Hull - Appendage Interaction of a Sailing Yacht, Investigated with Wave Cut Techniques

1997 ◽  
Author(s):  
Jonathan R. Binns ◽  
Kim Klaka ◽  
Andrew Dovell
Keyword(s):  
Approximate Method ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Full Scale ◽  
Research Centre ◽  
Cooperative Research ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht

The research explained in this paper was carried out to investigate the effects of hull-appendage interaction on the resistance of a sailing yacht, and the effects these changes have on the velocity prediction for a sailing yacht. To accomplish this aim a series of wave-cut experiments was carried out and analysed using a modified procedure. The processed results have then been incorporated into an existing velocity prediction program. For the purposes of this research two variables were investigated for the Australian Maritime Engineering Cooperative Research Centre (AMECRC) parent model 004, a model derived from the Delft IMS series of yachts. Wave-cut procedures inevitably raise questions about scaling procedures for full scale extrapolation as the inviscid wave-pattern resistance is calculated to be less than the residuary or wave resistance. These questions have been dealt with by an approximate method, briefly explained in this paper.

Toward Numerical VPP with the Full Coupling of Aerodynamic and Hydrodynamic Solvers for ACC Yachts

2005 ◽  
Author(s):  
Erwan Jacquin ◽  
Yann Roux ◽  
Bertrand Allessandrini
Keyword(s):  
Degrees Of Freedom ◽  
Computational Method ◽  
Motion Equations ◽  
Towing Tank ◽  
Six Degrees Of Freedom ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Full Coupling ◽  
Classical Interpolation

The classical approach of Velocity Prediction Program is to find the balance of Hydrodynamic and aerodynamic sensors acting on the yacht to determine sailing conditions and associated performance. Usually, this approach is based on the data given by towing tank, wind tunnel or numerical computations. We present in this paper the unsteady coupling between an hydrodynamic RANSE with free surface solver and a panel aerodynamic solver that allow to directly find the sailing condition of the yacht, and its performances, compute bay solving the six degrees of freedom motion equations of the ship in the hydrodynamic solver. The main advantage of this computational method is the decrease of numerical evaluation, compared to the classical interpolation approach to determine performances of a hull, and to directly rank several hills in the term of performances and not only in the term of drag in fixed conditions. Further, improvements will allow to simulate unsteady maneuvering of sailing yacht, and focus will for example on restart behavior after tacking, dynamic behavior in waves.

Enhanced Wind Tunnel and Full-Scale Sail Force Comparison

2007 ◽  
Author(s):  
Heikki Hansen ◽  
Peter J. Richards ◽  
Peter S. Jackson
Keyword(s):  
Wind Tunnel ◽  
Quantitative Agreement ◽  
Full Scale ◽  
Force Balance ◽  
Testing Procedures ◽  
Prediction Program ◽  
Surface Pressure Distribution ◽  
Velocity Prediction ◽  
The University ◽  
Scale Data

This paper presents a comparison between wind tunnel and full-scale aerodynamic sail force measurements using enhanced wind tunnel testing techniques to model the full-scale sailing conditions more accurately. The first comparison was conducted by Hansen et al., 2003a, in the Twisted Flow Wind Tunnel (TFWT) at The University of Auckland and followed standard testing procedures. Since then enhancements have been made and two aspects not considered in the original comparison are highlighted here. The interaction of the hull and sail forces is now considered and trim changes of the sails due to wind strength are included. For the enhanced comparison the interaction between the hull/deck and the sails is investigated by installing a secondary force balance inside the model to measure the hull/deck forces and by pressure tapping the hull/deck to determine the surface pressure distribution. It is found that the presence of the sails significantly affects the forces on hull/deck when sailing upwind, which should be accounted for consistently in comparisons of full-scale, wind tunnel, and computational fluid dynamics (CFD) data. In the original comparison the sails were trimmed in the wind tunnel to the aerodynamically optimal shape by maximizing the drive force. Trim variations due to wind strength were however noted in full-scale data so that depowering is considered in the enhanced comparison. The sails in the wind tunnel were trimmed based on the fullscale wind strength and the yacht performance by employing a Real-Time Velocity Prediction Program (VPP) to achieve realistically depowered sail shapes. Utilising the enhanced wind tunnel techniques a generally good qualitative and quantitative agreement with the full-scale data was achieved, but a conclusive judgment of the accuracy of the comparison cannot be made.

