scholarly journals Flow field and noise characteristics of manifold in natural gas transportation station

2019 ◽  
Vol 74 ◽  
pp. 70 ◽  
Author(s):  
Zhongya Su ◽  
Enbin Liu ◽  
Yawen Xu ◽  
Ping Xie ◽  
Chen Shang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flow Field ◽  
Noise Reduction ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Acoustic Analogy ◽  
Pressure Balance ◽  
Expansion Chamber ◽  
Flow Noise ◽  
Noise Characteristics

Manifolds play a role of pressure balance, buffering and rectification for different branch pipelines, the flow noise of manifolds has been a serious problem all this time in natural gas transmission station. By changing the number of outlet pipes of manifolds and the different positions of intake pipes, the distribution of the Sound Pressure Level (SPL) of the manifold flow noise is analyzed based on the Ffowcs Williams-Hawkings (FW-H) acoustic analogy theory and Large Eddy Simulations (LESs). The three-dimensional simulation analysis of the flow field shows that pressure pulsation is the mainly source of manifold noise, as the number of outlet pipe increases, the SPLs of fluid dynamic noise at the end of inlet pipes are significantly reduced by about 10 dB on average, when the inlet and outlet piping are oppositely connected, the SPL is 2 dB~3 dB lower than that in staggered connections. An expansion-chamber muffler is designed with the analysis of its noise reduction effect, the results show that after the muffler is installed, the noise reduction in the low-frequency ranges reaches up to 37.5 dB, which controls the maximum noise to around 82 dB.

scholarly journals Study on flow noise characteristics of Bionic cylinder based on acoustic analogy

2021 ◽  
Vol 336 ◽  
pp. 01003
Author(s):  
Zixian Cui ◽  
Hao Song ◽  
Qi Li ◽  
Buchao An ◽  
Lin Su
Keyword(s):  
Noise Reduction ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Cylinder Surface ◽  
Acoustic Analogy ◽  
Fluctuating Pressure ◽  
Flow Noise ◽  
Noise Characteristics ◽  
Reduction Effect ◽  
Serrated Structure

The drag and noise reduction of the flow around a cylinder is one of the important topics in hydrodynamics and acoustics. In this paper, three typical bionic cylinders are designed based on the serrated structure on the surface of shark skin. Using Large eddy turbulence model and Lighthill’s acoustic analogy method, the flow noise characteristics of smooth cylinder and three kinds of bionic cylinders at different Reynolds numbers were compared, and the structure of cylinder surface was optimized. The results show that the main source of the flow noise around a cylinder is dipole noise, which is caused by the periodic fluctuating pressure on the cylinder surface.The bionic cylinder can reduce the amplitude of the fluctuating pressure, improve the wake flow field and reduce the wake vorticity, so as to reduce the noise. Among the three kinds of bionic cylinder, V-shaped bionic cylinder has the best noise reduction effect, and the critical value of S/H of V-shaped cylinder is about 2.5. When s / h > 2.5, V-shaped bionic cylinder has no effect of noise reduction.

Prediction of Ship Acoustic Signature Due to Fluid Flow

2007 ◽  
Author(s):  
Mae L. Seto ◽  
Rubens Campregher ◽  
Stefan Murphy ◽  
Julio Militzer
Keyword(s):  
Flow Field ◽  
Immersed Boundary ◽  
Noise Power ◽  
Far Field ◽  
Acoustic Analogy ◽  
Noise Component ◽  
Cavitation Inception ◽  
Flow Noise ◽  
Acoustic Signature ◽  
Acoustic Ranging

