Flow-induced Noise Research Articles

Acoustic excitation source modeling for flow-induced noise of hermetic compressor using FSI analysis

Acoustic excitation source modeling for flow-induced noise of hermetic compressor using FSI analysis

Numerical analysis of flow-induced noise during the charging of a fuel cell electric vehicle

Numerical analysis of flow-induced noise during the charging of a fuel cell electric vehicle

Aircraft icing detection via flow-induced ambient random noise: from theory to wind tunnel experiments

Aircraft icing is a serious threat to flight safety. This paper presents a passive approach to detect ice accreted on an airfoil using flow-induced random noise considering spatially-inhomogeneous transient excitations. Under the assumption of diffuse-field, by computing the cross-correlation of ambient vibration measured at two receivers and band-pass filtering it, the guided wave dispersion curve of the structure can be well-reconstructed, by which one can estimate the ice thickness by matching the reconstructed dispersion curve with its theoretical model. In practice, however, the diffuse-field assumption may not hold as spatially-inhomogeneous strong transient excitations exist. The associated directional wave propagation generates additional peaks in the cross-correlation and this contaminates the ice detection result. Therefore, this paper proposes a signal processing technique to identify and suppress the contributions from the transient source in the measurements, by which a reliable dispersion curve reconstruction and an accurate ice detection can be retrieved. The proposed method is shown to be efficient via a wind tunnel experiment. The passive ice detection method is specifically suitable for aircraft online monitoring because only passive sensors are needed which can be tiny, light, and mounted on the internal surface of fuselage skin without any influence on aircraft aerodynamics.

Numerical simulation of the flow-induced noise of a ducted diaphragm using the Lattice Boltzmann Method

Acoustic discretion is of prime importance for submarines while operating, in order not to be detected. One of the submarine acoustic sources is the noise induced by water flows passing through singularities in pipes ending at the hull, thus radiating acoustic waves in the vessel surroundings. Predicting the noise induced by singularities in pipes is then fundamental to determine the acoustic signature of an underwater ship. Several Computational Aero-Acoustics methods have been implemented in order to predict the sound induced by singularities such as diaphragms and perforated plates. In this study, the Lattice Boltzmann Method (LBM) coupled to Large Eddy Simulation (LES) is used to simulate the flow passing through a diaphragm and to predict the induced noise. The method is first implemented for an airflow in a rectangular duct, with the final objective of being applied to confined water flows encountered in circular or rectangular ducts.

Numerical study of shell-side flow-induced noise characteristics of staggered straight tube bundle heat exchanger under different inflow conditions

This paper presents a numerical study on the shell-side flow noise characteristics of staggered straight tube bundle heat exchangers under varying inflow conditions. A three-dimensional numerical model of a compactly arranged staggered straight tube bundle heat exchanger was established. To validate the numerical model, a feasibility study using a cylindrical flow model was conducted. Subsequently, the large eddy simulation (LES) method was employed to investigate the unsteady shell-side flow field characteristics, and the vortex characteristics of the flow field were obtained based on the Q-criterion. Finally, the acoustic finite element method (FEM) was utilized to calculate and analyze the noise characteristics at the inlet and outlet positions of the heat exchanger shell side. The results show that the inflow angle has an influence on both the flow field and the acoustic field of the heat exchanger shell side. As the inflow angle increases, the flow stability decreases, horseshoe vortices replace boundary layer vortices, and the decrease in fluctuating pressure leads to a reduction in flow noise. Analysis of the sound pressure level spectrum indicates a line spectral characteristic at low frequencies, with high-frequency components experiencing rapid attenuation.

Separate prediction of underwater noise from drain pipes base on Vibration-acoustic coupling method

Abstract Since drain pipes on ships radiate underwater noise when in use, the components and radiation characteristics of flow noise and flow-induced noise from drain pipes on ships are explored, and the relationship between peak spectral values and wet mode frequencies is analyzed. The numerical calculation models of the flow field and structure for drain pipes are created respectively to obtain pulsating pressures in the flow field and structural mode values. Then, the flow noise and flow-induced noise are separately measured in an acoustic model developed for drain pipes upon the mapping of wall fluid meshes, structural meshes and acoustic meshes. A vibration-acoustic coupling model with the radiated sound field nephogram is presented based on the wall pulsating pressure and structural mode values. The numerical calculation indicated a significantly louder flow noise from drain pipes than the negligible flow-induced noise. The resulting wet mode of drain pipes solved by the Boundary Element Method (BEM) reflects the similarity between the peak spectral value and the wet mode frequency of flow-induced noise, marking that the fluid pulsating pressure excites noise.

