SUBMARINE MAST WAKE REDUCTION

A SUBMARINE MAST OR PERISCOPE WHICH PIERCES THE FREE SURFACE GENERATES A VISUALLY OBSERVABLE WAKE ON THE FREE SURFACE WHICH RENDERS THE SUBMARINE VULNERABLE TO DETECTION. IT IS PROPOSED TO INVESTIGATE THE FEASIBILITY OF REDUCING THIS WAKE BY A COMBINATION OF ACTIVE AND PASSIVE FLOW CONTROL DEVICES ATTACHED TO THE MAST OR PERISCOPE. A DEVICE SIMILAR TO A BULBOUS BOW ON SHIPS WILL BE USED TO REDUCE THE FREE SURFACE DISTURBANCES AROUND THE MAST, WHICH CONSIST OF WAVE HUMPS AND HOLLOWS, BREAKING WAVES WHICH ENTRAIN BUBBLES, A NECKLACK VORTEX, AND A ROOSTER TAIL AT HIGHER SPEEDS. THE 'BULBOUS BOW' DEVICE WILL BE DYNAMICALLY ADJUSTABLE TO PROVIDE NEAR-FIELD WAVE CANCELLATION AT VARIOUS SPEEDS, AND WITH THE MAST OR PERISCOPE SUBJECT TO VARYING EMERSION DUE TO SUBMARINE DEPTH FLUCTUATIONS AND OCEAN WAVES. THE TURBULENT WAKE BEHIND THE MAST WILL BE REDUCED BY FLUID BLOWING AT THE REAR OF THE MAST, TO REPLACE THE MOMENTUM LOST DUE TO THE DRAG OF THE MAST. THE BLOWING AT THE TRAILING EDGE WILL BE VARIED FROM SIDE TO SIDE TO COUNTERACT THE LIFT FLUCTUATIONS THAT WOULD OTHERWISE DEVELOP ON THE MAST DUE TO ANGLE OF ATTACK VARIATIONS RESULTING FROM OBLIQUE OCEAN WAVES.