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Tomographic TR-PIV measurement of coherent structure spatial topology utilizing an improved quadrant splitting method

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Science China(Physics,Mechanics & Astronomy) 2012年第10期55卷 1863-1872页

作者： yang shaoqiong JIANG Nan Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin 300072China State Key Laboratory of Non-linear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin 300072China

In this paper,we calculated the spatial local-averaged velocity strains along the streamwise direction at four spatial scales according to the concept of spatial local-averaged velocity structure function by using the three-dimensional three-component database of time series of velocity vector field in the turbulent boundary layer measured by tomographic time-resolved particle image *** improved quadrant splitting method,based on the spatial local-averaged velocity strains together with a new conditional sampling phase average technique,was introduced as a criterion to detect the coherent structure ***,we used them to detect and extract the spatial topologies of fluctuating velocity and fluctuating vorticity whose center is a strong second-quadrant event(Q2) or a fourth-quadrant event(Q4).Results illustrate that a closer similarity of the multi-scale coherent structures is present in the wall-normal direction,compared to the one in the other two *** relationship among such topological coherent structures and Reynolds stress bursting events,as well as the fluctuating vorticity was *** other burst events are surveyed(the first-quadrant event Q1 and the third-quadrant event Q3),a fascinating bursting period circularly occurs:Q4-S-Q2-Q3-Q2-Q1-Q4-S-Q2-Q3-Q2-Q1 in the center of such topological structures along the streamwise *** addition,the probability of the Q2 bursting event occurrence is slightly higher than that of the Q4 event *** spatial instable singularity that almost simultaneously appears together with typical Q2 or Q4 events has been observed,which is the main character of the mutual induction mechanism and vortex auto-generation mechanism explaining how the turbulence is produced and maintained.

关键词： turbulent boundary layer coherent structure burst TR-PIV Q2/Q4 local-averaged velocity strain quadrant splittingmethod

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Study on local topology model of low/high streak structures in wall-bounded turbulence by tomographic time-resolved particle image velocimetry

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Applied Mathematics and Mechanics(English Edition) 2015年第9期36卷 1121-1130页

作者： Haiping TIAN Nan JIANG Yongxiang HUANG shaoqiong yang Department of Mechanics Tianjin University Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The relationship between the in the logarithmic law （log-law） region of bursting event and the low/high-speed streak a turbulent boundary layer is investigated. A tomographic time-resolved particle image velocimetry （TRPIV） system is used to measure the instantaneous three-dimensional-three-component （3D-3C） velocity field. The momentum thickness based Reynolds number is about 2 460. The topological information in the log-law region is obtained experimentally. It is found that the existence of the quadrupole topological structure implies a three-pair hairpin-like vortex packet, which is in connection with the low/high-speed streak. An idealized 3D topological model is then proposed to characterize the observed hairpin vortex packet and low/high-speed streak.

关键词： wall turbulence quadrupole topological structure hairpin vortex low/highspeed streak tomographic time-resolved particle image velocimetry (TRPIV) system

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Design,hydrodynamic analysis,and testing of a bioinspired controllable wing mechanism with multi-locomotion modes for hybrid-driven underwater gliders

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Science China(Technological Sciences) 2021年第12期64卷 2688-2708页

作者： SUN TongShuai WANG YanHui yang shaoqiong WANG Cheng ZHANG LianHong Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education Tianjin UniversityTianjin 300072China Qingdao Pilot National Laboratory for Marine Science and Technology(QNLM) Qingdao 266237China

Hybrid-driven technology,which can improve the sailing performance of underwater gliders(UGs),has been successfully used in ocean ***,a hybrid-driven UG(HUG)with an added tail propeller is still unable to achieve backward and turning motion with a body length radius,and the hydrodynamic pitch moment acting on the HUG that is mainly caused by the fixed-wing makes it difficult to achieve high-precision attitude control during fixed-depth *** solve this problem,a two-degree-of-freedom bioinspired controllable wing mechanism(CWM)is proposed to improve the maneuverability and cruising ability of *** CWM can realize five motion modes:modifying the dihedral angle or anhedral angle,changing the frontal area of the wing,switching the wing from horizontal to be a vertical rudder,flapping the wing as propulsion,and rotating the wing as a vector ***,the design process of the CWM is provided,and hydrodynamic forces in each motion mode of three CWMs with different trailing edge sweepback angles(TESA)and attitude angles are analyzed through computational fluid dynamics *** relationship between hydrodynamics and the attitude angles or TESA of the CWM is ***,experiments are conducted to measure the hydrodynamics of the CWM when it is in a flapping wing mode and rotating the wing as a vector propeller,*** hydrodynamic forces obtained from the simulation are consistent with data measured by a force sensor,proving the credibility of the simulated ***,by applying the results of the hydrodynamic force in this study,the flapping trajectory of the wingtip is planned using the cubic spline interpolation ***,two underwater demo vehicles with a pair of CWMs are developed,and experiments are conducted in a water tank,further validating and demonstrating the feasibility of the proposed CWM.

