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Author: Zvi Sheingart Publisher: ISBN: Category : Languages : en Pages : 94
Book Description
The influence of a cambered shaped bottom step on the performance of sea going V-stepped planing hulls is investigated using numerical methods. The shape of the step was designed to decrease the Drag/Lift ratio of the hull in full planing regime (Fr[delta sign turned upside down] = 6 ). A numerical method, complementary to the existing empirical method developed by Clement for design of a cambered step has been developed. The numerical approach described in this thesis extends the empirical Clement's method for stepped hull design to hard chine hulls with higher deadrise. The stem trim stabilizer has been replaced by supercavitating hydrofoils. Several foil/step configurations were numerically tested. RANSE code is used to evaluate the performance of new hull design with a stepped bottom. Prototypes of the hull have been modeled in 3D using Rhino, NURBS surface modeler. Two validation cases have been considered to validate the RANSE models used for the numerical prediction of hydrodynamic characteristics: Geritsma's 25° deadrise hull series and original Clement's 12.5° deadrise hull (DTMB Model 5115). Numerical results showed good agreement with experimental data, except for the pre-planing regime, where an influence of the towing rig on the CG rise was not negligible. The baseline for the design of the hybrid stepped hull chosen to be Geritsma's 25° hull with length to maximum beam ratio of 4.09. The thesis confirms the applicability of Clement's method on deep-V seagoing hulls. Total reduction of 3% in Drag/Lift ratio has been achieved, but can be further reduced. All the RANSE calculations were performed using Star-CCM+® software package on the 400 cores HPC cluster of MIT i-Ship lab.
Author: Zvi Sheingart Publisher: ISBN: Category : Languages : en Pages : 94
Book Description
The influence of a cambered shaped bottom step on the performance of sea going V-stepped planing hulls is investigated using numerical methods. The shape of the step was designed to decrease the Drag/Lift ratio of the hull in full planing regime (Fr[delta sign turned upside down] = 6 ). A numerical method, complementary to the existing empirical method developed by Clement for design of a cambered step has been developed. The numerical approach described in this thesis extends the empirical Clement's method for stepped hull design to hard chine hulls with higher deadrise. The stem trim stabilizer has been replaced by supercavitating hydrofoils. Several foil/step configurations were numerically tested. RANSE code is used to evaluate the performance of new hull design with a stepped bottom. Prototypes of the hull have been modeled in 3D using Rhino, NURBS surface modeler. Two validation cases have been considered to validate the RANSE models used for the numerical prediction of hydrodynamic characteristics: Geritsma's 25° deadrise hull series and original Clement's 12.5° deadrise hull (DTMB Model 5115). Numerical results showed good agreement with experimental data, except for the pre-planing regime, where an influence of the towing rig on the CG rise was not negligible. The baseline for the design of the hybrid stepped hull chosen to be Geritsma's 25° hull with length to maximum beam ratio of 4.09. The thesis confirms the applicability of Clement's method on deep-V seagoing hulls. Total reduction of 3% in Drag/Lift ratio has been achieved, but can be further reduced. All the RANSE calculations were performed using Star-CCM+® software package on the 400 cores HPC cluster of MIT i-Ship lab.
Author: Miles Patrick Wheeler Publisher: ISBN: Category : Hydrofoils Languages : en Pages : 139
Book Description
This dissertation is focused on heavily loaded planing hulls and high-lift hydrofoils operating in moderate Froude-number regimes, which are important for a variety of military and civil marine applications. The research described here entails high-fidelity computational fluid dynamics simulations of flows around prismatic planing hulls and surface-piercing hydrofoils. The physical models involved in numerical simulations include viscous, multi-phase, turbulent, and unsteady phenomena. Verification and validation studies for all considered problems have been conducted, followed by parametric studies of selected hull and hydrofoil configurations.The planing-hull investigation analyzed constant-deadrise hulls with various bow shapes. Both normal and heavily loaded conditions were considered in broad speed regimes from the displacement to planing mode and two characteristic locations of the center of gravity. The hull with a concave bow was found to perform best, as it had lower drag at transitional speeds in the overloaded state and lower drag at fastest speeds at normal loading.The high-lift flexible hydrofoils having isotropic and orthotropic material properties, which imitate composite structures, were numerically modeled in calm water and in head waves. To investigate fluid-structure interactions associated with flexible hydrofoils, numerical solutions were obtained using coupled fluid and solid solvers, as well as morphing and overset meshing methodology. Effects of materials properties on hydrodynamic characteristics and structural deformations of hydrofoils were determined. Specifically, orthotropic hydrofoils with fibers directed from the fixed root to the leading edge exhibited negative twist, lower lift coefficients in calm water and lower lift oscillations in waves. Hydrofoils with fibers oriented towards the railing edge manifested higher twist and lift forces in calm water, and larger oscillations in wave conditions.Additional studies of high-lift surface-piercing hydrofoils subjected to ventilation by atmospheric air were conducted. The air ventilation usually results in substantial decrease of the lift force. To counteract this process, an application of small fences on the foil surface was numerically investigated. It was found that these elements can suppress air ventilation, thus increasing lifting capabilities and improving lift-drag ratio of hydrofoils at moderate Froude numbers.
