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Advanced Reliable Wide-Range Hydrodynamic Hull Appendage


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials OBJECTIVE: Develop an Advanced, Reliable, Wide-Range Hull Hydrodynamic Appendage (HHA) that provides fuel savings over a broad range of Froude numbers (0.15 – 0.75). DESCRIPTION: Unmanned Surface Vessels (USVs) and combatants require affordable, reliable, fuel efficient, proven hull forms. Commercially available hull designs provide a good baseline for affordable, reliable, proven hull forms; however, they are typically not designed for fuel efficient operations at the same broad operational speed ranges required for military vessels, i.e., lower transit speed, endurance range speed, and higher sustained sprint speed. The speed time profile for a USV will vary highly between peace time and war time operations, making broad range fuel efficiency more critical. Existing HHAs (stern flaps, wedges, interceptors, bow bulbs, etc.) [Refs 1 and 2] have demonstrated the ability to reduce hull resistance, and thereby, improve fuel efficiency; however, their benefits vary across the ship’s speed range, and have not provided a consistent benefit across a broad range of Froude numbers (0.15 – 0.75). Additionally, some of the HHAs rely on shipboard hydraulic systems, which can lead to cost and reliability issues. A reliable, wide-range HHA is required to enable commercially available hull designs to provide affordable, reliable, fuel efficient capability. Development of a reliable, wide-range HHA will better enable a modified Commercial Off The Shelf (COTS) hull-form to meet USV and combatant operational requirements, improving the autonomous systems endurance, persistence, and reliability. The development targets hulls 150’-400’ in length. Innovation is required to develop an advanced HHA that provides fuel savings across a wide range of Froude numbers and provides reliable operation with minimal maintenance. Additionally, the HHA must be readily integrated into an existing hull form, such that it does not require significant modification of existing commercial hull forms. The advanced HHA will provide a 5-10% fuel efficiency benefit at minimum across a wide operational speed range per Froude number range provided previously, and shall target an acquisition cost of less than $750K per unit to provide a Return on Investment (RoI) within 1-2 years. The number of units required is dependent on how broadly the technology can be applied; for planning purposes ~10-20 units would be required over a 10 year period. The advanced HHA’s performance will be assessed against the power delivered ratio for a hull form without an HHA as compared to a hull form with an HHA. The HHA shall be designed for (a) a 25-year service life, (b) fail safe operation, (c) 80% reliability, and (d) preventative maintenance requirements of no more than once per year. A reliability assessment shall be completed to assess whole system reliability, broken down by subsystems and components, to validate improvements relative to current systems (e.g., hydraulic actuated interceptors or trim tabs). PHASE I: Develop a concept for an advanced, reliable, wide-range HHA that explores methods to incorporate reliability and fail-safe operations into the system. Identify how the system would integrate into a range of USV and combatant hull forms. Conduct computational fluid dynamic (CFD) studies to demonstrate the feasibility of the concept and potential energy savings to hull forms across a wide Froude number range per range provided previously and verify integration requirements. Conduct reliability assessment broken down by subsystems and components. Provide final concept for an advanced, reliable, wide-range HHA. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II. PHASE II: Develop and deliver a full-scale or model-scale prototype of an advanced, reliable, wide-range HHA. The design shall be applicable to multiple hulls; however, only one prototype is required for one USV or combatant hull. Evaluate the prototype system through model or full-scale testing. Validate 5-10% fuel efficiency benefit across a wide operational speed range, relative to baseline hull performance. Update the reliability assessment based on final configuration and component selection, and document improvements to reliability. PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the advanced reliable wide range HHA to Navy use. Based on the evaluations completed under Phase II, make further modifications and improvements (compatibility with all Navy requirements), and refine the design for Navy specific USV or combatant uses. Work with the Navy in the implementation of an advanced, reliable, wide-range HHA on higher speed Naval platforms, such as MUSV or LCS. Work to identify commercial applications for Fast Support Vessels (FSVs) and ferries. In coordination with the Navy, conduct full-scale shipboard evaluations to validate effectiveness in a relevant environment to verify fuel savings are achieved. REFERENCES: 1. Jadmiko, Edi, et al. “Comparison of Stern Wedge and Stern Flap on Fast Monohull Vessel Resistance.” International Journal of Marine Engineering Innovation and Research, Vol. 3(2), Des. 2018, 041-049. 2. Seok, Woochan, et al. “An Experimental Study on the Stern Bottom Pressure Distribution of a High-Speed Planing Vessel with and without Interceptors.” International Journal of Naval Architecture and Ocean Engineering, 11 September 2020. KEYWORDS: Hull Appendage; Hull Resistance; Stern Flap; Stern Wedge; Interceptor; USV Fuel Saving
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