Cavitation Threshold with Respect to Dp/Dt: Evaluation in 29 Mm Bileaflet, Pyrolitic Carbon Heart Valves

1993 ◽  
Vol 16 (7) ◽  
pp. 515-520 ◽  
Author(s):  
C. Kingsbury ◽  
R. Kafesjian ◽  
G. Guo ◽  
P. Adlparvar ◽  
J. Unger ◽  
...  
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Video Recording ◽  
Pressure Curve ◽  
Threshold Detection ◽  
Jude Medical ◽  
Strobe Light ◽  
Video Systems ◽  
Cavitation Threshold ◽  
Pyrolitic Carbon

A total of 15 bileaflet mechanical heart valves were studied in a pulse duplicator at the Helmholtz Institute (Aachen, Germany) under conditions approximating first, a physiological pressure curve and subsequently, a sinusoidal pressure curve. In this study Edwards-Duromedics valves of the modified specification were compared with the earlier version of the Edwards-Duromedics valve as well as with St. Jude Medical valves. Each valve was tested at a series of nine (9) conditions. At each condition, without altering the valve installation or the systemic conditions, each valve was filmed by two separate video systems: the Helmholtz Institute strobe light system and a high speed video recording system. All data, as recorded by each system, was then independently analyzed by both of the two contributing groups and subsequently compared. In this manner, it was possible to objectively verify not only the consistency of the data obtained, but to also determine the relative reliability of the methods for cavitation threshold detection.

How Do Transcatheter Heart Valves Fit in Mitral Annuloplasty Rings and Which Combination Can be Recommended?

2018 ◽  
Vol 67 (04) ◽  
pp. 257-265
Author(s):  
Roya Ostovar ◽  
Ralf-Uwe Kuehnel ◽  
Michael Erb ◽  
Martin Hartrumpf ◽  
Thomas Claus ◽  
...  
Keyword(s):  
High Speed ◽  
Visual Inspection ◽  
Heart Valves ◽  
Mitral Annuloplasty ◽  
Jude Medical ◽  
Pulse Duplicator ◽  
Round Shape ◽  
Mitral Position ◽  
Transcatheter Heart Valve ◽  
Edwards Sapien

Background Transcatheter heart valve (THV) as valve-in-ring is increasingly used in the mitral position. Semi-rigid rings may serve as a more appropriate scaffold for proper anchoring of a THV as they may change from their oval to a round shape thereby fitting to the implanted THV. Methods One rigid and five semi-rigid rings of four manufacturers, Edwards Physio I and II, Sorin 3D Memo, Medtronic Simulus, and St. Jude Medical (SJM) Saddle and SJM Sequin, with sizes 28 to 36 mm and Edwards Sapien III THV 23, 26, and 29 mm were used. Preevaluation comprised insertion/inflation of the THV into the ring and visual inspection for the paravalvular gap ≥ 4 mm2. Only valves not showing paravalvular gap were then submitted to hemodynamic evaluation with a pulse duplicator. Cusp movement was assessed with a high-speed-camera. Mean transvalvular gradients (TVGs) were measured. Results SJM Saddle ring of all sizes and SJM Sequin ring 34 showed marked gaps combined with all THV sizes, thus not undergoing hemodynamic testing. It was further shown that ring sizes ≥ 36 mm did not allow for a proper fit of even the largest THV into the ring of all the manufacturers and were consequently not hemodynamically evaluated. The 23 mm THV was too small for any ring size. The lowest gradients were achieved with the 26 mm THV in 30 and 32 mm and the 29 mm THV in 32 and 34 mm rings. Conclusion Not all currently available annuloplasty rings are ideal scaffolds for THV placement. It appears that a more proper fit can be achieved with semi-rigid rings than with rigid ones. Note that 23 mm THV appeared to be too small for an adequate anchoring in even the smallest available ring. Thus, 26 mm as well as 29 mm THV fit properly in ring sizes between 28 and 34 mm. Surgeons may consider to choose from those ring brands and sizes which allow for good placement of a THV in view of possible valve degeneration in the later course.