关键词： controllable wing mechanism hybrid-driven underwater glider bioinspired design multi-locomotion modes

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Design,Hydrodynamic Analysis,and Testing of a Bio-inspired Movable Bow Mechanism for the Hybrid-driven Underwater Glider

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Journal of Bionic Engineering 2023年第4期20卷 1493-1513页

作者： Yanhui Wang Yudong Guo shaoqiong yang Tongshuai Sun Xi Wang Huihui Zhou Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education Tianjin UniversityTianjin300072China The Joint Laboratory of Ocean Observing and Detection Laoshan LaboratoryQingdao266237China

Hybrid-driven Underwater Glider(HUG)is a new type of underwater vehicle which integrates the functions of an Autonomous Underwater Glider(AUG)and an Autonomous Unmanned Vehicle(AUV).Although HUG has the characteristics of long endurance distance,its maneuverability still has room to be *** work introduces a new movement form of the neck of the underwater creature into HUG and proposes a parallel mechanism to adjust the attitude angle and displacement of the HUG’s bow,which can improve the steering ***,the influence of bow movement and rotation on the hydrodynamic force and flow field of the whole machine is analyzed by using the Computational Fluid Dynamics(CFD)*** degree of freedom,attitude control range and movement amount of the Movable Bow Mechanism(MBM)are obtained,and then the design of MBM is completed based on these ***,the kinematic and dynamic models of MBM are established based on the closed vector method and the Lagrange equation,respectively,which are fully verified by comparing the results of simulation in Matlab and Adams software,then a Radial Basis Function(RBF)neural network adaptive sliding mode controller is designed to improve the dynamic response effect of the output parameters of ***,a prototype of MBM is manufactured and *** kinematic,dynamics model and controller are verified by experiments,which provides a basis for applying MBM in HUGs.

关键词： Underwater glider Movable bow mechanism Hydrodynamic simulation Steering maneuverability

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Coherent structures over riblets in turbulent boundary layer studied by combining time-resolved particle image velocimetry(TRPIV),proper orthogonal decomposition(POD),and finite-time Lyapunov exponent(FTLE)

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Chinese Physics B 2018年第10期27卷 395-404页

作者： Shan Li Nan Jiang shaoqiong yang Yongxiang Huang Yanhua Wu School of Mechanical Engineering Tianjin University Tianjin 300072 China Xiamen University Xiamen 361102 China Nanyang Technological University Singapore 639798 Republic of Singapore

Time-resolved particle image velocimetry（TRPIV） experiments are performed to investigate the coherent structure＇s performance of riblets in a turbulent boundary layer（TBL） at a friction Reynolds number of 185. To visualize the energetic large-scale coherent structures（CSs） over a smooth surface and riblets, the proper orthogonal decomposition（POD） and finite-time Lyapunov exponent（FTLE） are used to identify the CSs in the TBL. Spatial-temporal correlation is implemented to obtain the characters and transport properties of typical CSs in the FTLE fields. The results demonstrate that the generic flow structures, such as hairpin-like vortices, are also observed in the boundary layer flow over the riblets, consistent with its smooth counterpart. Low-order POD modes are more sensitive to the riblets in comparison with the high-order ones,and the wall-normal movement of the most energy-containing structures are suppressed over riblets. The spatial correlation analysis of the FTLE fields indicates that the evolution process of the hairpin vortex over riblets are inhibited. An apparent decrease of the convection velocity over riblets is noted, which is believed to reduce the ejection/sweep motions associated with high shear stress from the viscous sublayer. These reductions exhibit inhibition of momentum transfer among the structures near the wall in the TBL flows.

关键词： turbulent boundary layer riblets proper orthogonal decomposition finite-time Lyapunov exponent

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3D Reconstruction Technique for Tomographic PIV

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Transactions of Tianjin University 2015年第6期21卷 533-540页

作者：姜楠包全杨绍琼 School of Mechanical Engineering Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics Haiying Enterprise Group Co. Ltd School of Mechanical and Aerospace Engineering Nanyang Technological University

Tomographic particle image velocimetry(Tomo-PIV) is a state-of-the-art experimental technique based on a method of optical tomography to achieve the three-dimensional(3D) reconstruction for threedimensional three-component(3D-3C) flow velocity measurements. 3D reconstruction for Tomo-PIV is carried out herein. Meanwhile, a 3D simplified tomographic reconstruction model reduced from a 3D volume light intensity field with 2D projection images into a 2D Tomo-slice plane with 1D projecting lines, i.e., simplifying this 3D reconstruction into a problem of 2D Tomo-slice plane reconstruction, is applied thereafter. Two kinds of the most well-known algebraic reconstruction techniques, algebraic reconstruction technique(ART) and multiple algebraic reconstruction technique(MART), are compared as well. The principles of the two reconstruction algorithms are discussed in detail, which has been performed by a series of simulation images, yielding the corresponding reconstruction images that show different features between the ART and MART algorithm, and then their advantages and disadvantages are discussed. Further discussions are made for the standard particle image reconstruction when the background noise of the pre-initial particle image has been removed. Results show that the particle image reconstruction has been greatly improved. The MART algorithm is much better than the ART. Furthermore, the computational analyses of two parameters(the particle density and the number of cameras), are performed to study their effects on the reconstruction. Lastly, the 3D volume particle field is reconstructed by using the improved algorithm based on the simplified 3D tomographic reconstruction model, which proves that the algorithm simplification is feasible and it can be applied to the reconstruction of 3D volume particle field in a Tomo-PIV system.

