Probing a subcritical instability with an amplitude expansion: An exploration of how far one can get

2009 ◽  
Vol 238 (18) ◽  
pp. 1827-1840 ◽  
Author(s):  
Paul Becherer ◽  
Alexander N. Morozov ◽  
Wim van Saarloos
Keyword(s):  
Subcritical Instability

A Model Equation Illustrating Subcritical Instability to Long Waves in Shear Flows

1987 ◽  
Vol 76 (3) ◽  
pp. 265-275
Author(s):  
I. H. Herron ◽  
S. A. Maslowe ◽  
S. Melkonian
Keyword(s):  
Model Equation ◽  
Shear Flows ◽  
Long Waves ◽  
Subcritical Instability

Practical Stability Limits in Turning

2009 ◽  
Author(s):  
Tama´s Kalma´r-Nagy
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Linear Stability ◽  
Global Model ◽  
Cutting Process ◽  
Practical Stability ◽  
Subcritical Instability ◽  
Process Comparison ◽  
The Creation ◽  
Stability Limits

In this paper we establish a practical formula that could be used to augment existing linear stability charts for turning to include the occurrence of contact loss between tool and workpiece in turning. We show that the contact loss discontinuity in the global model is responsible for the creation of the experimentally observed coexistence of subcritical instability and hysteresis in the cutting process. Comparison of experimental data with extensive numerical simulations nicely support the theoretical findings.

Investigation of Subcritical Instability in Ducted Premixed Flames

2011 ◽  
Author(s):  
Lipika Kabiraj ◽  
R. I. Sujith
Keyword(s):  
Experimental Investigation ◽  
Dynamical Behavior ◽  
Premixed Flames ◽  
Stability Diagram ◽  
Laminar Flames ◽  
Subcritical Instability ◽  
Bistable Region ◽  
Acoustic Forcing ◽  
The Stability

An experimental investigation of the bistable region of instability in a thermoacoustic system comprising of ducted, pre-mixed laminar flames has been performed. The stability diagram of the system is obtained and the bistable region for a range of flame locations at different fuel-air mixture equivalence ratios is identified. Subsequently, threshold amplitudes for triggering instability in the system using sinusoidal acoustic forcing, introduced externally, is obtained. It is observed that depending on how close the system is to the Hopf point and the nature of oscillations at the Hopf point, the triggered oscillations can exhibit different dynamical behavior.

A study of Bénard convection with and without rotation

1969 ◽  
Vol 36 (2) ◽  
pp. 309-335 ◽  
Author(s):  
H. T. Rossby
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Linear Theory ◽  
Silicone Oil ◽  
Taylor Number ◽  
Subcritical Instability ◽  
Two Fluids ◽  
Wide Range

An experimental study of the response of a thin uniformly heated rotating layer of fluid is presented. It is shown that the stability of the fluid depends strongly upon the three parameters that described its state, namely the Rayleigh number, the Taylor number and the Prandtl number. For the two Prandtl numbers considered, 6·8 and 0·025 corresponding to water and mercury, linear theory is insufficient to fully describe their stability properties. For water, subcritical instability will occur for all Taylor numbers greater than 5 × 104, whereas mercury exhibits a subcritical instability only for finite Taylor numbers less than 105. At all other Taylor numbers there is good agreement between linear theory and experiment.The heat flux in these two fluids has been measured over a wide range of Rayleigh and Taylor numbers. Generally, much higher Nusselt numbers are found with water than with mercury. In water, at any Rayleigh number greater than 104, it is found that the Nusselt number will increase by about 10% as the Taylor number is increased from zero to a certain value, which depends on the Rayleigh number. It is suggested that this increase in the heat flux results from a perturbation of the velocity boundary layer with an ‘Ekman-layer-like’ profile in such a way that the scale of boundary layer is reduced. In mercury, on the other hand, the heat flux decreases monotonically with increasing Taylor number. Over a range of Rayleigh numbers (at large Taylor numbers) oscillatory convection is preferred although it is inefficient at transporting heat. Above a certain Rayleigh number, less than the critical value for steady convection according to linear theory, the heat flux increases more rapidly and the convection becomes increasingly irregular as is shown by the temperature fluctuations at a point in the fluid.Photographs of the convective flow in a silicone oil (Prandtl number = 100) at various rotation rates are shown. From these a rough estimate is obtained of the dominant horizontal convective scale as a function of the Rayleigh and Taylor numbers.

scholarly journals Subharmonic resonant excitation of edge waves by breaking surface waves

2017 ◽  
Vol 24 (2) ◽  
pp. 157-165 ◽  
Author(s):  
Nizar Abcha ◽  
Tonglei Zhang ◽  
Alexander Ezersky ◽  
Efim Pelinovsky ◽  
Ira Didenkulova
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Parametric Excitation ◽  
Laboratory Experiments ◽  
Resonant Excitation ◽  
Edge Waves ◽  
Parametrically Excited ◽  
Subcritical Instability ◽  
Parametric Generation ◽  
Wave Parameters

Abstract. Parametric excitation of edge waves with a frequency 2 times less than the frequency of surface waves propagating perpendicular to the inclined bottom is investigated in laboratory experiments. The domain of instability on the plane of surface wave parameters (amplitude–frequency) is found. The subcritical instability is observed in the system of parametrically excited edge waves. It is shown that breaking of surface waves initiates turbulent effects and can suppress the parametric generation of edge waves.

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