scholarly journals A Performance Depowering Investigation for Wind Powered Cargo Ships Along a Route

2020 ◽  
Vol 5 (01) ◽  
pp. 47-60
Author(s):  
Fredrik Olsson ◽  
Laura Giovannetti ◽  
Sofia Werner ◽  
Christian Finnsgård
Keyword(s):  
Degrees Of Freedom ◽  
Structural Integrity ◽  
Prediction Program ◽  
Force Magnitude ◽  
Speed Performance ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
The Impact ◽  
Ship Speed ◽  
A Performance

Abstract. For a sailing yacht, depowering is a set of strategies used to limit the sail force magnitude by intentionally moving away from the point of maximum forward driving force, potentially reducing the ship speed. The reasons for doing this includes among others; reduction of quasi-static heeling angle, structural integrity of masts and sails and crew comfort. For a wind powered cargo ship, time spent on a route is of utmost importance. This leads to the question whether there is a performance difference between different depowering strategies and if so, how large. In this research, a wind-powered cargo vessel with rigid wings is described in a Velocity Prediction Program (VPP) with four-degrees of freedom, namely surge, sway, roll and yaw, with a maximum heel angle constraint. The resulting ship speed performance for different depowering strategies are investigated and the implications in roll and pitch-moments are discussed. The wind conditions when depowering is needed are identified. A statistical analysis on the probability of occurrence of these conditions and the impact of the different depowering strategies on the required number of days for a round-trip on a Transatlantic route is performed.

RVPP: Sailing Yacht Performance Prediction fully integrated into a RANSE based flow code

2011 ◽  
Author(s):  
Christoph Böhm ◽  
Kai Graf
Keyword(s):  
Equations Of Motion ◽  
Flow Simulation ◽  
Body Motion ◽  
Fully Integrated ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Ranse Solver ◽  
Hydrodynamic Data ◽  
Physical Phenomena

One of the most important tools in today’s sailing yacht design is the Velocity Prediction Program (VPP). VPPs calculate boat speed from the equilibrium of aero and hydrodynamic flow forces. Consequently their accuracy is linked to the accuracy of the aero- and hydrodynamic data used to represent a yacht. These data are usually derived from experimental or CFD results and processed by means of linearization and interpolation to represents the actual sailing state of the yacht, this interpolation being a source of inaccuracy. Furthermore, viscosity related effects are often estimated by simplified theoretical or empirical models potentially neglecting complex physical phenomena. The paper proposes a method circumventing these inaccuracies. It is based on the idea to directly derive Sailing Yacht performance from a RANSE flow simulation. This is done by coupling the prediction of sail forces with the hydrodynamic forces calculated by the flow code and solving the resulting imbalance in the equations of motion in the RANSE solver. The paper discusses implementation steps for the inclusion of sail forces and body motion into the flow code as well as calculation and grid setup. Results of the method christened RVPP are shown for a generic yacht design and are compared with results from a classical VPP approach on the same design. The paper finishes with a discussion of the pros and cons of the method and an overview at future development steps of RVPP.

