scholarly journals Numerical simulation of leakage flow field and acoustic characteristics for safety valve

2021 ◽  
Vol 336 ◽  
pp. 01007
Author(s):  
Fan Qian ◽  
Minghui Hu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Pressure Fluctuation ◽  
Large Scale ◽  
Safety Valve ◽  
Sound Field ◽  
Wall Pressure ◽  
Small Scale ◽  
Acoustic Analogy ◽  
Wall Pressure Fluctuation

Aiming at the internal leakage problem of spring type nuclear safety valve at the sealing surface, the flow field and sound field characteristics at the leakage height of 0.5mm between the valve disc and the valve seat sealing surface were studied, and the numerical simulation was carried out based on large eddy simulation(LES) and mohring acoustic analogy method, and compare the effects of acoustic wall pressure fluctuation(AWPF) and turbulent wall pressure fluctuation(TWPF) as the excitation source on the external sound field of the valve. The simulation results show that: the change gradient of velocity field and pressure field at the leakage port of safety valve is significant and form vortices of different sizes. The small-scale vortices are mainly in the leakage port, while the large-scale vortices mainly exist in the flow channel; When the valve is leaking, the noise is mainly dominated by high-pressure injection noise, its spectrum curve shows wide-band characteristics, and the external noise of the valve is mainly caused by AW P F. The above research results can provide a theoretical basis for the safety valve online detection method.

scholarly journals A study of the flow-field evolution and mixing in a planar turbulent jet using direct numerical simulation

2002 ◽  
Vol 450 ◽  
pp. 377-407 ◽  
Author(s):  
S. A. STANLEY ◽  
S. SARKAR ◽  
J. P. MELLADO
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Computational Study ◽  
Practical Interest ◽  
Small Scale ◽  
Mixing Process ◽  
Mean Velocity ◽  
Small Scales

Turbulent plane jets are prototypical free shear flows of practical interest in propulsion, combustion and environmental flows. While considerable experimental research has been performed on planar jets, very few computational studies exist. To the authors' knowledge, this is the first computational study of spatially evolving three-dimensional planar turbulent jets utilizing direct numerical simulation. Jet growth rates as well as the mean velocity, mean scalar and Reynolds stress profiles compare well with experimental data. Coherency spectra, vorticity visualization and autospectra are obtained to identify inferred structures. The development of the initial shear layer instability, as well as the evolution into the jet column mode downstream is captured well.The large- and small-scale anisotropies in the jet are discussed in detail. It is shown that, while the large scales in the flow field adjust slowly to variations in the local mean velocity gradients, the small scales adjust rapidly. Near the centreline of the jet, the small scales of turbulence are more isotropic. The mixing process is studied through analysis of the probability density functions of a passive scalar. Immediately after the rollup of vortical structures in the shear layers, the mixing process is dominated by large-scale engulfing of fluid. However, small-scale mixing dominates further downstream in the turbulent core of the self-similar region of the jet and a change from non-marching to marching PDFs is observed. Near the jet edges, the effects of large-scale engulfing of coflow fluid continue to influence the PDFs and non-marching type behaviour is observed.

Modeling of wall‐pressure fluctuation based on time‐mean flow field

2002 ◽  
Vol 112 (5) ◽  
pp. 2218-2218
Author(s):  
Yu‐Tai Lee ◽  
William Blake ◽  
Theodore Farabee ◽  
Michael Tse ◽  
Joseph Brown
Keyword(s):  
Flow Field ◽  
Pressure Fluctuation ◽  
Wall Pressure ◽  
Mean Flow ◽  
Wall Pressure Fluctuation

Numerical Study on Flow Characteristics and Flow Induced Noise of Flexible NACA0018 Airfoil

2015 ◽  
Author(s):  
Rui-xian Ma ◽  
Guang-hui Zhang ◽  
Zhan-sheng Liu ◽  
Dian-lai Li
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Vortex Shedding ◽  
Pressure Fluctuation ◽  
Wall Pressure ◽  
Attack Angle ◽  
Arbitrary Boundary ◽  
Wall Pressure Fluctuation ◽  
Flow Induced Noise ◽  
Naca0018 Airfoil