关键词： tomographic PIV image reconstruction ART MART ghost particle

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北风卷地白草折——漫话湍流边界层中的涡旋结构

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力学与实践 2020年第6期42卷 818-824页

作者：杨绍琼姜楠天津大学机械工程学院天津300354

通过欣赏唐朝著名边塞诗人岑参的《白雪歌送武判官归京》和《走马川行奉送出师西征》中描写北风的佳句,从流体力学的角度解释了“北风卷地白草折”的原因,向读者介绍了湍流基础研究的前沿课题——湍流边界层及其复杂的涡旋结构。

关键词：湍流边界层涡旋相干结构

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纵向沟槽壁面湍流边界层内类开尔文-亥姆霍兹涡结构的流动显示

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力学学报 2015年第3期47卷 529-533页

作者：杨绍琼崔宏昭姜楠诺丁汉大学工程学院天津大学机械工程学院力学系天津300072 天津市现代工程力学重点实验室天津300072

纵向沟槽壁面的湍流边界层,当沟槽的脊-脊内尺度无量纲展向间距s^+在一定范围内,与光滑壁面湍流边界层相比,具有减阻效应;并在s^+约为17个黏性长度单位时减阻效果达到最优,之后其减阻趋弱,直至增阻;其原因可能是沟槽壁面湍流边界层由于... 详细信息

纵向沟槽壁面的湍流边界层,当沟槽的脊-脊内尺度无量纲展向间距s^+在一定范围内,与光滑壁面湍流边界层相比,具有减阻效应;并在s^+约为17个黏性长度单位时减阻效果达到最优,之后其减阻趋弱,直至增阻;其原因可能是沟槽壁面湍流边界层由于"开尔文-亥姆霍兹"不稳定性而产生的一种"类开尔文-亥姆霍兹"展向涡结构.实验采用烟雾流动显示技术,首次在风洞中显示了这种"类开尔文-亥姆霍兹"展向涡结构,确认了其存在性,并在概念上简单勾勒了其结构模型.

关键词：湍流边界层开尔文-亥姆霍兹不稳定性 “类开尔文-亥姆霍兹”涡沟槽流动显示

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轻于粉蝶瘦于蜂——漫话蜻蜓的流体力学奥秘

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力学与实践 2019年第4期41卷 478-482页

作者：姜楠杨绍琼天津大学机械工程学院

从鉴赏描写蜻蜓的古代诗词入手,介绍了蜻蜓这种经过亿万年进化昆虫的神奇流体力学特性。重点介绍了蜻蜓的复眼、蜻蜓翅膀消除振颤、蜻蜓表皮的超疏水与鳞片减阻、蜻蜓幼虫的喷水推进等力学特性及其对工程技术发展的重要启示,同时介绍了... 详细信息

从鉴赏描写蜻蜓的古代诗词入手,介绍了蜻蜓这种经过亿万年进化昆虫的神奇流体力学特性。重点介绍了蜻蜓的复眼、蜻蜓翅膀消除振颤、蜻蜓表皮的超疏水与鳞片减阻、蜻蜓幼虫的喷水推进等力学特性及其对工程技术发展的重要启示,同时介绍了蜻蜓机器人的发展现状。

关键词：蜻蜓复眼机翼振颤超疏水蜻蜓机器人

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Antisymmetric quadrupole mode of coherent structures in wall-bounded turbulence

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Theoretical & Applied Mechanics Letters 2013年第5期3卷 58-61页

作者： Haiping Tian shaoqiong yang Lu Cheng Yuan Wang Nan Jiang Department of Mechanics Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics State Key Laboratory of Nonlinear Mechanics Institute of Mechanics CAS

Abstract Experiments were conducted in a water tunnel by tomographic time-resolved particle image velocimetry （Tomo-TRPIV）. The Reynolds number Reo is 2 460 on the base of momentum thickness. According to the physical mechanism of the stretch and compression of multi-scale vortex structures in the wall-bounded turbulence, the topological characteristics of turbulence statistics in logarithmic layer were illustrated by local-averaged velocity structure function. During coherent structures bursting, results reveal that the topological structures of velocity gradients, velocity strain rates and vorticities behave as antisymmetric quadrupole modes. A three-layer antisymmetric quadrupole vortex packet confirms that there is a tight relationship between the outer layer and the near-wall layer.

关键词： wall-bounded turbulence antisymmetric quadrupole mode Tomo-TRPIV vortex packet,coherent structure

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