Fast waves, slow waves and cochlear excitation

2013 ◽  
Vol 133 (5) ◽  
pp. 3508-3508 ◽  
Author(s):  
Elizabeth S. Olson
Keyword(s):  
Slow Waves ◽  
Fast Waves

scholarly journals Excitation of fast waves by slow waves near the lower-hybrid frequency

1976 ◽  
Vol 19 (9) ◽  
pp. 1392 ◽  
Author(s):  
R. L. Berger ◽  
Liu Chen
Keyword(s):  
Slow Waves ◽  
Lower Hybrid ◽  
Hybrid Frequency ◽  
Fast Waves

Bending waves on inviscid columnar vortices

1986 ◽  
Vol 173 ◽  
pp. 595-624 ◽  
Author(s):  
S. Leibovich ◽  
S. N. Brown ◽  
Y. Patel
Keyword(s):  
Dispersion Relation ◽  
Vortex Core ◽  
Schrodinger Equation ◽  
Phase Speed ◽  
Velocity Profiles ◽  
Long Waves ◽  
Slow Waves ◽  
Bending Waves ◽  
Zero Group ◽  
Fast Waves

Bending waves, perturbation modes leading to deflections of the vortex centreline, are considered for an infinitely long straight vortex embedded in an irrotational flow of unlimited extent. We first establish the general form of the dispersion relation for long waves on columnar vortices with arbitrary distributions of axial and azimuthal vorticity by a singular perturbation analysis of the Howard-Gupta equation. The asymptotic results are shown to compare favourably with numerical solutions of the Howard-Gupta equation for wavelengths comparable to the vortex core radius and longer. Dispersion relations are then found numerically for specific models of vortex core structures observed experimentally; here no restrictions are placed on wavelength. The linear dispersion relation has an infinite number of branches, falling into two families; one with infinite phase speed at zero wavenumber (which we call ‘fast’ waves), the other with zero phase speed (‘slow’ waves). In the long-wave limit, slow waves have zero group velocity, while the fast waves may have finite non-zero group speeds that depend on the form of the velocity profiles on the axis of rotation. Weakly nonlinear waves are described under most circumstances by the nonlinear Schrödinger equation. Solitons are possible in certain ‘windows’ of wavenumbers of the carrier waves. An example has already been presented by Leibovich & Ma (1983), who compute solitons and soliton windows on a fast-wave branch for a vortex with a particular core structure. Experimental data of Maxworthy, Hopfinger & Redekopp (1985) reveal solitons which appear to be associated with the slow branch, and these are computed for velocity profiles fitting their data. The nonlinear Schrödinger equation is shown to fail for long waves, and to be replaced by a nonlinear integro-differential equation.

Direct-simulation-based study of turbulent flow over various waving boundaries

2010 ◽  
Vol 650 ◽  
pp. 131-180 ◽  
Author(s):  
DI YANG ◽  
LIAN SHEN
Keyword(s):  
Water Waves ◽  
Slow Waves ◽  
Turbulence Structure ◽  
Wave Steepness ◽  
Wave Age ◽  
Wave Phase ◽  
Stokes Waves ◽  
Wave Nonlinearity ◽  
Fast Waves ◽  
Surface Drift

We use direct numerical simulation of stress-driven turbulent Couette flows over waving surfaces to study turbulence in the vicinity of water waves. Mechanistic study is performed through systematic investigation of different wavy surface conditions including plane progressive Airy and Stokes waves with and without wind-induced surface drift, as well as stationary wavy walls and vertically waving walls for comparison. Two different wave steepness values ak = 0.1 and 0.25 are considered, where a is the wave amplitude and k is the wavenumber. For effects of wave age, defined as the ratio between the wave phase speed c and the turbulence friction velocity u*, we consider three values, namely c/u* = 2, 14 and 25, corresponding to slow, intermediate and fast waves, respectively. Detailed analysis of turbulence structure and statistics shows their dependence on the above-mentioned parameters. Our result agrees with previous measurement and simulation results and reveals many new features unreported in the literature. Over progressive waves, although no apparent flow separation is found in mean flow, considerable intermittent separations in instantaneous flow are detected in slow waves with large steepness. The near-surface coherent vortical structures are examined. We propose two conceptual vortex structure models: quasi-streamwise and reversed horseshoe vortices for slow waves and bent quasi-streamwise vortices for intermediate and fast waves. Detailed examination of Reynolds stress with quadrant analysis, turbulent kinetic energy (TKE) and TKE budget with a focus on production shows large variation with wave phase; analysis shows that the variation is highly dependent on wave age and wave nonlinearity. Comparison between Airy waves and Stokes waves indicates that although the nonlinearity of surface water waves is a high-order effect compared with the wave age and wave steepness, it still makes an appreciable difference to the turbulence structure. The effect of wave nonlinearity on surface pressure distribution causes substantial difference in the wave growth rate. Wind-induced surface drift can cause a phase shift in the downstream direction and a reduction in turbulence intensity; this effect is appreciable for slow waves but negligible for intermediate and fast waves. In addition to providing detailed information on the turbulence field in the vicinity of wave surfaces, the results obtained in this study suggest the importance of including wave dynamics in the study of wind–wave interaction.

