Mechanisms of Self-Sustained Oscillations Induced by a Flow Over a Cavity

2008 ◽  
Vol 130 (5) ◽  
pp. 051001 ◽  
Author(s):  
Michel Massenzio ◽  
Alain Blaise ◽  
Claude Lesueur
Keyword(s):  
Sustained Oscillations ◽  
Flow Over A Cavity

Bifurcation in a Simple Model of the Cardiovascular System

2000 ◽  
Vol 39 (02) ◽  
pp. 118-121 ◽  
Author(s):  
S. Akselrod ◽  
S. Eyal
Keyword(s):  
Nonlinear Dynamics ◽  
Blood Pressure ◽  
Heart Rate ◽  
Fixed Point ◽  
Cardiovascular System ◽  
Modified Model ◽  
Mayer Waves ◽  
Sustained Oscillations ◽  
Human Cardiovascular System ◽  
Physiological Values

Abstract:A simple nonlinear beat-to-beat model of the human cardiovascular system has been studied. The model, introduced by DeBoer et al. was a simplified linearized version. We present a modified model which allows to investigate the nonlinear dynamics of the cardiovascular system. We found that an increase in the -sympathetic gain, via a Hopf bifurcation, leads to sustained oscillations both in heart rate and blood pressure variables at about 0.1 Hz (Mayer waves). Similar oscillations were observed when increasing the -sympathetic gain or decreasing the vagal gain. Further changes of the gains, even beyond reasonable physiological values, did not reveal another bifurcation. The dynamics observed were thus either fixed point or limit cycle. Introducing respiration into the model showed entrainment between the respiration frequency and the Mayer waves.

Impinging planar jets: hysteretic behaviour and origin of the self-sustained oscillations

2021 ◽  
Vol 913 ◽  
Author(s):  
Alessandro Bongarzone ◽  
Arnaud Bertsch ◽  
Philippe Renaud ◽  
François Gallaire
Keyword(s):  
The Self ◽  
Hysteretic Behaviour ◽  
Sustained Oscillations

Abstract

Aeroacoustic computation of cavity flow in self-sustained oscillations

2003 ◽  
Vol 17 (4) ◽  
pp. 590-598
Author(s):  
Sung-Ryong Koh ◽  
Yong Cho ◽  
Young J. Moon
Keyword(s):  
Cavity Flow ◽  
Sustained Oscillations

Simple conditions for the appearance of sustained oscillations in continuous crystallizers

1983 ◽  
Vol 38 (10) ◽  
pp. 1675-1681 ◽  
Author(s):  
G.R. Jerauld ◽  
Y. Vasatis ◽  
M.F. Doherty
Keyword(s):  
Sustained Oscillations

scholarly journals Activation of Cdc42 is necessary for sustained oscillations of Ca2+ and PIP2 stimulated by antigen in RBL mast cells

Biology Open ◽  
2014 ◽  
Vol 3 (8) ◽  
pp. 700-710 ◽  
Author(s):  
M. M. Wilkes ◽  
J. D. Wilson ◽  
B. Baird ◽  
D. Holowka
Keyword(s):  
Mast Cells ◽  
Sustained Oscillations

The mixing layer over a deep cavity at high-subsonic speed

2003 ◽  
Vol 475 ◽  
pp. 101-145 ◽  
Author(s):  
NICOLAS FORESTIER ◽  
LAURENT JACQUIN ◽  
PHILIPPE GEFFROY
Keyword(s):  
High Speed ◽  
Mixing Layer ◽  
Interaction Mechanism ◽  
Boundary Layer Separation ◽  
Mixing Layers ◽  
Deep Cavity ◽  
Collective Interaction ◽  
Flow Over A Cavity ◽  
Conditional Statistics ◽  
Forced Mixing

The flow over a cavity at a Mach number 0.8 is considered. The cavity is deep with an aspect ratio (length over depth) L/D = 0.42. This deep cavity flow exhibits several features that makes it different from shallower cavities. It is subjected to very regular self-sustained oscillations with a highly two-dimensional and periodic organization of the mixing layer over the cavity. This is revealed by means of a high-speed schlieren technique. Analysis of pressure signals shows that the first tone mode is the strongest, the others being close to harmonics. This departs from shallower cavity flows where the tones are usually predicted well by the standard Rossiter’s model. A two-component laser-Doppler velocimetry system is also used to characterize the phase-averaged properties of the flow. It is shown that the formation of coherent vortices in the region close to the boundary layer separation has some resemblance to the ‘collective interaction mechanism’ introduced by Ho & Huang (1982) to describe mixing layers subjected to strong sub-harmonic forcing. Otherwise, the conditional statistics show close similarities with those found in classical forced mixing layers except for the production of random perturbations, which reaches a maximum in the structure centres, not in the hyperbolic regions with which turbulence production is usually associated. An attempt is made to relate this difference to the elliptic instability that may be observed here thanks to the particularly well-organized nature of the flow.

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