Observations of persistent Leonid meteor trails: 4. Buoyant rise/vortex formation as mechanism for creation of parallel meteor train pairs

2005 ◽  
Vol 110 (A4) ◽  
Author(s):  
John Zinn ◽  
Jack Drummond
Keyword(s):  
Vortex Formation ◽  
Meteor Trails ◽  
Meteor Train

Intensification of Open Gutters Operation

2020 ◽  
pp. 66-70
Keyword(s):  
Water Flow ◽  
Vortex Formation ◽  
Hydraulic Testing ◽  
Polymer Materials ◽  
Bottom Surface ◽  
Artificial Roughness ◽  
Transport Capacity ◽  
Corrugated Surfaces ◽  
Inner Surface ◽  
Dispersed Inclusions

The intensification of the work of open gutter by applying textured shells to their bottom surface, forming an artificial roughness, is considered. It is shown that the presence of corrugated surfaces contributes to vortex formation during water flow and improves the separation and transportation of mineral impurities previously dropped into the bottom of the gutters. The implementation of operations to improve the structure of the gutters is possible during the repair and restoration works with the use of modern polymer materials. The design of a small-sized hydraulic stand, which makes it possible to study the transport capacity of flows containing solid inclusions, is presented. The method of research is hydraulic testing, accompanied by the use of chiaroscuro effect, as well as photo and film equipment. The optimal structure of the inner surface of the gutters and pipes providing vortex formation, which will improve the ability of the flow to carry out and transport foreign dispersed inclusions (sand) of different granulometric compositions, is determined.

DTNS3D Computer Code Simulation of Tip-Vortex Formation: RANS Code Validation

1997 ◽  
Author(s):  
John G. Telste ◽  
Roderick M. Coleman ◽  
Joseph J. Gorski
Keyword(s):  
Vortex Formation ◽  
Computer Code ◽  
Tip Vortex ◽  
Code Validation

Closed-Loop Control of Vortex Formation in Separated Flows with Application to Micro Air Vehicles

2010 ◽  
Author(s):  
Tim Colonius ◽  
Morteza Gharib ◽  
Clarence W. Rowley ◽  
Gilead Tadmor ◽  
David R. Williams
Keyword(s):  
Closed Loop ◽  
Vortex Formation ◽  
Micro Air Vehicles ◽  
Separated Flows ◽  
Closed Loop Control ◽  
Loop Control ◽  
Air Vehicles

Analysis of meteor trails providing combined forward and backward scattering of radio waves

2021 ◽  
Vol 195 ◽  
pp. 105135
Author(s):  
I. Lapshina ◽  
S. Kalabanov ◽  
A. Karpov ◽  
A. Sulimov
Keyword(s):  
Radio Waves ◽  
Meteor Trails

scholarly journals Circulation derived from 4D flow MRI correlates with right ventricular dysfunction in patients with tetralogy of Fallot

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nanae Tsuchiya ◽  
Michinobu Nagao ◽  
Yumi Shiina ◽  
Shohei Miyazaki ◽  
Kei Inai ◽  
...  
Keyword(s):  
Right Ventricular ◽  
Tetralogy Of Fallot ◽  
Main Pulmonary Artery ◽  
Vortex Formation ◽  
Cine Mri ◽  
Short Axis ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Mri ◽  
Rv Function

AbstractWe used 4D-flow MRI to investigate circulation, an area integral of vorticity, in the main pulmonary artery (MPA) as a new hemodynamic parameter for assessing patients with a repaired Tetralogy of Fallot (TOF). We evaluated the relationship between circulation, right ventricular (RV) function and the pulmonary regurgitant fraction (PRF). Twenty patients with a repaired TOF underwent cardiac MRI. Flow-sensitive 3D-gradient sequences were used to obtain 4D-flow images. Vortex formation in the MPA was visualized, with short-axis and longitudinal vorticities calculated by software specialized for 4D flow. The RV indexed end-diastolic/end-systolic volumes (RVEDVi/RVESVi) and RV ejection fraction (RVEF) were measured by cine MRI. The PR fraction (PRF) and MPA area were measured by 2D phase-contrast MRI. Spearman ρ values were determined to assess the relationships between circulation, RV function, and PRF. Vortex formation in the MPA occurred in 15 of 20 patients (75%). The longitudinal circulation (11.7 ± 5.1 m2/s) was correlated with the RVEF (ρ = − 0.85, p = 0.0002), RVEDVi (ρ = 0.62, p = 0.03), and RVESVi (ρ = 0.76, p = 0.003) after adjusting for the MPA size. The short-axis circulation (9.4 ± 3.4 m2/s) in the proximal MPA was positively correlated with the MPA area (ρ = 0.61, p = 0.004). The relationships between the PRF and circulation or RV function were not significant. Increased longitudinal circulation in the MPA, as demonstrated by circulation analysis using 4D flow MRI, was related to RV dysfunction in patients with a repaired TOF.

