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The Unsteady Forces on Slender Delta Wing Hydrofoils Oscillating in Heave


DeLong, Raymond Kay (1968) The Unsteady Forces on Slender Delta Wing Hydrofoils Oscillating in Heave. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/H7R1-KF18.


The investigations described herein are both experimental and theoretical. An experimental technique is described by which the models tested could be oscillated sinusoidally in heave. The apparatus used to gather the unsteady lift, drag and pitching moment data is also described.

The models tested were two flat delta wings with apex angles of 15° and 30° and they had sharp leading edges to insure flow separation. The models were fabricated from 0.25 inch aluminum plate and were approximately one foot in length.

Three distinct types of flow were investigated: 1) fully wetted, 2) ventilated and 3) planing. The experimental data are compared with existing theories for steady motions in the case of fully wetted delta wings. Ventilation measurements, made only for the 30° model at 20° angle of attack, of lift and drag are presented.

A correction of the theory proposed by M.P. Tulin for high speed planing of slender bodies is presented and it is extended to unsteady motions. This is compared to the experimental measurements made at 6° and 12° angle of attack for the two models previously described.

This is the first extensive measurement of unsteady drag for any shape wing, the first measurement of unsteady planing forces, the first quantitative documentation of unstable oscillations near a free surface, and the first measurements of the unsteady forces on ventilated delta wings. The results of these investigations, both theoretical and experimental, are discussed and further investigations suggested.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Mechanical Engineering)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Acosta, Allan J.
Thesis Committee:
  • Unknown, Unknown
Defense Date:24 May 1968
Record Number:CaltechTHESIS:12072015-164403874
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9314
Deposited On:14 Dec 2015 17:33
Last Modified:01 Apr 2024 21:21

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