Transient effects during transitions of bio-inspired flapping foils between two different schooling configurations

2021 ◽  
pp. 095440622110473
Author(s):  
Jiakun Han ◽  
Gang Chen
Keyword(s):  
Energy Saving ◽  
Influencing Factor ◽  
Cluster Formation ◽  
Three Dimensional ◽  
Research Field ◽  
Immersed Boundary ◽  
Transient Effects ◽  
Transition Mode ◽  
Transition Modes ◽  
Flapping Foils

Recently, there has been considerable interest in developing novel energy-saving vehicles that use flapping foils propulsion systems inspired by biology. Facing increasingly complex application tasks, the coordination of multiple vehicles will be a hot issue in the future this research field. We are inspired by changes in configurations of biological collective behavior (known as schooling) in nature, focused on studying transient effects during transitions of three-dimensional bio-inspired flapping foils between two different bionic schooling configurations. Numerical simulations employing the immersed boundary-lattice Boltzmann method (IB-LBM) for unsteady hydrodynamics of flapping foils in schooling transitions were performed. Effects of different mutual transition modes between tandem and diamond schooling configurations on their thrust performance were investigated. Meanwhile, we present hydrodynamics of flapping foils in a schooling with different downstream flapping frequencies under the best transition mode. The results show that during transitions between two schooling configurations, there is an optimal energy-saving transition mode. It has nothing to do with the length of transition distance. Different downstream flapping frequencies will affect the interacting vortices between fluid and structure and then affect transient effects during schooling transition. Although the transition modes were specified, our research takes the transients effects of schooling transitions as an influencing factor to be considered for formations changes, which will provide a new idea for the design bio-inspired vehicle cluster formation.

A three-dimensional immersed boundary method based on an algebraic forcing-point-searching scheme for water impact problems

2021 ◽  
Vol 233 ◽  
pp. 109189
Author(s):  
Bin Yan ◽  
Wei Bai ◽  
Sheng-Chao Jiang ◽  
Peiwen Cong ◽  
Dezhi Ning ◽  
...  
Keyword(s):  
Immersed Boundary Method ◽  
Three Dimensional ◽  
Immersed Boundary ◽  
Water Impact ◽  
Boundary Method ◽  
Impact Problems

Finite Element Analysis of Poor Distal Contact of the Femoral Component of a Cementless Hip Endoprosthesis

1993 ◽  
Vol 207 (4) ◽  
pp. 255-261 ◽  
Author(s):  
M Taylor ◽  
E W Abel
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Influencing Factor ◽  
Three Dimensional ◽  
Stress Distributions ◽  
Element Analysis ◽  
Hip Endoprosthesis ◽  
Applied Loading ◽  
Femoral Geometry ◽  
Contact Models

The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length. The resulting stress distributions within these were compared to the uniform contact models. The extent to which femoral geometry was an influencing factor on the stress distribution within the bone was also studied. Lack of distal contact with the prosthesis was found not to affect the proximal stress distribution within the femur, for distal gap lengths of up to 60 mm. In the region of no distal contact, the stress within the femur was at normal physiological levels associated with the applied loading and boundary conditions. The femoral geometry was found to have little influence on the stress distribution within the cortical bone. Although localized variations were noted, both femurs exhibited the same general stress distribution pattern.

Energy saving of schooling robotic fish in three-dimensional formations

2021 ◽  
pp. 1-1
Author(s):  
Liang Li ◽  
Xingwen Zheng ◽  
Rui Mao ◽  
Guangming Xie
Keyword(s):  
Energy Saving ◽  
Three Dimensional ◽  
Robotic Fish

Computational Investigation of Thrust Production of a Dolphin at Various Swimming Speeds

2021 ◽  
Author(s):  
Junshi Wang ◽  
Vadim Pavlov ◽  
Zhipeng Lou ◽  
Haibo Dong
Keyword(s):  
Surface Pressure ◽  
Swimming Performance ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Immersed Boundary ◽  
Reconstruction Method ◽  
Force Coefficient ◽  
Speed Increase ◽  
Generation Mechanisms ◽  
Thrust Production

Abstract Dolphins are known for their outstanding swimming performance. However, the difference in flow physics at different speeds remains elusive. In this work, the underlying mechanisms of dolphin swimming at three speeds, 2 m/s, 5 m/s, and 8 m/s, are explored using a combined experimental and numerical approach. Using the scanned CAD model of the Atlantic white-sided dolphin (Lagenorhynchus acutus) and virtual skeleton-based surface reconstruction method, a three-dimensional high-fidelity computational model is obtained with time-varying kinematics. A sharp-interface immersed-boundary-method (IBM) based direct numerical simulation (DNS) solver is employed to calculate the corresponding thrust production, wake structure, and surface pressure at different swimming speeds. It is found that the fluke keeps its effective angle of attack at high values for about 60% of each stroke. The total pressure force coefficient along the x-axis converges as the speed increase. The flow and surface pressure analysis both show considerable differences between lower (2 m/s) and higher (5 m/s and 8 m/s) speeds. The results from this work help to bring new insight into understanding the force generation mechanisms of the highly efficient dolphin swimming and offer potential suggestions to the future designs of unmanned underwater vehicles.

