On the interaction of a planar shock with a three-dimensional light gas cylinder

2017 ◽  
Vol 828 ◽  
pp. 289-317 ◽  
Author(s):  
Juchun Ding ◽  
Ting Si ◽  
Mojun Chen ◽  
Zhigang Zhai ◽  
Xiyun Lu ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Soap Film ◽  
Wave Pattern ◽  
Principal Curvatures ◽  
Gas Cylinder ◽  
Planar Shock ◽  
Restriction Method ◽  
Gas Cylinders

Experimental and numerical investigations on the interaction of a planar shock wave with two-dimensional (2-D) and three-dimensional (3-D) light gas cylinders are performed. The effects of initial interface curvature on flow morphology, wave pattern, vorticity distribution and interface movement are emphasized. In experiments, a wire-restriction method based on the soap film technique is employed to generate N$_{2}$ cylinders surrounded by SF$_{6}$ with well-characterized shapes, including a convex cylinder, a concave cylinder with a minimum-surface feature and a 2-D cylinder. The high-speed schlieren pictures demonstrate that fewer disturbance waves exist in the flow field and the evolving interfaces develop in a more symmetrical way relative to previous studies. By combining the high-order weighted essentially non-oscillatory construction with the double-flux scheme, numerical simulation is conducted to explore the detailed 3-D flow structures. It is indicated that the shape and the size of 3-D gas cylinders in different planes along the vertical direction change gradually due to the existence of both horizontal and vertical velocities of the flow. At very early stages, pressure oscillations in the vicinity of evolving interfaces induced by complex waves contribute much to the deformation of the 3-D gas cylinders. As time proceeds, the development of the shocked volume would be dominated by the baroclinic vorticity deposited on the interface. In comparison with the 2-D case, the oppositely (or identically) signed principal curvatures of the concave (or convex) SF$_{6}$/N$_{2}$ boundary cause complex high pressure zones and additional vorticity deposition, and the upstream interface from the symmetric slice of the concave (or convex) N$_{2}$ cylinder moves with an inhibition (or a promotion). Finally, a generalized 3-D theoretical model is proposed for predicting the upstream interface movements of different gas cylinders and the present experimental and numerical findings are well predicted.

scholarly journals On the interaction of a planar shock with an polygon

2015 ◽  
Vol 773 ◽  
pp. 366-394 ◽  
Author(s):  
Xisheng Luo ◽  
Minghu Wang ◽  
Ting Si ◽  
Zhigang Zhai
Keyword(s):  
High Speed ◽  
Soap Film ◽  
Von Neumann ◽  
Interface Characteristics ◽  
Planar Shock ◽  
Wave Patterns ◽  
Formation Method ◽  
Planar Shock Wave ◽  
Triple Points ◽  
Shock Refraction

The interaction of a planar shock wave ($M\approx 1.2$) with an $\text{SF}_{6}$ polygonal inhomogeneity surrounded by air is experimentally investigated. Six polygons including a square, two types of rectangle, two types of triangle, and a diamond are generated by the soap film technique developed in our previous work, in which thin pins are used as angular vertexes to avoid the pressure singularities caused by the surface tension. The evolutions of the shock-accelerated $\text{SF}_{6}$ polygons are captured by a high-speed schlieren system from which wave systems and the interface characteristics can be clearly identified. Both regular and irregular refraction phenomena are observed outside the volume, and more complex wave patterns, including transmitted shock, refracted shock, Mach stem and the interactions between them, are found inside the volume. Two typical irregular refraction phenomena (free precursor refraction, FPR, and free precursor von Neumann refraction, FNR) are observed and analysed, and the transition from FPR to FNR is found, providing the experimental evidence for the transition between different wave patterns numerically found in the literature. Combined with our previous work (Zhai et al., J. Fluid Mech., vol. 757, 2014, pp. 800–816), the reciprocal transitions between FPR and FNR are experimentally confirmed. The velocities and trajectories of the triple points are further measured and it is found that the motions of the triple points are self-similar or pseudo-stationary. Besides the shock dynamics phenomena, the evolutions of these shocked heavy polygonal volumes, which are quite different from the light ones, are captured and found to be closely related to their initial shapes. Specifically, for square and rectangular geometries, the different width–height ratios result in different behaviours of shock–shock interaction inside the volume, and subsequently different features for the outward jet and the interface. Quantitatively, the time-variations of the interface scales, such as the width and the normalized displacements of the edges, are obtained and compared with those from previous work. The comparison illustrates the superiority of the interface formation method and the significant effect of the initial interface shape on the interface features. Furthermore, the characteristics of the vortex core, including the velocity and vortex spacing, are experimentally measured, and the vortex velocity is compared with those from some circulation models to check the validity of the models. The results in the present work enrich understanding of the shock refraction phenomenon and the database of research into Richtmyer–Meshkov instability (RMI).

