By Edward Ammeen
BAYVIEW AND WEST BETHESDA—For more than two decades, the Division’s Maneuvering and Control Division (5600) has relied on 20th-scale radio-controlled model (RCM) technology and full-scale trials to characterize submarine maneuvering performance and develop Fleet operational guidance. Throughout the last decade, as submarine geometry has become more advanced and hydrodynamic phenomena correspondingly more complex, the Division desired a highly-instrumented vehicle to conduct large-scale hydrodynamic experiments to complement its small-scale and full-scale programs.
While the Large Scale Vehicle Kokanee (LSV I) had been a valuable asset for the propulsor and acoustics communities for many years, Kokanee could not provide the requisite capabilities for the Maneuvering and Control Division. Kokanee was not geometrically similar to a full-scale submarine (i.e., it had a different control surface configuration than Seawolf). It included limited instrumentation to measure hydrodynamic loads, and its operational performance was limited/ restricted.
When Code 5600 team members were asked to participate in the requirements definition for the advanced Large Scale Vehicle Cutthroat (LSV II), they knew it was just a matter of time until critical large-scale maneuvering and control data, complementing RCM and full-scale trials data, would be obtained. Today, Cutthroat provides a unique capability to conduct large-scale hydrodynamic experiments, including normal maneuvering and casualty recovery. The vehicle is geometrically similar to the Virginia. The appendages, control surfaces, and propulsor are instrumented with dynamometers that measure hydrodynamic loads. The onboard data acquisition system allows maneuvering-related flow phenomena to be measured. The guidance, navigation, and control (GNC) system includes the ability to execute scripted maneuvers that replicate diagnostic maneuvers, as well as simulated casualties.
Throughout the last few months, the Acoustic Research Detachment (ARD) has operated Cutthroat to provide the Maneuvering and Control Division critical large-scale data that could be used to increase the confidence in redictions of maneuvering-related events conducted during Virginia full-scale trials. Approximately 20 runs were conducted ranging from vertical overshoots (for measuring the effectiveness of the planes) to controlled and planes-fixed turns (for determining turning characteristics) to decelerations (for evaluating crashback characteristics) to control surface jams (for evaluating recovery actions and validating casualty boundaries). The data are being used to conduct correlation studies of the Virginia maneuvering and control simulation, which was used along with captive model and RCM data to predict the maneuvering and control performance of Virginia during full-scale trials. The correlation results for most maneuvers have proven to be excellent but have also identified possible future areas of research that would improve maneuvering and control predictions.
Recently, ARD has commenced conducting a sequence of runs that will characterize the maneuvering and control performance of Cutthroat. This suite of data is expected to provide the Maneuvering and Control Division a wealth of information. With this data, Code 5600 can conduct correlation studies among RCM, large-scale, full-scale, and simulation. These correlation studies will provide the maneuvering and control community the ability to address fundamental hydrodynamic issues, such as scaling, and understand the complex flow phenomena associated with maneuvering. This has the potential to provide significant improvements in the hydrodynamic maneuvering and control process. These correlation studies will also enable improvements in maneuvering and control tools to be determined that significantly enhance predictions, which lead to the provision of more accurate operational guidance for the Fleet and safer operation of the platforms.
Posted by yw at November 8, 2004 07:37 PM