scholarly journals A Novel Interpretation for Arterial Pulse Pressure Amplification in Health and Disease

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Manuel R. Alfonso ◽  
Ricardo L. Armentano ◽  
Leandro J. Cymberknop ◽  
Arthur R. Ghigo ◽  
Franco M. Pessana ◽  
...  
Keyword(s):  
Pulse Pressure ◽  
Stokes Equations ◽  
Kdv Equation ◽  
Navier Stokes ◽  
Pressure Waves ◽  
Arterial Tree ◽  
Navier Stokes Equations ◽  
Pathological Conditions ◽  
Pressure Amplification ◽  
Radial Artery Pressure

Arterial pressure waves have been described in one dimension using several approaches, such as lumped (Windkessel) or distributed (using Navier-Stokes equations) models. An alternative approach consists of modeling blood pressure waves using a Korteweg-de Vries (KdV) equation and representing pressure waves as combinations of solitons. This model captures many key features of wave propagation in the systemic network and, in particular, pulse pressure amplification (PPA), which is a mechanical biomarker of cardiovascular risk. The main objective of this work is to compare the propagation dynamics described by a KdV equation in a human-like arterial tree using acquired pressure waves. Furthermore, we analyzed the ability of our model to reproduce induced elastic changes in PPA due to different pathological conditions. To this end, numerical simulations were performed using acquired central pressure signals from different subject groups (young, adults, and hypertensive) as input and then comparing the output of the model with measured radial artery pressure waveforms. Pathological conditions were modeled as changes in arterial elasticity (E). Numerical results showed that the model was able to propagate acquired pressure waveforms and to reproduce PPA variations as a consequence of elastic changes. Calculated elasticity for each group was in accordance with the existing literature.

Structured tree outflow condition for blood flow in larger systemic arteries

1999 ◽  
Vol 276 (1) ◽  
pp. H257-H268 ◽  
Author(s):  
Mette S. Olufsen
Keyword(s):  
Boundary Condition ◽  
Blood Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Phase Lag ◽  
Tree Model ◽  
Arterial Tree ◽  
Windkessel Model ◽  
Navier Stokes Equations ◽  
Systemic Arteries

A central problem in modeling blood flow and pressure in the larger systemic arteries is determining a physiologically based boundary condition so that the arterial tree can be truncated after a few generations. We have used a structured tree attached to the terminal branches of the truncated arterial tree in which the root impedance is estimated using a semianalytical approach based on a linearization of the viscous axisymmetric Navier-Stokes equations. This provides a dynamic boundary condition that maintains the phase lag between blood flow and pressure as well as the high-frequency oscillations present in the impedance spectra. Furthermore, it accommodates the wave propagation effects for the entire systemic arterial tree. The result is a model that is physiologically adequate as well as computationally feasible. For validation, we have compared the structured tree model with a pure resistance and a windkessel model as well as with measured data.

Numerical Simulation of Overpressure about Muzzle Blast Flowfield

2012 ◽  
Vol 605-607 ◽  
pp. 2506-2509 ◽  
Author(s):  
Zhang Xia Guo ◽  
Yu Tian Pan ◽  
Kui Wu Li ◽  
Hai Yan Zhang
Keyword(s):  
Stokes Equations ◽  
Impulsive Noise ◽  
Critical Issue ◽  
Pressure Variation ◽  
Navier Stokes ◽  
Pressure Waves ◽  
Negative Effects ◽  
Navier Stokes Equations ◽  
Gun Barrel ◽  
Muzzle Blast

The high pressure waves created due to muzzle blast flowfield through the gun barrel during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems, so beyond the range of a flow field was simulated numerically. The calculation was based on the 2D axial symmetry Navier-Stokes equations and standard k-ε turbulence model. From numerical simulations, wave dynamic processes are simulated and discussed. The pressure variation of the blast flowfield is analyzed , The results of this study will be helpful in understanding muzzle blast wave and designing silencer .

Numerical Analysis of Sound Generation by a Two-Dimensional Cylinder in a Uniform Flow

2003 ◽  
Author(s):  
Ayaka Imamura ◽  
Nozomu Hatakeyama ◽  
Osamu Inoue
Keyword(s):  
Sound Pressure ◽  
Stokes Equations ◽  
Sound Field ◽  
Uniform Flow ◽  
Navier Stokes ◽  
Pressure Waves ◽  
Two Dimensional ◽  
Sound Generation ◽  
Navier Stokes Equations ◽  
Characteristic Features

The sound generated by a squarer cylinder in a uniform flow is investigated by direct numerical simulation of the two-dimensional compressible Navier–Stokes equations. The characteristic features of the generated sound are investigated and compared for different configurations and angles of attack. Results show that sound pressure waves are generated by vortex shedding from the cylinder into its wake. The sound field is dominated by lift dipole. The effect of the angle of attack on the sound generation and propagation is also analyzed.

TrenSen: A New Way to Study the Unsteady Behaviour of Air Inside Tunnels—Application to High Speed Railway Lines

2011 ◽  
Author(s):  
Manuel Rodri´guez Ferna´ndez ◽  
Evangelino Garrido Torres ◽  
Ricardo Ortega Garci´a
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Pressure Waves ◽  
High Speed Railway ◽  
Navier Stokes Equations ◽  
Traffic System ◽  
Railway Traffic ◽  
Fluid Dynamics Equations ◽  
Great Development

During the last decades, high speed railway traffic system has achieved a great development all over the world. Increasing speed in the train circulation implies the apparition of new aerodynamic phenomena that need to be studied. One of these problems has to do with the entrance and exit of high speed (HS) trains in tunnels. When this occurs, pressure waves propagate and reflect through the tunnel at sound speed, generating a non-stationary movement of the air which depends greatly on the speed of the train and the geometry between train and tunnel. A study has been carried on to determine the pressure and velocity fields of air inside the tunnel when the train passes through. As a result of this study, a new software, “TrenSen”, has been developed. This program solves numerically a particular case of the Navier-Stokes equations, a hyperbolic system of partial differential equations which describe the flow behaviour inside the tunnel. In the first section of the paper presented hereby a description of the algebra for the fluid dynamics equations is conducted. The second section will explain some features of the software, ending with some numerical results obtained from the program. To finish the paper, the software is validated by comparing the numeric results with available experimental data and with some other commercial software.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Sensitivity analysis for Navier-Stokes equations on unstructured meshes using complex variables

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 56-63
Author(s):  
W. Kyle Anderson ◽  
James C. Newman ◽  
David L. Whitfield ◽  
Eric J. Nielsen
Keyword(s):  
Sensitivity Analysis ◽  
Stokes Equations ◽  
Unstructured Meshes ◽  
Complex Variables ◽  
Navier Stokes ◽  
Navier Stokes Equations

Numerical solution of the reduced Navier-Stokes equations for internal incompressible flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1603-1614
Author(s):  
Martin Scholtysik ◽  
Bernhard Mueller ◽  
Torstein K. Fannelop
Keyword(s):  
Numerical Solution ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations
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