Author: Elmo J. MottardPublisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 32
Book Description
Hydrodynamic Characteristics of a Planing Surface with Convex Longitudinal Curvature and an Angle of Dead Rise of 20 Degrees
Author: Elmo J. MottardPublisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 32
Book Description
Hydrodynamic Characteristics of a Planing Surface with Convex Longitudinal Curvature and an Angle of Dead Rise of 20 Degrees
Author: Elmo J. MottardPublisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 28
Book Description
High-speed Hydrodynamic Characteristics of a Flat Plate and 20 Degrees Dead-rise Surface in Unsymmetrical Planing Conditions
Author: Daniel SavitskyPublisher:
ISBN:
Category : Plates (Engineering)
Languages : en
Pages : 93
Book Description
The collected test data are presented in summary plots which are readily applicable for use in determining the lift, drag, side force, pitching moment, rolling moment, and yawing moment. An analysis is presented of the variation of these quantities with unsymmetrical planing parameters.
High-speed Hydrodynamic Characteristics of a Flat Plate and 20 O Dead-rise Surface in Unsymmetrical Planning Conditions
Author: daniel SavitskyModel Testing and Computational Analysis of a High Speed Planing Hull with Cambered Planing Surface and Surface Piercing Hydrofoils
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 158
Book Description
As part of a 2014 thesis, the MIT Innovative Ship Laboratory (iShip) designed a high-speed planing hull form that was based on the Model Variant 5631 developed at the US Navy's David Taylor Model Basin [7] [3] [5]. This model was a variant of the parent hull 5628. The 5631 variant was a model of the 47 foot Motor Lifeboat of the US Coast Guard, which was a hard chine, deep-vee vessel. Model 5631 had no step, with a 20 degree dead rise angle. The Clement method [4] was used in order to design a cambered planing surface that would generate dynamic lift and support most of the weight of the vessel. A second cambered step was designed using an in-house lifting surface program. The step was designed such that, at top speed, the entire hull aft of the step would be ventilated. To accommodate this effect, the aft underbody design departed from the conventional dead-rise. Directional stability of the model in the pre-planing regime was increased by incorporating three vertices at the design dead-rise angle. A set of super-cavitating, surface-piercing hydrofoils were designed to be attached aft of the vessel transom in order to provide support and prevent re-wetting of the afterbody. The constructed hydrofoils were positioned in a vee configuration, differing from the anhedral design in the Faison thesis. A support manual control system for the hydrofoils was designed as part of this thesis. Known as Model 5631D, this dynaplane model underwent a series of tests at the 380 foot towing tank at the United States Naval Academy in Annapolis, Maryland, over the course of several days. Several parameters were varied during the tests: the cambered step (via the wedge insert), the carriage speed, and the model longitudinal center of gravity (LCG). In this thesis, data from the series of tests of Model 5631D will be compared to that of the tests of Model 5631 by combining methods from Savitsky [15] and Faltinsen [8] for data scaling of planing vessels. Both models were scaled to the same static waterline length in order to determine the efficacy of the new design changes of Model 5631D in reducing total drag. Additionally, comparisons of the test data were made to computational fluid dynamics models conducted under the same conditions in the virtual environment. An introduction and motivation for the thesis is presented in Chapter 1. Half and full factorial statistical analysis was performed on the testing data and presented in Chapter 2, along with the results of data scaling and comparison of Hull 5631D's performance to the parent hull. Results of the CFD simulations along with calculation of model stability is presented in Chapter 3. Conclusions and opportunities for future work are given in Chapter 4. A full catalogue of the testing data is given in Appendix A.