Research on flow-induced radiated noise of twin-screw pumps based on the Lighthill acoustic analogue theory

Abstract To optimize the control of twin-screw pumps (TSP), it is essential to ensure performance while simultaneously preventing noise levels from exceeding specified limits. In order to investigate the flow characteristics and the mechanism of flow-induced radiated noise under various operating conditions, a coupled numerical simulation approach using Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) was employed, and the findings were validated through experiments. The study reveals that the highest sound pressure levels of radiated noise occur near the rotor outlet surface, and the dynamic-static interference at the rotor-boundary interface is the primary cause of flow-induced noise in TSP. The flow-induced noise in TSP exhibits dipole characteristics, with the overall sound pressure level gradually increasing and then sharply rising with the increase in rotational speed (or flow rate). It stabilizes near the design operating point and continues to increase steadily with further increases in rotational speed (or flow rate). Modal testing using a dual-distributed measurement technique highlights significant interference effects between the rotor inlet and the dynamic rotor for the first two Blade Passing Frequencies (BPF) in TSP. The results of this study provide a theoretical foundation for the low-vibration and low-noise design and operation of TSP.

A Method for the Pattern Recognition of Acoustic Emission Signals Using Blind Source Separation and a CNN for Online Corrosion Monitoring in Pipelines with Interference from Flow-Induced Noise.

As a critical component in industrial production, pipelines face the risk of failure due to long-term corrosion. In recent years, acoustic emission (AE) technology has demonstrated significant potential in online pipeline monitoring. However, the interference of flow-induced noise seriously hinders the application of acoustic emission technology in pipeline corrosion monitoring. Therefore, a pattern-recognition model for online pipeline AE monitoring signals based on blind source separation (BSS) and a convolutional neural network (CNN) is proposed. First, the singular spectrum analysis (SSA) was employed to transform the original AE signal into multiple observed signals. An independent component analysis (ICA) was then utilized to separate the source signals from the mixed signals. Subsequently, the Hilbert-Huang transform (HHT) was applied to each source signal to obtain a joint time-frequency domain map and to construct and compress it. Finally, the mapping relationship between the pipeline sources and AE signals was established based on the CNN for the precise identification of corrosion signals. The experimental data indicate that when the average amplitude of flow-induced noise signals is within three times that of corrosion signals, the separation of mixed signals is effective, and the overall recognition accuracy of the model exceeds 90%.

Experimental and Simulation Study on Flow-Induced Vibration of Underwater Vehicle

At high speeds, flow-induced vibration noise is the main component of underwater vehicle noise. The turbulent fluctuating pressure is the main excitation source of this noise. It can cause vibration of the underwater vehicle’s shell and eventually radiate noise outward. Therefore, by reducing the turbulent pressure fluctuation or controlling the vibration of the underwater vehicle’s shell, the radiation noise of the underwater vehicle can be effectively reduced. This study designs a cone–column–sphere composite structure. Firstly, the effect of fluid–structure coupling on pulsating pressure is studied. Next, a machine learning method is used to predict the turbulent pressure fluctuations and the fluid-induced vibration response of the structure at different speeds. The results were compared with experimental and numerical simulation results. The results show that the deformation of the structure will affect the flow field distribution and pulsating pressure of the cylindrical section. The machine learning method based on the BP (back propagation) neural network model can quickly predict the pulsating pressure and vibration response of the cone–cylinder–sphere composite structure under different Reynolds numbers. Compared with the experimental results, the error of the machine learning prediction results is less than 7%. The research method proposed in this paper provides a new solution for the rapid prediction and control of hydrodynamic vibration noise of underwater vehicles.

