Accession Number : AD0283450

Title :   DYNAMIC BEHAVIOR OF GROUND EFFECT MACHINES IN MOTION OVER WAVES

Descriptive Note : Technical rept.,

Corporate Author : HYDRONAUTICS INC LAUREL MD

Personal Author(s) : LIN,J.D.

Report Date : APR 1962

Pagination or Media Count : 1

Abstract : AD-283 450Div. 9, 1U (TISTA/GEC) OTS price $3.60 Hydronautics, Inc. Rockville, Md. DYNAMIC BEHAVIOR OF GROUND EFFECT MACHINES IN MOTION OVER WAVES, by J. D. Lin. Apr 62, 23p. illus. 6 refs. (Technical rept. no. 011-4) (Contract Nonr-318900) Unclassified report DESCRIPTORS: *Flying platforms Dynamics, ater waves, Damping, Pitch, G s flow, Pro gramming, Digital computers, Simulation, Mathematical prediction, Theory, Motion Aerodynamics, Ground effect. Identifiers: Ground effect machines. Dynamic motion in heaving and pitching of a ground effect machine (GE ) traveling over a train of sinusoidal waves is formulated on the basis of the small-dist rba ce theory. E ations of motion are derived as two third-order ordinary differential equa ions with coefficients hich depend on the characteristics of the achine and the mass flow into or out of the cavity under the achine. The coefficients are linearized at the equilibrium height; then, the solutions are obtained for the natural fre uencies, he d mping, and the steady periodic responses to motion over waves. It is found that a GEM wit peripheral and central jet curtains is generally stable for heaving and pitching, but the damping is rather small. The effect of coupling due to the discontinuity of mass flow coefficients is very weak and thus may be neglected. A program, prepared for the IBM 1620 digital computer allows study of the dynamic stability of a machine through variation of pertinent parameters, and also investigations of its dynamic response to various wave encounter conditions. Theoretical predictions for practical machines, which have in model tests experienced dynamic motions over waves, are presented and compared with experimental results. Satisfactory agreements are indicated in the natural frequency and response for heaving and pitching. (Author)

Descriptors :   *FLYING PLATFORMS, AERODYNAMIC CHARACTERISTICS, DAMPING, DIGITAL COMPUTERS, DYNAMICS, GAS FLOW, GROUND EFFECT MACHINES, MATHEMATICAL PREDICTION, MOTION, PITCH (MATERIAL), PITCH (MOTION), PROGRAMMING (COMPUTERS), SIMULATION, THEORY, WATER WAVES

Distribution Statement : APPROVED FOR PUBLIC RELEASE