scholarly journals Мальформации как нарушение фрактальной структуры кровеносной системы организма

2020 ◽  
Vol 90 (9) ◽  
pp. 1506
Author(s):  
В. Антонов ◽  
П. Ефремов
Keyword(s):  
Heat Transfer ◽  
Blood Flow ◽  
Life Support ◽  
Vascular System ◽  
Circulatory System ◽  
Flow Simulation ◽  
Simulation Software ◽  
Heat Fluxes ◽  
The Body ◽  
Model Base

The article contains a description of mathematical models, the bases of which is the representation of the body circulatory system as a multifractal object. As examples, we consider the solution of two problems. The first issue is related to the normal state of the body’s life support system, namely, heat transfer in human skin. The model base is the equations of hydrodynamics and heat transfer. Quantitative results of calculating heat fluxes in three layers of the dermis are presented. The second issue deals with a violation of fractality due to the presence of arteriovenous malformation in the brain vascular system. The SolidWorks 2017 Flow Simulation software product serves as the basis for the implementation of a blood flow model in the presence of malformation. As a result of the simulation, data on the velocities and blood flow in the vessels were obtained for various cases of malformations.

A NUMERICAL STUDY ON THE HEMODYNAMIC AND SHEAR STRESS OF DOUBLE ANEURYSM THROUGH S-SHAPED VESSEL

2015 ◽  
Vol 27 (04) ◽  
pp. 1550033 ◽  
Author(s):  
Mahdi Halabian ◽  
Alireza Karimi ◽  
Borhan Beigzadeh ◽  
Mahdi Navidbakhsh
Keyword(s):  
Blood Flow ◽  
Mechanical Behavior ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
The Body ◽  
Sweep Angle ◽  
Abdominal Aortic ◽  
Hemodynamic Characteristics ◽  
Refined Meshes

Abdominal aortic aneurysm (AAA) is a degenerative disease defined as the abnormal ballooning of the abdominal aorta (AA) wall which is usually caused by atherosclerosis. The aneurysm grows larger and eventually ruptures if it is not diagnosed and treated. Aneurysms occur mostly in the aorta, the main artery of the chest and abdomen. The aorta carries blood flow from the heart to all parts of the body, including the vital organs, the legs, and feet. The objective of the present study is to investigate the combined effects of aneurysm and curvature on flow characteristics in S-shaped bends with sweep angle of 90° at Reynolds number of 900. The fluid mechanics of blood flow in a curved artery with abnormal aortic is studied through a mathematical analysis and employing Cosmos flow simulation. Blood is modeled as an incompressible non-Newtonian fluid and the flow is assumed to be steady and laminar. Hemodynamic characteristics are analyzed. Grid independence is tested on three successively refined meshes. It is observed that the abrupt expansion induced by AAA results in an immensely disturbed regime. The results may have implications not only for understanding the mechanical behavior of the blood flow inside an aneurysm artery but also for investigating the mechanical behavior of the blood flow in different arterial diseases, such as atherosclerosis.

Computational Study on the Effects of Peripheral Vessel Network on Blood Flow in the Arterial Circle of Willis

2007 ◽  
Author(s):  
Shigefumi Tokuda ◽  
Takeshi Unemura ◽  
Marie Oshima
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Vascular System ◽  
Computational Study ◽  
Circulatory System ◽  
Biological Data ◽  
Patient Specific ◽  
Peripheral Vessel

Cerebrovascular disorder such as subarachnoid hemorrhage (SAH) is 3rd position of the cause of death in Japan [1]. Its initiation and growth are reported to depend on hemodynamic factors, particularly on wall shear stress or blood pressure induced by blood flow. In order to investigate the information on the hemodynamic quantities in the cerebral vascular system, the authors have been developing a computational tool using patient-specific modeling and numerical simulation [2]. In order to achieve an in vivo simulation of living organisms, it is important to apply appropriate physiological conditions such as physical properties, models, and boundary conditions. Generally, the numerical simulation using a patient-specific model is conducted for a localized region near the research target. Although the analysis region is only a part of the circulatory system, the simulation has to include the effects from the entire circulatory system. Many studies have carried out to derive the boundary conditions to model in vivo environment [3–5]. However, it is not easy to obtain the biological data of cerebral arteries due to head capsule.