Approximation of the Calm Water Resistance on a Sailing Yacht Based on the 'Delft Systematic Yacht Hull Series'

1999 ◽  
Author(s):  
J. A. Kenning ◽  
U. B. Sonnenberg
Keyword(s):  
Water Resistance ◽  
Force Production ◽  
Data Set ◽  
Side Force ◽  
Prediction Program ◽  
Resistance Increase ◽  
The Past ◽  
Calm Water ◽  
Velocity Prediction ◽  
Sailing Yacht

Over the past years a considerable extension has been given to the Delft Systematic Yacht Hull Series (DSYHS) The DSYHS data set now contains information about both the bare hull and appended hull resistance in the upright and the heeled condition, the resistance increase due to the longitudinal trimming moment of the sails, the side force production and induced resistance due to side force at various combinations of forward speeds, leeway angles and heeling angles. New formulations for the relevant hydrodynamic forces as function of the hull geometry parameters have been derived to be able to deal with a larger variety of yacht hull shapes and appendage designs. During the past two years some results of this research have already been published. In the present paper an almost complete picture of the relevant expressions which may be used in a Velocity Prediction Program (VPP) will be presented.

Guides to the Approximation of Sailing Yacht Performance

1989 ◽  
Author(s):  
Olin J. Stephens
Keyword(s):  
Simple Form ◽  
Input Data ◽  
Full Range ◽  
Stability Estimates ◽  
Prediction Program ◽  
Design Program ◽  
Velocity Prediction ◽  
Minimal Data ◽  
Sailing Yacht ◽  
Limited Input Data

Two computer programs are presented for use, either singly or in sequence. The first will derive, from minimal data, a consistent set of parameters which, entered into the second, a velocity prediction program (VPP), will predict a sailing yacht's speed and course over a full range of wind strength and direction. Due to the limited input data as well as to the simple form of the VPP, approximate results must be accepted. The design program combines guidance with flexibility so that reasonably accurate and consistent dimensions, largely empirically derived, including weight and stability estimates, are quickly produced and tested, by the VPP, for performance.

The Nippon Challenge America's Cup 1992 - Progress in Hull Development

1993 ◽  
Author(s):  
Yoshihiro Nagami
Keyword(s):  
Full Scale ◽  
Wind Tunnel Testing ◽  
Design Development ◽  
Prediction Program ◽  
New Class ◽  
Simulation Techniques ◽  
Final Design ◽  
Velocity Prediction ◽  
America’S Cup ◽  
Fine Tune

In 1992, the class rule for the America's Cup was changed to the IACC. The Nippon Challenge decided that in order to build a successful challenger to a new class rule, the design would have to rely heavily on the results of a systematic series of tank and wind tunnel testing. The results of these simulations would then be used to build full scale boats which would be tested. The results of the full scale trials would be used to adjust the simulation techniques to fine tune the final design. The data from the model tests were used to develop the input parameters for a Velocity Prediction Program (VPP). The VPP was used to determine the specifications for the design of the first two boats. After full scale testing, the VPP was compared to the results for about 6 months. After this verification and refinement of the VPP, a final boat was built. Finally the results of the race were evaluated and confirm that the basic design development process was correct.

Improvement of Sailing Yacht Performance Prediction by Including Force-Moment Equilibrium for the Calculation of Helm Angle in a Velocity Prediction Program

1995 ◽  
Author(s):  
Peter van Oossanen
Keyword(s):  
Mathematical Model ◽  
Performance Prediction ◽  
Model Tests ◽  
Side Force ◽  
Prediction Program ◽  
Moment Equilibrium ◽  
Force Moment ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Rudder Angle

