Bearing system parameter optimization of the amphibian air-cushion vehicles

The phrase “Air-Cushioned Vehicle” describes the complete range of vehicles which obtain some or all of their support from a free pressurised cushion of air contained between the vehicle and the ground.Vickers’ interest in air cushion vehicles stems directly from the basic work carried out on the Hovercraft—one type of air cushion vehicle—by Mr. C. S. Cockerell and the initiative and encouragement displayed by the N.R.D.C. through its subsidiary Hovercraft Development Ltd.

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Application of the Hopf bifurcation theory to limit cycle prediction of short journal bearings with isotropic roughness effects

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1243/13506501jet310 ◽

2007 ◽

Vol 221 (8) ◽

pp. 869-879 ◽

Cited By ~ 8

Author(s):

J-R Lin

Keyword(s):

Surface Roughness ◽

Hopf Bifurcation ◽

Limit Cycles ◽

Critical Region ◽

System Parameter ◽

Journal Bearings ◽

Roughness Effects ◽

Critical Limit ◽

Bifurcation Behaviour ◽

Bearing System

On the basis of the Christensen stochastic theory, the effects of isotropic surface roughness upon the bifurcation behaviour of a short journal-bearing system are investigated. By applying the Hopf bifurcation theorem to the non-linear equations of motion of rough journal bearings, the steady-state performance, the linear characteristics, and the weakly non-linear bifurcationphenomenaarepresented. For the short bearing with length-to-diameter ratio l = 0. 5, the onset of oil-whirl rough bearing system can manifest a bifurcation behaviour exhibiting subcritical limit cycles or super-critical limit cycles for running speeds near the bifurcation point. For a particular system parameter, the effects of isotropic surface roughness are found to enlarge the size of sub-critical limit cycles and super-critical limit cycles when the Hopf bifurcation occurs. On the whole, the roughness effects of isotropic surface patterns upon the Hopf bifurcation phenomena of the short-bearing system are more pronounced for a smaller system parameter ( p = 0. 4 in the sub-critical region and Sp = 0. 05 in the super-critical region) and a higher roughness parameter (Λ = 0. 4).

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Modeling of the Transient Response for Compressible Air Cushion Vehicles (ACV)

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.560 ◽

2012 ◽

Vol 152-154 ◽

pp. 560-567 ◽

Cited By ~ 1

Author(s):

Ahmed S. Sowayan ◽

Khalid A. Alsaif

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Settling Time ◽

The Self ◽

Design Stage ◽

Transient Time ◽

Bernoulli’S Equation ◽

Air Cushion ◽

Air Cushion Vehicles

A model for compressible Air Cushion Vehicles (ACV) is presented. In this model the compressible Bernoulli's equation and the Newton's second law of motion are used to predict the dynamic behavior of the heave response of the ACV in both time and frequency domains. The mass flow rate inside the air cushion of this model is assumed to be constant. The self excited response and the cushion pressure of the ACV is calculated to understand the behavior of the system in order to assist in the design stage of such systems. It is shown in this study that the mass flow rate and the length of the vehicle's skirt are the most significant parameters which control the steady state behavior of the self excited oscillations of the ACV. An equation to predict the transient time of the oscillatory response or the settling time in terms of the system parameters of the ACV is developed. Based on the developed equations, the optimum parameters of the ACV that lead to minimum settling time are obtained.

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