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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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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Three-dimensional simulation for fast forward flight of a calliope hummingbird

Royal Society Open Science ◽

10.1098/rsos.160230 ◽

2016 ◽

Vol 3 (6) ◽

pp. 160230 ◽

Cited By ~ 6

Author(s):

Jialei Song ◽

Bret W. Tobalske ◽

Donald R. Powers ◽

Tyson L. Hedrick ◽

Haoxiang Luo

Keyword(s):

Immersed Boundary Method ◽

High Speed ◽

Computational Study ◽

Three Dimensional ◽

The Body ◽

Immersed Boundary ◽

Forward Flight ◽

Advance Ratio ◽

Dimensional Simulation ◽

Thrust Production

We present a computational study of flapping-wing aerodynamics of a calliope hummingbird ( Selasphorus calliope ) during fast forward flight. Three-dimensional wing kinematics were incorporated into the model by extracting time-dependent wing position from high-speed videos of the bird flying in a wind tunnel at 8.3 m s −1 . The advance ratio, i.e. the ratio between flight speed and average wingtip speed, is around one. An immersed-boundary method was used to simulate flow around the wings and bird body. The result shows that both downstroke and upstroke in a wingbeat cycle produce significant thrust for the bird to overcome drag on the body, and such thrust production comes at price of negative lift induced during upstroke. This feature might be shared with bats, while being distinct from insects and other birds, including closely related swifts.

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

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

10.1098/rspa.2014.0439 ◽

2014 ◽

Vol 470 (2171) ◽

pp. 20140439 ◽

Cited By ~ 5

Author(s):

Jiao Wang ◽

Caishan Liu ◽

Daolin Ma

Keyword(s):

Horizontal Plane ◽

High Speed ◽

Temporal Evolution ◽

Three Dimensional ◽

Vertical Vibration ◽

Stereoscopic Vision ◽

Granular Systems ◽

Straight Line ◽

Transport Behaviour ◽

Oscillating Plate

It has recently been shown that a dimer, composed of two identical spheres rigidly connected by a rod, under harmonic vertical vibration can exhibit a self-ordered transport behaviour. In this case, the mass centre of the dimer will perform a circular orbit in the horizontal plane, or a straight line if confined between parallel walls. In order to validate the numerical discoveries, we experimentally investigate the temporal evolution of the dimer's motion in both two- and three-dimensional situations. A stereoscopic vision method with a pair of high-speed cameras is adopted to perform omnidirectional measurements. All the cases studied in our experiments are also simulated using an existing numerical model. The combined investigations detail the dimer's dynamics and clearly show that its transport behaviours originate from a series of combinations of different contact states. This series is critical to our understanding of the transport properties in the dimer's motion and related self-ordered phenomena in granular systems.

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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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