Experimental study of transport of a dimer on a vertically oscillating plate

This study is aimed at developing a novel computational framework that can essentially simulate a tornadic wind field and investigate the wind loadings on ground constructions. It is well known that tornado is a highly turbulent airflow that simultaneously translates, rotates and updrafts with a high speed. Tornadoes induce a significantly elevated level of wind forces if compared to a straight-line wind. A suitably designed building for a straight-line wind would fail to survive when exposed to a tornadic-like wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. Since the study of tornado dynamics relying on field observations and laboratory experiments is usually expensive, restrictive, and time-consuming, computer simulation mainly via the large eddy simulation (LES) method has become a more attractive research direction in shedding light on the intricate characteristics of a tornadic wind field. For numerical simulation of a tornado-building interaction scenario, it looks quite challenging to seek a set of physically-rational and meanwhile computationally-practical boundary conditions to accompany traditional CFD approaches; however, little literature can be found, as of today, in three-dimensional (3D) computational tornado dynamics study. Inspired by the development of the immersed boundary (IB) method, this study employed a re-tailored Rankine-combined vortex model (RCVM) that applies the “relative motion” principle to the translational component of tornado, such that the building is viewed as “virtually” translating towards a “pinned” rotational flow that remains time-invariant at the far field region. This revision renders a steady-state kinematic condition applicable to the outer boundary of a large tornado simulation domain, successfully circumventing the boundary condition updating process that the original RCVM would have to suffer, and tremendously accelerating the computation. Wind loading and its influence factors are comprehensively investigated and analyzed both on a single building and on a multiple-building configuration. The relation between the wind loadings and the height and shape of the building is also examined in detail. Knowledge of these loadings may lead to design strategies that can enable ground construction to be more resistant to tornadoes, reducing the losses caused by this type of disastrous weather.

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The 3D Measuring Method Based on the Color Coding Grating

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.109.385 ◽

2011 ◽

Vol 109 ◽

pp. 385-389

Author(s):

Jian Chen ◽

Ke Tian Li ◽

Xiang Bo Ouyang ◽

Shao Hua Ding

Keyword(s):

High Speed ◽

Color Space ◽

Three Dimensional ◽

Measuring Method ◽

Depth Image ◽

Color Coding ◽

Straight Line ◽

World Coordinate System ◽

Structure Light ◽

Object Imaging

This paper puts forward a new method of 3D measurement which based on the color coding structure light technology, projects the specific color coding grating to a Calibration board in RGB three color space, gets the straight line equation of grating which projected to Calibration board in the world coordinate system, obtains each projection plane of code through plane fitting, then joins the projection planes and the object imaging straight strips which through the camera focus, it can be get that the three dimensional coordinates of the objects. This method is simple and reliable; only need one camera and one projector without scanning; only one image is needed to get the information of a full frame depth image. It is suitable for high speed, real-time online measurement.

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Construction of Three-Dimensional Crack Calculation Method for Transparent Rock-Like Materials Based on Stereo Vision Principle

Advances in Civil Engineering ◽

10.1155/2019/2021092 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13 ◽

Cited By ~ 3

Author(s):

Shu Zhu ◽

Zhihua Luo ◽

Zhu Zhende ◽

Yufeng Gao ◽

Nan Wu

Keyword(s):

Calculation Method ◽

High Speed ◽

Testing Machine ◽

Three Dimensional ◽

Initial Crack ◽

Surrounding Rock ◽

Stereoscopic Vision ◽

Deformation And Failure ◽

Rock Reinforcement ◽

Underground Caverns

Disasters of deep underground caverns often occur during excavation or operation stage, which is closely related to the growth and evolution of surrounding rock cracks. The understanding of spatial distribution of internal cracks in rock mass is the key to reveal its deformation and failure mechanism. The transparent resin material with prefabricated crack was used to simulate the initial crack inside the rock, and the uniaxial compression experiment of transparent rock material under complete stress-strain path was carried out by using the rock mechanical rigidity testing machine. Four high-speed cameras were arranged around it to record the images of the same moment from different angles. Based on the theory of stereoscopic vision, a calculation method for the three-dimensional constitutive structure of crack propagation inside the rock was proposed, which can quantitatively describe the crack spatial morphological change. Therefore, the calculation method provides a reliable theoretical support for the surrounding rock reinforcement of underground engineering.

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The Importance of Providing Stereoscopic Vision in Training for Nap-of-the-Earth (NOE) Flight

Proceedings of the Human Factors Society Annual Meeting ◽

10.1177/107118137802200121 ◽

1978 ◽

Vol 22 (1) ◽

pp. 81-86

Author(s):

Donald E. Erwin

Keyword(s):

High Speed ◽

Light Flash ◽

Three Dimensional ◽

Reaction Times ◽

Visual Display ◽

Stereoscopic Vision ◽

Flight Training ◽

Air Defense ◽

Weapon Systems ◽

The Earth

Nap-of-the-earth (NOE) flight in Army tactical helicopter operations necessitates high speed visual-motor coordinations in order to avoid obstacles in the flight path while making maximal use of the terrain for cover and concealment from enemy air defense weapon systems. The development of simulators for training pilots in NOE flight involves the design of visual display systems which provide all the important optical information available in actual flight. At the present time, however, there is insufficient information on the role of stereopsis in NOE flight to determine whether fully binocular displays must be designed into training simulators. This paper describes results from two preliminary studies which examined the importance of binocular disparity for the perception of three-dimensional layout of the terrain in NOE flight. In the first experiment, it was determined that stereoscopic movies taken from the cockpit of a helicopter in NOE flight produce more compelling impressions of three-dimensionality than a non-disparate bioptic display. The results of the second experiment show that simple reaction times for detection of three-dimensionality in static binocular displays were substantially longer than for detection of fusibility of otherwise identical bioptic displays. Additionally, it was found that detection of fusibility required much more time than detection of a light flash. These results are interpreted as inconclusive with respect to the desirability of stereoptic displays for NOE flight training simulators, and a program of further research needed to settle this issue is discussed.

