FLOW IN TUBES WITH COMPLICATED GEOMETRIES WITH SPECIAL APPLICATION TO BLOOD FLOW IN LARGE ARTERIES

2006 ◽  
pp. 279-304
Author(s):  
GIRIJA JAYARAMAN
Keyword(s):  
Blood Flow ◽  
Large Arteries ◽  
Complicated Geometries

Effects of arginine vasopressin on cerebral microvascular pressure

1988 ◽  
Vol 255 (1) ◽  
pp. H70-H76 ◽  
Author(s):  
F. M. Faraci ◽  
W. G. Mayhan ◽  
P. G. Schmid ◽  
D. D. Heistad
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Vascular Resistance ◽  
Arginine Vasopressin ◽  
Cerebral Arteries ◽  
Aortic Pressure ◽  
Artery Pressure ◽  
Large Arteries ◽  
Pial Artery ◽  
Vessel Resistance

The goal of this study was to examine effects of arginine vasopressin and angiotensin on cerebral microvascular pressure and segmental vascular resistance. We measured pressure (servo-null) in pial arteries that were approximately 200 micron in diameter and cerebral blood flow (microspheres) in anesthetized cats, and we calculated resistance of large and small cerebral vessels. Resistance of large arteries (greater than 200 micron diam) was approximately 45% of total cerebral vascular resistance under control conditions. Vasopressin (40 mU/kg iv) decreased resistance of large arteries by 22 +/- 7%, increased pial artery pressure by 10 +/- 2 mmHg when aortic pressure was maintained at control levels, and increased small vessel resistance by 27 +/- 11%. This increase in small vessel resistance apparently was an autoregulatory response to the increase in pial pressure. Cerebral blood flow was not changed (38 +/- 4 vs. 37 +/- 3 ml.min-1.100 g-1). Intravenous infusion of angiotensin (2 micrograms.kg-1.min-1) increased large artery resistance by 32 +/- 6%, decreased pial artery pressure 6 +/- 3 mmHg with aortic pressure maintained constant, and decreased cerebral blood flow by 12 +/- 1%. Thus circulating vasopressin, at concentrations similar to those observed during hemorrhage, selectively dilates large cerebral arteries and increases microvascular pressure without changes in cerebral blood flow. In contrast to vasopressin, angiotensin selectively increases resistance of large cerebral arteries and decreases cerebral microvascular pressure. Thus vasopressin and angiotensin, at doses that have minimal effects on cerebral blood flow, may play an important role in regulation of cerebral microvascular pressure.

Computational Fluid Dynamics Simulation of the Blood Flow in the Human Aortic Arch: Effects of Three Branches of the Arch on the Flow

2002 ◽  
Author(s):  
Daisuke Mori ◽  
Tomoaki Hayasaka ◽  
Takami Yamaguchi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Aortic Arch ◽  
Vascular Diseases ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Large Arteries ◽  
Vessel Structure ◽  
Flow Phenomena

The vascular diseases occurred in large arteries are suggested to relate with the blood flow as well as the vessel structure, which significantly influences the flow. In order to investigate these interactions, we have to understand the detailed flow phenomena in the complex vessel configuration.

A Realistic Representation of the Rabbit Aorta for Use in Computational Haemodynamic Studies

2009 ◽  
Author(s):  
Peter E. Vincent ◽  
Anthony A. E. Hunt ◽  
Leopold Grinberg ◽  
Spencer J. Sherwin ◽  
Peter D. Weinberg
Keyword(s):  
Cardiovascular Disease ◽  
Blood Flow ◽  
Rabbit Aorta ◽  
Flow Patterns ◽  
Large Arteries ◽  
Realistic Representation ◽  
Blood Flow Patterns

Atherosclerosis is a common cardiovascular disease, characterised by the formation of lipid rich lesions within the walls of large arteries. Onset of atherosclerosis is observed to occur in a spatially heterogeneous fashion, with lesion sites located in regions of arterial branching and high curvature. Since blood flow patterns are also spatially heterogeneous within arteries, it has been postulated that flow may play an important role in modulating atherogenesis.

