The 2-Dimensional (2D) and 3-Dimensional (3D) velocimetry based on schlieren/shadowgraph methods are reviewed in this article. The main content includes the basic optical setups and principles of schlieren and shadowgraph systems, as well as the velocimetry algorithms. For 2D measurement, there are mainly two types of velocimetry algorithms: one is cross-correlation algorithm adopted by PIV, while the other is the optical flow method. The basic formulas, advantages and limitations are introduced comparatively. A recent developed schlieren motion algorithm can provide high accuracy and dense estimation, which is promising and applicable in a wide range of applications. The 3D reconstruction and particle tracking algorithms highly rely on the systems. In this review, three different setups are introduced, including tomographic shadowgraphy, two-view collimated light path shadowgraphy and two-view converging path shadowgraphy. The two-view systems are more concise in setup, requiring less equipment, which are advantageous for high-speed measurements. The 3D particle tracking algorithms of two-view systems are introduced, while the main focus is placed on the image space-based tracking algorithms and the spatial-temporal tracking methods. The latter introduces the temporal predictions into the stereo matching process. The particle reconstruction and tracking correctness in dense particle situations is improved significantly by using the strongly coupled spatial and temporal constraints for optimisation. Its performance is superior to several artificial intelligence methods. The progress of the velocimetry algorithms, together with the imaging advantages of short exposure and high-frequency framing rate, has promoted schlieren/shadowgraph from conventional flow visualization to advanced velocimetry techniques, which can play a role for experimental study in a wide range of complex turbulent and transient flow conditions.
Multi-objective optimization method for light-field multi-spectral pyrometer
A schlieren motion estimation method for water flow velocimetry
实验流体力学
采用纹影法解耦流速与密度场的高速气流场压力分布重构方法
采用纹影法解耦流速与密度场的高速气流场压力分布重构方法
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A review on flow field velocimetry based on high-speed schlieren/shadowgraph systems
A review on flow field velocimetry based on high-speed schlieren/shadowgraph systems
A schlieren motion estimation method for water flow velocimetry
基于高速纹影/阴影成像的流场测速技术研究进展
基于高速纹影/阴影成像的流场测速技术研究进展
实验流体力学
Experimental study on flow characteristics of pitching hydrofoil via stereo shadowgraph