Naval Surface Warfare Center, Carderock Division Research Articles

Whirl Flutter Test of Swept-Tip Tiltrotor Blades

The first whirl flutter test of the Maryland Tiltrotor Rig (MTR) was recently completed in the Naval Surface Warfare Center Carderock Division (NSWCCD) 8- by 10-ft large subsonic wind tunnel. The MTR is a Froude-scaled, 4.75 ftdiameter, threebladed, semispan, floor-mounted, optionally powered, flutter rig. This paper focuses on the swept-tip blades developed for this test. The swept-tip begins at 80%R and sweeps aft 20° to alleviate whirl flutter. Whirl flutter testing was performed in four con gurations for both blade geometries. The frequency and damping of the wing beam and chord bending were collected at wind speeds up to 100 kt. This paper directly compares whirl utter results between the straight and swept-tip blades and demonstrates higher wing chord damping using swept-tip blades in freewheel conditions, even at lower flight speeds.

Estimation of torsional and global loads for a wave-piercing high-speed catamaran at full-scale in irregular bow quartering seas using CFD simulation

Catamarans experience more types of global load than monohulls, these include pitch connecting moment, transverse bending moment, and split force. High-speed catamarans are widely used for passenger transportation but as the speed and size increase the severity of loads rises due to slam induced effects. In this study, full-scale CFD simulations are undertaken to investigate the loads acting on a 98m Incat wave-piercer catamaran (Hull 061) HSV2 Swift. Simulations are performed for conditions of a selected sea trial run in bow quartering seas at 20 knots forward speed undertaken by the Naval Surface Warfare Center, Carderock Division (NSWCCD), enabling comparisons and validation. In order to estimate internal global loads at different sections of the vessel, rigid body dynamics is applied based on the hydrodynamic and inertia forces. Those internal loads include longitudinal bending moment (LBM), pitch connecting moment (PCM), torsional moment (TorM), transverse bending moment (TBM), split force and prying moment. The estimated and measured global loads are also compared with design loads limits provided by DNV GL rules, and peak values of pitch and roll accelerations corresponding to each slam load are determined at the same wave height and wave period as the sea trial. The application of CFD to simulate sea trials runs in oblique seas is shown to provide a reliable estimation of slam induced loads for application in early design stages.

Assessment of experiments and CFD for the semi-planing R/V Athena Model in calm water

The Naval Surface Warfare Center Carderock Division (NSWCCD) Model 5365 (R/V Athena) was chosen to facilitate the detailed comparison of experiments and simulations of a semi-planing hull in calm water and waves. This paper focuses on the comparison of the calm water experimental results from three different tests with four simulation predictions from two computational codes. The comparisons show differences with the same order of magnitude as comparisons of experimental and simulation with large displacement vessels. The MxN-order level analysis has shown that the scatter in the data between the three experiments dominates the experimental uncertainty in the semi-planing regime. The N-Version analysis of the four simulations shows that the scatter in results for both the experiments and the simulations drives the state-of-the-art uncertainty. The resistance, trim, and sinkage was validated at a variety of speeds for individual codes and the simulation mean. This study has shown the importance of experimental setup and the initial conditions of numerical simulations when comparing experimental and numerical simulation results. The errors due to the hydrostatic setup and the transom radius proved to be a contributor to the error between the experiments and simulations.

Lithium Battery Casualty Detection and Mitigation Developments for Navy Platforms

The growing need for large lithium batteries and lithium battery powered equipment aboard submarines provides major challenges to the US Navy; two of these challenges include (1) early battery casualty detection and (2) containment or mitigation of hazards associated from lithium-based battery casualties. Lithium ion rechargeable batteries used within research unmanned undersea vehicles (UUV) was abusively tested inside of its vehicle and was instrumented with water mitigation and various types of presumptive pre/post casualty onset detection sensors. These efforts were conducted under the requirements for the Navy’s Lithium Battery Safety Program, Naval Sea Systems Command Instruction 9310.1C and related documents as guidance for need. This effort followed similar recent works for the storage and carriage of large form lithium and lithium-ion batteries conducted preciously. This paper will review the results of these tests conducted by the Naval Surface Warfare Center, Carderock Division (NSWCCD), Naval Undersea Warfare Center, Newport (NUWC NWPT) and the Naval Research Center (NRL) over the past six years. These efforts have enabled the carriage and deployment of lithium battery powered systems from surface platforms and are expected to enable the deployment from undersea platforms.

