scholarly journals Particle position prediction based on Lagrangian coherency for flow over a cylinder in 4D-PTV

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Ali Rahimi Khojasteh ◽  
Dominique Heitz ◽  
Yin Yang
Keyword(s):  
Particle Tracking Velocimetry ◽  
Tracking Accuracy ◽  
Complex Flow ◽  
Time Resolved ◽  
Novel Technique ◽  
Finite Time Lyapunov Exponent ◽  
Smooth Cylinder ◽  
Recent Developments ◽  
Position Prediction ◽  
Temporal Coherency

Recent developments in time-resolved Particle Tracking Velocimetry (4D-PTV) consistently improved tracking accuracy and robustness. We propose a novel technique named ”Lagrangian coherent predictor” to estimate particle positions within the 4D-PTV algorithm. We add spatial and temporal coherency information of neighbour particles to predict a single trajectory using Lagrangian Coherent Structures (LCS). We found that even a weak signal from coherent neighbour motions improves particle prediction accuracy in complex flow regions. We applied Finite Time Lyapunov Exponent (FTLE) to quantify local boundaries (i.e. ridges) of coherent motions. Synthetic analysis of the wake behind a smooth cylinder at Reynolds number equal to 3900 showed enhanced estimation compared with the recent predictor functions employed in 4D-PTV. Results of the experimental study of the same flow configuration are reported. We compared predicted positions with the optimised final positions of Shake The Box (STB). It was found that the Lagrangian coherent predictor succeeded in estimating particle positions with minimum deviation to the optimised positions.

Transport and Mixing in Patient Specific Abdominal Aortic Aneurysms With Lagrangian Coherent Structures

2012 ◽  
Author(s):  
Amirhossein Arzani ◽  
Shawn C. Shadden
Keyword(s):  
Coherent Structures ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Lagrangian Coherent Structures ◽  
Patient Specific ◽  
Complex Flow ◽  
Flow Topology ◽  
Finite Time Lyapunov Exponent ◽  
Abdominal Aortic ◽  
High Gradients

Abdominal aortic aneurysms (AAA) are characterized by disturbed flow patterns, low and oscillatory wall shear stress with high gradients, increased particle residence time, and mild turbulence. Diameter is the most common metric for rupture prediction, although this metric can be unreliable. We hypothesize that understanding the flow topology and mixing inside AAA could provide useful insight into mechanisms of aneurysm growth. AAA morphology has high variability, as with AAA hemodynamics, and therefore we consider patient-specific analyses over several small to medium sized AAAs. Vortical patterns dominate AAA hemodynamics and traditional analyses based on the Eulerian fields (e.g. velocity) fail to convey the complex flow structures. The computation of finite-time Lyapunov exponent (FTLE) fields and underlying Lagrangian coherent structures (LCS) help reveal a Lagrangian template for quantifying the flow [1].

scholarly journals Recent developments towards high-flux time-resolved and terahertz SAXS experiments on the EMBL P12 BioSAXS beamline

2019 ◽  
Vol 75 (a2) ◽  
pp. e639-e639
Author(s):  
Martin A. Schroer ◽  
Siawosch Schewa ◽  
Clement E. Blanchet ◽  
Andrey Yu. Gruzinov ◽  
Till Zickmantel ◽  
...  
Keyword(s):  
High Flux ◽  
Time Resolved ◽  
Recent Developments

Contribution de la photogrammetrie numerique a l'etude spatio-temporelle de versants instables; l'exemple du glissement de terrain de Super-Sauze (Alpes-de-Haute-Provence, France)

2000 ◽  
Vol 171 (6) ◽  
pp. 637-648 ◽  
Author(s):  
Dominique Weber ◽  
Agnes Herrmann
Keyword(s):  
Aerial Photography ◽  
Morphological Evolution ◽  
Historical Evolution ◽  
Complex Flow ◽  
Glissement De Terrain ◽  
Digital Elevation ◽  
Recent Developments ◽  
Unstable Slope ◽  
Morphological Processes ◽  
Spatio Temporal

Abstract Recent developments in image processing and digital photogrammetry offer to the geomorphologists increasingly accessible and effective tools for the spatio-temporal knowledge of landslides. These techniques were used to reconstitute the historical evolution of a complex flow slide occurring in the "Terres Noires" of the Barcelonnette basin. The lithological and morphological environment of the studied site is characteristic of the whole southern French Prealps where are largely present Jurassic marly formations. Six digital elevation models (D.E.M.) generated from stereoscopic couples of aerial photography, but also various ortho-images and perspective views, allow to follow the morphological evolution of the unstable slope since the years 1950's -- before the releasing of the landslide -- until our days. Besides multitemporal descriptions of the landscape and of the morphological processes occurred on this site, the implemented method appears particularly useful for the quantitative analysis of the instabilities. It appears notably as a powerful tool for the 3-D reconstruction of the landslide geometry and by the same occasion for the calculation of its volume.

