out focusing on the fluid-dynamic behaviour of the air at the mouth of the pipe at different temperature conditions. Describing the air dynamic and the heat transfer at the mouth level of the pipe, it would be possible to predict the heating conditions within the pipe resonator, which was the main subject of the project. Multiple points on the pipe organ air blowing scheme were considered for simulation results extraction. Temperature, pressure, and audio measurements were performed and no significant influence of the temperature on those parameters was raised from measurements, rising questions about the effective behaviour of the blowed air at the mouth of the pipe. Simulations were performed to predict both the fluid dynamic and the heat transfer. A finite volume approach in Fluent environment was chosen. The SST k-omega model was considered in reliability vs computation time balance. 3D simulations were performed based on a CAD reconstructed model of a real pipe. The results of the simulations confirmed experimental data, and they may prove the absence of a significant mass exchange between the in and outside of the mouth of the pipe. The oscillation of the air membrane at the mouth of the pipe may be cleared from instabilities and turbulence regime phenomena, as usually described in the literature.

A method to analyze the radiation characteristics of a liquid column resonance transducer based on fluid motion.

Liquid column resonance (LCR) transducers have been widely used in deep-sea acoustic applications because of their fluid-filled structures. Until now, studies of pipe resonance have generally been based on the plane acoustic wave equation, but for a vibrating object, the velocity is the primary focus instead of the pressure. Thus, the motion equation of a pipe resonance mode can be deduced based on the Navier-Stokes (N-S) equations. In this work, the velocity of an LCR transducer is obtained using the finite element model, and the velocity distribution inside the liquid column is examined. In addition, the radiating surface of the LCR transducer is identified and a simplified model of the radiation that consists of concave pistons and ring sources is proposed and verified. The theory behind the high mechanical quality (Q) value of the LCR transducer is explained through the radiation of the LCR transducer and the low viscosity of the water. This is also verified through a finite element model and measurements. Due to the high mechanical Q value and the low frequency of the LCR transducer, such measurements should be carried out in open-field water and the pulse should be long enough to achieve a steady state.

Determination of gas parameters in resonant pipes and channels of engines with a periodic workflow using the piston analogy method

This paper investigates a process of gas flow in the resonant tube of an engine with a periodic workflow. Analysis of various flow models and comparison of known data have shown that the problems of constructing closed 0-dimensional models of the operating cycle for some types of engines remain unresolved. Given this, the question arises about the dimensionality of models of individual engine elements, including the resonant pipe model, which must be included in the general model of the cycle, especially at the initial stage of its development. To solve the identified problems, a mathematical model of air flow has been improved, built on the basis of an analogy with a '"liquid" piston. Unlike existing ones, the piston analogy model allows one to calculate the instantaneous velocity averaged over the length of the pipe using a numerical solution of the differential equation for velocity. To test the model built, an alternative finite-difference 1-dimensional gas-dynamic model was selected, with the help of which a test simulation of air flow in a pipe was performed. It has been established that the piston model allows one to find the flow velocity with an accuracy of 5 % for a pressure drop varying according to a sinusoidal law. The permissible limits for changes in the oscillation frequency and pipe length were found, at which the piston model has a minimum error. Based on the results of the study, it was concluded that with a small mass and inertia of the liquid piston, the proposed model gives results close to those provided by more complex models with higher dimensionality. This indicates the possibility of using a piston model for elements such as pipes as part of a 0-dimensional thermodynamic model of engines with a periodic operating process as an approximate alternative to traditional 1-dimensional flow models

A novel buried periodic in-filled pipe barrier for Rayleigh wave attenuation: Numerical simulation, experiment and applications

