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.

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

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.

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

Intrinsic Mode Entropy Analysis of Tube-Wall Pressure Fluctuation Signals in the Kenics Static Mixer

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Hui-Bo Meng ◽  
Zhi-Qiang Liu ◽  
Yan-Fang Yu ◽  
Qiang Xiong ◽  
Jian-Hua Wu
Keyword(s):  
Pressure Fluctuation ◽  
Tube Wall ◽  
Sample Entropy ◽  
Wall Pressure ◽  
High Frequency Component ◽  
Static Mixer ◽  
Flow Rates ◽  
Multi Scale ◽  
Wall Pressure Fluctuation ◽  
Macro Scale

The multi-scale nonlinear hydrodynamics in Kenics Static Mixer (KSM) with 100 mm in diameter and 2 in aspect ratio was investigated in this work. The time series of tube-wall pressure fluctuation signals were measured at different flow rates ranged of 100~600 L•h-1 and at different axial positions in the range of 420~580 mm away from the cross-section of mixer inlet. It is difficult for composite signals to make an effective analysis by Sample Entropy (SampEn) based on a single scale. The complexity of tube-wall pressure fluctuation signals in a Kenics static mixer was investigated using Intrinsic Mode Entropy (IMEn) based on Sample Entropy algorithm and Empirical Mode Decomposition (EMD) method. Data sampling length and tolerance are optimized based on intrinsic mode entropy. Results of multi-scale analysis of pressure fluctuations indicated that the Sample entropy reaches maximum in the first scale and progressively decreases according to increase of the decomposed order. It is clear that the movement of high frequency component of the pressure signal is the most complicated and is rich in randomness. With the decomposition scales increasing, the complexity of signal decreases and approaches periodic motion eventually. The intrinsic mode entropy of the tube wall pressure signals in KSM has similar development tendencies in different flow rates. Besides, as the flow rates increased, the macro-scale vortexes play a more and more important role and guide the system to develop toward the stable state.

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