|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | Evaluating the accuracy performance of Lucas-Kanade algorithm in the circumstance of PIV application显示文摘Lucas-Kanade(LK) algorithm, usually used in optical flow filed, has recently received increasing attention from PIV community due to its advanced calculation efficiency by GPU acceleration. Although applications of this algorithm are continuously emerging,a systematic performance evaluation is still lacking. This forms the primary aim of the present work. Three warping schemes in the family of LK algorithm: forward/inverse/symmetric warping, are evaluated in a prototype flow of a hierarchy of multiple two-dimensional vortices. Second-order Newton descent is also considered here. The accuracy & efficiency of all these LK variants are investigated under a large domain of various influential parameters. It is found that the constant displacement constraint, which is a necessary building block for GPU acceleration, is the most critical issue in affecting LK algorithm's accuracy, which can be somehow ameliorated by using second-order Newton descent. Moreover, symmetric warping outbids the other two warping schemes in accuracy level, robustness to noise, convergence speed and tolerance to displacement gradient, and might be the first choice when applying LK algorithm to PIV measurement. | PAN Chong XUE Dong XU Yang WANG JinJun WEI RunJie | 2015 | Science China(Physics,Mechanics & Astronomy)2015，58，10： | 9 |
| 2 | 用平均速度剖面法测量湍流边界层壁面摩擦速度的对比研究显示文摘基于不同雷诺数平板湍流边界层平均速度剖面,分别采用黏性底层拟合、对数律区拟合以及Spalding公式拟合算法计算了壁面摩擦速度,并对平均速度剖面进行无量纲化。通过比较无量纲化的平均速度剖面与理论规律曲线,验证了三种拟合计算方法的有效性。通过比较三种拟合算法所得的壁面摩擦速度与油膜干涉法直接测得的壁面摩擦速度之间的误差,并分析不同拟合算法误差形成的内在机制,验证了三种拟合算法计算结果的准确性与可靠性。结果表明Spalding拟合算法计算结果的准确性和可靠性都要优于其他两种拟合算法。 | 王康俊 白建侠 唐湛棋 姜楠 | 2019 | 实验力学2019，34，2： | 8 |
| 3 | Fourier mode decomposition of PIV data.显示文摘The modal decomposition technique is one of the most effective methods for studying the flow dynamics in a complex flow. By rejuvenating the discrete Fourier transform(DFT), this paper proposes a Fourier mode decomposition(FMD) method for the time series of particle image velocimetry(PIV) data from the fluid field. An experimental case concerning the control of the flow around a circular cylinder by a synthetic jet positioned at the rear stagnation point is used to demonstrate the use of the FMD method. In the three different regimes where the natural shedding frequency and actuation frequency dominate respectively or simultaneously, it is found that the FMD method is capable of extracting the dynamic mode along with its amplitude and phase according to the selected characteristic frequency based on the global power spectrum. For the quasiperiodic flow phenomena presented in this particular case, the FMD method can reconstruct the original flow field using the zero-th mode and the selected mode corresponding to the characteristic frequency. Similarities and differences between the FMD method and the dynamical mode decomposition(DMD) and proper orthogonal decomposition(POD) methods are also discussed. | MA LiQun FENG LiHao PAN Chong GAO Qi WANG JinJun | 2015 | Science China(Technological Sciences)2015，58，11： | 6 |
| 4 | Effects of the slip wall on the drag and coherent structures of turbulent boundary layer显示文摘A comparative experiment by time-resolved particle image velocimetry(TRPIV)of the turbulent boundary layer(TBL)over a smooth surface and an anisotropy superhydrophobic(SH)surface was carried out in an open-surface recirculating water channel at Re_(τ,smooth)=650.Thewall friction velocity is fittedwell from the velocity of the viscous sublayer calculated by the Single-pixel resolution ensemble correlation(SPEC).After that,a drag reduction rate of 17%,a slip velocity of 0.0119 m/s,and a slip length of 90.8μm are obtained