Yiqian Wang

Yiqian Wang
Soochow University (PRC) | SUDA · School of Mathematical Sciences

Ph.D.

About

43
Publications
3,938
Reads
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927
Citations
Citations since 2016
43 Research Items
921 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250

Publications

Publications (43)
Article
Vortex structures, detected by the existing popular vortex identification methods, of the same case are generally different if the results are measured by different observers, who are moving with different coordinate systems. These coordinate systems can be inertial or non-inertial. Galilean invariance can solve the moving observer problems in diff...
Article
The motion of the small vortices in the dissipation region (large wave number) is not fully understood due to the influence of the kinematic viscosity and energy dissipation rate. Studying the motion law of small vortices is of great significance to understand the physical mechanism of turbulence. It is well known that the motion of small vortices...
Preprint
Generally, the vortex structures should be independent of the observers who are moving, especially when their coordinates are non-inertial, which may result in confusions in communications between researchers. The property that not being influenced by the choice of coordinate is called objective. Mostly, researchers would like to gather data in the...
Article
Trails induced by air entrainment of bow wave breaking can be observed clearly around an advancing ship, making it prong to be detected and causing reduction in hydrodynamic performance. In breaking bow wave region, different scale of coherent vortex structures related closely to the air entrainment are generated. The formation and evolution of bub...
Article
Considered as the building blocks, vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship. In this paper, the computational fluid dynamics (CFD) solver, naoe-FOAM-SJTU, coupled with delayed detached-eddy simulation (DDES) is adopted to analyze the vortex structures around the benchmark mode...
Article
Full-text available
It is commonly known that riblets with sharper tip generally have better turbulent drag reduction capacity, which, however, poses great challenges for manufacturing and makes the riblets vulnerable to tip erosion. In this study, we show that a scalloped riblet which is not as sharp in the tip as corresponding triangular riblet with same height-widt...
Article
In this paper, numerical simulation is conducted via our in-house solver, vim-FOAM-SJTU, developed on open-source software, OpenFOAM. Flow around static rigid cylinders and elastically mounted rigid cylinder constrained to free stream with free end are numerically investigated. Some significant conclusions are made by analyzing the different result...
Book
Preface This book is a collection of papers presented in the invited workshop, “Liutex and Third Generation of Vortex Definition and Identification for Turbulence”, of CHAOS2020 conference, Florence, Italy, June 9-13, 2020. Due to the pandemic of COVID-19, the conference was finally held online as a virtual conference. We had 33 registered speakers...
Article
When studying the flow dynamics and the characteristics of fluid motion, vortex structure with their interactions is the key issue. In the present work, a vortex control method is investigated based on the vortex identification system of Liutex. The numerical study is carried out in OpenFOAM by directly adding a source term to the Navier-Stokes equ...
Article
Full-text available
For complex aerodynamic and hydrodynamic problems, the analysis of vortex is very important. The Liutex method is an eigenvalue-based method which is local, accurate, and unique, which can give an accurate definition of vortex, so the control of vortex can be implemented and effectively guaranteed. Based on Liutex method, two methodologies of centr...
Article
Vortical structures of a submarine with appendages are fully turbulent and complex. Thus, flow control and vortex manipulation are of great importance for the hydrodynamic performance and acoustic characteristics. Take the generic submarine model DARPA Suboff as the test case, a vortex tuning method based on the Liutex force field is proposed to ma...
Article
Recently, the Liutex-based force field models are proposed and applied to some two-dimensional flows to explore the possibility of direct vortex control strategies. In this paper, we applied the Liutex-based centripetal force model to three-dimensional flow around a circular cylinder at Re = 3 900 . The turbulent flows around the three-dimensional...
Article
The motion of fluid consists of different scales of coherent vortical structures. These vortical structures determine the characteristics of fluid motion and are key to understand fluid dynamics. In this paper, we study the fine control method of vortical structures based on the Liutex force field model. This is achieved by constructing a source te...
Article
Viewed as sinews and muscles of fluid motion, coherent vortical structures with their interactions are key to understanding the flow dynamics. Based upon this observation, we explore the possibility of efficient flow control by directly manipulating vortices numerically inside the flow field based on the vortex definition and identification system...
Book
This book collects papers presented in the Invited Workshop, “Liutex and Third Generation of Vortex Definition and Identification for Turbulence,” from CHAOS2020, June 9-12, 2020, which was held online as a virtual conference. Liutex is a new physical quantity introduced by Prof. Chaoqun Liu of the University of Texas at Arlington. It is a vector a...
Article
Vortex dynamics, with the possibility of efficient flow control, is explored in this study based on the new introduced vortex definition and identification system of Liutex. With the six core elements of vortex identification, including (1) absolute strength, (2) relative strength, (3) local rotational axis, (4) global rotational axis, (5) vortex c...
Preprint
The Navier-Stokes (NS) partial differential equations, as the governing equation of fluid dynamics, are based on particles with zero volume. In such a condition, conservation law of moment of momentum is automatically satisfied, and thus NS equations only contain conservation of mass, momentum and energy. Because of the difficulty to get an analyti...
Article