Relationship of flow pattern, vibration, and noise in automobile refrigerant system and flow pattern identification based on convolutional neural network

In recent years, the flow-induced vibration and noise in automotive refrigerant system gradually become the main factor affecting driving comfort. However, the relationship of flow pattern, vibration, and noise is not clear, and pattern identification is not easy but necessary. In this paper, a series of experiments are conducted to investigate the relationship of flow pattern, flow-induce vibration, and noise near the thermal expansion valve in an automobile refrigerant system. The flow pattern, vibration, and noise are closely related to startup processes. Mist flow, which contains more mist two-phase mixture than transition flow and wispy-annular flow, leads to the largest amplitude of vibration and strong broadband hiss noise. Moreover, the increase in compressor speed promotes the pattern transition and the vibration amplitude in time domain but has no effect on the distribution of vibration peaks in frequency spectrum. Finally, a short-time Fourier transform and convolutional neural network combined method for flow pattern identification is developed based on the relationship of flow pattern and flow-induced noise. After using transfer learning and data augmentation, four trained network architectures show relatively high accuracy above 94% for test set. Among them, ResNet34 not only has the highest accuracy of 98.8% but also can recognize each type of flow pattern. The generalization of this method can help engineers to recognize flow patterns in air conditioning without flow visualization but only need to measure sound signals.

Fluid-acoustic monolithic simulation based on spectral element method to solve flows past a slotted circular cylinder at low Reynolds numbers

Aerodynamic noise resulting from the flow around cylinders is a significant engineering challenge in aviation and wind engineering. The phenomenon of alternating vortex shedding in the flow leads to vibration and noise generation. However, accurately describing both the flow field and the sound field is challenging due to the significant difference in magnitude between them. To tackle this issue, this work introduces the application of the spectral element method (SEM) and flow-acoustic monolithic simulation for solving the two-dimensional compressible Navier–Stokes equations at low Reynolds numbers. This study is to investigate the reduction of flow-induced noise through the implementation of slotting technology on a circular cylinder. This study focuses on examining two different slit width ratios, s/d = 0.15 and 0.25, with a slit angle of attack of 0°. A comparative analysis is conducted between a complete circular cylinder and a slotted circular cylinder. The findings indicate that the slotted cylinder exhibits reduced intensity of vortex shedding and an extended region of downstream vortex generation compared to the complete cylinder. Notably, when s/d = 0.25, the slotted cylinder demonstrates minimal noise generation. Even at s/d = 0.15, a significant reduction in flow-induced noise is observed. These results highlight the potential of utilizing slotting technology on cylinders to effectively mitigate aerodynamic noise. The application of SEM and flow-acoustic monolithic simulation shows their relevance in analyzing and designing noise mitigation techniques in aerodynamics. This work can develop innovative solutions to reduce noise and improve the performance of various applications in aviation and wind engineering.

Isogeometric modeling and vibro-acoustic analysis of flow-excited irregular cavity-plate-exterior space coupled system

The flow-induced noise has become an important noise source in marine sonar self-noise, which can adversely affect the normal operation of sonar. The marine sonar cabin is simplified as a cavity-plate-exterior space coupled system whose flow-induced vibro-acoustic characteristics are investigated in this paper. An isogeometric vibro-acoustic formulation is proposed in which the cavity with an irregular geometry is precisely described by adjusting the control points and corresponding weights. The flow-induced vibro-acoustic response is obtained by transferring the turbulent pressure data from computational fluid dynamics into the isogeometric vibro-acoustic model. Imposing turbulent pressure into the isogeometric control points is proposed to achieve this objective using a node-based interpolation method. The vibro-acoustic modeling is validated and compared with previous experimental results. These comparisons demonstrate that the developed formulation accurately predicts the vibro-acoustic characteristics of the fluid-excited coupled system. The influences of flow speed, acoustic medium, and cavity shape on flow-excited vibration and sound radiation are discussed. Results show a decrease in radiated acoustic power and radiation efficiency in the exterior space, and a shift in the plate-exterior space coupling modal frequency to lower frequencies when the cavity changes from convex to concave.