On the Evolution of Double Shock-Accelerated Elliptic Gas Cylinders

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Liyong Zou ◽  
Wenbin Huang ◽  
Cangli Liu ◽  
Jun Yu ◽  
Xisheng Luo
Keyword(s):  
Cross Sections ◽  
High Speed ◽  
Vortex Pair ◽  
Elliptic Cylinder ◽  
Planar Shock ◽  
Planar Shock Wave ◽  
Flow Morphology ◽  
Heavy Gas ◽  
Elliptical Cylinders ◽  
Gas Cylinders

The evolution of double elliptic heavy-gas (SF6) cylinders impacted by a planar shock wave is studied by high-speed camera diagnostics. The minor axes (b) of the elliptic cross sections are aligned perpendicular to the shock direction. While the cylinder dimensions are fixed, we adjust the center-to-center separation s between the cylinders. The resulting flow morphologies are visualized and the interaction between double cylinders is analyzed. When s/b = 4.0 or 3.0, the two elliptical cylinders roll up into two counter-rotating vortex pairs and their interaction is weak. When s/b decreases to 2.0 or 1.2, due to strong interaction of the two inner vortices, the inner structure completely disappears and the flow morphology evolves into one counter-vortex pair. Compared with the s/b = 2.0 case, larger amount of baroclinic vorticity is produced in the s/b = 1.2 case, and the morphology is similar to the single elliptic cylinder case, with a second vortex phenomenon occurring at later times. As s/b increases, the extent of cylinder-cylinder interaction becomes weaker, and the integral height of double elliptic cylinders grows while the length decreases.

The Richtmyer–Meshkov instability of a three-dimensional interface with a minimum-surface feature

2013 ◽  
Vol 722 ◽  
Author(s):  
Xisheng Luo ◽  
Xiansheng Wang ◽  
Ting Si
Keyword(s):  
Three Dimensional ◽  
Symmetry Plane ◽  
Soap Film ◽  
Mie Scattering ◽  
Surface Feature ◽  
Late Time ◽  
Principal Curvatures ◽  
Time Resolved ◽  
Nonlinear Growth ◽  
Minimum Surface

AbstractA novel method to create a discontinuous gaseous interface with a minimum-surface feature by the soap film technique is developed for three-dimensional (3D) Richtmyer–Meshkov instability (RMI) studies. The interface formed is free of supporting mesh and the initial condition can be well controlled. Five air/SF6 interfaces with different amplitude are realized in shock-tube experiments. Time-resolved schlieren and planar Mie-scattering photography are employed to capture the motion of the shocked interface. It is found that the instability at the linear stage in the symmetry plane grows much slower than the predictions of previous two-dimensional (2D) impulsive models, which is ascribed to the opposite principal curvatures of the minimum surface. The 2D impulsive model is extended to describe the general 3D RMI. A quantitative analysis reveals a good agreement between experiments and the extended linear model for all the configurations including both the 2D and 3D RMIs at their early stages. An empirical model that combines the early linear growth with the late-time nonlinear growth is also proposed for the whole evolution process of the present configuration.

Vertical track irregularity analysis of high-speed railways on simply-supported beam bridges based on the virtual track inspection method

2020 ◽  
pp. 095440972092457
Author(s):  
Tianci Gao ◽  
Jianli Cong ◽  
Ping Wang ◽  
Jianxing Liu ◽  
Yuan Wang ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Vehicle Speed ◽  
Simply Supported Beam ◽  
Inspection Method ◽  
Track Geometry ◽  
Simply Supported ◽  
The Relationship ◽  
Track Irregularities

Understanding the relationship between the static and dynamic track geometry irregularities is crucial for the proper maintenance of rail infrastructures and the reduction of on-site workload. This paper focuses on the analysis of the dynamic and static track irregularities on simply-supported beam bridges for high-speed railways. Based on the simulation of three-dimensional vehicle–track–bridge dynamics, a virtual track inspection method is proposed according to the measurement principle with the inertial reference. With the static irregularity provided as the initial input to the simulation model, the virtual track inspection of dynamic track irregularities is carried out considering different supporting structures, i.e. subgrade and bridges. Furthermore, the characteristics and advantages of the proposed model are investigated in the “rigid track structure”. Then, using the virtual track inspection method, this paper analyzes the relationship between the dynamic and static track irregularities (in the vertical direction) on the simply-supported beam bridge in both the time and frequency domains with respect to different train speeds, and the simulation results are validated by real-world measurements. Numerical results show that the stiffness irregularity in the vertical direction is periodical, with the cycle length equal to the span of the bridge. Furthermore, there is an obvious linear relationship between the dynamic and static irregularities. Also, the regression coefficient increases with increasing vehicle speed.

scholarly journals On the interaction of a planar shock with a light polygonal interface

2014 ◽  
Vol 757 ◽  
pp. 800-816 ◽  
Author(s):  
Zhigang Zhai ◽  
Minghu Wang ◽  
Ting Si ◽  
Xisheng Luo
Keyword(s):  
High Speed ◽  
Vortex Pair ◽  
Soap Film ◽  
Remarkable Feature ◽  
Planar Shock ◽  
Shock Impact ◽  
Planar Shock Wave ◽  
Left Corner ◽  
Interface Structures ◽  
Late Stages

