Nonlinear Motion of an Air-Cushion Vehicle over Waves

Doctors, Lawrence J.

doi:10.2514/3.63019

Cited by 22 publications

(19 citation statements)

References 8 publications

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“…The rate of density change may then be expressed by dP dt~ ( 10) Thus, Eqs. (3)(4)(5)(6)(7)(8)(9)(10), which represent conservation of mass for the main cushion air flow, relate the cushion pressure to craft position, surface wave motion, and the rates of motion of the vehicle.…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Linear models for hovercraft motion in regular waves were also developed by Reynolds 3 and Reynolds et al 4 A nonlinear model for the coupled pitch and heave motion of an air cushion vehicle in regular waves was developed by Doctors. 5 The craft he considered was of the divided cushion type in which the main cushion is divided into subcushions by flexible longitudinal and transverse stability keels. More recently, Doctors has extended his analysis of divided cushion craft to include the effects of hydrodynamic influence and compressibility.…”

Section: Introductionmentioning

confidence: 99%

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Seakeeping dynamics of a single cushion, peripheral cell-stabilized air cushion vehicle

Carrier

Magnuson

Swift

1978

Journal of Hydronautics

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A study of air cushion vehicle (ACV) motion in waves is presented for a single cushion ACV having a cellular, peripheral cell-type skirt system. The craft is considered to be traveling at constant speed while encountering regular waves of arbitrary heading. The dynamic equations for pitch, heave, and roll motions are derived using the cushion and cell air flow equations. These equations are solved numerically using a digital computer. The results are shown as frequency response curves giving steady-state motion response amplitudes as a function of encounter frequency or wavelength for fixed craft speed and wave steepness. The theoretical predictions are then compared with experimental data taken from scale model, towing tank tests in head seas. The comparison shows good agreement for pitch motion, while heave motion damping is overpredicted. Nomenclaturearea of orifice between loop and vertical cell AQ -equilibrium leakage area b = beam C n = orifice coefficient / = cushion leakage fraction of gap height hi = depth below origin of fully extended skirt at /th jupe H = unit step function I x = craft moment of inertia about the x axis I y = craft moment of inertia about the y axis K = roll moment k = wavenumber k ]t k 2 = increase in cell width on inside, outside per unit change in height / = cushion length M = pitch moment m = mass of craft m c = mass of air in cushion P = cushion gage pressure P L = loop pressure Q = volume rate of flow Qo, 1,2 -f an performance parameters AS/ = length of skirt seal around cushion periphery T = effective width of skirt jupes U 0 = craft speed V c = cushion volume W -craft weight x c =x coordinate of cushion centroid z c = depth of top of cushion from origin Zo = heave coordinate Z = force on craft in the z direction /3/ = angle of outward normal at the /th cell with respect to the x axis 7 = angle of wave propagation direction with respect to the* axis y c = ratio of specific heats ( =c p /c v ) 77 = wave height B -pitch angle A = wavelength p = density = roll angle u e = encounter frequency oj = wave frequency Subscripts a = refers to atmosphere ij = refers to /th,./th seal (jupe) L = refers to loop 0 = refers to equilibrium conditions

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Section: Theoretical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seakeeping dynamics of a single cushion, peripheral cell-stabilized air cushion vehicle

Carrier

Magnuson

Swift

1978

Journal of Hydronautics

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“…The complexity of this phenomenon makes impossible to develop a theoretical background, and prompts many design parameters to be traditionally decided by empirical formulas [9]. Actually, only limited theoretical and computational models have been developed to analyze seal dynamics [11][12] [13]. This paper shows an extension of the work presented by Serván-Camas and García-Espinosa [6] in the development of an efficient seakeeping solver.…”

Section: Introductionmentioning

confidence: 97%

A FEM fluid–structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship

García¹,

Capua²,

Serván-Camas³

et al. 2015

Computer Methods in Applied Mechanics and Engineering

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This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a stream-line integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behavior of the seals in the interface between the air cushion, and the water. The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method. Several validations against experimental results have been carried out to demonstrate the developed algorithm.

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“…Combining the kinematic and dynamic free surface boundary conditions, the free surface condition reads: 66) and is implemented as a Neumann boundary condition that fulfils the flux boundary integral:…”

Section: Free Surface Boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A time-domain finite element method for seakeeping and wave resistance problems

Camas¹

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Nonlinear Motion of an Air-Cushion Vehicle over Waves

Cited by 22 publications

References 8 publications

Seakeeping dynamics of a single cushion, peripheral cell-stabilized air cushion vehicle

Seakeeping dynamics of a single cushion, peripheral cell-stabilized air cushion vehicle

A FEM fluid–structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship

A time-domain finite element method for seakeeping and wave resistance problems

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