Exploring cavitation dynamics and noise reduction in hydraulic machinery with bionic leading edge impeller

Cavitation and induced noise are common issues in the operation of mixed-flow pumps, affecting their stability. Studying these phenomena is of both academic and engineering interest. Previous research has mainly focused on modifying the impeller blade profile or optimizing the pump structure to reduce cavitation and noise. In this paper, we apply a bionic design to the mixed-flow pump impeller by mimicking the natural shape of a humpback whale's pectoral fin on the leading edge of the blade. We compare the cavitation suppression and noise reduction effects of this design with those of a conventional mixed-flow pump. Unsteady flow calculations for the original pump at different flow rates revealed that at its rated speed, increasing flow rates led to lower pressure in the low-pressure region on the suction surface of the impeller, expanding the cavitation-prone area. By applying the bionic design, we studied the unsteady cavitation flow and its induced noise. Results showed that the impeller and guide vane experienced larger pressure pulsations at the rotation frequency and its multiples. The bionic modification increased the cavitation initiation speed and reduced the cavity volume within the runner. With an NPSH (net positive suction head) of 6.76, the void volume in the bionic pump was only 79% of that in the original pump, and the head increased by 16%. Additionally, the bionic design reduced the maximum far-field sound pressure level by 12.5%, achieving significant noise reduction. This study demonstrates that the bionic design effectively controls dynamic flow separation, reduces flow-induced noise, and enhances the mixed-flow pump's performance. These findings have important theoretical and practical implications for optimizing mixed-flow pump design, improving energy efficiency, and reducing noise.

Numerical approach for the simulation of flow-induced noise around a structure with complex geometry: High-speed train bogie in a cavity

The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. The main challenge is to achieve a grid with adequate resolution, especially in the boundary layer, while ensuring computational affordability. This challenge is addressed here by employing a hybrid grid, integrating a structured hexahedral mesh near solid surfaces with an unstructured polyhedral mesh in the remaining volume. To limit the number of cells in the boundary layer region, the delayed detached eddy simulation method is adopted. Additionally, to achieve a further reduction in the cell count, the Reynolds number of the model is decreased by scaling down the model size and lowering the inflow speed. The hybrid grid generation and numerical settings are guided by validated simulations of flow over cylinders. A grid sensitivity study, conducted with a simplified half-width bogie model, reveals the meshing requirements for the full-width model. Aerodynamic results highlight the rear section of the cavity and bogie as primary noise sources, emphasizing the critical role of the detached shear layer from upstream components. Time-resolved surface pressure data are input into the Ffowcs Williams–Hawkings equation for far-field noise calculation. The results indicate that the sound energy is concentrated below 200 Hz in the full-scale model, with the cavity contributing more than the bogie. This study provides a practical numerical approach for simulating a structure with complex geometry, offering insights for realistic model simulations.

Vibro-acoustic modeling of the turbulent excited cavity-plate-exterior space coupled system

To mitigate flow-induced noise in sonar self-noise, this study introduces a vibro-acoustic modeling technique for sonar cabins. This technique couples a turbulent-flow-excited plate with the interior cavity and the exterior field within a unified model. Employing the Rayleigh-Ritz method, the Chebyshev spectral method, and the Rayleigh integral, the model accounts for general boundary restraints, wall impedances, and reinforcement configurations. Flow-induced responses are determined through the Monte Carlo quadruple integration of frequency response functions and the cross-spectral density model, which characterizes turbulent pressure fluctuations. The convergence and reliability of the present method are verified, achieving excellent agreement with numerical methods and previous results. The study reveals that periodic impedance arrangements in the cavity significantly attenuate sound wave propagation, especially when periodic arrangements are added at low frequencies. The reinforcement configuration perpendicular to the flow direction minimizes low-frequency vibrations. However, the influence of reinforcement on acoustic energy within the cavity is marginal and could potentially lead to increases under simply supported boundary conditions. This method effectively addresses vibro-acoustic challenges in sonar cabins, offering substantial practical value for the development of low-noise sonar systems.