The contribution of flow noise to the radiated acoustic signature of CFAV Quest is of interest. Quest is the research ship used by Defence R&D Canada as a quiet platform. It is difficult to identify the flow noise component in an acoustic ranging so there is interest in predicting the flow noise as a first step towards extracting it from range measurements. Below propulsor cavitation inception speeds, machinery-induced noise dominates. While flow noise does not usually dominate in the presence of machinery-induced noise or propulsor cavitation, it is unclear what fraction of the total noise power flow noise constitutes. A direct numerical simulation for a complex ship geometry was impractical so an alternative approach was sought. An immersed boundary method was used to model the presence of the ship in the flow domain. The unsteady flow field was calculated using a finite volume method over an unstructured Cartesian grid. The flow field around Quest in straight and level flight was calculated at Reynolds numbers between 1.8×108 and 4.3×108, corresponding to a full-scale speed range of 4 to 10 knots. Results from such flow field predictions become the hydrodynamic sources in the integrals of Lighthill’s acoustic analogy to predict the far-field acoustic signature from the flow past the hull. These far-field predictions consist of computing the propagation and radiation of the hydrodynamic sources. This assumes noise generation and its propagation are decoupled. Under certain circumstances, knowledge of the predicted flow component helps to extract it from a standard acoustic ranging.

scholarly journals Noise Characteristics Analysis of the Horizontal Axis Hydrokinetic Turbine Designed for Unmanned Underwater Mooring Platforms

2019 ◽  
Vol 7 (12) ◽  
pp. 465 ◽  
Author(s):  
Zhigao Dang ◽  
Zhaoyong Mao ◽  
Baowei Song ◽  
Wenlong Tian
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Pressure Fluctuations ◽  
Noise Pollution ◽  
Horizontal Axis ◽  
Acoustic Analogy ◽  
Noise Emission ◽  
Suction Surface ◽  
Noise Characteristics ◽  
Hydrokinetic Turbine

Operating horizontal axis hydrokinetic turbine (HAHT) generates noise affecting the ocean environment adversely. Therefore, it is essential to determine the noise characteristics of such types of HAHT, as large-scale turbine sets would release more noise pollution to the ocean. Like other rotating machinery, the hydrodynamic noise generated by the rotating turbine has been known to be the most important noise source. In the present work, the transient turbulent flow field of the HAHT is obtained by incompressible large eddy simulation, thereafter, the Ffowcs Williams and Hawkings acoustic analogy formulation is carried out to predict the noise generated from the pressure fluctuations of the blade surface. The coefficient of power is compared with the experimental results, with a good agreement being achieved. It is seen from the pressure contours that the 80% span of the blade has the most severe pressure fluctuations, which concentrate on the region of leading the edge of the airfoil and the suction surface of the airfoil. Then, the noise characteristics around a single turbine are systematically studied, in accordance with the results of the flow field. The noise characteristics around the whole turbine are also investigated to determine the directionality of the noise emission of HAHT.

The Effect of Wavy Leading Edge on Low Speed Turbine Cascade Aerodynamic and Acoustic Performance

2015 ◽  
Author(s):  
Fan Tong ◽  
Wei-Yang Qiao ◽  
Liang-Feng Wang ◽  
Kun-Bo Xu ◽  
Wei-Jie Chen ◽  
...  
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Pressure Fluctuation ◽  
Leading Edge ◽  
Temporal Correlation ◽  
Broadband Noise ◽  
Turbine Cascade ◽  
Acoustic Analogy ◽  
Downstream Flow ◽  
Cascade Interaction

LES and acoustic analogy are performed to investigate the effect of wavy leading edge on a linear low pressure turbine cascade aerodynamic performance and the turbulence cascade interaction noise. One straight leading edge cascade and two different wavy leading edge cascades are studied. In each case a rod with a diameter of 2.05mm is placed upstream of the cascade to produce wake which will then interact with the cascade leading edge. Results show that the wavy leading edge can reduce the turbulence cascade interaction noise peak by up to about 6∼8dB in narrow band and attenuate interaction broadband noise by about 3dB in the frequency range below 4000Hz. However, wavy leading edge can lead to a self noise increase in some frequency and increase cascade total pressure loss. Wavy leading edge can change the flow field near the leading edge while the further downstream flow field is altered only a little. The mechanism of noise reduction is also investigated. It is shown that wavy leading edge can reduce blade surface pressure fluctuation near the leading edge. In addition, the spatial-temporal correlation coefficient of pressure fluctuation near the blade leading edge is also decreased. These factors may work jointly and contribute to the final noise reduction.