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Three-Dimensional (3-D) Immersed-Boundary (IB) Based Tornado Model for Computational Analysis of Disastrous Wind Load on Buildings

10.32920/ryerson.14654037.v1 ◽

2021 ◽

Author(s):

Xixiong Guo ◽

Jun Cao

Keyword(s):

Wind Field ◽

High Speed ◽

Outer Boundary ◽

Three Dimensional ◽

Influence Factors ◽

Research Direction ◽

Wind Loading ◽

Immersed Boundary ◽

Design Strategies ◽

Straight Line

This study is aimed at developing a novel computational framework that can essentially simulate a tornadic wind field and investigate the wind loadings on ground constructions. It is well known that tornado is a highly turbulent airflow that simultaneously translates, rotates and updrafts with a high speed. Tornadoes induce a significantly elevated level of wind forces if compared to a straight-line wind. A suitably designed building for a straight-line wind would fail to survive when exposed to a tornadic-like wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. Since the study of tornado dynamics relying on field observations and laboratory experiments is usually expensive, restrictive, and time-consuming, computer simulation mainly via the large eddy simulation (LES) method has become a more attractive research direction in shedding light on the intricate characteristics of a tornadic wind field. For numerical simulation of a tornado-building interaction scenario, it looks quite challenging to seek a set of physically-rational and meanwhile computationally-practical boundary conditions to accompany traditional CFD approaches; however, little literature can be found, as of today, in three-dimensional (3D) computational tornado dynamics study. Inspired by the development of the immersed boundary (IB) method, this study employed a re-tailored Rankine-combined vortex model (RCVM) that applies the “relative motion” principle to the translational component of tornado, such that the building is viewed as “virtually” translating towards a “pinned” rotational flow that remains time-invariant at the far field region. This revision renders a steady-state kinematic condition applicable to the outer boundary of a large tornado simulation domain, successfully circumventing the boundary condition updating process that the original RCVM would have to suffer, and tremendously accelerating the computation. Wind loading and its influence factors are comprehensively investigated and analyzed both on a single building and on a multiple-building configuration. The relation between the wind loadings and the height and shape of the building is also examined in detail. Knowledge of these loadings may lead to design strategies that can enable ground construction to be more resistant to tornadoes, reducing the losses caused by this type of disastrous weather.

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Three-dimensional flow structures and vorticity control in fish-like swimming

Journal of Fluid Mechanics ◽

10.1017/s002211200200143x ◽

2002 ◽

Vol 468 ◽

pp. 1-28 ◽

Cited By ~ 151

Author(s):

Q. ZHU ◽

M. J. WOLFGANG ◽

D. K. P. YUE ◽

M. S. TRIANTAFYLLOU

Keyword(s):

Structural Model ◽

Three Dimensional ◽

Travelling Wave ◽

The Body ◽

Cross Sectional ◽

Propulsive Efficiency ◽

Straight Line ◽

Giant Danio ◽

Oscillating Plate ◽

High Thrust

We employ a three-dimensional, nonlinear inviscid numerical method, in conjunction with experimental data from live fish and from a fish-like robotic mechanism, to establish the three-dimensional features of the flow around a fish-like body swimming in a straight line, and to identify the principal mechanisms of vorticity control employed in fish-like swimming. The computations contain no structural model for the fish and hence no recoil correction. First, we show the near-body flow structure produced by the travelling-wave undulations of the bodies of a tuna and a giant danio. As revealed in cross-sectional planes, for tuna the flow contains dominant features resembling the flow around a two-dimensional oscillating plate over most of the length of the fish body. For the giant danio, on the other hand, a mixed longitudinal–transverse structure appears along the hind part of the body. We also investigate the interaction of the body-generated vortices with the oscillating caudal fin and with tail-generated vorticity. Two distinct vorticity interaction modes are identified: the first mode results in high thrust and is generated by constructive pairing of body-generated vorticity with same-sign tail-generated vorticity, resulting in the formation of a strong thrust wake; the second corresponds to high propulsive efficiency and is generated by destructive pairing of body-generated vorticity with opposite-sign tail-generated vorticity, resulting in the formation of a weak thrust wake.

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Rolling friction and energy dissipation in a spinning disc

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2014.0191 ◽

2014 ◽

Vol 470 (2169) ◽

pp. 20140191 ◽

Cited By ~ 14

Author(s):

Daolin Ma ◽

Caishan Liu ◽

Zhen Zhao ◽

Hongjian Zhang

Keyword(s):

High Speed ◽

Temporal Evolution ◽

Rolling Friction ◽

Stereoscopic Vision ◽

Experiment Data ◽

Resistance Torque ◽

Theoretical Investigations ◽

Steel Disc ◽

Experimental Findings ◽

Spinning Disc

This paper presents the results of both experimental and theoretical investigations for the dynamics of a steel disc spinning on a horizontal rough surface. With a pair of high-speed cameras, a stereoscopic vision method is adopted to perform omnidirectional measurements for the temporal evolution of the disc's motion. The experiment data allow us to detail the dynamics of the disc, and consequently to quantify its energy. From our experimental observations, it is confirmed that rolling friction is a primary factor responsible for the dissipation of the energy. Furthermore, a mathematical model, in which the rolling friction is characterized by a resistance torque proportional to the square of precession rate, is also proposed. By employing the model, we perform qualitative analysis and numerical simulations. Both of them provide results that precisely agree with our experimental findings.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168827 ◽

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.

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