An Approach for Assessing Turbulent Flow Damage to Blood in Medical Devices

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Mesude Ozturk ◽  
Dimitrios V. Papavassiliou ◽  
Edgar A. O'Rear
Keyword(s):  
Turbulent Flow ◽  
Blood Cells ◽  
Capillary Tube ◽  
Jet Flow ◽  
Flow Conditions ◽  
Contributing Factors ◽  
Kolmogorov Length Scale ◽  
Extensive Property ◽  
Kolmogorov Scale ◽  
Flow Experiments

In this work, contributing factors for red blood cell (RBC) damage in turbulence are investigated by simulating jet flow experiments. Results show that dissipative eddies comparable or smaller in size to the red blood cells cause hemolysis and that hemolysis corresponds to the number and, more importantly, the surface area of eddies that are associated with Kolmogorov length scale (KLS) smaller than about 10 μm. The size distribution of Kolmogorov scale eddies is used to define a turbulent flow extensive property with eddies serving as a means to assess the turbulence effectiveness in damaging cells, and a new hemolysis model is proposed. This empirical model is in agreement with hemolysis results for well-defined systems that exhibit different exposure times and flow conditions, in Couette flow viscometer, capillary tube, and jet flow experiments.

scholarly journals Where do small, weakly inertial particles go in a turbulent flow?

2012 ◽  
Vol 698 ◽  
pp. 160-167 ◽  
Author(s):  
Mathieu Gibert ◽  
Haitao Xu ◽  
Eberhard Bodenschatz
Keyword(s):  
Turbulent Flow ◽  
Particle Density ◽  
Inertial Particles ◽  
Flow Conditions ◽  
Particle Inertia ◽  
Heavy Particles ◽  
Preferential Sampling ◽  
Fully Developed Turbulent Flow ◽  
Kolmogorov Scale ◽  
Preferential Alignment

AbstractWe report experimental results on the dynamics of heavy particles of the size of the Kolmogorov scale in a fully developed turbulent flow. The mixed Eulerian structure function of two-particle velocity and acceleration difference vectors $\langle {\delta }_{r} \mathbi{v}\boldsymbol{\cdot} {\delta }_{r} {\mathbi{a}}_{\mathbi{p}} \rangle $ was observed to increase significantly with particle inertia for identical flow conditions. We show that this increase is related to a preferential alignment between these dynamical quantities. With increasing particle density the probability for those two vectors to be collinear was observed to grow. We show that these results are consistent with the preferential sampling of strain-dominated regions by inertial particles.

Influence of different flow regimes on the performance characteristics of a four-pad hydrostatic squeeze film damper loaded between pads

2019 ◽  
Vol 71 (3) ◽  
pp. 440-446
Author(s):  
Amina Nemchi ◽  
Ahmed Bouzidane ◽  
Aboubakeur Benariba ◽  
Hicham Aboshighiba
Keyword(s):  
Turbulent Flow ◽  
Load Capacity ◽  
Flow Regimes ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Flow Conditions ◽  
Content Type ◽  
Turbulent Flow Regime ◽  
Squeeze Film Dampers

Purpose The purpose of this paper is to study the influence of different flow regimes on the dynamic characteristics of four-pad hydrostatic squeeze film dampers (SFDs) loaded between pads. Design/methodology/approach A numerical model based on Constantinescu’s turbulent lubrication theory using the finite difference method has been developed and presented to study the effect of eccentricity ratio on the performance characteristics of four-pad hydrostatic SFDs under different flow regimes. Findings It was found that the influence of turbulent flow on the dimensionless damping of four-pad hydrostatic SFDs appears to be essentially controlled by the eccentricity ratio. It was also found that the laminar flow presents higher values of load capacity compared to bearings operating under turbulent flow conditions. Originality/value In fact, the results obtained show that the journal bearing performances are significantly influenced by the turbulent flow regime. The study is expected to be useful to bearing designers.