Contemporary Velocity Prediction Programs (VPP's) consider the equilibrium of forces acting on a sailing yacht in the thrust direction and in the direction of the developed side force on canoe body and appendages. In addition, force-moment equilibrium is considered in the transverse plane of the yacht. In this way a solution is found for the three main unknowns in performance prediction, viz: boat speed, leeway angle and heel angle. The impact of helm angle on performance is herein ignored. In the velocity prediction program developed by Van Oossanen & Associates, a fourth equilibrium condition is included, viz: force-moment equilibrium in the horizontal plane for the calculation of the helm angle required for the equilibrium sailing condition. In this paper a description is given of some of the main problems that need to be solved when introducing this fourth equilibrium requirement. One of these is associated with the development of accurate mathematical expressions for the calculation of rudder side force and resistance, as influenced by heel angle and the proximity of the free surface. Model tests can be utilized for obtaining insight into the physical phenomena involved in such cases. Model tests were carried out in the context of an optimization study for the design of a yacht according to the International Level Class 40 (ILC40) Rule, under the International Measurement System (IMS). The analysis of some of the results of these tests with respect to improving the mathematical model for rudder side force and resistance, is described in the paper. The effect of including this mathematical model in a VPP is demonstrated in the paper by providing the results of calculations which reveal that a variation in rudder angle causes significant speed differences. It is shown that the IMS VPP that is used to calculate the rating and speed potential of ILC40 and other IMS Class yachts, in not taking into account the significant variations in performance associated with different values of the equilibrium rudder angle (and the associated rudder side force and resistance), is not sufficiently accurate.

A Velocity Prediction Program for a Planning Dinghy

2005 ◽  
Author(s):  
Todd Carrico
Keyword(s):  
Hydrodynamic Resistance ◽  
Side Force ◽  
Prediction Program ◽  
Fundamental Goal ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Series Of Experiments ◽  
College Of Engineering ◽  
The University ◽  
Visual Basic 6.0

This paper summarizes the author’s graduate thesis in Naval Architecture accepted by the University of New Orleans, College of Engineering. The author sought to investigate the complicated interactions between the hydrodynamics and aerodynamics of a sailboat. The type of sailboat investigated was the Olympic dinghy class called the Laser. It was the author’s understanding that at that time, no work has been completed in the area of velocity prediction for this type of sailboat. Thus, the fundamental goal of this thesis was to develop a velocity prediction program specific to the Laser. In order to accomplish the goal of creating a velocity prediction program, multiple essential pieces of the data were needed. In particular, the hydrodynamic resistance data, aerodynamic drive and side force data, and hydrodynamic side forces were needed. To determine the dynamic trim of the dinghy, a series of experiments were conducted. In addition, a data acquisition system was developed in which full scale tow testing could be done. Next, a complete tow test series was conducted for the Laser. The aerodynamic sail coefficients were derived from Marchaj’s Aero-Hydrodynamics of Sailing. To determine the hydrodynamic side force, a two dimensional approach was employed. The coding of the velocity prediction program was done using Microsoft’s Visual Basic 6.0 and Excel 2000. The algorithms published in the 15th Chesapeake Sailing Yacht Symposium and Principles of Yacht Design pertaining to velocity prediction were used as a baseline. Finally, validation and verification was performed with the shareware program PCSAIL.

The Effects of Streamlined Rigging on Sailboat Performance

2011 ◽  
Author(s):  
Bruce J. Martin ◽  
Grzegorz P. Filip ◽  
Kevin J. Maki ◽  
Robert F. Beck ◽  
Eric Hall
Keyword(s):  
Cross Section ◽  
Circular Section ◽  
Prediction Program ◽  
The Past ◽  
Performance Change ◽  
Physical Experiments ◽  
Vortex Induced Vibrations ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Time Required

The design of sailboat rigging influences the yacht’s performance through the change in vertical center of gravity, windage, and ability to control the shape of the rig. In the past, designers have attempted to minimize this drag through the use of streamlined shapes, because it is well known that a streamlined section has much less drag with respect to a circular shape. Streamlined shapes have not been commonly used in practice probably because they are difficult and costly to manufacture. Also, some shapes may exhibit worse vortex induced vibrations (VIV) when compared to circular rigging. New manufacturing capabilities using composite materials have suggested that streamlined shapes be reconsidered for yacht standing rigging. This paper investigates the influence of two cross-section shapes of the rigging on the performance of an IMS40 sailing yacht. A modified NACA foil and a circular section are selected for the comparison, and both shapes are analyzed with numerical simulations and physical experiments. We study the change in sailboat performance due to the different aerodynamic and material properties of the rigging. A velocity prediction program (VPP) is used to quantify the performance change by comparing the time required to sail two different race courses.

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