Numerical Analysis of the Multiple-Horseshoe-Vortex Effects on the Endwall Heat Transfer in the Leading-Edge Region of a Symmetric Bluff Body

2010 ◽  
Author(s):  
A. M. Levchenya ◽  
E. M. Smirnov
Keyword(s):  
Heat Transfer ◽  
Bluff Body ◽  
Stokes Equations ◽  
Correction Term ◽  
Low Frequency ◽  
Flow Simulation ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
The Body ◽  
Present Contribution

The present contribution covers results of a CFD analysis of the 3D flow and endwall heat transfer for a generic junction configuration with a wall-mounted symmetric bluff body experimentally investigated by Praisner and Smith [1, 2]. The computations based on the Reynolds-averaged Navier-Stokes equations (RANS) were performed using two codes of second order accuracy: the in-house code SINF and the commercial package ANSYS-CFX 12.0. For the turbulence closure problem, the Menter SST turbulence model with and without the streamline-curvature correction term was used. The grid sensitivity of solution was studied using a set of grids, the finest of which was of about five million cells. In accordance with the experiments, the computations with both the codes predict development of multiple horseshoe vortices and several bands of high values of the Stanton (St) number upstream of the body leading edge. The spatial relationships between the vorticity in individual planes and the associated endwall Stanton number are generally same in the measurements and in the computations. Some quantitative distinctions between the predictions and experimental data are attributed to the smoothing effect of the low-frequency unsteadiness of the horseshoe vortex system developing in the real flow. Simulation of this effect is outside of RANS-based formulations.

Three Dimensional Simulation of Blood Flow in the Small Arteries of a Truncated Vascular System With Three Levels of Bifurcation

2014 ◽  
Author(s):  
Kamil Kahveci ◽  
Bryan R. Becker
Keyword(s):  
Boundary Condition ◽  
Blood Flow ◽  
Blood Vessel ◽  
Velocity Profile ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Vascular System ◽  
Three Dimensional ◽  
Simulation Software ◽  
Small Arteries

Three dimensional blood flow in a truncated vascular system is investigated numerically using a commercially available finite element analysis and simulation software. The vascular system considered in this study has three levels of symmetric bifurcation. Geometric parameters for daughter vessels, such as their diameters and their angles of bifurcation, are specified according to Murray’s law based on the principle of minimum work. The ratio of blood vessel length to diameter is based upon experimental data found in the literature. An experimentally obtained velocity profile, available in the literature, is used as the inlet boundary condition. An outflow boundary model, consisting of a contraction tube to represent the pressure drop of the small arteries, arterioles, and capillaries that would follow the truncated vascular system, is used to specify the boundary condition at the eight outlets. The results show that although the blood flow velocity experiences a sudden decrease after the bifurcation points due to the higher total cross-sectional area of the daughter vessels as compared to the parent vessel, this decrease in velocity is partially recovered due to the tapering of the blood vessels as they approach the next bifurcation point. The results also show that the secondary flow which is typical after the bifurcation of large arteries does not develop after the bifurcation of small arteries due to the presence of laminar blood flow with very low Reynolds number in the small arteries. The numerical model yields pressure distributions and pressure drops along the vascular system that agree quite well with the physiological data found in the literature. Finally, the results show that, immediately following a bifurcation, the blood flow velocity profile is not symmetrical about the longitudinal axes of blood vessel. However, symmetry is recovered as the blood flow proceeds down the vessel.

scholarly journals The Role of the Endothelin System in the Vascular Dysregulation Involved in Retinitis Pigmentosa

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Francesco Saverio Sorrentino ◽  
Claudio Bonifazzi ◽  
Paolo Perri
Keyword(s):  
Blood Flow ◽  
Retinitis Pigmentosa ◽  
Vascular System ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Ocular Blood Flow ◽  
The Body ◽  
Vascular Dysregulation ◽  
Endothelin System

