Improved Numerical Simulations of Self-Sustained Oscillations of a NACA0012 with Transition Modeling

2011 ◽  
Author(s):  
Simon Lapointe ◽  
Guy Dumas
Keyword(s):  
Numerical Simulations ◽  
Sustained Oscillations ◽  
Transition Modeling

Helmholtz-Like Resonator Self-Sustained Oscillations, Part 2: Detailed Flow Measurements and Numerical Simulations

AIAA Journal ◽  
2003 ◽  
Vol 41 (3) ◽  
pp. 416-423 ◽  
Author(s):  
S. Dequand ◽  
S. Hulshoff ◽  
H. van Kuijk ◽  
J. Willems ◽  
A. Hirschberg
Keyword(s):  
Numerical Simulations ◽  
Flow Measurements ◽  
Sustained Oscillations

Control of Vortical Flows Past Open Cavities

2013 ◽  
Vol 332 ◽  
pp. 21-26
Author(s):  
Marius Stoia-Djeska ◽  
Carmen Anca Safta ◽  
Adina Cotuna
Keyword(s):  
Aspect Ratio ◽  
Numerical Simulations ◽  
Compressible Flows ◽  
Leading Edge ◽  
Control Device ◽  
Spanwise Direction ◽  
Large Aspect Ratio ◽  
Pressure Oscillations ◽  
Sustained Oscillations ◽  
Open Cavities

Numerical simulations are used to verify the possibility to mitigate the undesired flow self-sustained oscillations of the compressible flows past open cavities. The simple control device proposed in this work consists in a large aspect ratio wing with an non-symmetric thin airfoil mounted in the spanwise direction of the cavity and located immediately upstream with respect the leading edge of the cavity . The results show that this control device is efficient and diminishes the pressure oscillations.

scholarly journals A TB Model with Infectivity in Latent Period and Imperfect Treatment

2012 ◽  
Vol 2012 ◽  
pp. 1-19 ◽  
Author(s):  
Juan Wang ◽  
Sha-Sha Gao ◽  
Xue-Zhi Li
Keyword(s):  
Asymptotic Stability ◽  
Numerical Simulations ◽  
Latent Period ◽  
Global Asymptotic Stability ◽  
Endemic Equilibrium ◽  
Epidemiological Model ◽  
Free State ◽  
Local Asymptotic Stability ◽  
Sustained Oscillations ◽  
Disease Free

An epidemiological model of TB with infectivity in latent period and imperfect treatment is introduced. As presented, sustained oscillations are not possible and the endemic proportions either approach the disease-free equilibrium or an endemic equilibrium. The expanded model that stratified the infectious individuals according to their time-since-infectionθis also carried out. The global asymptotic stability of the infection-free state is established as well as local asymptotic stability of the endemic equilibrium. At the end, numerical simulations are presented to illustrate the results.

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

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.

CHARACTERIZATION OF SPLASH-PLATE ATOMIZERS USING NUMERICAL SIMULATIONS

2007 ◽  
Vol 17 (4) ◽  
pp. 347-380 ◽  
Author(s):  
Mohammad P. Fard ◽  
Denise Levesque ◽  
Stuart Morrison ◽  
Nasser Ashgriz ◽  
J. Mostaghimi
Keyword(s):  
Numerical Simulations
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