Evaluation of Creep-Fatigue Damage Interaction in HK40 Alloy

1993 ◽  
Vol 115 (1) ◽  
pp. 41-46 ◽  
Author(s):  
S. Konosu ◽  
T. Koshimizu ◽  
T. Iijima ◽  
K. Maeda
Keyword(s):  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
Strain Range ◽  
Slow Waves ◽  
Design Criteria ◽  
Peak Strain ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fast Waves

In order to establish design criteria for materials which may sustain creep-fatigue damage, the creep rupture and creep-fatigue behavior of a high-carbon centrifugal cast steel was investigated at three different temperatures of 800, 900, and 1000°C, using HK-40 alloy which is a typical furnace tube material for fuel cell plant reformers and so on. The strain waveforms used for the creep-fatigue tests consisted of triangular waveforms—pp waves (fast-fast waves), cc waves (slow-slow waves), pc waves (fast-slow waves), and cp waves (slow-fast waves)—and a trapezoidal waveform holding the peak strain at the tension side. The applicability of various creep-fatigue interaction damage assessment methods were evaluated with particular emphasis on the life fraction rule (LFR) employed in ASME Section III, Boiler & Pressure Vessel Code Case N-47 and the strain range partitioning method (SRP). As it turned out that through the LFR life evaluation of HK-40 alloy subjected to strain cycling with holding at the tension side was well interpreted, design criteria for reformer tubes were established by applying the LFR to creep-fatigue life evaluation.

Invariant NNM Manifolds for Studying Localized and Chaotic Dynamics of an Array Composed of STIFF/SOFT Elements

1997 ◽  
Author(s):  
Ioannis T. Georgiou ◽  
Alexander F. Vakakis
Keyword(s):  
Phase Space ◽  
Singular Perturbation ◽  
Chaotic Dynamics ◽  
Invariant Manifolds ◽  
Normal Modes ◽  
Slow Waves ◽  
Two Dimensional ◽  
Perturbation Problem ◽  
Propagation Of Waves ◽  
Fast Waves

Abstract This study concerns propagation of waves in a coupled array of soft/stiff oscillators. We show that the array supports a family of purely slow waves, including a solitary one, and a family of purely fast waves. The slow and fast waves interact to give rise to chaotically modulated slow/fast and fast/slow waves. Slow and fast waves are realized as two-dimensional invariant manifolds (normal modes) in phase space of a singular perturbation problem.

Evaluation of Creep-Fatigue Damage Interaction in HK40 Alloy

1991 ◽  
Author(s):  
Shinji Konosu ◽  
Tamotsu Koshimizu ◽  
Takahiro Iijima ◽  
Keikichi Maeda
Keyword(s):  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
Strain Range ◽  
Slow Waves ◽  
Design Criteria ◽  
Peak Strain ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fast Waves

Abstract In order to establish design criteria for materials which may sustain creep-fatigue damage, the creep rupture and creep-fatigue behavior of a high-carbon centrifugal cast steel was investigated at three different temperatures of 800, 900, and 1000°C, using HK-40 alloy which is a typical furnace tube material for fuel cell plant reformers and so on. The strain waveforms used for the creep-fatigue tests consisted of triangular waveforms (pp waves [fast-fast waves], cc waves [slow-slow waves], pc waves [fast-slow waves], and cp waves [slow-fast waves]) and a trapezoidal waveform holding the peak strain at the tension side. The applicability of various creep-fatigue interaction damage assessment methods were evaluated with particular emphasis on the life fraction rule (LFR) employed in ASME Section III, Boiler & Pressure Vessel Code Case N-47 and the strain range partitioning method (SRP). As it turned out that through the LFR life evaluation of HK-40 alloy subjected to strain cycling with holding at the tension side was well interpreted, design criteria for reformer tubes were established by applying the LFR to creep-fatigue life evaluation.

Wave Mixing Effects on a Periodically Ribbed Cylindrical Shell

1996 ◽  
Vol 118 (1) ◽  
pp. 100-106 ◽  
Author(s):  
D. M. Photiadis
Keyword(s):  
Cylindrical Shell ◽  
Flexural Vibration ◽  
Dispersion Curves ◽  
Slow Waves ◽  
Wave Mixing ◽  
Frequency Space ◽  
Weak Wave ◽  
Mixing Effects ◽  
Fast And Slow Waves ◽  
Fast Waves

An examination of the response of a periodically ribbed cylindrical shell shows several effects due to the mixing of fast and slow waves on the shell. In wavenumber-frequency space, this mixing manifests itself in the formation of hybrid modes, for example, mixtures of part shear and part flexural vibration. The mixing is strongest when the phase speeds of the different wave types coincide and so reflect the dispersion curves of the flexural Bloch wavenumber. The dispersion curves may be significantly altered by mixing effects, and even for weak wave mixing the polarization of the fast waves can be changed significantly. This effect greatly alters the coupling of the fast waves to an external fluid.

Sign in / Sign up

Export Citation Format

Share Document