Volumetric Three-Componential Velocity Measurements (V3V) of Flow Structure Behind Mangrove-Root Type Models

2020 ◽  
Author(s):  
Amirkhosro Kazemi ◽  
Eduardo E. Castillo ◽  
Oscar Curet ◽  
Ruben Hortensius ◽  
Pothos Stamatios
Keyword(s):  
Flow Structure ◽  
Vortex Structure ◽  
Streamwise Velocity ◽  
Circular Cylinders ◽  
Complex Flow ◽  
Time Resolved ◽  
Mangrove Root ◽  
Mangrove Roots ◽  
A Chain ◽  
Complex Flow Structure

Abstract Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.

scholarly journals Some Recent Developments in Atomic Lifetime Determinations

1986 ◽  
Vol 39 (5) ◽  
pp. 829 ◽  
Author(s):  
P Hannaford ◽  
RM Lowe
Keyword(s):  
Laser Excitation ◽  
Pulsed Laser ◽  
Fluorescence Decay ◽  
Gas Discharge ◽  
Rare Gas ◽  
Time Resolved ◽  
Atomic Systems ◽  
Refractory Elements ◽  
Wide Range ◽  
Recent Developments

A lifetimes technique that is readily applicable to neutral and singly ionised atoms of a wide range of elements, including the highly refractory elements, is reviewed. With this technique an atomic vapour of the element under study is generated by cathodic sputtering in a low pressure rare-gas discharge and fluorescence decay signals emitted by the vapour following pulsed laser excitation are recorded directly in a fast transient digitiser. Theoretical expressions are presented for the form of the time-resolved fluor~scence signal appropriate to the collisional environment of a rare-gas sputtering discharge. A summary is given of the atomic systems studied to date using this technique, and some new results for Sm and Ba are compared with recently reported results for these elements.

OSCAT: Novel Technique for Time-Resolved Experiments Without Moveable Optical Delay Lines

2010 ◽  
Vol 32 (5) ◽  
pp. 596-602 ◽  
Author(s):  
Rafał Wilk ◽  
Thomas Hochrein ◽  
Martin Koch ◽  
Michael Mei ◽  
Ronald Holzwarth
Keyword(s):  
Delay Lines ◽  
Time Resolved ◽  
Novel Technique ◽  
Optical Delay

Time resolved optical beam induced currents: A novel technique to image spatio-temporal phenomena in semiconductors

1995 ◽  
Vol 152 (1) ◽  
pp. 281-286
Author(s):  
J. H. Wolter ◽  
C. M. van Es ◽  
J. E. M. Haverkort ◽  
E. A. E. Zwaal
Keyword(s):  
Optical Beam ◽  
Time Resolved ◽  
Novel Technique ◽  
Induced Currents ◽  
Spatio Temporal

Metal deformation and phase transitions at extremely high strain rates

MRS Bulletin ◽  
2010 ◽  
Vol 35 (12) ◽  
pp. 999-1006 ◽  
Author(s):  
R. E. Rudd ◽  
T. C. Germann ◽  
B. A. Remington ◽  
J. S. Wark
Keyword(s):  
Phase Transitions ◽  
High Pressures ◽  
Materials Science ◽  
Strain Rates ◽  
Ambient Conditions ◽  
Time Resolved ◽  
Study Materials ◽  
Recent Developments ◽  
Metal Deformation ◽  
Kinetic Effects

The powerful lasers being constructed for inertially confined fusion generate enormous pressures extremely rapidly. These extraordinary machines both motivate the need and provide the means to study materials under extreme pressures and loading rates. In this frontier of materials science, an experiment may last for just 10s of nanoseconds. Processes familiar at ambient conditions, such as phase transformations and plastic flow, operate far from equilibrium and show significant kinetic effects. Here we describe recent developments in the science of metal deformation and phase transitions at extreme pressures and strain rates. Ramp loading techniques enable the study of solids at high pressures (100s of GPa) at moderate temperatures. Advanced diagnostics, such as in situ x-ray scattering, allow time-resolved material characterization in the short-lived high-pressure state, including crystal structure (phase), elastic compression, the size of microstructural features, and defect densities. Computer simulation, especially molecular dynamics, provides insight into the mechanisms of deformation and phase change.

Sign in / Sign up

Export Citation Format

Share Document