scholarly journals Effects of phase difference between instability modes on boundary-layer transition

2021 ◽  
Vol 927 ◽  
Author(s):  
Minwoo Kim ◽  
Seungtae Kim ◽  
Jiseop Lim ◽  
Ray-Sing Lin ◽  
Solkeun Jee ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Phase Difference ◽  
Fundamental Mode ◽  
Initial Phase ◽  
Subharmonic Resonance ◽  
Boundary Layer Transition ◽  
Modal Interaction ◽  
Initial Phase Difference ◽  
Nonlinear Stage ◽  
Instability Modes

Phase effect on the modal interaction of flow instabilities is investigated for laminar-to-turbulent transition in a flat-plate boundary-layer flow. Primary and secondary three-dimensional (3-D) oblique waves at various initial phase differences between these two instability modes. Three numerical methods are used for a systematic approach for the entire transition process, i.e. before the onset of transition well into fully turbulent flow. Floquet analysis predicts the subharmonic resonance where a subharmonic mode locally resonates for a given basic flow composed of the steady laminar flow and the fundamental mode. Because Floquet analysis is limited to the resonating subharmonic mode, nonlinear parabolised stability equation analysis (PSE) is conducted with various phase shifts of the subharmonic mode with respect to the given fundamental mode. The application of PSE offers insights on the modal interaction affected by the phase difference up to the weakly nonlinear stage of transition. Large-eddy simulation (LES) is conducted for a complete transition to turbulent boundary layer because PSE becomes prohibitively expensive in the late nonlinear stage of transition. The modulation of the subharmonic resonance with the initial phase difference leads to a significant delay in the transition location up to $\Delta Re_{x, tr} \simeq 4\times 10^5$ as predicted by the current LES. Effects of the initial phase difference on the spatial evolution of the modal shape of the subharmonic mode are further investigated. The mechanism of the phase evolution is discussed, based on current numerical results and relevant literature data.

Experiments on subharmonic resonance in a shear layer

1995 ◽  
Vol 304 ◽  
pp. 343-372 ◽  
Author(s):  
Hyder S. Husain ◽  
Fazle Hussain
Keyword(s):  
Shear Layer ◽  
Phase Difference ◽  
Initial Phase ◽  
Subharmonic Resonance ◽  
Resonance Phenomenon ◽  
Hot Wire ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Theory ◽  
Initial Phase Difference ◽  
Laminar Shear

The subharmonic resonance phenomenon is studied using hot-wire measurements and flow visualization in an initially laminar shear layer forced with two-frequencies for various choices of the fundamental frequency f and its subharmonic f/2 with controlled initial phase difference ϕin between them. We explore the effects of the controlling parameters, namely: (i) forcing frequencies and their initial amplitudes, (ii) initial phase difference ϕin, and (iii) detuning (i.e. when the second forcing frequency is slightly different from f/2). While several of our experimental observations support predictions based on weakly nonlinear theory, others do not. We explain our data in terms of vortex dynamics concepts.

scholarly journals Influence of initial phase on subharmonic resonance in an incompressible boundary layer

2021 ◽  
Vol 33 (4) ◽  
pp. 044101
Author(s):  
Donghun Park ◽  
Jaeyoung Park ◽  
Minwoo Kim ◽  
Jiseop Lim ◽  
Seungtae Kim ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Initial Phase ◽  
Subharmonic Resonance ◽  
Incompressible Boundary Layer ◽  
Incompressible Boundary

SUPPRESSING OR INDUCING CHAOS BY WEAK RESONANT EXCITATIONS IN AN EXTERNALLY-FORCED FROUDE PENDULUM

2004 ◽  
Vol 14 (03) ◽  
pp. 1115-1120 ◽  
Author(s):  
HONGJUN CAO ◽  
XUEBIN CHI ◽  
GUANRONG CHEN
Keyword(s):  
Phase Difference ◽  
Initial Phase ◽  
Vital Role ◽  
Melnikov Function ◽  
Chaotic Motions ◽  
Numerical Investigations ◽  
Chaotic Vibrations ◽  
Initial Phase Difference ◽  
Froude Pendulum ◽  
Melnikov Function Method

Based on analytic and numerical investigations of chaotic vibrations and quasiperiodic rotations of the Froude pendulum, we present a sufficient condition for controlling chaos by means of a weak resonant excitation as the initial phase difference Ψ varies. It is shown via the Melnikov function method that the initial phase difference Ψ plays a vital role in suppressing or inducing chaotic motions or quasiperiodic rotations.