Surface Stiffness of Patient-Specific Arterial Segments With Varying Plaque Compositions

2013 ◽  
Author(s):  
Craig J. Bennetts ◽  
Ahmet Erdemir ◽  
Melissa Young
Keyword(s):  
United States ◽  
Blood Flow ◽  
Peripheral Arterial Disease ◽  
Arterial Disease ◽  
The United States ◽  
Patient Specific ◽  
Large Arteries ◽  
Surface Stiffness ◽  
Peripheral Arterial

Peripheral arterial disease (PAD), resulting from the accumulation of plaque, causes obstruction of blood flow in the large arteries in the arm and leg. In the United States, approximately 8.4 million people over the age of 40 have PAD [1]. If not treated, PAD can cause ischemic ulcerations and gangrene, which could eventually lead to amputation. Approximately, 25% of patients with PAD have worsening limb symptoms over 5 years, 7% requiring revascularization, and 4% requiring amputation [2].

scholarly journals INVESTIGATION OF THE BLOOD FLOW IN DEFORMABLE VESSELS USING STABILIZED FINITE ELEMENT METHOD

2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Evandro Dias Gaio ◽  
José Jerônimo Camata ◽  
Lucas Arantes Berg ◽  
Rafael Alves Bonfim de Queiroz
Keyword(s):  
Blood Flow ◽  
Degrees Of Freedom ◽  
Numerical Solutions ◽  
Fluid Dynamic ◽  
Rigid Wall ◽  
Good Alternative ◽  
Stabilized Finite Element ◽  
Large Arteries ◽  
Stabilized Finite Element Method ◽  
Planning And Design

The study and simulation of blood flow in the cardiovascular system have many applications such as pathologies studies, surgical planning, and design of medical devices. Several works within this area consider the problem using a rigid wall assumption, while blood velocity and pressure in large arteries are greatly influenced by vessel wall dynamics. The Coupled Momentum Method (CMM) is based on a strong coupling of degrees-of-freedom of the fluid and the solid domains. This coupling is made by considering that the deformation of the wall, in a variational level, become a boundary condition for the fluid domain. As an advantage, description of motion (Eulerian) may be kept the same and a fixed mesh. In this study, blood is considered a Newtonian fluid and the wall a thin-walled linear elastic. This work is focused on using fluid-structure interaction in 3D geometries to evaluate the blood and vessel dynamics in contrast to the rigid wall formulation what is considered only a fluid dynamic problem. For realistic and physiological parameters, CMM has demonstrated to be a good alternative for the simulation of blood flow in large arteries by virtue of representing more realistic phenomena than a rigid wall model. The results were obtained using FEniCS and Python, and are in agreement with the theoretical and numerical solutions from the literature.

On the Microcirculation in the Human Conjunctiva

2013 ◽  
Author(s):  
William Dow ◽  
Frank Jacobitz ◽  
Peter Chen
Keyword(s):  
Blood Flow ◽  
Rheological Properties ◽  
Organ Damage ◽  
Microvascular Network ◽  
Large Arteries ◽  
Human Conjunctiva ◽  
The Common ◽  
Common Function

The microcirculation includes the smallest arterioles, capillaries, and venules with vessel diameters ranging from 8 to 150 μm and it represents a region where active and passive exchanges of nutrients and gasses take place. The microvessels’ rheological properties differ from large arteries: they are less viscous, and demonstrate autoregulation [3]. Epidemiologists study the microcirculation in detail and have identified associations between microvascular disorder and organ damage. The organization of the microvascular network can be different in different sites but the networks serve the common function in the delivery of nutrients to the surrounding tissues. This is controlled by a distribution of blood flow based on local metabolic needs. Under challenge or in the development of diseases, the microcirculation responds by selectively regulating blood flow. A comparison between healthy and diseased states may lead to the identification of changes in the microcirculation that can be used as diagnosis for a variety of vascular related disorders [4, 5].

