Dynamics of Stepped Planing Hulls and Hydrofoils in Waves FY2019-000248-AS
Abstract
ABSTRACT: The proposed research aims to create fundamental knowledge about the hydrodynamics ofstepped planning hulls with particular respect to their dynamic (unsteady) behavior in calm water(dynamic instabilities) and in waves. We will bridge the gap between high fidelity RANSEsimulations and reduced order models, based on empirical coefficient, for the prediction of theplanning crafts dynamic stability and motions in waves.Various steps configurations are nowadays used on high performance high speed planningcrafts, due to the proven drag reduction capabilities, but very little is known about their effect interms of motion damping and dynamic loads (due to motions in waves and slamming impacts).Contrary to this last example, most of stepped hull technologies lack of scientific evidence of theirclaimed advantages, and even more importantly their hydrodynamic working/design principles areunknown. Different steps configuration exist: transverse steps can be swept aft, forward or purelytransversal; longitudinal which can follow buttocks, waterlines, or oblique planes. Steps can besmall in height or deep as in the case of the sea blade (Navatek, 2019). The hull shape upstream ofthe step may be flat (in conventional planning hulls), cambered (as in the SCPH2 conceptintroduced by Brizzolara et al., 2018).The core of the proposed study consists in a coordinated and synergetic CFD/EFDinvestigation aimed to characterize the hydrodynamics of different types of steps configurationson planning hulls in calm water (dynamic stability) and in waves. Towing We will bridge the gapbetween high fidelity RANSE simulations and reduced order models, based on empiricalcoefficient, for the prediction of the planning crafts dynamic stability and motions in waves.The proposers have acquired a good experience in URANS and system identification inoccasion of the ONRT project and in other ONR projects (Hosseini et al., 2010, 2011 and Araki2012; Brizzolara, 2019, Li et al., 2019; Brizzolara & Federici, 2013, 2010) that may be of help toattack this problem, though the hydrodynamics is very different and URANSE method will likelyneed different spatial/temporal numerical schemes especially in conjunction with the violent natureof the flows and fragmentation of the free surface, characterized by wave breaking, jet sprays andslamming. URANSE models have been tested in few planing hulls and typically without steps.Accuracy of RANSE solvers for the prediction of stepped planing hulls motions in regular andirregular waves is still to be properly assessed. Currently, one of the preferred method to predictmotions in waves relies in highly approximate low-order models with concentrated parameterscalculated by semi-empirically methods. In fact, state of the art reduced order models, routinelyused by USN for design and analysis are very inaccurate as the unsteady hydrodynamicscoefficients are based on few and outdated experimental results and
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 29, 2020
- Source ID
- N000142012252
Entities
People
- Stefano Brizzolara
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech