Numerical simulation regarding flow-induced noise in variable cross-section pipelines based on large eddy simulations and Ffowcs Williams–Hawkings methods
About: This article is published in AIP Advances.The article was published on 2021-06-01 and is currently open access. It has received 3 citations till now. The article focuses on the topics: Noise & Cross section (physics).
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TL;DR: In this paper , the frequency domain sound pressure level (SPL) distribution under various inlet flow velocities is stable, the structure-borne noise of the T-shaped tee is a high-frequency noise, and the SPL curves provide a peak distribution.
Abstract: In order to research the structure-borne noise characteristics of a T-shaped tee considering fluid-structure interaction (FSI), the Large Eddy Simulation (LES) and acoustic Finite Element Methods (FEM) were used to simulate the flow field and structure-borne noise related to T-shaped tees under different inlet and outlet combinations. The results show that the frequency domain sound pressure level (SPL) distribution under various inlet flow velocities is stable, the structure-borne noise of the T-shaped tee is a high-frequency noise, and the SPL curves provide a peak distribution. Meanwhile, the distribution characteristics of the structure-borne noise in the frequency domain follows similar trends under different inlet flow velocities. Additionally, the structure-borne noise won't produce the mechanical resonance of the system. When the inlet velocity increases from 1 m/s to 3 m/s, the total sound pressure level (TSPL) increases from 83.71 dB to 98.18 dB, a relative increase of 17.3%. In addition, the frequency domain distributions of the SPL under various inlet and outlet combinations are basically similar. The TSPL of four inlet and outlet combinations for the structure-borne noise are III, IV, II, and I in descending order. When the inlet flow velocity is 1 m/s, 2 m/s, and 3 m/s, in the case of combination I, the TSPL of the structure-borne noise decreases by 6.28 dB, 5.59 dB, and 6.39 dB, in contrast to the combination III, respectively. This study provides the guidance for the noise control and structural optimization design of a T-shaped tee considering the FSI.
2 citations
TL;DR: In this article , a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy, and the pressure distribution and sound power level distribution characteristics of the blade surface are explored with variable blade installation angles.
Abstract: In this paper, a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy. The pressure distribution and sound power level distribution characteristics of the blade surface are explored with variable blade installation angles. Based on the Q-criterion, the study reveals the spatial distribution of the channel and trailing edge shedding and channel vortexes in the flow field. Then, the evolution laws of the fan's aerodynamic noise sound pressure level are also investigated, and its frequency domain characteristics with variable blade installation angles are obtained. The results show that when the rotor blade installation angle is -5{degree sign}, the front-guide vane matches the installation angle of the first-stage impeller. The upper limit of sound power level is the smallest with variable blade installation angles, which is 123.56 dB. Meanwhile, the number and size of vortex structures in the front-guide vane area are the smallest, and the turbulent flow in the flow field is moderate. As the moving blade installation angle is deflected from -10{degree sign} to 10{degree sign}, the total sound pressure level of aerodynamic noise at each component of the fan first decreases and then increases. The minimum value is 121.40 dB and 128.40 dB at the inlet and outlet when the blade installation angle is -5{degree sign}. In addition, the number of eddies periodically shed in the fan flow field is the least. This research can supply technical support for the noise reduction of the two-stage adjustable blade axial fan.
1 citations
TL;DR: In this paper , the authors employed a numerical simulation method based on the volume of fluid model and evaporation-condensation model to investigate the noise generated by gas-liquid two-phase flow within capillary tubes in refrigeration systems.
Abstract: In order to research the noise generated by gas–liquid two-phase flow within capillary tubes in refrigeration systems, this study employs a numerical simulation method based on the volume of fluid model and evaporation-condensation model. The noise of gas–liquid two-phase flows is generated by refrigerant vaporization in capillary tubes under different inlet temperatures and diameters. The results of this study showed that two-phase flow noise in capillary tubes predominantly exists in the frequency range of 0–200 Hz, corresponding to low-frequency noise. Under different inlet temperature and diameter conditions, the total sound pressure level (TSPL) of a two-phase flow noise increased with the increase in the capillary tube diameter. Moreover, when the inlet temperature was 316.6 K, as the diameter increased from 1 to 1.9 mm, TSPL increased from 32.02 to 34.36 dB. In addition, as the inlet temperature gradually decreased, TSPL increased. Furthermore, it was found that the lower the inlet temperature, the greater the increase in TSPL. When the inlet temperatures were 316.6, 313.6, 310.6, and 307.6 K, and the diameter increased from 1 to 1.9 mm, TSPL increased by 2.34, 3.41, 4.1, and 5.38 dB, respectively, corresponding to the relative increase of 7.31%, 10.23%, 11.85%, and 15.34%. Finally, using an orthogonal analysis, a criterion relationship was obtained for predicting the TSPL of gas–liquid two-phase flow noises in capillary tubes under different conditions. This study provides guidance for noise control and structural optimization of capillary tubes considering the gas–liquid two-phase flow.
References
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TL;DR: In this paper, a theory for estimating the sound radiated from a fluid flow, with rigid boundaries, which as a result of instability contains regular fluctuations or turbulence is initiated, based on the equations of motion of a gas.
Abstract: A theory is initiated, based on the equations of motion of a gas, for the purpose of estimating the sound radiated from a fluid flow, with rigid boundaries, which as a result of instability contains regular fluctuations or turbulence. The sound field is that which would be produced by a static distribution of acoustic quadrupoles whose instantaneous strength per unit volume is ρv i v j + p ij - a 2 0 ρ δ ij , where ρ is the density, v i the velocity vector, p ij the compressive stress tensor, and a 0 the velocity of sound outside the flow. This quadrupole strength density may be approximated in many cases as ρ 0 v i v j . The radiation field is deduced by means of retarded potential solutions. In it, the intensity depends crucially on the frequency as well as on the strength of the quadrupoles, and as a result increases in proportion to a high power, near the eighth, of a typical velocity U in the flow. Physically, the mechanism of conversion of energy from kinetic to acoustic is based on fluctuations in the flow of momentum across fixed surfaces, and it is explained in § 2 how this accounts both for the relative inefficiency of the process and for the increase of efficiency with U . It is shown in § 7 how the efficiency is also increased, particularly for the sound emitted forwards, in the case of fluctuations convected at a not negligible Mach number.
4,697 citations
08 May 1969-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this article, sound generation by turbulence and surfaces in arbitrary motion is discussed, and sound and multipole fields and governing equations are discussed. But sound generation is not discussed in this paper.
Abstract: Monograph on sound generation by turbulence and surfaces in arbitrary motion, discussing sound and multipole fields and governing equations
3,121 citations
TL;DR: In this paper, an extension to Lighthill's general theory of aerodynamic sound was made to incorporate the influence of solid boundaries upon the sound field, and it was shown that these effects are exactly equivalent to a distribution of dipoles, each representing the force with which unit area of solid boundary acts upon the fluid.
Abstract: An extension is made to Lighthill's general theory of aerodynamic sound, so as to incorporate the influence of solid boundaries upon the sound field. This influence is twofold, namely (i) reflexion and diffraction of the sound waves at the solid boundaries, and (ii) a resultant dipole field at the solid boundaries which are the limits of Lighthill's quadrupole distribution. It is shown that these effects are exactly equivalent to a distribution of dipoles, each representing the force with which unit area of solid boundary acts upon the fluid. A dimensional analysis shows that the intensity of the sound generated by the dipoles should at large distances x be of the general form I$\propto $ $\rho \_{0}$ U$\_{0}^{6}$a$\_{0}^{-3}$ L$^{2}$x$^{-2}$, where U$\_{0}$ is a typical velocity of the flow, L is a typical length of the body, a$\_{0}$ is the velocity of sound in fluid at rest and $\rho \_{0}$ is the density of the fluid at rest. Accordingly, these dipoles should be more efficient generators of sound than the quadrupoles of Lighthill's theory if the Mach number is small enough. It is shown that the fundamental frequency of the dipole sound is one half of the frequency of the quadrupole sound.
1,760 citations
TL;DR: In this article, the sound generated by the interaction of two identical thin vortex rings was analyzed and it was shown that each vortex can be replaced acoustically by a dipole related to the impulse of the vortex.
Abstract: A transformation is described which relates the sound generated by low Mach number flow to the flow vorticity. For compact flow fields the apparent sound source is of quadrupole type and linear in the vorticity and therefore also linear in the flow velocity. This scheme is applied to the sound generated by the interaction of two identical thin vortex rings. Then a flow field with a number of compact vortices is discussed. It is found that each vortex can be replaced acoustically by a dipole related to the impulse of the vortex, plus the quadrupole just mentioned plus a spherically symmetric sound source related to the energy of the vortex. An application to low Mach number free-space turbulence shows that the generated sound is related to the vorticity correlation tensor.
247 citations
TL;DR: In this paper, the authors extended the theory of sound generation by multibladed single-stage fans operating in a free field and showed that the quadrupole effects are important for low-speed, few-bladed fans in the first harmonics.
162 citations