THE EFFECT OF FLOW SEPARATION FROM THE HULL ON THE STABILITY OF A HIGH-SPEED SUBMARINE.
Technical rept. no. 1,
ITEK CORP PALO ALTO CALIF VIDYA DIV
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The problem of predicting theoretically the force distribution induced on a submarine hull by flow separation at high angle of attack is considered. The hull is taken to be a body of revolution with a pointed tail. The flow is assumed to be i5compressible and inviscid. The assumptions of slender-body theory are used, and the steady, three-dimensional vortex configuration on the leeward side of the inclined body is represented by an unsteady, two-dimensional vortex motion in a normal plane. The resulting force distribution is determined in terms of an assumed variation of the location of the separation line on the body with axial length. The theory is applied to the case of a high-speed submarine at angle of attack. The total forces and moments on the submarine are determined as the sum of the forces predicted by slender-body theory in the absence of separation and the forces predicted by the separation theory. Experimental data on the location of separation on an inclined cylindrical body are used with the theory to predict the normal force and pitching moment for angles of attack up to 20 degrees for a typical submarine configuration. Nonlinear effects attributable to separation are found to start at an angle of attack of approximately 8 degrees. Author