A numerical investigation of unsteady flow field and flow induced noise frequency characteristics of a 2-D NACA0018 airfoil taking into account the airfoil’s deformation with different angles of attack is presented. The large eddy simulation (LES) method is employed to compute the unsteady flow field, the dynamic response of structure is simulated with finite element code, and the two different fields are coupled via a two way coupling method with the exchange of pressure and displacement. The far field sound levels and frequency features are calculated using FW-H equation with arbitrary boundary movement involved. The flow field results show that flow separation and wall pressure fluctuation are controlled by the deformation of flexible airfoil significantly, which indicates the effects of attack angle are attenuated. Compared with common quasi-periodic vortex shedding, the vortex shedding at 0 degree is obtained to be a restrict periodic process, and the shedding frequency is about 950Hz, and this phenomenon is confirmed both by wall pressure fluctuation and acoustic spectrum characteristics. In addition, the overall sound pressure levels in chordwise and normal direction are influenced by attack angle in different ways.

Development of Rotating Stall Cell Under Coexisting Phenomena of Surge and Rotating Stall in an Axial-Flow Compressor

2019 ◽  
Author(s):  
Yuu Sakata ◽  
Shuji Ando ◽  
Nobumichi Fujisawa ◽  
Yutaka Ohta
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Rotating Stall ◽  
Wall Pressure ◽  
Stable Operation ◽  
Wall Pressure Fluctuation ◽  
Peak Point ◽  
Unsteady Characteristics ◽  
Large Cycle

Abstract The relationship between the growth of the stall cell and variation in the surge behavior was experimentally investigated. The aim of this study was to reveal the effect of the stall cell on the surge behavior from the viewpoint of the inner flow structure. In the experiment, the unsteady compressor characteristics during the surge and rotating stall were obtained by using a precision pressure transducer and a one-dimensional single hotwire anemometer. Under the coexisting states of surge and rotating stall, various surge behaviors were observed by throttling the mass flow rate. When the flow rate was set such that the surge behavior switched, an irregular surge was observed. During the irregular cycle, two different cycles were selected randomly corresponding to the stall behavior. When the amplitude of the plenum pressure is relatively large among the measurement results, the absolute value of the time-change rate in the flow coefficient and the static pressure-rise coefficient tend to be high. This shows that the flow field during stable operation near the peak point of the unsteady characteristics changes rapidly. In this case, an auto-correlation function of the wall-pressure fluctuation data showed that the stall inception of the compressor was induced earlier in the large cycle compared with the case of the top cycle. When studying the growth of the stall cell during the stalling process of the large cycle, the wall-pressure fluctuation data showed that the stall cell rapidly grew by gathering more than one spike-type disturbance into one stall cell. In this case, the stall cell fully expanded along the circumferential direction and developed into a deep stall. Therefore, the key factors that determine the surge behavior are the sudden change in the flow field near the peak point of the unsteady characteristics and the rapid growth in the stall cell during the stalling process.

Wall pressure-fluctuation spectra at small backward-facing steps

2000 ◽  
Author(s):  
B. Efimtsov ◽  
N. Kozlov ◽  
S. Kravchenko ◽  
A. Andersson
Keyword(s):  
Pressure Fluctuation ◽  
Wall Pressure ◽  
Wall Pressure Fluctuation

Analysis of the pressure fluctuation in the flow field of a large-scale cyclone separator

2019 ◽  
Vol 343 ◽  
pp. 49-57 ◽  
Author(s):  
Mengda Jia ◽  
Di Wang ◽  
Chaoyu Yan ◽  
Jianfei Song ◽  
Qiang Han ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Fluctuation ◽  
Large Scale ◽  
Cyclone Separator

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2018 ◽  
Author(s):  
Feng Jie Zheng ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Pressure Fluctuation ◽  
Large Scale ◽  
Three Dimensional ◽  
Industrial Process ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial process. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operation such as rapid valve opening/closing. To investigate the pressure especially the pressure fluctuation in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled by a zero-dimensional virtual point, the pipe is modeled by a one-dimensional MOC, and the valve is modeled by a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted, in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve are obtained. The results show that the proposed model is in good agreement with the full CFD model in both large-scale and small-scale spaces. Moreover, the proposed model is more computationally efficient than the CFD model, which provides a feasibility in the analysis of complex RPV system within an affordable computational time.

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