Coupled Bending-Torsional Vibration Analysis of Rotor System with Two Asymmetric Disks

2011 ◽  
Vol 130-134 ◽  
pp. 2335-2339
Author(s):  
Jun Hong Zhang ◽  
Zhen Peng He ◽  
Wen Peng Ma ◽  
Liang Ma ◽  
Gui Chang Zhang
Keyword(s):  
Phase Difference ◽  
Vibration Analysis ◽  
Initial Phase ◽  
Rotor System ◽  
Dynamic Equations ◽  
Force Model ◽  
Torsional Angle ◽  
Kutta Method ◽  
Internal Damping ◽  
Initial Phase Difference

The dynamic equations derived based on the actual rotor system with two asymmetric disks. In the analysis, the eccentric, rubbing fault characteristics and internal damping effects is considered, and all the analysis is established based on nonlinear oil film force model and coupled bending-torsional differential equations. The Rugge-Kutta method is used to solve numerical model, the torsional displacement response, torsion angle and Poincare map are obtained. The results show torsion amplitudes with initial phase difference π / 2 is larger than initial phase difference of π and 0. In order to eliminate the rigid rolling component the relative torsional angle must be considered.

scholarly journals Measurement of Microvibration by Using Dual-Cavity Fiber Fabry-Perot Interferometer for Structural Health Monitoring

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Dae-Hyun Kim ◽  
Jin-Hyuk Lee ◽  
Byung-Jun Ahn
Keyword(s):  
Phase Difference ◽  
Initial Phase ◽  
Structural Integrity ◽  
Fiber Optic ◽  
Fiber Optic Sensor ◽  
Experimental Result ◽  
Optic Sensor ◽  
Initial Phase Difference ◽  
Fabry Perot ◽  
Micro Vibration

Extensive researches have recently been performed to study structural integrity using structural vibration data measured by in-structure sensors. A fiber optic sensor is one of candidates for the in-structure sensors because it is low in cost, light in weight, small in size, resistant to EM interference, long in service life, and so forth. Especially, an interferometric fiber optic sensor is very useful to measure vibrations with high resolution and accuracy. In this paper, a dual-cavity fiber Fabry-Perot interferometer was proposed with a phase-compensating algorithm for measuring micro-vibration. The interferometer has structurally two arbitrary cavities; therefore the initial phase difference between two sinusoidal signals induced from the interferometer was also arbitrary. In order to do signal processing including an arc-tangent method, a random value of the initial phase difference is automatically adjusted to the exact 90 degrees in the phase-compensating algorithm part. For the verification of the performance of the interferometer, a simple vibration-test was performed to measure micro-vibration caused by piezoelectric transducer (PZT). As an experimental result, the interferometer attached on the PZT successfully measured the 50 Hz-vibration of which the absolute displacement oscillated between −424 nm and +424 nm.

TAMING CHAOS IN A DRIVEN JOSEPHSON JUNCTION

2001 ◽  
Vol 11 (07) ◽  
pp. 1897-1909 ◽  
Author(s):  
R. CHACÓN ◽  
F. PALMERO ◽  
F. BALIBREA
Keyword(s):  
Josephson Junction ◽  
Phase Difference ◽  
Initial Phase ◽  
Chaotic Dynamics ◽  
Numerical Results ◽  
Initial Phase Difference ◽  
Theoretical Predictions ◽  
Melnikov Analysis ◽  
Analytical Expressions ◽  
Good Agreement

We present analytical and numerical results concerning the inhibition of chaos in a single driven Josephson junction by means of an additional weak resonant perturbation. From Melnikov analysis, we theoretically find parameter-space regions, associated with the chaos-suppressing perturbation, where chaotic states can be suppressed. In particular, we test analytical expressions for the intervals of initial phase difference between the two excitations for which chaotic dynamics can be eliminated. All the theoretical predictions are in overall good agreement with numerical results obtained by simulation.

Sign in / Sign up

Export Citation Format

Share Document