Spatiotemporal Superresolution Measurement based on POD and Sparse Regression applied to a Supersonic Jet measured by PIV and Near-field Microphone

Large-amplitude undulatory swimming near a wall

The propulsive dynamics of a flexible undulating foil in a self-propelled swimming configuration near a wall is studied experimentally. Measurements of the swimming speed and the propulsive force are presented, together with image acquisition of the kinematics of the foil and particle image velocimetry (PIV) in its wake. The presence of the wall enhances the cruising velocity in some cases up to 25% and the thrust by a 45%, for swept angles of 160 and 240 degrees. The physical mechanisms underlying this effect are discussed by studying the vorticity dynamics in the wake of the foil. Proper Ort…

利用未标记探针数据的高效数据半监督流估计方法

Data-efficient semi-supervised learning for flow estimation using unlabelled probe data

提出一种结合简单平流模型时间推进和半监督学习的框架，利用未标记探针数据增强PIV训练集，通过两个神经网络预测POD模态时间系数及其导数，提高速度场重建精度和压力估计可靠性。

台式水力分离器内湍流的时间分辨PIV测量与模态分析

Time-resolving PIV measurements and modal analysis of turbulent flow in a bench-scale hydrodynamic separator

本研究利用时间分辨PIV与模态分解技术分析了水力分离器内的湍流，量化了测量参数对统计收敛性的影响，基于POD和SPOD构建了降阶模型，并建立了开源湍流数据库以指导系统设计与CFD开发。

Experiments on wave propagation in grease ice: combined wave gauges and PIV measurements

Water wave attenuation by grease ice is a key mechanism for the polar regions, as waves in ice influence many phenomena such as ice drift, ice breaking, and ice formation. However, the models presented so far in the literature are limited in a number of regards, and more insights are required from either laboratory experiments or fieldwork for these models to be validated and improved. Unfortunately, performing detailed measurements of wave propagation in grease ice, either on the field or in the laboratory, is challenging. As a consequence, laboratory data are relatively scarce, and often con…

基于稀疏温度测量的数据驱动流场重构建模

Data-driven modeling for flow reconstruction from sparse temperature measurements

本文提出一种结合POD与全连接神经网络的数据驱动框架，从稀疏温度测量重构流场，并探讨最优传感器布置，在单相射流和蒸汽冷凝射流上验证了可行性。

Sparse reduced-order modeling : Sensor-based dynamics to full-state estimation

We propose a general dynamic reduced-order modeling framework for typical experimental data: time-resolved sensor data and optional non-time-resolved PIV snapshots. This framework contains four steps. First, the sensor signals are lifted to a dynamic feature space. Second, we identify a sparse human-interpretable nonlinear dynamical system for the feature state based on the sparse identification of nonlinear dynamics (SINDy). Third, if PIV snapshots are available, a local linear mapping from the feature state to velocity fields is shown to be orders of magnitudes more accurate than optimal mod…

Reconstruction of irregular flow dynamics around two square cylinders from sparse measurements using a data-driven algorithm

We propose a data-driven algorithm for reconstructing the irregular, chaotic flow dynamics around two side-by-side square cylinders from sparse, time-resolved, velocity measurements in the wake. We use Proper Orthogonal Decomposition (POD) to reduce the dimensionality of the problem and then explore two different reconstruction approaches: in the first approach, we use the subspace system identification algorithm n4sid to extract a linear dynamical model directly from the data (including the modelling and measurement error covariance matrices) and then employ Kalman filter theory to synthesize…

利用尖头瓣片实现椭圆超声速射流形态操控

Elliptic supersonic jet morphology manipulation using sharp-tipped lobes

本研究通过实验证明，在椭圆超声速射流喷嘴短轴两端加装尖头瓣片，可抑制射流扑动、降低噪声，并使近场混合速率提升约一倍，势核长度缩短40%。