Surface wave is a major concern in ambient vibration mitigation. To this end, a novel shallow buried periodic in-filled pipe barrier is proposed. Complex dispersion analysis is conduced to evaluate the decay of surface waves and the influence of material damping. Through a combination of numerical simulations and lab-scale experiments, the effectiveness and robustness of surface wave attenuation are verified. Result shows that the proposed periodic in-filled barrier exhibits excellent performance in low-frequency surface wave attenuation. Both the energy dissipation induced by material damping and local resonance of in-filled pipes contribute to surface wave attenuation. The influence of viscosity also enhances wave attenuation and it should be taken into full account in practice. In addition, these novel wave barriers are suitable for passive isolation as well as active isolation. To further widen the attenuation zones, the gradient layouts of in-filled pipes could be a good alternative considering the limited barrier width. Besides, the feasibility of periodic in-filled barriers to train-induced vibration mitigation is preliminary verified by analyzing the measured acceleration record in the time-domain. Thanks to the subwavelength size and shallow depth, these novel wave barriers are convenient for construction and cost-effective, thus showing great potential in ambient vibration mitigation.

The history and prehistory of Asian free reed instruments

The free reed pipes and mouth organs are among the most significant indigenous musical instruments of East and Southeast Asia. The origin and development of these instruments involve the history and prehistory of a multitude of ethnic groups. The basic principles of operation and construction of the free reed are simple, and it seems likely that similar instruments may have had multiple places and times of origin. A number of examples of these instruments, ranging from very simple to fairly complex. These include mouth resonated lamellophones, a single free reed coupled to a bamboo pipe or buffalo horn resonator, a reed pipe with multiple s finger holes, and multipipe mouth organs. These instruments have traditionally been constructed with very simple tools using natural materials, primarily bamboo and wood. Bamboo is often still used for the reeds as well as the pipes, although metal reeds have been common for some time.

Research on the effect of tire pattern design on noise and its reduction.

This paper studies pattern noise in original equipment fitment through four approaches, including pitch arrangement optimization, pipe resonance experiment, orthogonal experimental design of tread transverse groove, and block shift simulation. An in-cab noise test is conducted to verify the effectiveness. Results show an 8.7% reduction in total harmonic energy and 12% decrease in the highest harmonic peak through pitch optimization. This paper introduces the 3-Sum concept to measure the difficulty of exciting a certain pitch harmonic. Meanwhile, the optimal width combination is found for central and shoulder longitudinal grooves. Transverse groove width, angle, and direction are studied using analysis of range and analysis of variance with the best match producing an indoor drum noise value of 76.09 dB. The simulation by the tread noise prediction system shows that the optimal misalignment of the central rib should be -7 mm, and its noise prediction value has a 2.21 dB(A) decrease from the original plan while the optimal misalignment of the shoulder rib is at its initial position. In the in-cab noise test, the sound pressure level of the optimized plan is reduced by 0.46 dB(A). Notably, the root mean square value within the frequency band 700-1300 Hz is reduced by 3.26 dB(A), which is a figure that fulfills the expected tread noise reduction.

A design strategy for multi-span pipe conveying fluid away from resonance by graphene platelets reinforcement

The operation of mechanical systems generates vibrations with a certain range of frequencies. Pipes conveying fluid have multiple natural frequencies. It is difficult to avoid one or more natural frequencies of pipes in the operating frequency range of the system, which can lead to resonance and fatigue failure. In this paper, a design strategy to modulate the multi-span pipe's natural frequency by reinforcing pipes with graphene platelets (GPLs) nanofiller is proposed to solve the pipe resonance in engineering. The multi-span functionally graded (FG) pipe is constructed based on an integral pipe model with GPLs uniformly or non-uniformly distributed in the metal matrix. The effective properties of the nanocomposite are determined by using the Halpin-Tsai micromechanics model and rule of mixture. Subsequently, the safety range and resonance range of the multi-span FG pipe are obtained by comparing the first tenth-order natural frequency and preserved frequency band. A comprehensive investigation on the effect of patterns, weight fraction, and geometric parameters of GPL is conducted to identify the most effective way to modulate the pipe's natural frequency. The results indicate that GPL weight fraction is able to modulate the multi-span pipe's natural frequency and safety range over a wide range. In addition, the natural frequency and safety range of the FG pipe reinforced with GPLs increase as the stiffness and number of retaining clip increase. Based on the results, a pipe design strategy with fewer retaining clips is proposed for pipes away from resonance by reinforcing pipes with GPL nanofiller. In the case of an aircraft hydraulic pipe, the natural frequency of the pipe reinforced with GPLs is far away from the preserved frequency band and without resonance in operation. In summary, the design strategy of pipe reinforced with GPLs shed important insights on reducing the vibration level of multimodal structures.

