Time-Resolved PIV Measurements of Vortical Structures in the Upper Human Airways

2008 ◽  
pp. 35-53 ◽  
Author(s):  
Sebastian Groß e ◽  
Wolfgang Schröder ◽  
Michael Klaas
Keyword(s):  
Time Resolved ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Human Airways

Time-resolved PIV measurements of the flow field in a stenosed, compliant arterial model

2013 ◽  
Vol 54 (5) ◽  
Author(s):  
P. H. Geoghegan ◽  
N. A. Buchmann ◽  
J. Soria ◽  
M. C. Jermy
Keyword(s):  
Flow Field ◽  
Time Resolved ◽  
Piv Measurements ◽  
Arterial Model

Time-Resolved Particle Image Velocimetry (PIV) Measurements in a Radial Diffuser Pump

2009 ◽  
Author(s):  
Jianjun Feng ◽  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Time Resolved ◽  
Piv Measurements ◽  
Part Load ◽  
Channel Characteristic ◽  
Image Velocimetry ◽  
Pump Stage ◽  
Low Specific Speed ◽  
Load Conditions

The truly time-variant unsteady flow in a low specific speed radial diffuser pump stage has been investigated by time-resolved Particle Image Velocimetry (PIV) measurements. The measurements are conducted at the midspan of the blades for the design condition and also for some severe part-load conditions. The instantaneous flow fields among different impeller channels are analyzed and compared in detail, and more attention has been paid to flow separations at part-load conditions. The analysis of the measured results shows that the flow separations at two adjacent impeller channels are quite different at some part-load conditions. The separations generally exhibit a two-channel characteristic.

Time-Resolved DPIV Analysis of Vortex Dynamics in a Left Ventricular Model Through Bileaflet Mechanical and Porcine Heart Valve Prostheses

2004 ◽  
Vol 126 (6) ◽  
pp. 714-726 ◽  
Author(s):  
Olga Pierrakos ◽  
Pavlos P. Vlachos ◽  
Demetri P. Telionis
Keyword(s):  
Mitral Valve ◽  
Vortex Formation ◽  
Flow Patterns ◽  
Left Ventricular ◽  
Time Resolved ◽  
Vortical Structures ◽  
Jude Medical ◽  
Image Velocimetry ◽  
Valve Prostheses ◽  
Physical Phenomena

The performance of the heart after a mitral valve replacement operation greatly depends on the flow character downstream of the valve. The design and implanting orientation of valves may considerably affect the flow development. A study of the hemodynamics of two orientations, anatomical and anti-anatomical, of the St. Jude Medical (SJM) bileaflet valve are presented and compared with those of the SJM Biocor porcine valve, which served also to represent the natural valve. We document the velocity field in a flexible, transparent (LV) using time-resolved digital particle image velocimetry (TRDPIV). Vortex formation and vortex interaction are two important physical phenomena that dominate the filling and emptying of the ventricle. For the three configurations, the following effects were examined: mitral valve inlet jet asymmetry, survival of vortical structures upstream of the aortic valve, vortex-induced velocities and redirection of the flow in abidance of the Biot–Savart law, domain segmentation, resonant times of vortical structures, and regions of stagnant flow. The presence of three distinct flow patterns, for the three configurations, was identified by the location of vortical structures and level of coherence corresponding to a significant variation in the turbulence level distribution inside the LV. The adverse effect of these observations could potentially compromise the efficiency of the LV and result in flow patterns that deviate from those in the natural heart.

Time-resolved PIV measurements of a tip leakage flow

2016 ◽  
Vol 15 (6-7) ◽  
pp. 662-685 ◽  
Author(s):  
Marc C Jacob ◽  
Emmanuel Jondeau ◽  
Bo Li
Keyword(s):  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Time Resolved ◽  
Piv Measurements ◽  
Tip Leakage

scholarly journals Importance of Sub-Grid Scale Modeling for Accurate Aerodynamic Simulations

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Petter Ekman ◽  
James Venning ◽  
Torbjörn Virdung ◽  
Matts Karlsson
Keyword(s):  
The Body ◽  
Small Scale ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Scale Modeling ◽  
Simple Geometry ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Near Wall ◽  
Ahmed Body

Abstract The Ahmed body is one of the most well-investigated vehicle bodies for aerodynamic purposes. Despite its simple geometry, the flow around the body, especially at the rear, is very complex as it is dominated by a large wake with strong interaction between vortical structures. In this study, the flow around the 25 deg Ahmed body has been investigated using large eddy simulations and compared to high-resolution particle image velocimetry (PIV) measurements. Special emphasis was put on studying three commonly used sub-grid scale (SGS) models and their ability to capture vortical structures around the Ahmed body. The ability of the SGS models to capture the near-wall behavior and small-scale dissipation is crucial for capturing the correct flow field. Very good agreement between simulations and PIV measurements were seen when using the dynamic Smagorinsky-Lilly and the wall-adopting local eddy-viscosity SGS models, respectively. However, the standard Smagorinsky-Lilly model was not able to capture the flow patterns when compared to the PIV measurements due to shortcomings in the near-wall modeling in the standard Smagorinsky-Lilly model, resulting in overpredicted separation.

Experimental and Numerical Flow Visualization in Patient Specific Pre Operative Human Airway Geometry

2011 ◽  
Author(s):  
Mathias Vermeulen ◽  
Cedric Van Holsbeke ◽  
Tom Claessens ◽  
Jan De Backer ◽  
Peter Van Ransbeeck ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Particle Image ◽  
Patient Specific ◽  
Lung Volume Reduction ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Specific Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Human Airways

An experimental and numerical platform was developed to investigate the fluidodynamics in human airways. A pre operative patient specific geometry was used to create an identical experimental and numerical model. The experimental results obtained from Particle Image Velocimetry (PIV) measurements were compared to Computational Fluid Dynamics (CFD) simulations under stationary and pulsatile flow regimes. Together these results constitute the first step in predicting the clinical outcome of patients after lung surgeries such as Lung Volume Reduction.

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