Hydrodynamic and Supportive Structure for Gated Ship Sterns: Amphibious Ship Stern Flap

Stern flaps have now been at sea for more than two decades, on a variety of U.S. Navy (USN) and U.S. Coast Guard (USCG) classes, including destroyers, cruisers, frigates, cutters, and patrol craft. Application of flaps to large-deck amphibious-type ships is a fairly recent extension of the technology. Ship performance improvements such as delivered power reduction and fuel savings, and maximum speed increases, have been proven during at-sea trials and are well documented. U.S. Navy amphibious ships contain well decks, which are accessed through large folding stern gates. When open, the gates are supported by sizable structures, which are partially submerged and affixed to the transom. A new concept, the hydrodynamic and supportive structure for gated ship sterns, i.e. the amphibious stern flap, was developed and patented by the author. This design combines a stern flap’s hydrodynamic performance surface with the stern gate support structure. The Naval Surface Warfare Center, Carderock Division (NSWCCD), has now designed and implemented this new type of integrated stern flap and gate support structure on several U.S. Navy amphibious ship classes. U.S. Navy ship design and R&D programs have resulted in amphibious stern flaps being implemented as new construction items on two new Navy amphibious ship classes and one new subclass. Fleet Readiness R&D programs have funded amphibious stern flap design, retrofit installation, and evaluation trials on two existing amphibious ships. Each amphibious stern flap design spiral, model-test series, optimization, full-scale implementation, as well as performance benefits and fuel savings will be discussed.

Algae Based Hydroprocessed Fuel Use on a Marine Gas Turbine

The Naval Surface Warfare Center, Carderock Division (NSWCCD) Philadelphia conducted a full scale gas turbine engine test using Rolls Royce engine models 501-K34 and 250-KS4 to assess engine performance and fuel combustion characteristics of an algae based hydroprocessed fuel. The fuel, hereafter described as alternate fuel, consisted of a 50/50 blend of NATO F-76 fuel and the algae based formulation. It is the first time that the U.S. Navy has used a nonpetroleum based fuel on a marine gas turbine. The test was conducted at the DDG 51 Land Based Engineering Site (LBES) of NSWCCD during Jan. 16–21, 2011. The alternate fuel test conducted on the 501-K34 engine consisted of seven cycles of engine operation, one using NATO F-76 fuel to develop a baseline run and six cycles using alternate fuel. Each cycle was 7 h and 20 min in duration and was composed of 27 distinct load scenarios. The total duration of the test was 44 h. The 250-KS4 engine was used as the starter mechanism for the 501-K34 engine. During the test, parameters for combustion temperature, fuel demand, fuel manifold pressure, engine start time, and operation under various load conditions were recorded. This paper discusses the results of the above test by comparing engine operation using alternate fuel to engine performance using NATO F-76 fuel.

