The Naval Undersea Warfare Center is the United States Navy's full-spectrum research, development, test and evaluation, engineering and fleet support center for submarines, autonomous underwater systems, and offensive and defensive weapons systems associated with undersea warfare. One of the corporate laboratories of the Naval Sea Systems Command, NUWC is headquartered in Newport, Rhode Island, and has two major subordinate activities — Division Newport and Division Keyport . NUWC also controls the Fox Island Facility and Gould Island.NUWC employs more than 4,400 civilian and military personnel, with budgets of over US$1 billion. Wikipedia.
Incze M.L.,Naval Undersea Warfare Center
Ocean Dynamics | Year: 2011
Lightweight Autonomous Underwater Vehicles (AUVs) were developed for Naval Special Warfare (NSW) Group 4 search and survey missions from a commercial AUV baseline (Iver 2) through integration of commercial off-the-shelf (COTS) hardware components, and through software development for enhanced on-board Command and Control functions. The development period was 1 year under a project sponsored by the Office of Naval Research TechSolutions Program Office. Hardware integration was completed by the commercial AUV vendor, OceanServer Technology, Inc., and software development was conducted by the Naval Undersea Warfare Center, Naval Oceanographic Office, and U MASS Dartmouth, with support from hardware and software application providers (YSI, Inc., Imagenex Technology Corp., and CARIS). At the conclusion of the integration and development period, an at-sea performance evaluation was scheduled for the Lightweight NSW AUVs with NSWG-4 personnel. The venue for this evaluation was the NATO exercise Recognized Environmental Picture 10A (REP 10A), hosted by Marinha Portuguesa, and coordinated by the Faculdade de Engenharia-Universidade do Porto. REP 10A offered an opportunity to evaluate the performance of the new AUVs and to explore the Concept of Operations (CONOPS) for employing them in military survey operations in shallow coastal waters. Shore- and ship-launched scenarios with launch/recovery by a single operator in a one-to-many coordinated survey, on-scene data product generation and visualization, data push to Reach Back Cells for product integration and enhancement, and survey optimization to streamline survey effort and timelines were included in the CONOPS review. Opportunities to explore employment of hybrid AUV fleets in Combined Force scenarios were also utilized. The Naval Undersea Warfare Center, Marinha Portuguesa, the Faculdade de Engenharia-Universidade do Porto, and OceanServer Technology, Inc., were the primary participants bringing in-water resources to REP 10A. Technical support and products were provided by the Naval Research Laboratory-Stennis Space Center, Naval Oceanographic Office, NATO Undersea Research Centre, University of Massachusetts-Dartmouth, and YSI, Inc. REP 10A proved to be a very effective exercise in meeting each of the critical goals. Results of the performance evaluation guided final development and Independent Verification and Validation (IV&V) for the Lightweight NSW AUV, leading to on-time, successful Factory Acceptance Testing and delivery of the three contracted vehicles to NSWG-4 in September, 2010. © 2011 Springer-Verlag (outside the USA).
Donovan G.T.,Naval Undersea Warfare Center
IEEE Journal of Oceanic Engineering | Year: 2012
This paper presents comprehensive testing and analysis of a particle filter (PF) framework for real-time terrain navigation on an autonomous underwater vehicle (AUV). The goal is to obtain georeferenced localization for an AUV navigation system using reference bathymetry maps and bathymetric measurements in lieu of Global Positioning System (GPS) updates or acoustic localization methods such as long baseline (LBL). The algorithms are tested using navigation and sensor data collected during a long-distance run of the midsize autonomous reconfigurable vehicle (MARV) AUV, during which the Inertial Navigation System (INS) accumulated significant horizontal position error (>100 m). Run data sets over areas of both high and low bathymetric relief are used to compare performance with different altitude sensors, including multibeam and single-beam sonar, and four-beam Doppler velocity logger (DVL) sonar. A comparison of established techniques for dealing with tide levels is also presented. The technique of adding a third dimension to the PF state vector to compensate for changing water levels allowed the estimator to work consistently in areas of low bathymetric relief, where relative terrain profiling methods broke down and even slight errors in tide prediction models otherwise caused significant position errors. The effects of decreased vertical resolution and accuracy of the reference map is also investigated. To address problems of insufficient sample size, a novel PF resampling technique is presented in which jittering noise added to duplicate samples is scaled based on the particle cloud volume. This technique allows the PF to consistently recover a position fix over a search area of several kilometers without needing to significantly increase the number of particles used. © 2012 IEEE.