Computation of Flow Through a Three-Dimensional Periodic Array of Porous Structures by a Parallel Immersed-Boundary Method

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Zhenglun Alan Wei ◽  
Zhongquan Charlie Zheng ◽  
Xiaofan Yang
Keyword(s):  
Porous Media ◽  
Parallel Implementation ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Periodic Array ◽  
Immersed Boundary ◽  
Navier Stokes Equation ◽  
Flow Through ◽  
Ib Method

A parallel implementation of an immersed-boundary (IB) method is presented for low Reynolds number flow simulations in a representative elementary volume (REV) of porous media that are composed of a periodic array of regularly arranged structures. The material of the structure in the REV can be solid (impermeable) or microporous (permeable). Flows both outside and inside the microporous media are computed simultaneously by using an IB method to solve a combination of the Navier–Stokes equation (outside the microporous medium) and the Zwikker–Kosten equation (inside the microporous medium). The numerical simulation is firstly validated using flow through the REVs of impermeable structures, including square rods, circular rods, cubes, and spheres. The resultant pressure gradient over the REVs is compared with analytical solutions of the Ergun equation or Darcy–Forchheimer law. The good agreements demonstrate the validity of the numerical method to simulate the macroscopic flow behavior in porous media. In addition, with the assistance of a scientific parallel computational library, PETSc, good parallel performances are achieved. Finally, the IB method is extended to simulate species transport by coupling with the REV flow simulation. The species sorption behaviors in an REV with impermeable/solid and permeable/microporous materials are then studied.

scholarly journals Three-dimensional Sonography in the Assessment of Normal Fetal Anatomy in Late Pregnancy

2010 ◽  
Vol 4 (3) ◽  
pp. 217-231
Author(s):  
Badreldeen Ahmed ◽  
Ulrich Honemeyer
Keyword(s):  
Continuous Wave ◽  
Power Doppler ◽  
Three Dimensional ◽  
Late Pregnancy ◽  
Research Field ◽  
Surface Rendering ◽  
Volume Data ◽  
Data Set ◽  
3D Volume ◽  
Color And Power Doppler

Abstract Three-dimensional, multiplanar sonography, using a volume data set acquired with a 3D probe, has revolutionized ultrasonographic imaging and takes sonographers to a new perception of the fetus in 3 dimensions. Real time scanning, until the late nineties only possible in B-mode, can now be performed in 3D with up to 40 frames/sec. Fetal neurology emerged as a new perinatal research field with the 4D visualization of fetal behavior. Doppler ultrasound, diversified and refined from continuous wave and pulsed Doppler to Color – and Power Doppler, when added to 3D sonography, creates fascinating options of noninvasive fetal vascular mapping (sonoangiography) and vascular assessment of placenta. The diagnostic and demonstrative potential of an acquired 3D volume data set can be maxed with the help of postprocessing and rendering software. After storage, the evaluation of fetal 3D data sets can happen without the patient, with the option of specialist consultation, using telemedicine. In the article, the new 3D “modes” like surface rendering, maximum mode, 3D Color and Power Doppler, STIC, volume rendering, and glass body rendering, are described and illustrated in their display of normal fetal anatomy.

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

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.

3D Structural Bioinformatics of Proteins and Antibodies: State of the Art Perspectives and Challenges

2013 ◽  
Vol 2 (3) ◽  
pp. 67-74
Author(s):  
Arianna Filntisi ◽  
Dimitrios Vlachakis ◽  
George Matsopoulos ◽  
Sophia Kossida
Keyword(s):  
Quantum Mechanics ◽  
Quantum Chemical ◽  
State Of The Art ◽  
Three Dimensional ◽  
Research Field ◽  
Important Class ◽  
Structural Components ◽  
Molecular Systems ◽  
Mechanical Methods ◽  
Harmful Substances

Proteins are an important class of biochemical molecules, as the structural components of animal and human tissue are based on them. Antibodies are proteins that play a crucial role in the preservation of life since they are produced by the body's immune system as a response to harmful substances. The modelling of proteins and antibodies in particular is a vibrant research field which facilitates the design of drugs, a process otherwise demanding in terms of time and resources. A variety of computational methods and tools are being developed towards that goal, among which are hybrid quantum chemical/molecular mechanical methods and three-dimensional antibody modelling. In this review the authors discuss the knowledge concerning proteins and antibodies, as well as the use of quantum mechanics in the simulation of molecular systems and the three-dimensional antibody modelling.

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