Rolls Royce/Allison 501-K Gas Turbine Antifouling Compressor Coatings Evaluation

The Naval Surface Warfare Center, Carderock Division (NSWCCD) Gas Turbine Emerging Technologies Code 9334 was tasked by NSWCCD Shipboard Energy Office Code 859 to research and evaluate fouling resistant compressor coatings for Rolls Royce Allison 501-K Series gas turbines. The objective of these tests was to investigate the feasibility of reducing the rate of compressor fouling degradation and associated rate of specific fuel consumption (SFC) increase through the application of anti-fouling coatings. Code 9334 conducted a market investigation and selected coatings that best fit the test objective. The coatings selected were Sermalon for compressor stages 1 and 2 and Sermaflow S4000 for the inlet guide vanes and remaining 12 compressor stages. Both coatings are manufactured by Sermatech International, are intended to substantially decrease blade surface roughness, have inert top layers, and contain an anti-corrosive aluminum-ceramic base coat. Sermalon contains a Polytetrafluoroethylene (PTFE) topcoat, a substance similar to Teflon, for added fouling resistance. Tests were conducted at the Philadelphia Land Based Engineering Site (LBES). Testing was first performed on the existing LBES 501-K17 gas turbine, which had an uncoated compressor. The compressor was then replaced by a coated compressor and the test was repeated. The test plan consisted of injecting a known amount of salt solution into the gas turbine inlet while gathering compressor performance degradation and fuel economy data for 0, 500, 1000, and 1250 KW generator load levels. This method facilitated a direct comparison of compressor degradation trends for the coated and uncoated compressors operating with the same turbine section, thereby reducing the number of variables involved. The collected data for turbine inlet, temperature, compressor efficiency, and fuel consumption were plotted as a percentage of the baseline conditions for each compressor. The results of each plot show a decrease in the rates of compressor degradation and SFC increase for the coated compressor compared to the uncoated compressor. Overall test results show that it is feasible to utilize antifouling compressor coatings to reduce the rate of specific fuel consumption increase associated with compressor performance degradation.

Facilitating Innovation through Knowledge Sharing: A Look at the Us Naval Surface Warfare Center-Carderock Division

One of the key reasons for engaging in knowledge management is to stimulate innovation in organizations. This would hopefully lead to new products and services in the e-business age. Through knowledge management, a knowledge sharing culture will emerge to foster better collaboration and communication through communities of practice. This paper looks at knowledge sharing techniques and metrics for facilitating innovation and then discusses an organization, the US Naval Surface Warfare Center, pondering the use of these techniques. An approach for knowledge sharing selection is then discussed in context with this organization

Advanced Double Hull Structural Design Technology

ABSTRACT The Mid‐Term Sealift Ship Technology Development Program is a multiyear research and development effort to examine promising technologies for application to construction of sealift ships. One of the goals of this program is to enhance the competitiveness of U.S. shipbuilders by investigating a new method of hull construction that would be easier and cheaper to build and pre‐outfit. The concept consists of a long‐spanned, unidirectionally‐stiffened structural system where the main structural elements are arranged longitudinally. This technology is referred to as advanced double hull (ADH).This paper describes the second year of study in which a new design criterion was applied. This criterion was based upon the results of structural testing and analysis conducted by the Naval Surface Warfare Center Carderock Division (NSWCCD) to determine the ultimate strength of cellular structure. A full ship finite element model was developed to help validate the structural criteria.

The Installation, Testing, and Lessons Learned of the TF40B Gas Turbine Test Facility

The TF40B Gas Turbine Test Facility is the only dedicated Landing Craft, Air Cushion main propulsion engine test complex available to the U.S. Navy. This facility, located at the Naval Surface Warfare Center, Carderock Division (NSWCCD) in Philadelphia, PA, began operation in August, 1992. Since then, the test engine has logged approximately 230 starts and 350 operating hours. This paper will present the installation, testing, and lessons learned of the TF40B test facility. The installation section will discuss the modifications made to the existing test facility to accept the TF40B engine. The test section will include the Foreign Object Damage (FOD) screen evaluation, both on-line and crank wash detergent fluid evaluations, cold weather fuel testing, engine vent line testing and Aerojet 5 oil evaluation. The lessons learned section will include problems related to the electric starter, waterbrake, inlet and exhaust systems, data acquisition system, instrumentation control panel, and the test cell equipment arrangement.

Navy High-Pressure Waterjet Closed-Loop Paint Stripping System

The marine refurbishment industry currently utilizes abrasive blasting for hull coatings removal. These processes generate extreme amounts of waste material, which must be contained and disposed of properly. The cost of containment, the hazardous work environment and the amounts of hazardous waste produced are all significant disadvantages of the existing processes. Additionally, environmental regulations and safety standards are being introduced which demand new techniques for marine coatings removal. In light of these factors, the U.S. Navy's Naval Surface Warfare Center-Carderock Division entered into a joint initiative with the U.S. Air Force to introduce an alternative paint and marine growth removal method, including complete effluent recovery at the source. This system, using only high-pressure water, is semi-automatic and mobile. The system can operate independently in a dry dock without external utilities. In the end, the system will eliminate the current problems associated with coatings removal and reduce the overall operational costs.