Open Water Free-Running Model Testing for High-Speed Craft Hydrodynamics

The hydrodynamic and hull performance of High-Speed Craft (HSC) are often evaluated in costly, restricted environments such as towing tanks, which limit vessel motion and do not replicate real-world sea conditions. Free-running outdoor model testing provides a cost-effective alternative, allowing full six degrees of freedom in natural environments. This study presents the development of a scaled free-running model incorporating a propulsion system, data acquisition system, and environmental monitoring methods. Preliminary tests were conducted at Texas A&M University's Offshore Technology Research Center (OTRC) and Lake Bryan, Texas, United States, with additional system validation at Lake Somerville, Texas, United States. INTRODUCTION The United States Navy operates High-Speed Crafts (HSC) at many of their installations to complete important missions across the globe to ensure the Navy's mission statement of protecting America at sea. This includes defending America and its allies, preserving economic prosperity, and keeping the seas free and open. High-Speed Crafts allow the Navy to complete covert missions that would otherwise be impossible This is due to the HSC's ability to move quickly without setting a large footprint, ultimately allowing personnel and equipment to move without the enemy to detect them. They are also used for maritime security, coastal interception, and special operations. HSC are also used search and rescue operations, and recreational activities among others. These types of fast agile vessels often operate in coastal (sometimes shallow) waters. HSC can reach higher speeds than displacement vessels of the same size. This is because the hull acts as a lifting surface and the vessel can plane, meaning the vessel is supported by lift rather buoyancy. To transition from displacement to planing mode, the vessel's thrust must be sufficient to overcome the increased drag associated with the resistance hump and propel the vessel into the planing regime. Planing hulls accelerate vertically in waves. This causes the vessel to slam against the water, making it vital to choose the appropriate material that will be able to absorb these forces. Slamming loads are affected by the hull shape, deadrise angle, wave encounter frequency, craft speed, and the ship structure flexibility. In addition, motions of the vessel are important since these affect operability, safety and crew comfort. Heave motions and accelerations also affect fuel consumption. These motions affect autonomous operations as well. Sensors are not able to operate if the platform is not stable.