Experimental Determination of the Added Inertia and Damping of a 30 Degree Deadrise Planing Boat in Roll
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 38
Book Description
This is the fourth of four reports on research designed to obtain basic hydrodynamic information about planing hulls through the use of captive models tests. The information is to be used for the general study of dynamic stability while underway, course keeping, turning and maneuvering, etc. The models tested were of idealized patrol boats having an LBP of 100 ft., a beam of 20 ft., and a displacement of 100 long tons. The models had prismatic hull forms with 10, 20, and 30 degrees of deadrise. The report presents the results of free oscillation tests on an unappended prismatic hull with 30 degrees of deadrise. The tests were conducted at a beam loading coefficient of 0.4375, at three speeds Cv = 1.5, 3.0, and 4.0, three trim angles 0, 3, AND 6 DEGREES, and at yaw angles of 0,10, and 15 degrees. Roll extinction records were taken with four different spring stiffnesses, first at rest in air and then underway in water, at each test condition. The roll period and logarithmic decrement were determined from these records and tabulated. The added mass moment of inertia and damping in roll were deduced from these data assuming a linear damped harmonic oscillator. Empirical expressions for the inertia and damping are presented and compared with the data. These expressions are used to predict the rolling characteristics of a prototype 100 ft. boat.
Hydrodynamics of High Speed Planing Hulls with Partially Ventilated Bottom and Hydrofoils
Author: Zvi SheingartPublisher:
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.
Design of a High Speed Planing Hull with a Cambered Step and Surface Piercing Hydrofoils
Author: Leon Alexander FaisonPublisher:
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.
Experimental Determination of the Added Inertia and Damping of a 30 Degree Deadrise Planing Boat in Roll
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 38
Book Description
This is the fourth of four reports on research designed to obtain basic hydrodynamic information about planing hulls through the use of captive models tests. The information is to be used for the general study of dynamic stability while underway, course keeping, turning and maneuvering, etc. The models tested were of idealized patrol boats having an LBP of 100 ft., a beam of 20 ft., and a displacement of 100 long tons. The models had prismatic hull forms with 10, 20, and 30 degrees of deadrise. The report presents the results of free oscillation tests on an unappended prismatic hull with 30 degrees of deadrise. The tests were conducted at a beam loading coefficient of 0.4375, at three speeds Cv = 1.5, 3.0, and 4.0, three trim angles 0, 3, AND 6 DEGREES, and at yaw angles of 0,10, and 15 degrees. Roll extinction records were taken with four different spring stiffnesses, first at rest in air and then underway in water, at each test condition. The roll period and logarithmic decrement were determined from these records and tabulated. The added mass moment of inertia and damping in roll were deduced from these data assuming a linear damped harmonic oscillator. Empirical expressions for the inertia and damping are presented and compared with the data. These expressions are used to predict the rolling characteristics of a prototype 100 ft. boat.
Directional Stability Tests of a 30 Degree Deadrise Prismatic Planing Hull
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 216
Book Description
This is the second of four reports on research designed to obtain basic hydrodynamic information about planing hulls through the use of captive model tests. The information is to be used for the general study of dynamic stability while underway, course keeping, turning and maneuvering, etc. The models tested were of idealized patrol boats having an LBP of 100 ft., a beam of 20 ft., and a displacement of 100 long tons. The models had prismatic hull forms with 10, 20, and 30 degrees of deadrise. The report presents the results of tests on the 30 degree of deadrise hull. Most of the data is for the unappended hull. Straight course and rotating arm tests were conducted at three speeds Cv = 1.5, 3.0, and 4.01, three angular velocities LIR = 0, 0.117, and 0.234 and a single beam loading Cv = 0.4375. The tests covered the following angular parameter ranges. Trim: -2 to 6 degrees, roll: -10 to 20 degrees, and yaw: -15 to 15 degrees. Twin rudders were fined during the straight course tests at zero degrees of roll and yaw, and three degrees of trim. The effect of rudder deflection from -20 to 20 degrees was investigated. Measurements were made of the drag and side forces, and the roll, pitch, and yaw moments. Draft was recorded. Underwater photographs were taken, and the wetted lengths and areas determined from these photographs. Video recordings were made of all runs. The data are presented in extensive tables, in wind axes and body axes, and in both dimentional and non-dimensional form.