Study on the Mechanism and Characteristics of Transient Noise of the Steam Discharge Pipes

2018 ◽  
Author(s):  
Lu Dai ◽  
Zhiguo Wei ◽  
Jun Wu ◽  
Yong Liu ◽  
Can Ma ◽  
...  
Keyword(s):  
Flow Field ◽  
Control Valve ◽  
Simulation Method ◽  
Opening Angle ◽  
Key Factors ◽  
Noise Sources ◽  
Steam Power ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

While the steam power plant runs at low load, the drastic vibration and noise of the steam discharge pipes will be induced by the discharging process of high temperature and high pressure steam. Motived by this, the analytical model of inner flow field of the steam discharge pipes is modeled in this paper. The large eddy simulation method is used to analyze the characteristics of the inner flow field of the steam discharge pipes. The mechanism of transient noise in the process of steam discharging, by the comparison of variation law of the inner flow field with different opening angles of control valve or different time, is obtained. On this basis, the K-FWH method is employed to calculate the transient noise of steam discharging. The results show that the key factors of transient noise generation can be owed to the impact effect of steam jet flow on the surface of valve structure, the shear and friction effect induced by the uneven flow, the energy loss of vortex collapse in the process of valve throttling, and the surface noise sources induced by turbulent flow and so on. The throttle noise induced by control valve is presented as significant broadband characteristics in the frequency domain, and the level of transient noise increases with the decreasing of the opening angle of control valve.

scholarly journals Subgrid-scale models and large-eddy simulation of oxygen stream disintegration and mixing with a hydrogen or helium stream at supercritical pressure

2011 ◽  
Vol 679 ◽  
pp. 156-193 ◽  
Author(s):  
EZGI S. TAŞKINOĞLU ◽  
JOSETTE BELLAN
Keyword(s):  
Heat Flux ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Correction Term ◽  
A Priori ◽  
Supercritical Pressure ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

For flows at supercritical pressure, p, the large-eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equations utilize transport properties depending on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid-scale (SGS) fluxes but also new SGS terms, each denoted as a ‘correction’. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations and represent differences, other than contributed by the convection terms, between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) which is the difference between the filtered divergence of the molecular heat flux and the divergence of the molecular heat flux computed as a function of the filtered flow field. We revisit here a previous a priori study where we only had partial success in modelling the q-correction term and show that success can be achieved using a different modelling approach. This a priori analysis, based on a temporal mixing-layer direct numerical simulation database, shows that the focus in modelling the q-correction should be on reconstructing the primitive variable gradients rather than their coefficients, and proposes the approximate deconvolution model (ADM) as an effective means of flow field reconstruction for LES molecular heat-flux calculation. Furthermore, an a posteriori study is conducted for temporal mixing layers initially containing oxygen (O) in the lower stream and hydrogen (H) or helium (He) in the upper stream to examine the benefit of the new model. Results show that for any LES including SGS-flux models (constant-coefficient gradient or scale-similarity models; dynamic-coefficient Smagorinsky/Yoshizawa or mixed Smagorinsky/Yoshizawa/gradient models), the inclusion of the q-correction in LES leads to the theoretical maximum reduction of the SGS molecular heat-flux difference; the remaining error in modelling this new subgrid term is thus irreducible. The impact of the q-correction model first on the molecular heat flux and then on the mean, fluctuations, second-order correlations and spatial distribution of dependent variables is also demonstrated. Discussions on the utilization of the models in general LES are presented.

Computational investigation and passive control of vehicle sunroof buffeting

2019 ◽  
Vol 26 (9-10) ◽  
pp. 747-756
Author(s):  
Yansong He ◽  
Quanzhou Zhang ◽  
Changfa An ◽  
Yong Wang ◽  
Zhongming Xu ◽  
...  
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
The Road ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Utility Vehicle

A computational fluid dynamics simulation method based on large eddy simulation is presented and applied to compute the sunroof buffeting of a sport utility vehicle. The simulation result, i.e. the buffeting level curve, coincides well with the road test. The simulation method is then employed to investigate the sunroof buffeting of a vehicle during the development process in the range of 30 km/h–90 km/h. The results show that the most severe sunroof buffeting occurs at 70 km/h, which corresponds to the resonant frequency of the cabin. Flow field visualizations reveal that strong pressure fluctuations are generated inside the cabin due to vortex shedding from the leading edge and impinging onto the trailing edge of the sunroof opening, which explains the mechanism of sunroof buffeting. A new deflector with a gap and a notched upper edge is designed to replace the original castle type deflector. The simulation results show that the newly designed deflector can reduce the buffeting level to 97.9 dB; that is, the sunroof buffeting is completely eliminated. Moreover, the phenomenon of sunroof buffeting reduction is explained by comparing and analyzing the flow field between the newly designed deflector and the original deflector.