Replication of left ventricular haemodynamics with a simple planar mitral valve model

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Anna Daub ◽  
Jochen Kriegseis ◽  
Bettina Frohnapfel
Keyword(s):  
Mitral Valve ◽  
Computational Models ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Left Ventricular ◽  
Computational Effort ◽  
Type Model ◽  
Diastolic Phase ◽  
Valve Model ◽  
Modelling Approach

AbstractTools for the numerical prediction of haemodynamics in multi-disciplinary integrated heart simulations have to be based on computational models that can be solved with low computational effort and still provide physiological flow characteristics. In this context the mitral valve model is important since it strongly influences the flow kinematics, especially during the diastolic phase. In contrast to a 3D valve, a vastly simplified valve model in form of a simple diode is known to be unable to reproduce the characteristic vortex formation and unable to promote a proper ventricular washout. In the present study, an adaptation of the widely used simplest modelling approach for the mitral valve is employed and compared to a physiologically inspired 3D valve within the same ventricular geometry. The adapted approach shows enhanced vortex formation and an improved ventricular washout in comparison to the diode type model. It further shows a high potential in reproducing the main flow characteristics and related particle residence times generated by a 3D valve.

An Experimental Study on the Vertical Flow Past a Finite-Length Horizontal Cylinder at Low Reynolds Numbers

2014 ◽  
Vol 493 ◽  
pp. 68-73 ◽  
Author(s):  
Willy Stevanus ◽  
Yi Jiun Peter Lin
Keyword(s):  
Finite Length ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Horizontal Cylinder ◽  
Vortex Street ◽  
Vertical Flow ◽  
Low Reynolds Numbers ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

The research studies the characteristics of the vertical flow past a finite-length horizontal cylinder at low Reynolds numbers (ReD) from 250 to 1080. The experiments were performed in a vertical closed-loop water tunnel. Flow fields were observed by the particle tracer approach for flow visualization and measured by the Particle Image Velocimetry (P.I.V.) approach for velocity fields. The characteristics of vortex formation in the wake of the finite-length cylinder change at different regions from the tip to the base of it. Near the tip, a pair of vortices in the wake was observed and the size of the vortex increased as the observed section was away from the tip. Around a distance of 3 diameters of the cylinder from its tip, the vortex street in the wake was observed. The characteristics of vortex formation also change with increasing Reynolds numbers. At X/D = -3, a pair of vortices was observed in the wake for ReD = 250, but as the ReD increases the vortex street was observed at the same section. The vortex shedding frequency is analyzed by Fast Fourier Transform (FFT). Experimental results show that the downwash flow affects the vortex shedding frequency even to 5 diameters of the cylinder from its tip. The interaction between the downwash flow and the Von Kármán vortex street in the wake of the cylinder is presented in this paper.

THE DISTRIBUTION OF IONIZATION ALONG UNDERDENSE METEOR TRAILS

1964 ◽  
Vol 42 (11) ◽  
pp. 2035-2047 ◽  
Author(s):  
D. W. Rice ◽  
P. A. Forsyth
Keyword(s):  
Upper Atmosphere ◽  
Sources Of Error ◽  
Signal Characteristics ◽  
Radio Signals ◽  
Meteor Trails

Attempts to use the decay of radio signals reflected from individual meteor trails to study the upper atmosphere have revealed a puzzling inconsistency in the signal behavior. An earlier paper pointed out that this inconsistency remained even when the previously postulated sources of error were eliminated. As a result, an irregularly ionized trail model was proposed and shown, by calculation of signal characteristics, to be capable of accounting for the observations. This paper presents results of a new experiment which permitted the determination of the ionization profiles as the meteor trails were formed. The predicted irregularities were found, even for trails which exhibited apparently "ideal" underdense signal characteristics.

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