Author: Odd M. Faltinsen Publisher: Cambridge University Press ISBN: 1139447939 Category : Technology & Engineering Languages : en Pages : 490
Book Description
Hydrodynamics of High-Speed Marine Vehicles, first published in 2006, discusses the three main categories of high-speed marine vehicles - vessels supported by submerged hulls, air cushions or foils. The wave environment, resistance, propulsion, seakeeping, sea loads and manoeuvring are extensively covered based on rational and simplified methods. Links to automatic control and structural mechanics are emphasized. A detailed description of waterjet propulsion is given and the effect of water depth on wash, resistance, sinkage and trim is discussed. Chapter topics include resistance and wash; slamming; air cushion-supported vessels, including a detailed discussion of wave-excited resonant oscillations in air cushion; and hydrofoil vessels. The book contains numerous illustrations, examples and exercises.
Author: Leon Alexander Faison Publisher: ISBN: Category : Languages : en Pages : 82
Book Description
Design of a high speed planing hull is analyzed by implementing a cambered step and stem, surface piercing hydrofoils, commonly known as a Dynaplane hull. This configuration combines the drag reduction benefits of a stepped hull with a fully ventilated after body by using a stem stabilizer. The largest obstacle with this design is maintaining trim control and stability at high speeds. There has been limited research on the Dynaplane design since Eugene Clement first conducted tow tank tests in the David Taylor Model Basin (DTMB) in the 1960s. Modem experimental methods such as computational fluid dynamics (CFD) allow the designer to run multiple simulations at once while testing a variety of parametric variables. The analysis will combine theoretical, empirical, and computational methods to determine the hydrodynamic characteristics of the design and develop a new Dynaplane configuration that allows for speeds in excess of 50 knots. The design approach begins with using a reference hull named Model 5631 from a small systematic series of resistance tests at the DTMB. This modeled hull is based on the U.S. Coast Guard 47 ft Motor Lifeboat which is a hard chine, deep V planing hull. Clement's Dynaplane design process was followed with exception of the stem stabilizer recommendation. Instead, a surface piercing super cavitating (SPSC) hydrofoil designed by Dr. Stefano Brizzolara was used. These designs further improve upon the powering requirements of a conventional planing hull by effectively increasing the lift to drag ratio. A commercially available CFD software program called Star-CCM+ is used for the computational portion. The computational model is first validated using results from the Model 5631 tow tank tests. Three series of CFD tests were then conducted on the new Dynaplane design; which include developing wake geometry predictions for a swept back stepped hull, and then varying the trim angle and longitudinal center of gravity. These tests were run at an FnV=5 in a calm sea state. Results from the analysis demonstrate the benefits of a fully ventilated afterbody using the SPSC hydrofoils and predict the hydrodynamic behavior for the new design. Also, the results extend the range of application of Clement's Dynaplane design to hulls with 20 degree deadrise. This thesis gives naval architects design guidance for such a hullform and demonstrates the potential of CFD as a tool for analyzing these parametric variables.
Author: Volker Bertram Publisher: Elsevier ISBN: 0080971504 Category : Science Languages : en Pages : 392
Book Description
Practical Ship Hydrodynamics provides a comprehensive overview of hydrodynamic experimental and numerical methods for ship resistance and propulsion, maneuvering, seakeeping and vibration. Beginning with an overview of problems and approaches, including the basics of modeling and full scale testing, expert author Volker Bertram introduces the marine applications of computational fluid dynamics and boundary element methods. Expanded and updated, this new edition includes: Otherwise disparate information on the factors affecting ship hydrodynamics, combined to provide one practical, go-to resource. Full coverage of new developments in computational methods and model testing techniques relating to marine design and development. New chapters on hydrodynamic aspects of ship vibrations and hydrodynamic options for fuel efficiency, and increased coverage of simple design estimates of hydrodynamic quantities such as resistance and wake fraction. With a strong focus on essential background for real-life modeling, this book is an ideal reference for practicing naval architects and graduate students.
Author: Liang Yun Publisher: Springer Science & Business Media ISBN: 1461408695 Category : Technology & Engineering Languages : en Pages : 379
Book Description
High Performance Marine Vessels (HPMVs) range from the Fast Ferries to the latest high speed Navy Craft, including competition power boats and hydroplanes, hydrofoils, hovercraft, catamarans and other multi-hull craft. High Performance Marine Vessels covers the main concepts of HPMVs and discusses historical background, design features, services that have been successful and not so successful, and some sample data of the range of HPMVs to date. Included is a comparison of all HPMVs craft and the differences between them and descriptions of performance (hydrodynamics and aerodynamics). Readers will find a comprehensive overview of the design, development and building of HPMVs.
Author: National Research Council Publisher: National Academies Press ISBN: 0309065372 Category : Science Languages : en Pages : 1039
Book Description
The Twenty-Second Symposium on Naval Hydrodynamics was held in Washington, D.C., from August 9-14, 1998. It coincided with the 100th anniversary of the David Taylor Model Basin. This international symposium was organized jointly by the Office of Naval Research (Mechanics and Energy Conversion S&T Division), the National Research Council (Naval Studies Board), and the Naval Surface Warfare Center, Carderock Division (David Taylor Model Basin). This biennial symposium promotes the technical exchange of naval research developments of common interest to all the countries of the world. The forum encourages both formal and informal discussion of the presented papers, and the occasion provides an opportunity for direct communication between international peers.
Author: John Carlton Publisher: Butterworth-Heinemann ISBN: 0080971237 Category : Technology & Engineering Languages : en Pages : 539
Book Description
The early development of the screw propeller. Propeller geometry. The propeller environment. The ship wake field, propeller performance characteristics.
Author: Zvi Sheingart
Author: Zvi Sheingart
Author: Miles Patrick Wheeler
Author: Odd M. Faltinsen
Author: Leon Alexander Faison
Author: Volker Bertram
Author: 
Author: Liang Yun
Author: Harold Eugene Saunders
Author: National Research Council
Author: John Carlton