An Innovative Approach to CTCs’ Liquid Surgery

2020 ◽  
Author(s):  
Luca Fontanili ◽  
Massimo Milani ◽  
Luca Montorsi ◽  
Letizia Scurani ◽  
Matteo Venturelli ◽  
...  
Keyword(s):  
Blood Flow ◽  
Physical Properties ◽  
Tumor Cells ◽  
Medical Device ◽  
Electric Fields ◽  
Ad Hoc ◽  
Starting Point ◽  
Baseline Information ◽  
Flow Through ◽  
Complicated Geometries

Abstract Circulating Tumor Cells (CTCs) can be defined as cancerous cells, which detach from a tumor and flow through the vascular or lymphatic systems. The blood flow can carry the tumor cells in another region of human body where they can become the starting point for the growth of additional metastases. Because of this behavior, in the CTCs study it is paramount to acquire new data and knowledge to understand the mechanisms that lead to the separation of the cell from the tumor as well as the major characteristics of these cells. The aim of this work is the development of an innovative therapeutic and diagnostic approach able to lead to a new medical device for removing CTCs from the peripheral blood of a patient. The main target of the approach is to detect the CTCs and separate them during a conventional extracorporeal circulation procedure, similar to that used for renal failure. In this work, the CTCs physical properties are investigated in order to explore the possible characteristics that can be exploited in an ad-hoc developed medical device to remove them from the blood flow. The CTCs physical properties are analyzed numerically, and their behavior is studied by means of CFD simulations. The preliminary numerical tests have been carried out on simple geometries in order to assess the influence of magnetic and electric fields on tumor cells’ trajectory. These results are the baseline information to develop more complicated geometries and prototypes for real operations.

scholarly journals Rarefaction and blood pressure in systemic and pulmonary arteries

2012 ◽  
Vol 705 ◽  
pp. 280-305 ◽  
Author(s):  
Mette S. Olufsen ◽  
N. A. Hill ◽  
Gareth D. A. Vaughan ◽  
Christopher Sainsbury ◽  
Martin Johnson
Keyword(s):  
Blood Flow ◽  
Theoretical Calculations ◽  
Pulmonary Arteries ◽  
Cross Sectional ◽  
Small Arteries ◽  
Large Arteries ◽  
Vascular Bed ◽  
Vascular Beds ◽  
The Impact ◽  
Averaged Model

AbstractThe effects of vascular rarefaction (the loss of small arteries) on the circulation of blood are studied using a multiscale mathematical model that can predict blood flow and pressure in the systemic and pulmonary arteries. We augmented a model originally developed for the systemic arteries by Olufsen and coworkers and Ottesen et al. (2004) to (a) predict flow and pressure in the pulmonary arteries, and (b) predict pressure propagation along the small arteries in the vascular beds. The systemic and pulmonary arteries are modelled as separate bifurcating trees of compliant and tapering vessels. Each tree is divided into two parts representing the ‘large’ and ‘small’ arteries. Blood flow and pressure in the large arteries are predicted using a nonlinear cross-sectional-area-averaged model for a Newtonian fluid in an elastic tube with inflow obtained from magnetic resonance measurements. Each terminal vessel within the network of the large arteries is coupled to a vascular bed of small ‘resistance’ arteries, which are modelled as asymmetric structured trees with specified area and asymmetry ratios between the parent and daughter arteries. For the systemic circulation, each structured tree represents a specific vascular bed corresponding to major organs and limbs. For the pulmonary circulation, there are four vascular beds supplied by the interlobar arteries. This paper presents the first theoretical calculations of the propagation of the pressure and flow waves along systemic and pulmonary large and small arteries. Results for all networks are in agreement with published observations. Two studies were done with this model. First, we showed how rarefaction can be modelled by pruning the tree of arteries in the microvascular system. This was done by modulating parameters used for designing the structured trees. Results showed that rarefaction leads to increased mean and decreased pulse pressure in the large arteries. Second, we investigated the impact of decreasing vessel compliance in both large and small arteries. Results showed that the effects of decreased compliance in the large arteries far outweigh the effects observed when decreasing the compliance of the small arteries. We further showed that a decrease of compliance in the large arteries results in pressure increases consistent with observations of isolated systolic hypertension, as occurs in ageing.

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