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: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

On the Co-Existence of TD-LTE and Radar Over 3.5 GHz Band: An Experimental Study

Abstract: This letter presents a pioneering study based on a series of experiments on the operation of commercial Time-Division Long-Term Evolution (TD-LTE) systems in the presence of pulsed interfering signals in the 3550-3650 MHz band. TD-LTE operations were carried out in channels overlapping and adjacent to the high power SPN-43 radar with various frequency offsets between the two systems to evaluate the susceptibility of LTE to a high power interfering signal. Our results demonstrate that LTE communication using low antenna heights was not adversely affected by the pulsed interfering signal operating on adjacent frequencies irrespective of the distance of interfering transmitter. Performance was degraded only for very close distances (1-2 km) of overlapping frequencies of interfering transmitter.

Turbulence Ingestion Noise, Part 1: Experimental Characterization of Grid-Generated Turbulence

Abstract: Results are presented of an experimental investigation into the aeroacoustic response characteristics of rotor turbulence ingestion. To fully characterize the rotor response, both the ingested velocity field and the resulting far-field sound were measured. The results are presented of a detailed velocity characterization, which was performed upstream of the rotor. The velocity measurements included an evaluation of the streamwise development of turbulence characteristics downstream of the grid, a high-resolution mapping of the spatial distribution of the mean velocity and rms turbulence fluctuations in the rotor inlet plane, and the development of a semi-empirical, functional representation of the three-dimensional wave number spectral density of the ingested turbulence

A temperature-mapping molecular sensor for polyurethane-based elastomers

Abstract: We present a crosslinked polyurethane elastomer featuring a thermochromic molecular sensor for local temperature analysis. The thermochrome is a modified donor-acceptor Stenhouse adduct (DASA) that was dispersed homogeneously into the polymer blend in minuscule amounts. Rapid temperature jump measurements in a pyroprobe and impacts in a Hopkinson bar show that the DASA has suitable kinetics for detecting localized temperature increase following impact or rapid heating. The thermochrome retains a signature of the peak temperature in the elastomer, allowing post-mortem mapping of micron-scale temperature localization in materials such as explosive and propellant composites. We demonstrate the concept by using the kinetics of the DASA activation to determine peak temperatures reached during bullet perforation of the polyurethane.

Optimal Fixed-Interval Integrated Guidance-Control Laws for Hit-to-Kill Missiles

Abstract: Due to their potential for reducing the weapon size and efficiency, design methods for realizing hitto-kill capabilities in missile systems are of significant research interest in the missile flight control community. As defined in this paper, hit-tokill capability requires the missile to consistently achieve point-mass miss distances less than half the minimum dimension of the target. It has been noted in the literature that the chief contributors to the miss distance in homing missiles are the seeker errors, autopilot lag, target maneuvers, and target state estimation lag. Guidance laws for ameliorating the effects of each of these miss distance components have been discussed in several recent publications. The present research addresses the hit-to-kill missile flight control problem by casting it as an integrated guidance-control problem. By including the complete dynamics of the missile, the integrated guidance-control formulation automatically compensates for the impact of the autopilot lag on the miss distance. The resulting finite-interval control problem is then solved using a transformation approach. Interception by a kinetic warhead is used as an example to illustrate the performance of the integrated guidance-control law.

Modeling of Wall Pressure Fluctuations Based on Time Mean Flow Field

Abstract: Time-mean flow fields and turbulent flow characteristics obtained from solving the Reynolds averaged Navier-Stokes equations with a κ-e turbulence model are used to predict the frequency spectrum of wall pressure fluctuations. The vertical turbulent velocity is represented by the turbulent kinetic energy contained in the local flow. An anisotropic distribution of the turbulent kinetic energy is implemented based on an equilibrium turbulent shear flow, which assumes flow with a zero streamwise pressure gradient. The spectral correlation model for predicting the wall pressure fluctuation is obtained through a Green's function formulation and modeling of the streamwise and spanwise wave number spectra