Imaging and Measurement of the Separation Surface Between Converging Fluids of Differing Viscosity at a Microscopic Branch

2000 ◽  
Author(s):  
J. P. Peach ◽  
D. L. Hitt
Keyword(s):  
Blood Flow ◽  
Oxygen Transport ◽  
Nonuniform Distribution ◽  
Transport Processes ◽  
Blood Components ◽  
Microvascular Network ◽  
Separation Surface ◽  
Flow Mixing ◽  
Flow Impedance ◽  
Reverse Situation

Abstract The mechanics of branching blood flow is of fundamental importance in understanding the nonuniform distribution of blood components within a microvascular network and, indeed, even within an individual vessel. The nonuniformity resulting from the branch can in turn impact microvascular flow impedance and oxygen transport processes. A construct known as the “separation surface” is often used to describe the flow at converging (venular) and diverging (arteriolar) branches. In the case of two converging flows, the separation surface identifies the portions of the flow in the outlet branch which originated from each of the two feeding branches. The reverse situation holds for a diverging branch. If the converging fluids are immiscible, then the separation surface is a persistent, physical surface within the flow. For converging blood flow, mixing occurs and the separation surface loses its definition with downstream position.

The Effect of Incorporating Vessel Compliance in a Computational Model of Blood Flow in a Total Cavopulmonary Connection (TCPC) with Caval Centerline Offset

2004 ◽  
Vol 126 (6) ◽  
pp. 709-713 ◽  
Author(s):  
J. C. Masters ◽  
M. Ketner ◽  
M. S. Bleiweis ◽  
M. Mill ◽  
A. Yoganathan ◽  
...  
Keyword(s):  
Blood Flow ◽  
Power Loss ◽  
Fluid Dynamic ◽  
Reducing Power ◽  
Pressure Head ◽  
Congenital Defects ◽  
Total Cavopulmonary Connection ◽  
Flow Mixing ◽  
The Right ◽  
Cavopulmonary Connection

Background—The total cavopulmonary connection (TCPC), a palliative correction for congenital defects of the right heart, is based on the corrective technique developed by Fontan and Baudet. Research into the TCPC has primarily focused on reducing power loss through the connection as a means to improve patient longevity and quality of life. The goal of our study is to investigate the efficacy of including a caval offset on the hemodynamics and, ultimately, power loss of a connection. As well, we will quantify the effect of vessel wall compliance on these factors and, in addition, the distribution of hepatic blood to the lungs. Methods—We employed a computational fluid dynamic model of blood flow in the TCPC that includes both the non-Newtonian shear thinning characteristics of blood and the nonlinear compliance of vessel tissue. Results—Power loss in the rigid-walled simulations decayed exponentially as caval offset increased. The compliant-walled results, however, showed that after an initial substantial decrease in power loss for offsets up to half the caval diameter, power loss increased slightly again. We also found only minimal mixing in both simulations of all offset models. Conclusions—The increase in power loss beyond an offset of half the caval diameter was due to an increase in the kinetic contribution. Reduced caval flow mixing, on the other hand, was due to the formation of a pressure head in the offset region which acts as a barrier to flow.

Viscosity of normal human blood under normothermic and hypothermic conditions

1964 ◽  
Vol 19 (1) ◽  
pp. 117-122 ◽  
Author(s):  
Peter W. Rand ◽  
Eleanor Lacombe ◽  
Hamilton E. Hunt ◽  
William H. Austin
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Heart Surgery ◽  
Blood Rheology ◽  
Normal Subjects ◽  
Future Studies ◽  
Flow Impedance ◽  
Normal Human ◽  
Technical Details ◽  
Normal Human Blood

Although blood viscosity varies in relation to shear rate, hematocrit, and temperature, equipment is now available with which it may be measured in respect to each of these variables. A simple, clinically practical technique for such measurement is presented. Blood from 60 normal subjects was adjusted to hematocrits 0, 20, 40, 60, and 80, and the viscosity-shear rate relationships measured at 37.0, 32.0, 27.0, and 22.0 C. The data obtained are presented as a reference for future studies using this method. Technical details are discussed and some deserving areas of application are considered. shear rate; cone-plate viscometer; hematocrit-viscosity relationships; blood, plasma; hematocrit; temperature; blood flow impedance; perfusion; shock; oliguria; dyspnea; coma; heart surgery; blood rheology; metabolism Submitted on May 31, 1963

scholarly journals A Kernel for Calculating PEM Fuel Cell Distribution of Relaxation Times

2021 ◽  
Vol 9 ◽  
Author(s):  
Andrei Kulikovsky
Keyword(s):  
Fuel Cell ◽  
Oxygen Transport ◽  
Relaxation Times ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Negative Real Part ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Transport Layer ◽  
Cathode Side

Impedance of all oxygen transport processes in PEM fuel cell has negative real part in some frequency domain. A kernel for calculation of distribution of relaxation times (DRT) of a PEM fuel cell is suggested. The kernel is designed for capturing impedance with negative real part and it stems from the equation for impedance of oxygen transport through the gas-diffusion transport layer (doi:10.1149/2.0911509jes). Using recent analytical solution for the cell impedance, it is shown that DRT calculated with the novel K2 kernel correctly captures the GDL transport peak, whereas the classic DRT based on the RC-circuit (Debye) kernel misses this peak. Using K2 kernel, analysis of DRT spectra of a real PEMFC is performed. The leftmost on the frequency scale DRT peak represents oxygen transport in the channel, and the rightmost peak is due to proton transport in the cathode catalyst layer. The second, third, and fourth peaks exhibit oxygen transport in the GDL, faradaic reactions on the cathode side, and oxygen transport in the catalyst layer, respectively.

scholarly journals Resistance Index of Cerebral Artery Blood Flow Impedance in Preterm Neonates.† 939

1998 ◽  
Vol 43 ◽  
pp. 162-162
Author(s):  
S Abbasi ◽  
J Anderson ◽  
G Agrons ◽  
R Dworanczyk ◽  
J Gerdes
Keyword(s):  
Blood Flow ◽  
Cerebral Artery ◽  
Resistance Index ◽  
Preterm Neonates ◽  
Artery Blood Flow ◽  
Flow Impedance
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