槽道内涡波流场的POD分析
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摘要
对槽道内涡波流场的瞬态速度矢量场进行了2DPIV测量实验,将2DPIV测量的矢量场数据进行POD分析,根据POD分解的各阶模态的能量比确定了表征涡波流场主导结构的前15阶模态。结果表明,POD分解的前15阶模态发现槽道内涡波流场是由槽道壁面剪切层诱导的涡列以及伴随的波状主流组成;流场中大尺度的涡旋发展为涡对,对波状主流的脉动频率产生影响;根据涡波流场中的驻点和鞍点,获取了流场的大尺度涡对、平均流场以及Helmholtz涡环等明显特征;最后根据POD分解的前15阶模态对槽道内涡波流场进行重组,重组流场表征了槽道内层流状态下波状主流的形态和涡旋共存的涡波结构以及驻点和鞍点的位置处涡旋的变化等主要特征,有效地剔除了PIV测量流场中的随机信息,保留了PIV测量流场的主导特征。
Transient velocity vector field of the channel vortex wave field was experimentally measured out using two-Dimension Particle Image Velocimetry(2 DPIV).Proper Orthogonal Decomposition(POD) technique was used to analyze the vector field data measured by 2 DPIV,and the first 15 modes were determined by the mode energy rate,which represented characteristics of dominated structure of the vortex wave field.The results showed that the first 15 modes of POD decomposition reflected the characteristics of the channel vortex wave field comprised of vortex columns induced by channel wall shear layers and accompanied wavy mainstream.The mainstream wavy pulsation frequency was affected by the vortex pair through the development of large-scale vortexes;According to vortex wave field in the stagnation point and the saddle point, distinctive features were obtained,i.e.,a large-scale vortex pair of the field,an average flow field and Helmholtz vortex ring.The vortex wave field was reconstructed in accordance with the first 15 modal vortexes.The reconstructed field represented the main features of a vortex wave structure of wavy mainstream forms,vortex of coexistence conditions,and the characteristics of the vortex flow changes in the stagnation points,saddle point position of field of channel laminar flow,remove.The random information of PIV measurements flow field was removed effectively,and the dominant features PIV measurements flow fields were retained.
Transient velocity vector field of the channel vortex wave field was experimentally measured out using two-Dimension Particle Image Velocimetry(2 DPIV).Proper Orthogonal Decomposition(POD) technique was used to analyze the vector field data measured by 2 DPIV,and the first 15 modes were determined by the mode energy rate,which represented characteristics of dominated structure of the vortex wave field.The results showed that the first 15 modes of POD decomposition reflected the characteristics of the channel vortex wave field comprised of vortex columns induced by channel wall shear layers and accompanied wavy mainstream.The mainstream wavy pulsation frequency was affected by the vortex pair through the development of large-scale vortexes;According to vortex wave field in the stagnation point and the saddle point, distinctive features were obtained,i.e.,a large-scale vortex pair of the field,an average flow field and Helmholtz vortex ring.The vortex wave field was reconstructed in accordance with the first 15 modal vortexes.The reconstructed field represented the main features of a vortex wave structure of wavy mainstream forms,vortex of coexistence conditions,and the characteristics of the vortex flow changes in the stagnation points,saddle point position of field of channel laminar flow,remove.The random information of PIV measurements flow field was removed effectively,and the dominant features PIV measurements flow fields were retained.
引文
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[19] Wei Z Y,Zang B,New T H,et al.A proper orthogonal decomposition study on the unsteady flow beha-viour of a hydrofoil with leading-edge tubercles[J].Ocean Engineering,2016,121:356-368.
[20] Greig D,Siddiqui K,Karava P,et al.Investigation of fundamental flow mechanisms over a corrugated waveform using proper orthogonal decomposition and spectral analyses[J].International Journal of Thermal Sciences,2015,96:160-172.
[2] Saha P,Biswas G,Mandal A C,et al.Investigation of coherent structures in a turbulent channel with buil-tin longitudinal vortex generators[J].International Journal of Heat and Mass Transfer,2017,104:178-198.
[3] Grenier E,Guo Y,Nguyen T T.Spectral instability of general symmetric shear flows in a two-dimensional channel[J].Advances in Mathematics,2016,292:52-110.