Multi-harmonic resonance of pipes conveying fluid with pulsating flow

The parametric excitation analysis of pipes conveying pulsating fluid usually focuses on the principal parametric resonance. In this paper, the principal parametric resonance and the combination resonance under parametric excitation are compared for the first time. A dynamic model of a fluid-conveying pipe with elastic torsional constraints at both ends is established. The nonlinear partial differential-integral equation is derived for governing the transverse vibration. The natural frequencies and modes of pipe are obtained. Moreover, the analytical solutions of stable region and nonlinear amplitude-frequency responses for three kinds of parametric resonances are derived. Then, the analytical results are verified numerically. The results show that there is no differential-type combination parametric resonance for pipes supported at both ends. Increasing material damping or torsional stiffness and decreasing mean velocity can increase the stable region of the pipe. However, it is interesting to note that when combination parametric resonance occurs between symmetric and antisymmetric modes, the effect of mean velocity on stability is reduced. In addition, more than one form of resonance occurs in some regions. The sum-type combination resonance is easier to be excited than the principal parametric resonance. Among them, the combination of first-fourth mode is the most sensitive to the torsional boundary, and its response is the largest. In summary, this paper demonstrates that the combination parametric resonance, which has not been researched deeply yet, can be more destructive than the principal parametric resonance.

Study of dynamic characteristics of air cavity resonances from tyre-pavement interaction noise using single frequency filtering.

Air cavities in the tyre tread and the gap formed between tyre and pavement are excited during vehicle movement on a pavement. The former results in pipe resonance, and the latter results in horn resonance. These effects will be varying with speed of the vehicle and also because of conditions of tyre, pavement and, tyre-pavement interaction (TPI). The objective of this paper is to study the dynamic characteristics of air cavity resonances from the signals of the tyre-pavement interaction noise, which was collected by a pair of microphones, when a two wheeler is driven on a pavement at different speeds. The dynamic characteristics of the resonances are analysed using single frequency filtering (SFF) analysis of signals. The method gives spectral information at every sampling instant. The effects of impacts of the tyre treads, pavement characteristics, and TPI on the resulting cavity resonances are examined at four different vehicle speeds and for two different types of pavements. The analysis shows that the SFF spectra bring out the distinct characteristics of the pavements on the formation of air cavities and excitation of the resonances of these cavities. This analysis may help in determining the condition of the tyre and pavement.

Low-frequency band gap characteristics of a novel spinning metamaterial pipe with Timoshenko model

As a representative artificial periodic composite, metamaterials have presented broad application prospects in vibration attenuation and noise reduction of engineering devices owing to their extraordinary band gap (BG) properties. In this paper, a novel type of dynamic metamaterial structure is proposed on the basis of a spinning locally resonant (LR) pipe conveying fluid, and the coupled BG characteristics of such meta-structure are investigated. By applying the Timoshenko beam model, the differential equations governing the orthogonally transverse vibrations of spinning pipes conveying fluid are deduced by the Hamilton principle. Based upon the two resulting transverse waves, a dynamic two-dimensional LR pipe structure is developed by periodically encircling the pipe with dual-layer rings. An additional centrifugal force due to spin as well as the conventional inertial force is introduced into the local resonators. It is revealed that the present LR pipe makes a great contribution to the formation of low-frequency BGs below 500 Hz, which is conducive to the vibration suppression of large-size structures in engineering. Moreover, original BGs of non-spin structures will separate to different pseudo BGs towards the precession motions, while the true BGs are actually located in their coincident areas. Numerical results also demonstrate the significant effects of various physical, geometrical and motional parameters on the low-frequency BGs of the pipe.