Electrochemical Kinetic of a Low Carbon Steel in Seawater at Different Flow Speed

2015 ◽  
Vol 1766 ◽  
pp. 73-80
Author(s):  
A. Carmona ◽  
R. Orozco-Cruz ◽  
E. Mejía-Sánchez ◽  
A. Contreras ◽  
R. Galván-Martínez
Keyword(s):  
Turbulent Flow ◽  
Rotation Speed ◽  
Electrochemical Impedance ◽  
Static Condition ◽  
Flow Speed ◽  
Localized Corrosion ◽  
Low Carbon ◽  
Flow Conditions ◽  
Static Conditions ◽  
Turbulent Flow Conditions

ABSTRACTAn electrochemical impedance spectroscopy (EIS) corrosion study of API X70 steel was carried out in synthetic seawater with different rotation speeds using a rotating cylinder electrode (RCE) to control the hydrodynamic conditions at room temperature, atmospheric pressure and 24 h of exposure time. A superficial analysis through a scanning electron microscope (SEM) was used to analyze the corrosion type. The rotation speed used was 0 rpm (static condition), 1000, 3000 and 5000 rpm (turbulent flow). The results show that the turbulent flow conditions affect directly the corrosion rate (CR) of the steel, because all values of the CR under turbulent flow conditions are higher than the CR values at static conditions. In addition, it is important to point out that at turbulent flow conditions, the CR increased as the rotation speed also increased. The morphology of the corrosion in all experiments was localized corrosion.

Frossling Number Assessment for Airfoil Under Fully Turbulent Flow Conditions

2021 ◽  
pp. 1-10
Author(s):  
Abdallah Samad ◽  
Gitsuzo B. S. Tagawa ◽  
Rasoul Rajabi Khamesi ◽  
François Morency ◽  
Christophe Volat
Keyword(s):  
Turbulent Flow ◽  
Flow Conditions ◽  
Turbulent Flow Conditions

scholarly journals Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 683
Author(s):  
Gilbert Accary ◽  
Duncan Sutherland ◽  
Nicolas Frangieh ◽  
Khalid Moinuddin ◽  
Ibrahim Shamseddine ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Forest Canopy ◽  
Prescribed Burning ◽  
Second Phase ◽  
Flow Conditions ◽  
Developed Turbulence ◽  
Large Eddy ◽  
Long Time ◽  
Two Phases ◽  
The Impact

The behavior of a grassland fire propagating downstream of a forest canopy has been simulated numerically using the fully physics-based wildfire model FIRESTAR3D. This configuration reproduces quite accurately the situation encountered when a wildfire spreads from a forest to an open grassland, as can be the case in a fuel break or a clearing, or during a prescribed burning operation. One of the objectives of this study was to evaluate the impact of the presence of a canopy upstream of a grassfire, especially the modifications of the local wind conditions before and inside a clearing or a fuel break. The knowledge of this kind of information constitutes a major element in improving the safety conditions of forest managers and firefighters in charge of firefighting or prescribed burning operations in such configurations. Another objective was to study the behavior of the fire under realistic turbulent flow conditions, i.e., flow resulting from the interaction between an atmospheric boundary layer (ABL) with a surrounding canopy. Therefore, the study was divided into two phases. The first phase consisted of generating an ABL/canopy turbulent flow above a pine forest (10 m high, 200 m long) using periodic boundary conditions along the streamwise direction. Large Eddy Simulations (LES) were carried out for a sufficiently long time to achieve a quasi-fully developed turbulence. The second phase consisted of simulating the propagation of a surface fire through a grassland, bordered upstream by a forest section (having the same characteristics used for the first step), while imposing the turbulent flow obtained from the first step as a dynamic inlet condition to the domain. The simulations were carried out for a wind speed that ranged between 1 and 12 m/s; these values have allowed the simulations to cover the two regimes of propagation of surfaces fires, namely plume-dominated and wind-driven fires.

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