DRAG-FORCE MEASUREMENTS
A three-component force gage suitable for measurement of transient aerodynamic drag loads on sting-mounted models was successfully developed and used on Shot l2 of Operation Teapot, using 3- and l0-inch-diameter spheres as models. Gages were positioned in three specially prepared areas: (1) a thermally absorbing, nondusty asphalt area; (2) a thermally reflecting, ideal water area; and (3) a thermally absorbing, dusty desert area. Comparison of peak forces at a 3-foot height over these surfaces indicated the highest forces in the dusty desert area, with lower forces in inconclusive order over the asphalt and water areas. These results compare favorably with the Ballistics Research Laboratory (BRL) drag-force measurements and vehicle-damage evaluation. Because of the presence of dust and other inhomogeneities in the air stream and because the gage readings depended on the uncertain properties of the pressure seal between model shell and sting, it was not considered valid to calculate field drag coefficients from the force and q data. Further, the extreme variability of the laboratory drag measurements indicated that many more field readings would be required for a signifwcant comparison of field and laboratory results. Therefore, the only comparisons of drag coefficients were made between laboratory results and previously published drag coefficients of spheres at high Reynolds numbers and subsonic and transonic Mach numbers. Laboratory investigation revealed the high sensitivity of the sphere-sting configuration to angle of flow and, also, the difficulty of determining the actual angle of flow from the orthogonal force components. However, because the field forces recorded in the transverse and vertical directions were negligibly small and because dust scouring of the aluminum models was restricted to the front facing ground zero, it was concluded that on Shot l2 (at the 3-foot height) the air flow in the blast was parallel to the ground and directed radially outwvard from ground zero. The spherical force gages were tested in wind tunnel and shock tubes in the range of Mach numbers from 0.2 to 0.7, with Reynolds numbers from about 3 x l0/sup 5/ x l0/sup 6/ and shock overpressures from about 2 to 20 psi. Fair agreement is obtained between wind-tunnel and shock-tube drag coefficients, although the considerable scatter of the laboratory results indicates the need for more extensive investigation (auth)
- Research Organization:
- Naval Ordnance Lab., White Oak, Md.
- NSA Number:
- NSA-16-003987
- OSTI ID:
- 4826087
- Report Number(s):
- WT-1111
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AERODYNAMICS
AIR
ALUMINUM
ANGULAR DISTRIBUTION
BITUMENS
CONFIGURATION
DESERT
DUSTS
EXPLOSIONS
FLUID FLOW
GAGES
GAS FLOW
GENERAL AND MISCELLANEOUS
MACH NUMBER
MEASURED VALUES
PRESSURE
REACTOR FUELING
REFLECTION
REYNOLDS NUMBER
SENSITIVITY
SHELLS
SHOCK WAVES
SPHERES
SURFACES
TESTING
THERMAL RADIATION
TRANSIENTS
TUBES
TURBULENCE
VECTORS
VELOCITY
WATER
ZONES