CONTROL OF BOUNDARY LAYER TURBULENCE

THE DOLPHIN, AS A SELF-PROPELLED UNDERWATER PLATFORM, IS CHARACTERIZED BY UNUSUALLY SMALLHYDRODYNAMIC DRAG, EXCEPT IONALLY LOW FLOW NOISE, AND MARKED DELAY OF THE ONSET OF BOUNDARY LAYER TURBULENCE. DOLPHINS, SWINNING IN BIOLUMINES CENT OPEN OCEAN WATER AT SPEEDS UP TO 10 KTS, FOR EXAMPLE, ARE VIRTUALLY FREE OF ANY BOUNDARY LARYER BIOLUMINESCENCE; WHEREAS, BY CONTRAST, DIVERS IN WET SUITS SHED COPIOUS SHEETS OF BRIGHT BIOLUMINESCENCE AT MUCH LOWER SPEEDS OF 0.5 KTS. THE HYPOTHESIS WAS PUT FOURTH BY FITZGERALD (1968) THAT THIS REMARKABLE BOUNDARY LAYER CONTROL IS ASSOCIATED WIWITH THE COMPLEX DYNAMIC MECHANICAL PROPERTIES OF THE D DOLPHIN'S THICK (1") COMPLIANT BLUBBER (NTO THE THIN DOLPHINSKIN, RE KRAMER (1960). THE SURFACE OF THE COMPLAINT M MATERIAL WILL BE DEFORMED BY THE FLUCTUATING SURFACE FORCES OF THE TURBULENT BOUNDARY LAYER (TBL) IN SOME STATISTICAL FASHION DETERMINED BY THE SCALE AND INTENSITY OF THE T TURBULENCE. SINCE THE COMPLIANT MATERIAL IS VISCOELASTIC, THIS FLUCTUATING DEFORMATION MUST RESULT IN SOME ABSORPT ION OF ENERGY FROM THE TURBULENT FIELD, THUS REDUCING THE INTENSITY OF TURBULENCE (OR DELAYING ITS ONSET). IN TERMS OF CIRCUIT ANALOGIES, THE COMPLIANT VISCOELASTIC MATERIAL REPRESENTS A "LOAD" ON THE TBL "GENERATOR". IN ORDER TO MAXIMIZE THE TRANSFER OF ENERGY (POWER) FROM TBL GENERATOR TO THE COMPLIANT SURFACE LOAD, THE LOAD INPENDANCE SHOULD BE "MATCHED" TO THE IMPEDANCE OF THE GENERATOR; THAT IS, THE COMPLEX DRIVING-POINT SHEAR IMPEDANCE OF THE COMPLIANT SURFACE SHOULD BE THE COMPLEX CONJUGATE OF THE COMPLEX IMPEDANCE "LOOKING" INTO THE TBL.