The third-generation vortex identification method of Liutex (previously called Rortex) was introduced by the team led by Prof. Chaoqun Liu from University of Texas at Arlington to mathematically extract the rigid rotation part from the fluid motion, and thus to define and visualize vortices. Unlike the vorticity-based first generation and the scala...
Article
Kolmogorov’s 1941 theory (K41) of similarity hypotheses and the −5/3 law for energy spectrum are considered as the most important theoretical achievement in turbulence research and the success of the modern turbulence theory. The assumptions of sufficient high Reynolds number and isotropy of turbulence that K41 based upon, however, cannot generally...
Article
The vortex core detection method based on the Liutex vector is utilized to investigate the alternation of vortical structures on a boundary layer transition subjected to spanwise-wall oscillation. Compared with iso-surface based methods, the Liutex core line method is shown to be precise, free of threshold and capable to capture both strong and wea...
Article
According to Liu et al (2019), the development of vortex identification methods can be classified into three generations. The first-generation methods are based on the vorticity, with the implication that the antisymmetric part (vorticity tensor) of the velocity gradient tensor obtained by the Cauchy-Stokes decomposition represents the rigid-body r...
Article
In the present study, the physical meaning of vorticity is revisited based on the Liutex-Shear (RS) decomposition proposed by Liu et al. in the framework of Liutex (previously called Rortex), a vortex vector field with information of both rotation axis and swirling strength (Liu et al. 2018). It is demonstrated that the vorticity in the direction o...
Article
A new vortex identification method.(Liu et al. 2016) was proposed to represent the rotation relative strength and capture and visualize the vortices in our previous study. The basic idea of the Ω method is that a ratio of the vorticity squared over the summation of the vorticity squared and the deformation squared should be used to measure the rela...
Article
In the new vortex identification method (Liu C. et al. 2016) to represent the rotation level and capture and visualize the vortices, proposed in our previous study, the independence of the reference frame and the Galilean invariant were not proved. In the present study, the Galilean invariance of the omega vortex identification method is proved and...
Article
A vortex is intuitively recognized as the rotational/swirling motion of fluids, but a rigorous and universally-accepted definition is still not available. Vorticity tube/filament has been regarded equivalent to a vortex since Helmholtz proposed the concepts of vorticity tube/filament in 1858 and the vorticity-based methods can be categorized as the...
Preprint
Full-text available
A new vortex identification method [C. Liu et al., "New omega vortex identification method," Science China Physics, Mechanics and Astronomy, 2016, 59(8): 684711] was proposed to represent the rotation level and capture and visualize the vortices in our previous study. However the vortex identification method should be independent of the reference f...
Preprint
Full-text available
The Ω method is a new vortex identification method, which can capture weak and strong vortex simultaneously. The basic idea of the Ω method is that a ratio of the vorticity tensor norm square over the summation of the vorticity tensor norm square and deformation tensor norm square should be used to measure the rotation strength. However, the vortic...
Chapter
Several vortex identification methods along with a newly proposed \(\Omega \) method are examined in the Burgers vortex and the Sullivan vortex. Of particular interest is the physical meaning of the parameter, especially the thresholds. While all the methods are capable of capturing precise vortex boundaries in these two analytical vortices, only t...
Preprint
In the present study, the physical meaning of vorticity is revisited based on the RS decomposition proposed by Liu et al. in the framework of Liutex (previously named Rortex), a vortex vector field with information of both rotation axis and swirling strength [ C. Liu et al., "Rortex-A new vortex vector definition and vorticity tensor and vector dec...
Article
Epsilon (ε) in the Omega vortex identification criterion (Ω method) is defined as an explicit function in order to apply the Ω method to different cases and even different time steps in the study of unsteady cases. In the present paper, a newly proposed criteria for the determination of ε is tested in several typical flow cases and is proved to be...
Article
Experimental and numerical investigations have suggested the existence of a strong correlation between the passage of coherent structures and events of bursting and intermittency. However, a detailed cause-and-effect study on the subject is rarely found in the literature due to the complexity and the nonlinear multiscale nature of turbulent flows....
Article
Vortex and vorticity are two correlated but fundamentally different concepts which have been the central issues in fluid mechanics research. Vorticity has rigorous mathematical definition (curl of velocity), but no clear physical meaning. Vortex has clear physical meaning (rotation) but no rigorous mathematical definition. For a long time, many peo...
Article
Full-text available
A new vortex identification criterion called Ω-method is proposed based on the ideas that vorticity overtakes deformation in vortex. The comparison with other vortex identification methods like Q-criterion and λ 2-method is conducted and the advantages of the new method can be summarized as follows: (1) the method is able to capture vortex well and...
Article
The issue whether transition from laminar flow to turbulent flow on a flat plate should be characterized as a vorticity redistribution process or a vorticity increasing process is investigated by a high-order direct numerical simulation on a flat plate boundary layer. The local vorticity can either increase or decrease due to tilting and stretching...
Article
Previous experimental and numerical studies have revealed that the hairpin vortex is a basic flow element of transitional boundary layer. The hairpin vortex is believed to have legs, necks and a ring head. Based on our DNS study, the legs and the ring head are generated separately by different mechanisms. The legs function like an engine to generat...

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