Unsteady Flows Within a 2D Model of Multiple Lung Bifurcations

1999 ◽  
Author(s):  
A. Ramuzat ◽  
H. Richard ◽  
M. L. Riethmuller
Keyword(s):  
Unsteady Flows ◽  
Aerosol Deposition ◽  
Bronchial Tree ◽  
Pollution Effects ◽  
Medical Treatments ◽  
Pressure Fields ◽  
Successive Generations ◽  
Lung Bifurcations

Abstract In our environment, chronic pulmonary illness due to pollution effects or asthmatic problems are increasing. To identify the contribution of pollution effect on the alterations in breath patterns, a better understanding of the human pulmonary system is needed. As a result, fields to be investigated are mostly flows in the lungs at high breathing frequency and aerosol deposition in lung bifurcations under unsteady conditions. The respiration pattern has to be better understood and investigated, to have the possibility to get the most appropriate palliative treatment. Most of the medical treatments are based on aerosol deposition in the bronchial tree. The lung is a complex network of 23 successive generations of bifurcation (Weibel, 1963). The airways, from the trachea to the alveolar zone, divide by dichotomy and become shorter and narrower as they penetrate deeper into the lung. As a result, in vivo investigations of pulmonary flows are not possible, and in vitro experiments in models have to be performed. Flows in the bifurcating airways of the lung are modeled to determine velocities and pressure fields. A complete description of steady flow in a single 3D bifurcation has been previously performed by experimental and numerical modeling. As a result of this study, it has been shown that the first bifurcation influences the flow in the second and in the third bifurcation when the length of the second bifurcation is not sufficiently long. To extend the investigations to a system of three generations, an experimental study of steady and unsteady flows has been carried out on a 2D multiple bifurcations model.

Improvements to a dual-time-stepping method for computating unsteady flows

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1548-1550 ◽  
Author(s):  
S. DeRango ◽  
D. W. Zingg
Keyword(s):  
Unsteady Flows ◽  
Time Stepping ◽  
Dual Time Stepping

Numerical Optimization Algorithm for Unsteady Flows of Rotor based on Web Service

2019 ◽  
pp. -1--1
Author(s):  
Jilin Zhang ◽  
Xuechao Liu ◽  
Jian Wan ◽  
Yongjian Ren ◽  
Binglin Xu ◽  
...  
Keyword(s):  
Web Service ◽  
Optimization Algorithm ◽  
Numerical Optimization ◽  
Unsteady Flows

Aerodynamic Asymmetry Analysis of Unsteady Flows in Turbomachinery

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Kivanc Ekici ◽  
Robert E. Kielb ◽  
Kenneth C. Hall
Keyword(s):  
Harmonic Balance ◽  
Coupling Effect ◽  
Unsteady Flows ◽  
Unsteady Aerodynamic ◽  
Blade Row ◽  
Balance Technique ◽  
Turbomachinery Blades ◽  
Aerodynamic Asymmetry ◽  
Frequency Domain Approach ◽  
Harmonic Balance Technique

A nonlinear harmonic balance technique for the analysis of aerodynamic asymmetry of unsteady flows in turbomachinery is presented. The present method uses a mixed time-domain/frequency-domain approach that allows one to compute the unsteady aerodynamic response of turbomachinery blades to self-excited vibrations. Traditionally, researchers have investigated the unsteady response of a blade row with the assumption that all the blades in the row are identical. With this assumption the entire wheel can be modeled using complex periodic boundary conditions and a computational grid spanning a single blade passage. In this study, the steady/unsteady aerodynamic asymmetry is modeled using multiple passages. Specifically, the method has been applied to aerodynamically asymmetric flutter problems for a rotor with a symmetry group of 2. The effect of geometric asymmetries on the unsteady aerodynamic response of a blade row is illustrated. For the cases investigated in this paper, the change in the diagonal terms (blade on itself) dominated the change in stability. Very little mode coupling effect caused by the off-diagonal terms was found.

On nonlocal fractal laminar steady and unsteady flows

2021 ◽  
Vol 232 (4) ◽  
pp. 1413-1424
Author(s):  
Rami Ahmad El-Nabulsi
Keyword(s):  
Unsteady Flows ◽  
Steady And Unsteady Flows
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