scholarly journals In vivotranscranial cavitation threshold detection during ultrasound-induced blood–brain barrier opening in mice

2010 ◽  
Vol 55 (20) ◽  
pp. 6141-6155 ◽  
Author(s):  
Yao-Sheng Tung ◽  
Fotios Vlachos ◽  
James J Choi ◽  
Thomas Deffieux ◽  
Kirsten Selert ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Threshold Detection ◽  
Blood Brain ◽  
Cavitation Threshold ◽  
Barrier Opening ◽  
Blood Brain Barrier Opening

ASSESSMENT OF MULTALL AS CFD CODE FOR THE ANALYSIS OF TUBE-AXIAL FANS

2021 ◽  
pp. 1-12
Author(s):  
Piero Danieli ◽  
Massimo Masi ◽  
Giovanni Delibra ◽  
Alessandro Corsini ◽  
Andrea Lazzaretto
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Velocity Distribution ◽  
High Speed ◽  
State Of The Art ◽  
Stable Operation ◽  
Pressure Curve ◽  
Analysis Tool ◽  
Low Speed ◽  
Axial Fans

Abstract This work deals with the application of the open source CFD code MULTALL to the analysis of tube-axial-fans. The code has been widely validated in the literature for high-speed turbomachine flows but not applied yet to low speed tutbomachines. The aim of this work is to assess the degree of reliability of MULTALL as a tool for simulating the internal flow in industrial axial-flow fan rotors. To this end, the predictions of the steady-state air flow field in the annular sector of a 315 mm tube-axial fan obtained by MULTALL 18.3 are compared with those obtained by two state-of-the-art CFD codes and experimental data of the global aerodynamic performance of the fan and the pitch-wise averaged velocity distribution downstream of the rotor. All the steady-state RANS calculations were performed on either fully structured hexahedron or hexa-dominant grids using classical formulations of algebraic turbulence models. The pressure curve and the trend of the aeraulic efficiency in the stable operation range of the fan predicted by MULTALL show very good agreement with both the experimental data and the other CFD results. Although the estimation of the fan efficiency predicted by MULTALL can be noticeably improved by the more sophisticated state-of-the-art CFD codes, the analysis of the velocity distribution at the rotor exit supports the use of MULTALL as a reliable CFD analysis tool for designers of low-speed axial fans.

scholarly journals Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed

2019 ◽  
Vol 3 (1) ◽  
pp. 17
Author(s):  
Villads Schultz
Keyword(s):  
High Speed ◽  
Sheet Material ◽  
Video Recording ◽  
Laser Beam Welding ◽  
Butt Joint ◽  
Filler Wire ◽  
Laser Material Processing ◽  
Melt Pool ◽  
Transition Area ◽  
Beam Oscillation

Beam oscillation in laser material processing makes it possible to influence process behavior in terms of energy distribution, stability, melt pool dynamics and solidification. Within the setup presented here, the beam is oscillated transverse to the welding direction, and the filler wire is fed to the melt pool of a butt joint with an air gap. One advantage of this setup is the large gap bridging ability. Certain parameter sets lead to the so-called buttonhole welding method, which allows laser welding of smooth and nearly ripple-free seams. Observations showed a transition area between conventional keyhole and buttonhole welding in which the process is destabilized. Welds made with parameter sets from this area contain critical seam defects. Welding experiments with high-speed video recording and a simplified analytical model about the wire-beam interaction have helped to elucidate the mechanisms behind this. EN AW-6082 sheet material in 1.5 mm thickness and ML 4043 filler wire with 1.2 mm diameter were used. The investigations lead to the conclusion that partially melted wire segments result at certain parameter relations which hinder the formation of a buttonhole. If these segments are prevented, buttonhole welding occurs. In the transition area, these segments are very small and can lead to the detachment of a buttonhole, resulting in the named seam defects.

scholarly journals High-speed Video Recording of Particle Trajectory via Rotating Chute of Nagoya No.3 Blast Furnace and its Comparison with Simulated Behavior Using DEM