Jordan S.A.,Naval Undersea Warfare Center
Physics of Fluids | Year: 2015
Notable deviations of the asymmetric turbulent boundary layer (TBL) statistics from their axisymmetric counterpart along long thin circular cylinders are vitally important to the naval and oceanographic jurisdictions. Although the available experimental evidence backs their concern, the realm of parametric variability (both geometric and kinematic) is extremely limited to draw solid conclusions. We know that only small misalignments which quantify less than one degree of incidence between the freestream and the straight cylinder axis can substantially alter the boundary layer thicknesses, mean axial velocity, and Reynolds stresses. But the statistical database is plainly inadequate to justify modifying the design tools that were founded solely for axisymmetric flow conditions. Herein, we begin rectifying this drawback by numerical means. The investigation centers on low turbulent Reynolds numbers (500 ≤ Rea ≤ 2500) and small angles-of-incidence (0° < α < 9°) to validate and complement the lions-share of the present database (Rea = aUo/ν, where a, Uo, and ν are the cylinder radius, freestream velocity, and kinematic viscosity, respectively). In particular, we numerically resolved the statistical responses of the TBL, mean axial velocity, Reynolds stresses, and skin friction under angles-of-incidence up to the earliest signs of Strouhal-type shedding. Clearly, the first prominent response was the thinning and thickening of the TBL along the respective windward and leeward sides to only a minor misalignment. Tilting the straight cylinder to slightly higher yaw angles transformed the TBL to a transitional boundary layer along the windward side for all simulated Reynolds numbers. For yaw angles α > 2°, all turbulent statistics of the asymmetric boundary layer were measurably dissimilar to those of the axisymmetric state. © 2015 U.S. Government.
Jordan S.A.,Naval Undersea Warfare Center
Journal of Fluids and Structures | Year: 2011
Understanding the salient physics within the turbulent boundary layer of towed thin cylinders is paramount to the Navy sonar array communities. However, the required long array length to achieve wide acoustic aperture creates unique and consistent flow characteristics that suggest simplified tangential forcing expressions suitable for design purposes. One well-known fact is that the majority of the array surface experiences very thick turbulent boundary layers (TBL) and large Reynolds numbers. The resultant statistics are most commonly dependent on the inner and outer length scales. Herein, we resolve the near-wall TBL structure under those flow conditions by large-eddy simulation. The turbulent mean-flow statistics showed near-wall consistency using only inner scaling. But both inner and outer variables were found necessary to properly scale the turbulent fluctuations. An expression for the tangential wall-friction coefficient (C t) indicates two distinct flow regimes as characterized by the near-wall turbulent flow structure. The respective parameters appear independent of the outer length scale. Thickening (or thinning) the cylinder near their common threshold (defined by a radius-based Reynolds number) transitioned the turbulent character between the two regimes. © 2010.
Jordan S.A.,Naval Undersea Warfare Center
Physics of Fluids | Year: 2011
The experimental evidence leads us to believe that long slender circular cylinders have similar axisymmetric turbulent statistics along most of their axial length. The respective boundary layer reaches a maximum thickness (δ) with no further downstream net growth. Despite their small radius (a), these long cylinders still own high radius-based Reynolds numbers (Rea) as well as transverse curvatures (δ/a). The influence of these flow conditions (and others) on the turbulent statistics is still chiefly unknown. The present effort begins an investigation that targets axial similarity (or homogeneity) of the long thin cylinder statistics. The database is a collection of previous experimental measurements and observations as well as the present computational results by the large-eddy simulation methodology. Interestingly, this investigation shows that reaching axial homogeneity is reliant essentially on Rea with lesser influence by the transverse curvature. But the Rea value depends on the turbulent statistic of interest. Likewise, this same result was found for spotting the radial location of the respective statistical peak. Axial homogeneity starts near the cylinder wall then migrates outward radially with increasing Rea until full saturation through the turbulent intermediate layer. © 2011 American Institute of Physics.