over the SH surface.In the main modes of the reduced-order flow fields,the wave packet structures over the SH surface become“upright”.Such large-scale structures in motion are also found in the instantaneous field.According to the statistical results of the correlation,it is found that the slip wall leads to the change of the convection velocity at different positions of the structure,which leads to the change of structure morphology and the distortion of the shear layer. | Xinwei Wang Yufei Wang Haiping Tian Nan Jiang | 2021 | Acta Mechanica Sinica2021，37，8： | 2 |
| 5 | 高焓流动中的可压缩颗粒求解器(第1部分):考虑多物理效应的点力颗粒两相流理论方程显示文摘从含烧蚀颗粒的高超声速边界层到航空发动机燃烧室或火箭发动机燃烧室里的气液、气固两相燃烧等问题,都存在弥散相颗粒调制携带流体的两相耦合物理过程。尽管不可压颗粒两相流的理论、数值工具和实验都比较成熟,但可压缩颗粒两相流与不可压缩的情况是截然不同的。本文首先对可压缩颗粒两相流动力学和热力学进行理论研究,理论分析了经典的可压缩流体动力学和热力学方程,把颗粒动力学对不可压流动的调制理论修正拓展到了可压缩情况,发现了可压缩颗粒两相流特有的动量和能量调制无量纲参数;推导了考虑多物理效应的颗粒动力学方程,并将其与携带流体相的控制方程耦合。研究发现,尽管多物理效应下的颗粒动力学是复杂的,但其影响携带流体相的路径是唯一确定的,即:多物理效应的颗粒动力学仅能通过相间阻力调制携带流体相的动量,通过相间阻力做功和热对流调制携带流体相的能量。 | 李青 涂国华 李婷婷 陈坚强 袁先旭 | 2023 | 空气动力学学报2023，41，8： | 1 |
| 6 | 基于卷积神经网络的近壁流动高分辨率平均速度场预测方法显示文摘本文设计并验证了基于卷积神经网络的边界层近壁流动高分辨率平均速度场预测方法:首先采用示踪粒子图像对数据集训练卷积神经网络,通过调整神经网络参数可以预测示踪粒子在数据集上的平均跨帧位移;然后使用该卷积神经网络预测像素空间中各像素位置的单粒子位移,得到高分辨率的平均速度场信息。将该方法用于预测湍流脉动较小的边界层近壁区的平均流动,能够将空间分辨率提高到单像素精度。误差分析发现,该方法获得的测速精度略优于传统单像素系综平均互相关算法,且对粒子浓度和示踪粒子图像对数目的要求明显低于后者。 | 王少飞 潘翀 齐中阳 | 2022 | 实验流体力学2022，36，3： | 0 |
| 7 | 湍流边界层大尺度相干结构空间相位平均拓扑显示文摘湍流边界层大尺度相干结构(large-scale coherent structure,LSCS)是目前湍流边界层研究的热点之一。湍流边界层中存在大尺度相干结构均是通过各种谱的低波数峰值证实的,而对大尺度相干结构各种物理量的空间拓扑形态及其发展演化规律还缺乏研究。应用高时间分辨粒子图像测速多相机阵列系统,测量湍流边界层大尺度相干结构各种状态的空间拓扑。实验雷诺数Reτ=422,采用沿流向方向按顺序排列四个高速相机同步拍摄,得到约6.7δ×1.2δ的大视场。在所有法向层沿流向方向进行空间多尺度连续小波变换,根据分尺度小波系数得到湍动能随流向尺度和法向位置的分布,根据各尺度小波系数的正负极值点检测各尺度相干结构喷射和扫掠的拓扑中心,使用条件采样和空间相位平均的方法测得各尺度相干结构喷射和扫掠阶段的空间拓扑形态,分别得到喷射与扫掠事件的脉动速度矢量、展向涡量、流线等物理量的空间相位平均拓扑,发现大尺度喷射和扫掠事件的结构都是多个小涡组成的大尺度涡包结构,每个小涡的流线形成鞍点和焦点组成的局部不稳定动力系统。 | 岳巾会 范子椰 姜楠 | 2022 | 力学与实践2022，44，1： | 0 |
| 8 | Effects of single circular synthetic jet on turbulent boundary layer显示文摘The periodic synthetic jet emerging from a circular orifice actively controls the turbulent boundary layer(TBL).A time-resolved particle image velocimetry(TR-PIV)system was designed to capture the velocity field database and based on the single-pixel ensemble correlation(SPEC)algorithm,an average drag reduction rate of 6.2%was obtained.The results show that the synthetic jet causes a wide range of low momentum zones and a low-speed streak in the downstream flow field.And the places where the disturbance intensity is strong are often accompanied by a larger velocity deficit.The instantaneous flow fields are visualized with the Finite-Time Lyapunov Exponent(FTLE),and the hairpin vortex packet composed of five hairpin vortices and the generation of new hairpin vortices are observed when there is no control.Under the action of the synthetic jet,the hairpin vortices are continuously generated from the jet orifice.The synthetic jet mainly achieves the drag reduction effect mainly by modulating the mean convection term cC and the spatial development term c^(D).The drag reduction effect appears in the region of x/δ0>0.38,and the maximum drag reduction rate is 12.2%at x/δ0=0.75,and then gradually decreased.Using proper orthogonal decomposition(POD),it is found that the synthetic jet reduces the energy proportion of the large-scale energetic structures.After the conditional average,the synthetic jet limits the influence range of bursting events at various scales in the near-wall region,and weakens the normal transport of momentum and energy brought about by large-scale ejection events(Q2 events)and the wall friction resistance caused by large-scale sweep events(Q4 events). | Jin-hao Zhang Biao-hui Li Tian-hai Ping Nan Jiang | 2023 | Journal of Hydrodynamics2023，35，3： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员