Investigation of the effects of pipe diameter of internal multiphase flow on pipe elbow vibration and resonance

Computational fluid dynamics modelling of internal two-phase flow induced transient forces at 90° elbows have been carried out to evaluate the effect of pipe diameter on the characteristics of multiphase flow induced vibration. Simulations of two-phase flows of slug, cap bubbly and churn induced vibration at a pipe elbow were carried out using the volume of fluid model for the two-phase flows and the k – ε model for turbulence. Modal analysis has been carried out to evaluate the risk of resonance. Results were compared across three geometrically similar pipes of different diameters. Simulation results showed that the behaviours of the flow induced forces at the pipe elbow as a function of gas velocity for internal diameters of 0.0525 and 0.2032 m are similar. However, the multiphase flow induced force characteristics are different in the 0.1016 m diameter (intermediate) pipe. It can be attributed to the transition behaviour of gas–liquid two-phase flows caused by Taylor instability in an intermediate sized pipe. The predicted root-mean-square flow induced forces as a function of Weber number were correlated with an existing empirical correlation for a wider range of pipe sizes and gas volume fractions between 40% and 80%. Furthermore, the pipe natural frequencies increase with the increase of gas volume fraction in smaller pipes and the resonance risk increases with the increase of pipe diameter.

Introducing a procedure for predicting and reducing tire/road noise using a fast-computing hybrid model.

Prediction and reduction of tire noise are some of the main concerns of tire designers nowadays. Due to tire noise's sophisticated nature, low-noise tire design is like a maze path improbable to achieve without a scientific understanding of the underlying causes. This paper develops a knowledge-based hybrid model, incoherent summation of sounds generated and amplified by texture impact, tread impact, air-pumping, Helmholtz resonance, pipe resonance, horn effect, and air cavity resonance. The required data have been carried out by measuring C1 radial tires' noise levels in a semi-anechoic chamber. The developed model [with about a 1.7 dB(A) error on total noise prediction] presents mechanisms' contributions to the overall sound. The model is substituted with a fast-computing statistical model employing data generated based on Taguchi design. Machine learning methods are implemented for this aim, and the support vector machine provides the most accurate model. The proposed fast-computing hybrid model, developed based on a scientific description of underlying mechanisms, is applicable for noise reduction. The model's sensitivity to 21 tire parameters is analyzed, leading to valuable tips on lower tire noise. The results show the critical role of tread pattern characteristics, especially groove angle, in tire noise.

Non-dimensional analysis of the bandgap formation in a locally resonant metamaterial pipe conveying fluid

The objective of this paper is to investigate the effects of fluid flow velocity on the edge frequencies of the bandgap in an acoustic metamaterial pipe in a non-dimensional framework. Two methodologies are presented to predict the formation of the bandgap. In the first methodology, the pipe is considered to be infinitely long and the dispersion of an elastic wave in a single representative periodic unit cell of the structure is used to estimate the bandgap edge frequencies. In the second method, the pipe is modeled as a finite structure with defined boundary conditions and a modal analysis-based method is used to estimate the edge frequencies. A parametric study is performed wherein parameters identified from the non-dimensional analysis are varied, namely, the dimensionless flow velocity, the ratio of the resonator’s mass to that of the pipe and the fluid and the ratio of the fluid’s mass to that of the pipe and the fluid. It is shown that a close agreement in the bandgap edge frequencies is achieved using both methodologies. Furthermore, it is observed that an increase in the fluid velocity induces a decrease in the bandgap width, an increase of the mass ratio of the fluid to that of the pipe and the fluid results in a small decrease in the bandgap width and finally an increase in the mass of the resonators relative to that of the pipe leads to an increase in the bandgap width.