Supersonic Jet Noise Reduction Technologies for Gas Turbine Engines

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
David Munday ◽  
Nick Heeb ◽  
Ephraim Gutmark ◽  
Junhui Liu ◽  
K. Kailasanath
Keyword(s):  
Flow Field ◽  
Near Field ◽  
Supersonic Jet ◽  
Acoustic Emissions ◽  
Nozzle Geometry ◽  
Axial Position ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
The Impact

This paper presents observations and simulations of the impact of several technologies on modifying the flow-field and acoustic emissions from supersonic jets from nozzles typical of those used on military aircraft. The flow-field is measured experimentally by shadowgraph and particle image velocimetry. The acoustics are characterized by near- and far-field microphone measurements. The flow- and near-field pressures are simulated by a monotonically integrated large eddy simulation. Use of unstructured grids allows accurate modeling of the nozzle geometry. The emphasis of the work is on “off-design” or nonideally expanded flow conditions. The technologies applied to these nozzles include chevrons, fluidic injection, and fluidically enhanced chevrons. The fluidic injection geometry and the fluidic enhancement geometry follow the approach found successful for subsonic jets by employing jets pitched 60 deg into the flow, impinging on the shear layer just past the tips of the chevrons or in the same axial position when injection is without chevrons.

scholarly journals Large Eddy Simulation and Flow Field Analysis of Car on the Bridge under Turbulent Crosswind

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Juyue Ding ◽  
Weitan Yin ◽  
Yongqi Ma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Wind Tunnel Test ◽  
Simulation Method ◽  
Field Analysis ◽  
Long Span Bridges ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics

As more long-span bridges continue to be completed and opened to traffic, the safety of cars driving across the bridge has attracted more and more attention, especially when the car is suddenly affected by the crosswind, the car is likely to have direction deviation or even a rollover accident. In this paper, the large eddy simulation method is used to study the flow field characteristics and safety of the car on the bridge under the turbulent crosswind. The numerical simulation model is established by referring to the Donghai Bridge, and the correctness of the car model is validated by combining with the data of wind tunnel test. The influence of factors such as the porosity and height of the bridge guardrail and the Reynolds number of airflow on the flow field characteristics is analyzed. The study shows that, in order to ensure the safety of cars on the bridge, the bridge guardrail porosity should be small, 35.8% is more suitable, the guardrail height should be more suitable within the range of 1.5–1.625 meters, and the Reynolds number should not be 3.51e + 5. The research results of this paper will provide reference for the optimal design of bridge guardrail.

Large-Eddy Simulation of Turbine Rim Seal Flow

2018 ◽  
Author(s):  
Alexej Pogorelov ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Level Set ◽  
Large Scale ◽  
Stokes Equations ◽  
Axial Flow ◽  
Dominant Mode ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

The flow field in a complete one-stage axial-flow turbine with 30 stator and 62 rotor blades is investigated by large-eddy simulation (LES). To solve the compressible Navier-Stokes equations, a massively parallelized finite-volume flow solver based on an efficient Cartesian cut-cell/level-set approach, which ensures a strict conservation of mass, momentum and energy, is used. This numerical method contains two adaptive Cartesian meshes, one mesh to track the embedded surface boundaries and a second mesh to resolve the fluid domain and to solve the conservation equations. The overall approach allows large scale simulations of turbomachinery applications with multiple relatively moving boundaries in a single frame of reference. The relative motion of the geometries is described by a kinematic motion level-set interface method. The focus of the numerical analysis is on the flow inside the cavity between the stator and the rotor disks. Full 360° computations of the turbine stage with a single lip rim seal geometry are conducted. First, the impact of the mesh resolution on the LES results is analyzed. Second, the LES results are compared to experimental data, followed by a detailed analysis of the flow field inside the rotor-stator wheel space. A dominant mode unrelated to the rotor frequency and its harmonics is identified, which shows a major impact on the ingress of the hot gas into the rotor-stator wheel space.

A numerical investigation of flow-induced cavity noise control

2021 ◽  
Vol 263 (6) ◽  
pp. 298-306
Author(s):  
Zhenan Song ◽  
Daoqing Chang ◽  
Hongling Sun
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Shear Layer ◽  
Numerical Investigation ◽  
Leading Edge ◽  
Simulation Method ◽  
Peak Amplitude ◽  
Flow Rates ◽  
Eddy Simulation ◽  
Large Eddy

The influence of the multiple ultrasound transmitting units and the steady injecting water or suck-ing water on the shear layer oscillation and noise by flow-induced cavity is numerically investi-gated in this paper. The ultrasound transmitting units and the steady injecting water or sucking water are located upstream of the leading edge of the cavity. The flow field near the cavity is com-puted based on the large eddy simulation method (LES). The calculation and analysis results show that the peak amplitude of noise can be reduced by the steady injecting water at the leading edge of the opening. And within a specific range of flow rates, the greater the injecting rate is, the more obvious the peak amplitude of noise decreases

Recent improvements of actuator line-large-eddy simulation method for wind turbine wakes

2021 ◽  
Vol 42 (4) ◽  
pp. 511-526
Author(s):  
Zhiteng Gao ◽  
Ye Li ◽  
Tongguang Wang ◽  
Shitang Ke ◽  
Deshun Li
Keyword(s):  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Simulation Method ◽  
Eddy Simulation ◽  
Large Eddy
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