This project will investigate the dynamics of novel air-assisted marine vehicles that include energy-efficient air-cavity hulls and fast amphibious platforms. The dynamics of these vehicles is very complex due to unsteady phenomena in compliant air zones between hulls and water and high-speed body motions near the air-sea interface. The main research goals are to derive and investigate dynamical systems for vehicle motions and to establish methods for determining static and dynamic stability, motions in waves and transient regimes, and effective control approaches. The scope of this work include derivation of mathematical models for vehicle dynamics, determination of forces with help of simplified modeling, detailed computational simulations, and experiments, and validation of theoretical findings on scaled experimental models of air-assisted marine vehicles.
This research will provide understanding on how to design and control novel sea-going air-assisted marine vehicles with exceptional efficiency and speed characteristics. Cargo ships will benefit from air cavity systems that can decrease drag by up to 30 percent. Reductions in underwater noise and wake wash will be additional environmentally friendly by-products. Ultra-fast heavy-lift amphibious craft with speeds well above 100 mph will provide efficient transportation means for Arctic regions and for rescue and security operations in oceans and on islands. Obtained research results will be broadly disseminated and integrated into existing and new courses and summer schools. Demonstrator models of advanced marine vehicles will provide an effective means to recruit students to careers in engineering.
Air-assisted marine vehicles (AAMV) can provide drastic improvements in efficiency and speed of marine transportation. The main problem preventing wider use of these vehicles is little understood dynamics, especially in the presence of waves and wind gusts. Our primary objectives in this project were to analyze aero-hydrodynamics and dynamics of novel types of AAMV and to advance educational and outreach activities for attracting and retaining students in engineering. We have developed simplified mathematical models aimed at determining longitudinal static stability and more complex nonlinear unsteady models for transient and periodic motions of amphibious power-augmented-ram vehicles (PARV) and tunnel hulls. The influence of main vehicle parameters and environmental conditions on the stability and dynamics of several vehicle types were investigated. PARV represent a transformative innovation in amphibious transportation; they can be used for Arctic operations, rescue missions in oceans and islands, and as intercepting craft and landing platforms. We have also developed computationally economic models for air-ventilated hulls that employ air layers on ship bottoms to reduce friction resistance. With help of these methods, design of air-cavity hulls can be made more efficient by reducing a number of experimental tests usually used to develop high-performance air-cavity hulls. We also discovered that usage of compact hydrodynamic actuators can substantially improve drag-reducing capabilities of air-cavity systems. A series of drop tests was conducted with catamaran and air-cavity hulls to provide understanding of shock-reducing effects of trapped air cavities arranged on ship hull bottoms during slamming events that often occur in rough seas and present one of the most critical limitations for oceanic transportation. It was discovered that air cavities substantially decreased peak accelerations; and a simplified mathematical model was developed to evaluate this phenomenon. We constructed several self-propelled, radio-controlled power-augmented ram vehicles and air-cavity hulls that were tested in outdoor conditions. These tests provided additional insight on practical factors affecting stability, dynamics, and performance of AAMV. With help of this grant, several graduate and undergraduate students, including those from groups underrepresented in engineering, received training in advanced areas of dynamics and marine vehicles. Our outreach and educational activities included efforts aimed at attracting and retaining students in engineering, disseminating research results, and incorporating new topics in engineering courses.