CFD-based prediction of flow noise in offshore pipeline systems

Abstract The ship’s water injection system exhibits significant vibration and noise issues, necessitating the prompt implementation of targeted control measures. In this study, the simulation technique of computational fluid dynamics (CFD) combined with the finite element method and automatic matching layer method was applied to emulate the flow field environment of the outlet pipeline of a side valve in a seawater cooling system. Pulsating pressure data on the pipeline and valve’s wall were extracted from the flow field calculation and utilized as dipole noise sources and structural vibration excitations, enabling the prediction and separation of flow noise and flow-induced vibration noise in the water injection system. Leveraging the data from the flow field simulation, an analysis was conducted on the radiated noise at the side valve’s outlet, comparing the impact of different underwater depths and outlet pipe diameters on the underwater flow noise. The findings suggest that measures such as increasing the side valve’s diameter and lowering the discharge port’s underwater position can effectively reduce system flow noise, offering valuable insights for the design of noise reduction in seawater cooling systems for silent surface ships and submarines.

Flow-induced noise and vibration in axial fan: a case study

AbstractReducing axial fan noise is crucial in residential, commercial, and industrial applications. This study explores how attaching different add-on designs to axial fans reduces aerodynamic noise. Eight design cases were examined, including extending the outlet and inlet ducts, using Chevron nozzles, placing internal spherical balls in staggered and straight patterns, applying a wavy inner wall treatment, and combining some of these nozzle designs. CFD and acoustic analyses were performed using Ansys Fluent 2022 R1. Noise reduction was measured at the nozzle outlet in each design case. All nozzle modifications reduced noise levels, with noise reductions ranging from 3 to 10% at the blade tip and 26–55% at the outlet. As an add-on to existing fan cases, the design cases investigated in this study can potentially improve the acoustic environment in various settings. The findings of this study can contribute to the development of quieter axial fans.

Analysis of Flow-induced Noise Characteristics of Ethylene Cracking Furnace Tubes before and after Coking

Analysis of Flow-induced Noise Characteristics of Ethylene Cracking Furnace Tubes before and after Coking

Impact of helical grooves on drag force and flow-induced noise of a cylinder under subcritical Reynolds numbers

The drag force and flow-induced noise of underwater vehicles significantly affect their hydrodynamic and stealth performance. This paper investigates the impact of helical grooves on the drag force and flow-induced noise of underwater vehicles through numerical simulations of the flow around cylinders with two types of helical grooves under various subcritical Reynolds numbers. The simulation scheme employs the large-eddy simulation framework combined with the Lighthill acoustic analogy method. The results show that the helical-groove structure can achieve reductions of up to 30% in drag and 5 dB in noise. These helical grooves have a significant effect in terms of suppressing the formation of a Karman vortex street downstream of the cylinder. Under subcritical Reynolds numbers, the drag-reduction effect of the helically grooved cylinder decreases as the number of helical grooves increases, while the noise-reduction effect increases with increasing number of helical grooves.

Acoustic comfort improvement of simultaneous heating and cooling heat pumps using control logic for flow-induced noise reduction

Acoustic comfort in buildings can be achieved by minimizing unwanted noise generated primarily from heating, ventilation, and air-conditioning systems. However, research on noise reduction in simultaneous heating and cooling heat pumps (SHCHP) is limited. This study proposes a novel noise reduction control logic (NRCL) based on experiments on flow-induced noise through electronic expansion valves (EEVs) in an SHCHP. The flow-induced noise through EEVs was measured and analyzed regarding the degree of subcooling, differential pressure between indoor unit and evaporation (ΔPindoor), EEV opening speed (Vo), and opening (Oeev) while switching operation mode in an SHCHP. For all the operating and controllable variables, the peak sound pressure level (SPLpeak) was decreased by evenly distributing sound energy (SE). The sensitivity analysis indicated that Oeev and Vo were the most significant variables for achieving uniformly distributed SE. Therefore, a novel NRCL was proposed in terms of the initial EEV opening (Oeev,i) and dimensionless control time (CT) derived from the relationship between Oeev and Vo. The optimal CT for EEVs in SHCHP with NRCL was 1. At this point, the difference between SPLpeak and average SPL decreased by 46.2%, and the converging time for ΔPindoor to 0 increased by 17.8% compared with those of baseline.