Accession Number : ADA471455


Title :   Design of Gages for Direct Skin Friction Measurements in Complex Turbulent Flows with Shock Impingement Compensation


Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF AEROSPACE AND OCEAN ENGINEERING


Personal Author(s) : Rolling, August J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a471455.pdf


Report Date : 07 Jun 2007


Pagination or Media Count : 133


Abstract : This research produced a new class of skin friction gages that measures wall shear even in shock environments. One test specimen separately measured wall shear and variable-pressure induced moment. Through the investigation of available computational modeling methods, techniques for accurately predicting gage physical responses were developed. The culmination of these model combinations was a design optimization procedure. This procedure was applied to three disparate test conditions: 1) short duration, high-enthalpy testing, 2) blow-down testing, and 3) flight testing. The resulting optimized gage designs were virtually tested against each set of nominal load conditions. The finalized designs each successfully met their respective test condition constraints while maximizing strain output due to wall shear. These gages limit sources of apparent strain: inertia, temperature gradient, and uniform pressure. A unique use of bellows provided a protective shroud for surface strain gages. Oil fill provided thermal and dynamic damping while eliminating uniform pressure as a source of output voltage. Two Wheatstone bridge configurations were developed to minimize temperature effects first from temperature gradient and then from spatially varying heat flux induced gradient. An inertia limiting technique was developed that parametrically investigated mass and center of gravity impact on strain output. Multiple disciplinary computational simulations of thermal, dynamic, shear, moment, inertia, and instrumentation interaction were developed. Examinations of instrumentation error, settling time, filtering, multiple input dynamic response, and strain gage placement to avoid thermal gradient were conducted. Detailed mechanical drawings for several gages were produced for fabrication and future testing.


Descriptors :   *TURBULENT FLOW , *SHOCK , *SKIN FRICTION , TEST AND EVALUATION , SHEAR PROPERTIES , THERMAL PROPERTIES , MATHEMATICAL MODELS , INPUT , OUTPUT , FLIGHT TESTING , SOURCES , MEASUREMENT , TEMPERATURE , COMPUTATIONS , INERTIA , ENVIRONMENTS , IMPACT , MODELS , INTERACTIONS , PHYSICAL PROPERTIES , IMPINGEMENT , BLOWDOWN , BELLOWS , GRADIENTS , GAGES , ENTHALPY , HEAT FLUX , COMPENSATION , NUMERICAL METHODS AND PROCEDURES , MECHANICAL DRAWING , COVERINGS , GRAVITY , WALLS , INSTRUMENTATION , STRAIN GAGES , PRESSURE , EMPLACEMENT , LIMITATIONS , TEMPERATURE GRADIENTS , SURFACES , SHORT RANGE(TIME) , VOLTAGE , LOADS(FORCES) , DYNAMIC RESPONSE , DAMPING


Subject Categories : Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE