scholarly journals Computational Modeling of Blood Hydrodynamics and Blockage Formation Phenomena in the Human Cardiovascular System

2010 ◽  
Vol 4 (2) ◽  
Author(s):  
Adrian Tentner ◽  
Georgy Guria ◽  
Andrey Ioilev ◽  
Simon Lo ◽  
Andros Onoufriou ◽  
...  
Keyword(s):  
Blood Flow ◽  
Porous Media ◽  
Cardiovascular System ◽  
Circulatory System ◽  
System Model ◽  
Porous Media Flow ◽  
Cfd Model ◽  
Human Cardiovascular System ◽  
Organ Models ◽  
The Impact

An international collaborative effort to develop a computational fluid dynamics (CFD) model of the human cardiovascular system (HCVS) has been initiated in 2008. The HCVS model is designed to describe (a) the blood flow hydrodynamics and associated heat transport phenomena, (b) the blood flow interactions with the essential organs, and (c) the vessel blockage formation associated with atherosclerosis and thrombosis. The CFD-HCVS model is being developed as a new specialized software module using as a foundation the CFD code, STAR-CD, that is developed and distributed by CD-adapco, Ltd., a member of the project team. The CFD-HCVS module includes the following components and capabilities. (1) A simplified 3D coarse mesh CFD model of the HCVS, which allows the simulation of hemodynamic transient phenomena. The circulatory system model is closed with porous-media flow components having a hydraulic resistance equivalent to the lumped flow resistance of the smaller vessels, including microcirculation. Both hydrodynamic and thermodynamic phenomena are described, allowing the study of blood flow transients in the presence of temperature changes. (2) Simplified zero-dimensional models of the essential organs (e.g., heart, kidneys, brain, liver, etc.) describing the time-dependent consumption or production of various blood components of interest. The organ models exchange information with the CFD system model through interfaces designed to allow their replacement, in the future, with more complex 3D organ models. (3) Selected sections of the circulatory system can be replaced by realistic 3 fine mesh vessel models allowing the detailed study of the 3D blood flow field and the vascular geometry changes due to blockage formation. (4) Models of local blockage formation due to atherosclerosis and thrombosis. Three HCVS models of increasing complexity have been designed. These models contain 27 vessels, 113 vessels, and 395 vessels. The initial CFD-HCVS model development is based on the medium HCVS model with 113 vessels. A closed circuit CFD model describing the major vessels and containing 0D models of the heart and kidneys has been developed. The CFD-HCVS model includes porous-media models describing the blood flow in the smaller vessels and capillaries. Initial simulations show that the calculated blood flow rates in the vessels modeled are in reasonably good agreement with the corresponding physiological values. A simplified model of thrombosis has also been developed. Current development efforts are focused on the addition of new vessels and 0D organ models and the development of atherosclerosis models. The HCVS model provides a flexible and expandable modeling framework that will allow the researchers from universities, research hospitals and the medical industry to study the impact of a wide range of phenomena associated with diseases of the circulatory system and will help them develop new diagnostics and treatments.

scholarly journals The Impact of Soil Hydrothermal Properties on Geothermal Power Generation (GPG): Modeling and Analysis

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 448
Author(s):  
Zhengguang Liu ◽  
Gaoyang Hou ◽  
Ying Song ◽  
Hessam Taherian ◽  
Shuaiwei Qi
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Porous Media ◽  
Power Plant ◽  
Geothermal Energy ◽  
Collection Efficiency ◽  
Porous Media Flow ◽  
Geothermal Power Plant ◽  
Geothermal Power ◽  
The Impact

Geothermal power plants have become the main application that utilizes geothermal energy. The utilization of deep geothermal energy adheres great importance to the soil condition. One of the biggest challenges faced by geothermal power plant designers is to reduce the risk of soil exploration. To solve this problem, forecasting by modeling has proven to be an important tool to address the problem. In this research, a geo-model was established by modeling three geological layers with different hydraulic and thermal properties to solve the above dilemma. The layers, elevation, and fault zones were simulated using interpolation functions from an artificial dataset. The coupled porous media flow and heat transfer problem using Darcy’s law, as well as heat transfer in porous media interfaces, were studied. The evolution of the flow field, hydrothermal performance, and temperature gradient were also analyzed for a period of 10 years. The results showed the recoverable thermal energy area gradually moved downwards during the 10-year simulation time. When the distance between the recharge well and the production well exceeded 200 m, the collection efficiency was significantly decreased. After 5 years of extraction, the power generation efficiency of the heat source will be less than 9.75%. These results effectively avoided the exploration cost of geothermal power plant site selection, which is significant for the efficiency improvement of geothermal energy.