AbstractThe interaction of a planar shock wave with a polygonal $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\mathrm{N}}_2$ volume surrounded by ${\mathrm{SF}}_6$ is investigated experimentally and numerically. Three polygonal interfaces (square, triangle and diamond) are formed by the soap film technique developed in our previous work, in which thin pins are introduced as angular vertexes to connect adjacent sides of polygonal soap films. The evolutions of the shock-accelerated polygonal interfaces are then visualized by a high-speed schlieren system. Wave systems and interface structures can be clearly identified in experimental schlieren images, and agree well with the numerical ones. Quantitatively, the movement of the distorted interface, and the length and height of the interface structures are further compared and good agreements are achieved between experimental and numerical results. It is found that the evolution of these polygonal interfaces is closely related to their initial shapes. In the square interface, two vortices are generated shortly after the shock impact around the left corner and dominate the flow field at late stages. In the triangular and diamond cases, the most remarkable feature is the small ‘${\mathrm{SF}}_6$ jet’ which grows constantly with time and penetrates the downstream boundary of the interface, forming two independent vortices. These distinct morphologies of the three polygonal interfaces also lead to the different behaviours of the interface features including the length and height. It is also found that the velocities of the vortex pair predicted from the theory of Rudinger and Somers (J. Fluid Mech., vol. 7, 1960, pp. 161–176) agree with the experimental ones, especially for the square case. Typical free precursor irregular refraction phenomena and the transitions among them are observed and analysed, which gives direct experimental evidence for wave patterns and their transitions at a slow/fast interface. The velocities of triple points and shocks are experimentally measured. It is found that the transmitted shock near the interface boundary has weakened into an evanescent wave.

High-speed brightfield 3-D imaging and 3-D image analysis of thick and overlapped cell clusters in cytological preparations

1994 ◽  
Vol 52 ◽  
pp. 218-219
Author(s):  
Robert W. Mackin
Keyword(s):  
Image Analysis ◽  
High Speed ◽  
Three Dimensional ◽  
Image Data ◽  
Ccd Camera ◽  
Objective Lens ◽  
Array Processor ◽  
Vaginal Smears ◽  
Low Contrast ◽  
Computer Controlled

This paper presents two advances towards the automated three-dimensional (3-D) analysis of thick and heavily-overlapped regions in cytological preparations such as cervical/vaginal smears. First, a high speed 3-D brightfield microscope has been developed, allowing the acquisition of image data at speeds approaching 30 optical slices per second. Second, algorithms have been developed to detect and segment nuclei in spite of the extremely high image variability and low contrast typical of such regions. The analysis of such regions is inherently a 3-D problem that cannot be solved reliably with conventional 2-D imaging and image analysis methods.High-Speed 3-D imaging of the specimen is accomplished by moving the specimen axially relative to the objective lens of a standard microscope (Zeiss) at a speed of 30 steps per second, where the stepsize is adjustable from 0.2 - 5μm. The specimen is mounted on a computer-controlled, piezoelectric microstage (Burleigh PZS-100, 68/μm displacement). At each step, an optical slice is acquired using a CCD camera (SONY XC-11/71 IP, Dalsa CA-D1-0256, and CA-D2-0512 have been used) connected to a 4-node array processor system based on the Intel i860 chip.

Effects of Three-Dimensional Pressure Gradients on High-Speed Turbulent Boundary Layers

2021 ◽  
Author(s):  
Scott J. Peltier ◽  
Brian E. Rice ◽  
Ethan Johnson ◽  
Venkateswaran Narayanaswamy ◽  
Marvin E. Sellers
Keyword(s):  
Boundary Layers ◽  
High Speed ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients

About the Development of Brick-Design in Russia

2020 ◽  
Vol 787 (12) ◽  
pp. 21-24
Author(s):  
Y.A. Bozhko ◽  
◽  
K.A. Lapunova ◽  
Keyword(s):  
Functional Role ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Basic Unit ◽  
Design Development ◽  
European Cities ◽  
Unique Material ◽  
Decisive Action ◽  
Color Combinations ◽  
Insufficient Number

The article reflects the authors view on the technical and aesthetic side of the use of face bricks in the architecture of our country. The term brick design combines such indicators of brickwork as the color, size and surface of the brick itself, as well as the type of masonry and seam parameters. Unfortunately, the analysis of the current situation shows that the culture of consumption of face bricks in Russia remains at a low level, which is due to the lack of proper knowledge and insufficient number of qualified master masons. The main goal of brick design development is to popularize various types of three-dimensional masonry and reveal the potential of using bricks as a basic unit. The comparison shows the architecture of European cities, which does not differ in the complexity of architectural forms, but has advantages in the form of unusual masonry, color combinations, vertical direction of masonry and other elements of technical aesthetics. The use of bricks in various levels of brick design will allow you to avoid using architectural decoration on the facades of buildings, while preserving its authenticity and individuality. The brick, as a basic unit, is self-sufficient and is able to fulfill not only its functional role, but also its aesthetic one. In this situation, a necessary and decisive action will be competent communication with industry specialists, architects and designers, leading manufacturers and technologists who realize that we have a unique material that does not need additional wrapping when used efficiently.

Sign in / Sign up

Export Citation Format

Share Document