[4] Wilson H J,Loridan V.Linear instability of a highly shear-thinning fluid in channel flow[J].Journal of Non-Newtonian Fluid Mechanics,2015,223:200-208.
[5] 赵慧,韦安阳,罗坤,等.湍流槽道内近壁区域脉动速度特性研究[J].工程热物理学报.2016,37(3):551-555.(ZHAO Hui,WEI An-yang,LUO Kun,et al.Velocity fluctuations in the near-wall region of the turbulent channel flow[J].Journal of Engineering Thermophysics,2016,37(3):551-555.(in Chinese))
[6] Stephanoff K D,Pedley T J,Lawrence C J,et al.Fluid flow along a channel with an asymmetric oscillating constriction[J].Nature,1983,305(5936):692-695.
[7] Sobey I J.Observation of waves during oscillatory channel flow[J].Journal of Fluid Mechanics,1985,151:395-426.
[8] Bertram C D,Pedley T J.Steady and unsteady separation in an approximately two-dimensional indented channel[J].Journal of Fluid Mechanics,1983,130:315-345.
[9] 刘凤霞,刘志军,李丰,等.非对称槽道中涡旋波的特性研究 [J].力学学报,2005,37(6):682-688.(LIU Feng-xia,LIU Zhi-jun,LI Feng,et al.The study of the characteristic of vortex wave in an asymmetric channel [J].Chinese Journal of Theoretical and Applied Mechanics,2005,37(6):682-688.(in Chinese))
[10] Chaouat B,Schiestel R.Reynolds stress transport modelling for steady and unsteady channel flows with wall injection[J].Journal of Turbulence,2002,3(3):1-15.
[11] Bandyopadhyay S,Layek G C.Numerical computation of pulsatile flow through a locally constricted channel[J].Communications in Nonlinear Science and Numerical Simulation,2011,16(1):252-265.
[12] Deshmukh A,Vasava V,Patankar A,et al.Particle velocity distribution in a flow of gas-solid mixture through a horizontal channel[J].Powder Technology,2016,298:119-129.
[13] Duan F,Song K W,Li H R,et al.Numerical study of laminar flow and heat transfer characteristics in the fin side of the intermittent wavy finned flat tube heat exchanger[J].Applied Thermal Engineering,2016,103:112-127.
[14] Ayati A A,Kolaas J,Jensen A,et al.A PIV investigation of stratified gas-liquid flow in a horizontal pipe[J].International Journal of Multiphase Flow,2014,61:129-143.
[15] Besbes S,El Hajem M,Ben Aissia H,et al.PIV measurements and Eulerian-Lagrangian simulations of the unsteady gas-liquid flow in a needle sparger rectangular bubble column[J].Chemical Engineering Science,2015,126:560-572.
[16] Zou Y,Ye S S,Wang Y D,et al.CFD simulation and PIV measurement of liquid-liquid two-phase flow in pump-mix mixer[J].Journal of the Taiwan Institute of Chemical Engineers,2016,60:15-25.
[17] 傅鑫,李秋锋,黄国平,等.采用FFT-POD的非定常流动控制频谱和能谱特性研究[J].工程热物理学报,2016,37(7):1450-1458.(FU Xin,LI Qiu-feng,HUANG Guo -ping,et al.A study on frequency spectrum and energy spectrum of unsteady flow control by FFT-POD method[J].Journal of Engineering Thermophysics,2016,37(7):1450-1458.(in Chinese))
[18] Buhl S,Hartmann F,Hasse C.Identification of Large -Scale structure fluctuations in IC Engines using POD -Based conditional averaging[J].Oil & Gas Science and Technology,2016,71(1):1-10.
[19] Wei Z Y,Zang B,New T H,et al.A proper orthogonal decomposition study on the unsteady flow beha-viour of a hydrofoil with leading-edge tubercles[J].Ocean Engineering,2016,121:356-368.
[20] Greig D,Siddiqui K,Karava P,et al.Investigation of fundamental flow mechanisms over a corrugated waveform using proper orthogonal decomposition and spectral analyses[J].International Journal of Thermal Sciences,2015,96:160-172.