Accession Number : AD0622875

Title :   STUDY OF HYDROFOIL SINGING.

Descriptive Note : Final rept. for 1 May 64-31 Aug 65,

Corporate Author : GRUMMAN AIRCRAFT ENGINEERING CORP BETHPAGE N Y

Personal Author(s) : Bradley,Joseph W. ; Rogers,James

Report Date : AUG 1965

Pagination or Media Count : 75

Abstract : An experimental investigation of hydrofoil 'singing' was conducted. A supercavitating model hydrofoil was operated in a high speed whirling tank from 25 through 80 knots at selected angles of attack, various flow conditions and mechanical constraints. The hydrofoil was found to 'sing' readily as specific attack angles for speeds of 45 knots and above. 'Singing' is present when the hydrofoil is fully wetted on the lower hydrofoil surface and either fully or partially wetted on the upper hydrofoil surface. The predominant 'singing' frequencies, which remained constant regardless of speed, were associated with fundamental resonances of the hydrofoil, such that it bent chordwise rather than spanwise, causing large oscillations of the leading edge. The maximum 'singing' amplitude also remained constant over the entire velocity range. 'Singing' started intermittently previous to steady-state 'singing'. Indications are that the 'singing' phenomenon is a selfexcited system and the controlling parameter is angle of attack at all speeds of 45 knots and above. Hydrofoil 'singing' was completely eliminated by the use of a rubber damping material that restrained the tip chords of the hydrofoil. (Author)

Descriptors :   (*HYDROFOILS, ELASTIC PROPERTIES), (*ACOUSTIC PROPERTIES, HYDROFOILS), NOISE, FREQUENCY, OSCILLATION, VIBRATION, FAILURE(MECHANICS), ANGLE OF ATTACK, DAMPING, RESONANCE, HYDRODYNAMICS

Distribution Statement : APPROVED FOR PUBLIC RELEASE