Kinematical measurement of hydraulic tortuosity of fluid flow in porous media

2015 ◽  
Vol 26 (02) ◽  
pp. 1550017 ◽  
Author(s):  
Y. Jin ◽  
J. B. Dong ◽  
X. Li ◽  
Y. Wu
Keyword(s):  
Porous Media ◽  
Flow Direction ◽  
Estimation Method ◽  
Mean Value ◽  
Calculation Model ◽  
Flow In Porous Media ◽  
Porous Media Flow ◽  
Average Value ◽  
The Mean ◽  
The Impact

It is hard to experimentally or analytically derive the hydraulic tortuosity (τ) of porous media flow because of their complex microstructures. In this work, we propose a kinematical measurement method for τ by introducing the concept of local tortuosity, which is defined as the ratio of fluid particle velocity to its component along the macro flow. And then, the calculation model of τ is analytically deduced in terms of that τ is the mean value of the local tortuosity. To avoid the impact from the singularity of local tortuosity, the velocity is normalized, and τ is then approximated by the ratio of the mean normalized velocity to the average value of its component along the macro-flow direction. The new estimation method is verified by flow through different types of porous media via the lattice Boltzmann method, and the relationships between permeabilities and tortuosities obtained by different methods are examined. The numerical results show that tortuosity by the novel approach is in good agreement with the existing theory, and the kinematic definition of hydraulic tortuosity is also proven.

Effects of peptide YY on the human cardiovascular system: reversal of responses to vasoactive intestinal peptide

1992 ◽  
Vol 263 (4) ◽  
pp. E740-E747 ◽  
Author(s):  
R. J. Playford ◽  
M. A. Benito-Orfila ◽  
P. Nihoyannopoulos ◽  
K. A. Nandha ◽  
J. Cockcroft ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Cardiovascular System ◽  
Vasoactive Intestinal Peptide ◽  
Brachial Artery ◽  
Peptide Yy ◽  
Intestinal Secretion ◽  
Venous Occlusion ◽  
Human Cardiovascular System

Peptide YY (PYY) reverses the increased intestinal secretion stimulated by vasoactive intestinal peptide (VIP) in humans. VIP also dilates blood vessels, so we investigated the effect of PYY on the cardiovascular system. Six volunteers received PYY, 0.4 and 1.2 pmol.kg-1 x min-1 i.v. for 2 h, reproducing plasma levels seen postprandially and during a diarrheal illness, respectively. Cardiac function was assessed by echocardiography. PYY infused at 0.4 pmol.kg-1 x min-1 had no effect on cardiovascular parameters. PYY infused at 1.2 pmol.kg-1 x min-1 caused a fall in both stroke volume from 128 +/- 8 to 110 +/- 8 ml/beat (mean +/- 95 confidence interval, P < 0.01) and cardiac output from 7.2 +/- 0.4 to 6.1 +/- 0.4 l/min (P < 0.01). Effects of infusion of PYY into the brachial artery at doses of 0-16 pmol/min were assessed using venous occlusion plethysmography in six subjects. PYY infusion caused a dose-dependent fall in forearm blood flow. Six subjects received VIP, 5 pmol.kg-1 x min-1 i.v., causing a rise in heart rate from 55 +/- 3 to 70 +/- 3 beats/min and increased cardiac output from 7.3 +/- 1.1 to 13.1 +/- 1.1 l/min. The addition of PYY, 0.4 pmol.kg-1 x min-1 i.v., did not affect the heart rate significantly but decreased the cardiac output to 10.4 +/- 1.1 l/min (P < 0.01). Infusions of PYY into the brachial artery at 5 pmol/min decreased local vasodilation induced by VIP infused at 2 pmol/min at the same site by 40% (P < 0.01), even though this dose of PYY had no significant effect on local blood flow when given alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Agent-based modeling and simulation of blood vessels in the cardiovascular system

SIMULATION ◽  
2017 ◽  
Vol 95 (4) ◽  
pp. 297-312 ◽  
Author(s):  
Şebnem Bora ◽  
Vedat Evren ◽  
Sevcan Emek ◽  
Ibrahim Çakırlar
Keyword(s):  
Blood Flow ◽  
Blood Vessel ◽  
Cardiovascular System ◽  
Adaptive Behavior ◽  
Physical Parameters ◽  
Adaptive Agents ◽  
Agent Based ◽  
Proposed Model ◽  
Human Cardiovascular System

The purpose of this study is to develop a model to simulate the behavior of the human cardiovascular system for use in medical education. The proposed model ensures that the output of the system is accurately represented in both equilibrium conditions and imbalance conditions including in the presence of adaptive agents. In this study, field experts develop an agent-based blood vessel model, i.e., a submodel for the stated purpose. In the proposed blood vessel model, vessels are represented by agents whereas blood flow is represented by the interaction between agents. Adaptive behavior shown by vessels in terms of resistance to the blood flow is defined by the agents’ properties, which are used as the basis for calculating and graphically representing the physical parameters of blood flow, specifically blood pressure, blood flow velocity, and the resistance of the vessel. The adaptation of the vessel agents is supported by a case study, which demonstrates the adaptive behavior of the blood vessel agents through a negative feedback control mechanism. The blood vessel model proposed is flexible in nature such that it can be adapted to account for the behavior of the vessel sections in any vascular structure.