Retinitis pigmentosa is a clinical and genetic group of inherited retinal disorders characterized by alterations of photoreceptors and retinal pigment epithelium leading to a progressive concentric visual field restriction, which may bring about severe central vision impairment. Haemodynamic studies in patients with retinitis pigmentosa have demonstrated ocular blood flow abnormalities both in retina-choroidal and in retroocular vascular system. Moreover, several investigations have studied the augmentation of endothelin-1 plasma levels systemically in the body and locally in the eye. This might account for vasoconstriction and ischemia, typical in vascular dysregulation syndrome, which can be considered an important factor of reduction of the ocular blood flow in subjects affected by retinitis pigmentosa.

scholarly journals Investigation of changes in the skin blood microcirculation when performing the hatha yoga breathing technique

2022 ◽  
Vol 20 (4) ◽  
pp. 33-44
Author(s):  
A. V. Frolov ◽  
Yu. I. Loktionova ◽  
E. V. Zharkikh ◽  
V. V. Sidorov ◽  
A. I. Krupatkin ◽  
...  
Keyword(s):  
Blood Flow ◽  
Laser Doppler Flowmetry ◽  
Circulatory System ◽  
Low Frequency ◽  
Brain Perfusion ◽  
The Body ◽  
Laser Doppler ◽  
Regulatory Mechanisms ◽  
Doppler Flowmetry ◽  
Breathing Exercises

Introduction. Yoga breathing exercises improve the ability to significantly reduce the respiratory rate. A decrease of the minute respiration volume results in compensatory reactions of the microcirculatory bed caused by changes in the gas composition. The reaction of the regulatory mechanisms of the microvascular bed can be evaluated by the optical non-invasive laser Doppler flowmetry method. The aim of the study was to assess the tissue microcirculation parameter changes in people performing yoga breathing exercises. Materials and methods. 25 volunteers performed yoga breathing exercises at a frequency of 3 times per minute, 2 times per minute, 1.5 times per minute, 1 time per minute for 5 minutes, and free breathing for 6 minutes before and after breathing exercises. Parameters aimed to defin the reaction of skin microcirculation in different body areas were simultaneously recorded in six sites by laser Doppler flowmetry using a distributed system of wearable analyzers. The parameters of tissue microcirculation recorded by the method of laser Doppler flowmetry were: the index of microcirculation (Im), nutritive blood flow (Imn), the amplitude of myogenic (Am), neurogenic (An), endothelial (Ae), respiratory (Ar) and cardiac (Ac) regulation circuits. Results. Yoga breathing exercises led to increase of microcirculation index at all breathing frequencies. Breathing at a frequency of 1.5 and 1/minute leads to a significant increase in nutritional blood flow. Low-frequency breathing exercises lead to an increase in blood pressure at the lowest breathing rates – 1.5/minute and 1/minute. The most significant changes were achieved at the lowest respiration rates (1 and 1.5/minute), that could be associated with hypoxic-hypercapnic mechanisms. Conclusion. The absence of significant changes in microcirculation parameters after low-frequency respiration during measurements in the supraorbital arteries in both groups characterizes the work of homeostatic mechanisms for maintaining brain perfusion in stressful situations for the body (low-frequency types of respiration, hypercapnia and hypoxia). When measured in the extremities, a change in the effect of the circulatory system regulatory mechanisms was observed; along with an increase in skin perfusion and the nutritional component, it can characterize the compensatory reaction of the microcirculation to respiration change.

scholarly journals Contractile pericytes determine the direction of blood flow at capillary junctions

2020 ◽  
Vol 117 (43) ◽  
pp. 27022-27033
Author(s):  
Albert L. Gonzales ◽  
Nicholas R. Klug ◽  
Arash Moshkforoush ◽  
Jane C. Lee ◽  
Frank K. Lee ◽  
...  
Keyword(s):  
Blood Flow ◽  
Circulatory System ◽  
The Body ◽  
Capillary Network ◽  
Transitional Region ◽  
Capillary Networks ◽  
Efficiency And Effectiveness ◽  
The Central Nervous System ◽  
Essential Function ◽  
The Brain