Numerical Simulation and Experimental Research of Hydrophone Flow Noise

2020 ◽  
Author(s):  
Mingyuan Li ◽  
Jianzhang Liu ◽  
Yan Wei ◽  
Fengzhong Qu ◽  
Minhao Zhang ◽  
...  
Keyword(s):  
Flow Field ◽  
Acoustic Communication ◽  
Communication System ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Sound Field ◽  
Underwater Acoustic Communication ◽  
Acoustic Analogy ◽  
Underwater Acoustic ◽  
Flow Noise

Abstract Underwater acoustic communication is an important technology in deep-sea research. In underwater acoustic communication system, when hydrophone as acoustic receiver is exposed to sea environment and moves along with an underwater vehicle, its performance is prone to be affected by various ambient noises, among which its generated flow noise is the major source. This would especially influence the performance and shorten the communication distance of underwater acoustic communication system. In this paper, we try to unveil how the flow field is correlated with the flow noise of hydrophone. The Large Eddy Simulation (LES) method and acoustic analogy were used to simulate the flow field and the sound field around hydrophone, respectively. The flow noise of hydrophone at different moving velocities was obtained. Then experiments in an anechoic tank were carried out to verify the simulation results. The subsequent analysis of the experimental results shows that the flow noise has obvious influence on underwater communication, and as the hydrophone moves faster, its sound pressure level climbs up higher. This study also further verifies the reliability of simulating the flow noise of bare hydrophone by computational fluid dynamics, and provides the theoretical basis for improving the signal-to-noise ratio of low-frequency underwater acoustic communication system.

scholarly journals Prediction of flow noise around a cylinder based on Large-Eddy Simulation and acoustic analogy method

2019 ◽  
Vol 283 ◽  
pp. 08003
Author(s):  
Qikai Qin ◽  
Dejiang Shang ◽  
Yongwei Liu ◽  
Tianyu Wang
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Transient Flow ◽  
Turbulent Model ◽  
Acoustic Analogy ◽  
Flow Around A Cylinder ◽  
Flow Noise ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Field Noise

In this article, a hybrid method combining large eddy simulation with acoustic analogy is presented to predict three-dimensional far field noise induced by flow around a cylinder. Firstly, the governing equation including RANS equations with shear-stress transport (SST) k-ω turbulent model is numerically solved for steady flow field by using Ansys Fluent. Transient flow field is numerically solved by LES. Then, the flow field simulation results are used to compute the flow-induced noise with the FW-H integral equation method and BEM method based on Lighthill acoustic analogy equation in Actran. Before using for flow around a cylinder, accuracy of flow turbulent model in predicting turbulent flow around a cylinder is tested by comparing with available experimental data. According on the simulation result, the characteristic of the acoustic field, noise at some special points in frequency domain, the noise radiation directivity are studied. Analysis of noise distribution and frequency spectrum curves shows that dipole source takes the dominant place in the noise around a cylinder under the conditions of this article. The flow noise around a cylinder is mainly concentrated in the low frequency range.

scholarly journals The Flow Noise Characteristics of a Control Valve

2014 ◽  
Vol 8 (1) ◽  
pp. 960-966
Author(s):  
Xin Nie ◽  
Yangyang Zhu ◽  
Lei Li
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Acoustic Pressure ◽  
Low Frequency ◽  
Control Valve ◽  
Pressure Amplitude ◽  
Acoustic Analogy ◽  
Flow Noise ◽  
Noise Characteristics ◽  
Valve Opening

Using the enterprise’s valve as the research object, the research studied the characteristics of the flow field and noise of the valve. The theory of (LES) LES and Lighthill acoustic analogy is applied to study the flow noise at 100% opening and at 70% opening of valve in the same flow. The result shows that the region of variation of pressure and velocity is in the valve sleeve window. The sound pressure spectrum characteristics of the same group of monitoring points were similar, when they were in low frequency. Acoustic pressure amplitude was observed to be relatively small, when monitoring points were in high frequency. When the valve opening decreased, because of the throttle effect of valve windows, the whole dB SPL of valve became strong. The noise outside the valve exhibited dipole characteristics.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

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