Finite element digital model for longitudinal dispersion of pollutant in porous media

1996 ◽  
Vol 33 (8) ◽  
pp. 79-87
Author(s):  
K. Srinivasa Rao
Keyword(s):  
Finite Element ◽  
Porous Media ◽  
Groundwater Quality ◽  
Groundwater Resources ◽  
Longitudinal Dispersion ◽  
Digital Model ◽  
Porous Media Flow ◽  
Rapid Urbanization ◽  
Groundwater Environment ◽  
The Impact

Surface and groundwater sources of water are being contaminated in the course of rapid urbanization and industrialization. The groundwater environment is being assaulted with an ever increasing number of soluble chemicals and human and industrial wastes which are let out on to the surface without treatment. Groundwater pollution often results in aquifers being damaged beyond repair. To prevent the pollution of groundwater resources, first we should identify the areas and mechanisms by which the pollutants enter the groundwater systems and the development of reliable predictions of the transport of the contaminant within the flow systems. These predictions will become the basis for minimizing the impact of existing or proposed industrial, agricultural and municipal activities which may affect the groundwater quality. It is necessary to study the different engineering aspects of groundwater quality control. The different aspects include 1) anticipating the probable future solute concentration distribution in the groundwater aquifer at any time since the beginning of the contamination and 2) deciding whether the contamination of a particular groundwater zone has crossed the limits of tolerance. From the above points, it is strongly felt that there is need to study the phenomenon of dispersion of pollutant in the porous media flow. The study necessitates the solution of a differential equation describing the solute transport process. In this study, a finite element digital model has been developed for longitudinal dispersion of the pollutant in the porous media. The results obtained from the above model are found to be in close agreement with those of the analytical solution given by earlier researchers.

A Computational Technique for Uncertainty Quantification and Robust Design in Cardiovascular Systems

2009 ◽  
Author(s):  
Sethuraman Sankaran ◽  
Jeffrey A. Feinstein ◽  
Alison L. Marsden
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Boundary Conditions ◽  
Cardiovascular System ◽  
A Priori ◽  
Optimization Technique ◽  
Random Variable ◽  
Computational Technique ◽  
Human Cardiovascular System ◽  
Fontan Surgery

Numerical simulations of blood flow in the human cardiovascular system are usually performed using custom Finite element methods and specialized boundary conditions. These simulations are performed to (a) understand the physics of blood flow in the human cardiovascular system and (b) a priori testing of proposed treatments/interventions whether surgical or endovascular. To perform these simulations, we require prior knowledge of parameters such as cardiovascular geometry, boundary conditions (inflow/outflow/pressure), etc. In the past, researchers have assumed exact values for these parameters. However, in reality, each of these parameters is uncertain. For example, inflow conditions into the model are dictated by the heart rate and cardiac output of the patient. Even during rest, there are variations in cardiac output and hence the corresponding blood inflow velocities need to be modeled as a random variable. Additionally, the cardiovascular geometry is built based on MRI-images. These are subject to uncertainties due to noise in the data and variability between users during model construction. We develop a computational toolbox that can account for uncertainties in such parameters in hemodynamic simulations. The uncertainties examined in this work include i) variation and accuracy of image-based model geometry ii) variability in inflow condition of the patient and iii) variability in the implementation of the final surgical design. The last source of uncertainty stems from the fact that optimally designed surgical parameters may not be exactly implemented in the operating room. We show numerical examples of (a) blood flow in stenotic vessels (b) effect of uncertainty in carotid sinus size on blood flow and (iii) develop a stochastic optimization technique to compute optimal parameters of an idealized Y-graft model for the Fontan surgery accounting for sources of uncertainties listed above.

Modeling of the Human Cardiovascular System: Analysis of the Blood Flow Rate

2019 ◽  
Author(s):  
André Jorge ◽  
Fabrício Junqueira ◽  
Diolino José Santos Filho ◽  
Paulo Miyagi
Keyword(s):  
Blood Flow ◽  
Cardiovascular System ◽  
Flow Rate ◽  
System Analysis ◽  
Blood Flow Rate ◽  
Human Cardiovascular System
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