The essential function of the circulatory system is to continuously and efficiently supply the O2 and nutrients necessary to meet the metabolic demands of every cell in the body, a function in which vast capillary networks play a key role. Capillary networks serve an additional important function in the central nervous system: acting as a sensory network, they detect neuronal activity in the form of elevated extracellular K+ and initiate a retrograde, propagating, hyperpolarizing signal that dilates upstream arterioles to rapidly increase local blood flow. Yet, little is known about how blood entering this network is distributed on a branch-to-branch basis to reach specific neurons in need. Here, we demonstrate that capillary-enwrapping projections of junctional, contractile pericytes within a postarteriole transitional region differentially constrict to structurally and dynamically determine the morphology of capillary junctions and thereby regulate branch-specific blood flow. We further found that these contractile pericytes are capable of receiving propagating K+-induced hyperpolarizing signals propagating through the capillary network and dynamically channeling red blood cells toward the initiating signal. By controlling blood flow at junctions, contractile pericytes within a functionally distinct postarteriole transitional region maintain the efficiency and effectiveness of the capillary network, enabling optimal perfusion of the brain.

The Circulatory Physiology of Helix Pomatia

1973 ◽  
Vol 59 (2) ◽  
pp. 291-303
Author(s):  
BARBARA A. SOMMERVILLE
Keyword(s):  
Blood Flow ◽  
Helix Pomatia ◽  
Circulatory System ◽  
Mantle Cavity ◽  
Heart Beat ◽  
The Body ◽  
Pericardial Cavity ◽  
Circulatory Physiology ◽  
Pressure Changes ◽  
Characteristic Pressure

1. The pressure changes in the mantle cavity and various parts of the circulatory system of Helix pomatia have been measured. 2. There are characteristic pressure changes associated with the breathing movements, the pattern depending upon the point at which the measurement was made and, in the case of the heart, the position of the body at the time of recording. These pressure changes fail mainly within the range 2-8 cm H2O. 3. The pressure changes associated with contraction of the heart chambers fall within the range 1-2 cm H2O in pulmonary vein and auricle, 10-32 cm H2O in the ventricle, 1-3 cm H2O in the aorta and 1-8 cm H2O in the pericardial cavity. 4. An increased frequency and amplitude of heart beat was associated with an increased rate of blood flow.

scholarly journals Thermal Analysis of Heat Transfer from Catheters and Implantable Devices to the Blood Flow

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 230
Author(s):  
Hossein Zangooei ◽  
Seyed Ali Mirbozorgi ◽  
Seyedabdollah Mirbozorgi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Blood Flow ◽  
Temperature Rise ◽  
Implantable Devices ◽  
The Body ◽  
Transfer Model ◽  
Governing Equations ◽  
Blood Flow Velocities ◽  
Flow Velocities

Implantable devices, ultrasound imaging catheters, and ablation catheters (such as renal denervation catheters) are biomedical instruments that generate heat in the body. The generated heat can be harmful if the body temperature exceeds the limit of almost 315 K. This paper presents a heat-transfer model and analysis, to evaluate the temperature rise in human blood due to the power loss of medical catheters and implantable devices. The dynamic of the heat transfer is modeled for the blood vessel, at different blood flow velocities. The physics and governing equations of the heat transfer from the implanted energy source to the blood and temperature rise are expressed by developing a Non-Newtonian Carreau–Yasuda fluid model. We used a Finite Element method to solve the governing equations of the established model, considering the boundary conditions and average blood flow velocities of 0–1.4 m/s for the flow of the blood passing over the implanted power source. The results revealed a maximum allowable heat flux of 7500 and 15,000 W/m2 for the blood flow velocities of 0 and 1.4 m/s, respectively. The rise of temperature around the implant or tip of the catheter is slower and disappeared gradually with the blood flow, which allows a higher level of heat flux to be generated. The results of this analysis are concluded in the equation/correlation T=310+H3000(1+e−7V), to estimate and predict the temperature changes as a function of heat flux, H, and the blood flow velocity, V, at the implant/catheter location.

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