Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Characteristics of a Dual-Slotted Circulation Control Wing of Low Aspect Ratio Intended for Naval Hydrodynamic Applications

Abstract: : An experimental investigation was conducted in a water tunnel to explore the application of Coanda-effect circulation control to low aspect ratio wings. The facility was the Large Cavitation Channel in Memphis, TN. The intended application is to high-lift control surfaces (appendages) on underwater naval vehicles. Test results are interpreted in light of both theory and the extensive experience with circulation control (CC) technology at NSWCCD. The semi-span wing test model with a taper ratio of 0.76 was mounted on a load cell; a reflection plane provided for an effective aspect ratio of 2. Dual upper/lower trailing edge tangential jet slots were incorporated for bi-directional force generation. Findings include: finite-span effects on CC augmented lift are consistent with the effects on conventional lift-due-to-angle-of-attack, and cavitation in the Coanda wall jet region does not result in jet detachment or an abrupt lift stall. Wing lift augmentation ratios are up to 36 and meet expectations. Unexpected virtues of a dual-slotted configuration were found that enhance the value of CC to ship and VSTOL aircraft applications. A small flow from the second slot will significantly extend the lift capability beyond that of single slot operation by preventing what is believed to be the adverse effects of excessive turning of the wall jet at high momentum coefficients. Dual slot flow produces a merger of the two wall jets into a free planar jet that enables static thrust vectoring of the jet momentum flux over the full 0-360 degree range. This steerable-jet provides a jet-flap mode of lift development for use at very low vehicle speeds, as an extension of the high efficiency CC mode.

Ab initio equation of state of an organic molecular crystal: 1,1-diamino-2,2-dinitroethylene.

Abstract: A complete equation of state for the molecular crystal 1,1 -diamino-2,2-dinitroethylene has been calculated from first principles for temperatures between 0 and 400 K, and for specific volumes from 61 to 83 cm 3 /mol, corresponding to relative volumes from 0.78 to 1.06. The calculated 300 K isotherm agrees very well with the experimentally measured pressure-volume relation reported by Peiris et al. (Peiris, S. M.; Wong, C. P.; Zerilli, F. J. J. Chem. Phys. 2004, 120, 8060). The volumetric thermal expansion coefficient is calculated to be 140 ppm/K at 300 K and atmospheric pressure and varies considerably with specific volume as well as temperature. The Gruneisen parameter varies significantly with temperature, but its variation with specific volume is small. The calculated specific heat (160 J/mol/K at 300 K and atmospheric pressure) has only a very small dependence on specific volume.

Factors influencing the ballistic impact resistance of elastomer-coated metal substrates

Abstract: An experimental study was carried out of various factors affecting the ballistic penetration resistance of elastomer/steel bilayers. For blunt penetrators, the contribution of the coating to performance is optimized using the hardest substrates, front surface placement of the elastomer, and (when normalizing by added weight) thin, ca. 2–3 mm, coatings. These results, none of which are predicted by existing models, evince the marked coupling of coating and substrate in the impact response of the bilayer. We also show that nanoparticle fillers have a modest effect on ballistic performance of polyurea coatings, changing the penetration velocity by a few percent or less. This contrasts with the linear dynamic mechanical behavior, which shows much more significant increases in energy absorption due to nano-reinforcement.

Effects of Phase Change and Oxygen Permeability in Oxide Scales on Oxidation Kinetics of ZrB2 and HfB2

Abstract: : A wide range of experimental data on the oxidation of ZrB2 and HfB2 as a function of temperature (800 - 1500 degrees Celsius) is interpreted using a mechanistic model that relaxes two significant assumptions made in prior work. First, inclusion of the effect of volume change associated with monoclinic to tetragonal phase change of the MeO2 phases is found to rationalize the observations by several investigators of abrupt changes in weight gain, recession, and oxygen consumed, as the temperature is raised through the transformation temperatures for ZrO2 and HfO2. Second, the inclusion of oxygen permeability in ZrO2 is found to rationalize the enhancement in oxidation behavior at very high temperatures (>1800 degrees Celsius) of ZrB2, while the effect of oxygen permeability in HfO2 is negligible. Based on these considerations, the significant advantage of HfB2 over ZrB2 is credited to the higher transformation temperature and lower oxygen permeability of HfO2 compared with ZrO2.