2017 ◽  
Vol 57 (2) ◽  
pp. 272-278 ◽  
Author(s):  
Hiroshi Mio ◽  
Toshiki Nakauchi ◽  
Yuuki Kawaguchi ◽  
Takashi Enaka ◽  
Yoichi Narita ◽  
...  
Keyword(s):  
Blast Furnace ◽  
High Speed ◽  
Particle Trajectory ◽  
Video Recording ◽  
High Speed Video

Highly resolved pulsatile flows through prosthetic heart valves using the entropic lattice-Boltzmann method

2014 ◽  
Vol 754 ◽  
pp. 122-160 ◽  
Author(s):  
B. Min Yun ◽  
L. P. Dasi ◽  
C. K. Aidun ◽  
A. P. Yoganathan
Keyword(s):  
Lattice Boltzmann Method ◽  
Pulsatile Flow ◽  
Lattice Boltzmann ◽  
Heart Valves ◽  
Prosthetic Heart Valves ◽  
Spatiotemporal Resolution ◽  
Jude Medical ◽  
High Spatiotemporal Resolution ◽  
Flow Through ◽  
Boltzmann Method

AbstractProsthetic heart valves have been widely used to replace diseased or defective native heart valves. Flow through bileaflet mechanical heart valves (BMHVs) have previously demonstrated complex phenomena in the vicinity of the valve owing to the presence of two rigid leaflets. This study aims to accurately capture the complex flow dynamics for pulsatile flow through a 23 mm St Jude Medical (SJM) Regent™ BMHV. The lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through the valve with the inclusion of reverse leakage flow at very high spatiotemporal resolution that can capture fine details in the pulsatile BMHV flow field. For higher-Reynolds-number flows, this high spatiotemporal resolution captures features that have not been observed in previous coarse resolution studies. In addition, the simulations are able to capture with detail the features of leaflet closing and the asymmetric b-datum leakage jet during mid-diastole. Novel flow physics are visualized and discussed along with quantification of turbulent features of this flow, which is made possible by this parallelized numerical method.

scholarly journals Foraging at the edge of the world: low-altitude, high-speed manoeuvering in barn swallows

2016 ◽  
Vol 371 (1704) ◽  
pp. 20150391 ◽  
Author(s):  
Douglas R. Warrick ◽  
Tyson L. Hedrick ◽  
Andrew A. Biewener ◽  
Kristen E. Crandell ◽  
Bret W. Tobalske
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Ground Effect ◽  
Natural State ◽  
Wingbeat Frequency ◽  
High Speeds ◽  
Aerial Insectivores ◽  
Video Systems ◽  
Shear Gradient ◽  
Barn Swallows

While prior studies of swallow manoeuvering have focused on slow-speed flight and obstacle avoidance in still air, swallows survive by foraging at high speeds in windy environments. Recent advances in field-portable, high-speed video systems, coupled with precise anemometry, permit measures of high-speed aerial performance of birds in a natural state. We undertook the present study to test: (i) the manner in which barn swallows ( Hirundo rustica ) may exploit wind dynamics and ground effect while foraging and (ii) the relative importance of flapping versus gliding for accomplishing high-speed manoeuvers. Using multi-camera videography synchronized with wind-velocity measurements, we tracked coursing manoeuvers in pursuit of prey. Wind speed averaged 1.3–2.0 m s −1 across the atmospheric boundary layer, exhibiting a shear gradient greater than expected, with instantaneous speeds of 0.02–6.1 m s −1 . While barn swallows tended to flap throughout turns, they exhibited reduced wingbeat frequency, relying on glides and partial bounds during maximal manoeuvers. Further, the birds capitalized on the near-earth wind speed gradient to gain kinetic and potential energy during both flapping and gliding turns; providing evidence that such behaviour is not limited to large, fixed-wing soaring seabirds and that exploitation of wind gradients by small aerial insectivores may be a significant aspect of their aeroecology. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight'.

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