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

Control of Cavity Flow Oscillations by High Frequency Forcing

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
M. A. Martinez ◽  
G. M. Di Cicca ◽  
M. Iovieno ◽  
M. Onorato
Keyword(s):  
Shear Layer ◽  
High Frequency ◽  
Cavity Flow ◽  
Mean Velocity ◽  
Time Resolved ◽  
Piv Measurements ◽  
Sustained Oscillations ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Cavity Flow Oscillations

Time resolved two-dimensional particle image velocimetry (2DPIV) experiments have been conducted to contribute to the understanding of the physics governing the suppression mechanism of cavity flow self-sustained oscillations by means of high frequency excitation of the cavity shear layer. High frequency excitation was introduced by the spanwise coherent vortex shedding in the wake of a cylindrical rod positioned just upstream the cavity entrance, at the edge of the incoming boundary layer. The effectiveness of this suppression was demonstrated for a cavity having the length-to-depth ratio equal to three, in incompressible flow. The spatial and time resolved PIV measurements of the whole flow field in the plane normal to the cavity floor, linear stability analysis of the measured shear layer mean velocity profiles, and preliminary PIV measurements in a plane parallel to the cavity allowed us to offer a better insight into the involved physical mechanisms in suppressing cavity self-sustained oscillations.

A Formula for Prediction of Frequency of Tonal Sound in Cavity Flows With Acoustic Resonance

2011 ◽  
Author(s):  
Hiroshi Yokoyama ◽  
Keitaro Terao ◽  
Tatsuya Suzuki ◽  
Akiyoshi Iida
Keyword(s):  
Sound Pressure ◽  
Cavity Length ◽  
Time Lag ◽  
Acoustic Resonance ◽  
Cavity Flow ◽  
Expansion Wave ◽  
Cavity Flows ◽  
Computational Results ◽  
Sustained Oscillations ◽  
New Formula

Self-sustained oscillations with tonal sound in flows over a cavity are investigated by experiments using a wind tunnel and direct numerical simulation of flow and acoustic fields. The effects of the length-to-depth ratio of the cavity and the ratio of the cavity length L to the momentum thickness of the incoming boundary layer on the mode of the oscillations are clarified. The simultaneous measurements of flow pattern and sound pressure are also performed. The results show that a time lag between the generation of an expansion wave due to the collision of a vortex with the downstream edge and the radiation of the expansion wave from the cavity becomes larger for the cavity flow with the acoustic resonance. The computational results explain why the delay becomes larger. Moreover, considering this delay, a new formula for the frequency of the tonal sound in cavity flows with the acoustic resonance is proposed. The frequencies predicted by this formula agree well with those measured.

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.

Experimental study of shear-layer/acoustics coupling in Mach 5 cavity flow

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 242-252
Author(s):  
O. H. Unalmis ◽  
N. T. Clemens ◽  
D. S. Dolling
Keyword(s):  
Experimental Study ◽  
Shear Layer ◽  
Cavity Flow

scholarly journals Large-eddy simulation of wall-bounded turbulent flow with high-order discrete unified gas-kinetic scheme

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Rui Zhang ◽  
Chengwen Zhong ◽  
Sha Liu ◽  
Congshan Zhuo
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
Parallel Implementation ◽  
Kinetic Scheme ◽  
Cavity Flow ◽  
Equilibrium Distribution Function ◽  
Third Order ◽  
Two Stage ◽  
Large Eddy ◽  
Unified Gas Kinetic Scheme

AbstractIn this paper, we introduce the discrete Maxwellian equilibrium distribution function for incompressible flow and force term into the two-stage third-order Discrete Unified Gas-Kinetic Scheme (DUGKS) for simulating low-speed turbulent flows. The Wall-Adapting Local Eddy-viscosity (WALE) and Vreman sub-grid models for Large-Eddy Simulations (LES) of turbulent flows are coupled within the present framework. Meanwhile, the implicit LES are also presented to verify the effect of LES models. A parallel implementation strategy for the present framework is developed, and three canonical wall-bounded turbulent flow cases are investigated, including the fully developed turbulent channel flow at a friction Reynolds number (Re) about 180, the turbulent plane Couette flow at a friction Re number about 93 and lid-driven cubical cavity flow at a Re number of 12000. The turbulence statistics, including mean velocity, the r.m.s. fluctuations velocity, Reynolds stress, etc. are computed by the present approach. Their predictions match precisely with each other, and they are both in reasonable agreement with the benchmark data of DNS. Especially, the predicted flow physics of three-dimensional lid-driven cavity flow are consistent with the description from abundant literature. The present numerical results verify that the present two-stage third-order DUGKS-based LES method is capable for simulating inhomogeneous wall-bounded turbulent flows and getting reliable results with relatively coarse grids.

Compressible subsonic cavity flow in a nozzle

2021 ◽  
Vol 62 (1) ◽  
pp. 011505
Author(s):  
Xiaohui Wang
Keyword(s):  
Cavity Flow
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