Upwind Sail Performance Prediction for a VPP including “Flying Shape” Analysis

2009 ◽  
Author(s):  
Brian Maskew ◽  
Frank DeBord
Keyword(s):  
Grid Point ◽  
Flow Simulation ◽  
Lattice Method ◽  
Prediction Program ◽  
Aerodynamic Pressure ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
Coupled Structures ◽  
And Performance ◽  
Ultimate Objective

A coupled aerodynamic/structures approach is presented for predicting the flying shape and performance of yacht sails in upwind conditions. The method is incorporated in a flow simulation computer program, and is part of an ultimate objective for a simultaneous aeroelastic/hydro analysis in a Dynamic Velocity Prediction Program (DVPP), that will include a 6DOF motion solver, and at some point could include calculations in waves. The time-stepping aerodynamic module uses an advanced vortex lattice method for the sails and a panel method with special base separation treatment to represent the abovewater part of the hull and mast. A coupled inverse boundary layer analysis is applied on all surfaces including both sides of each sail membrane; this computes the skinfriction drag and the source displacement effects of the boundary layers and wakes, including bubble and leeside “trailing-edge” type separations. . At each step, the computed aerodynamic pressure and skin-friction loads are transferred to a coupled structures module that uses a network grid of tension “cords” in each sail membrane, each cord representing a collection of fiber “strings”. The solution of a structural equilibrium matrix provides the displacements needed to achieve balance between the aerodynamic and tension loads at each grid point as the shape iterations proceed. Details of the methodology used are presented and comparisons of predicted aerodynamic forces to wind tunnel results and an existing VPP sail model are provided. In addition, predictions are compared to some simple experiments to demonstrate the aerodynamic/structural coupling necessary to predict flying shape. Finally, an outline is given for incorporation of this methodology into the planned Dynamic Velocity Prediction Program.

scholarly journals High Froude Number Experimental Investigation of the 2 DOF Behavior of a Multihull Float in Head Waves

2021 ◽  
Vol 6 (01) ◽  
pp. 1-20
Author(s):  
Paul Kerdraon ◽  
Boris Horel ◽  
Patrick Bot ◽  
Adrien Letourneur ◽  
David David Le Touzé
Keyword(s):  
High Performance ◽  
Good Representation ◽  
Prediction Program ◽  
Modeling Approach ◽  
Head Waves ◽  
Wide Range ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
High Froude Number ◽  
Stability Issues

Dynamic Velocity Prediction Programs are taking an increasingly prominent role in high performance yacht design, as they allow to deal with seakeeping abilities and stability issues. Their validation is however often neglected for lack of time and data. This paper presents an experimental campaign carried out in the towing tank of the Ecole Centrale de Nantes, France, to validate the hull modeling in use in a previously presented Dynamic Velocity Prediction Program. Even though with foils, hulls are less frequently immersed, a reliable hull modeling is necessary to properly simulate the critical transient phases such as touchdowns and takeoffs. The model is a multihull float with a waterline length of 2.5 m. Measurements were made in head waves in both captive and semi-captive conditions (free to heave and pitch), with the model towed at constant yaw and speed. To get as close as possible to real sailing conditions, experiments were made at both zero and non-zero leeway angles, sweeping a wide range of speed values, with Froude numbers up to 1.2. Both linear and nonlinear wave conditions were studied in order to test the limits of the modeling approach, with wave steepness reaching up to 7% in captive conditions and 3.5% in semi-captive ones. The paper presents the design and methodology of the experiments, as well as comparisons of measured loads and motions with simulations. Loads are shown to be consistent, with a good representation of the sustained non-linearities. Pitch and heave motions depict an encouraging correlation which confirms that the modeling approach is valid.

scholarly journals The Influence of Sailor Position and Motion on the Performance Prediction of Racing Dinghies

2016 ◽  
Author(s):  
Joshua C. Taylor ◽  
Joseph Banks ◽  
Stephen R. Turnock
Keyword(s):  
Water System ◽  
Body Representation ◽  
Video Camera ◽  
Main Body ◽  
Motion Sensors ◽  
Prediction Program ◽  
Initial Stage ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
Race Performance

The time-varying influence of a sailor’s position is typically neglected in dinghy velocity prediction programs. When applied to the assessment of dinghy race performance the position and motions of the crew become significant but are practically hard to measure as they interact with the motions of the sailboat. As the initial stage in developing a time accurate dinghy velocity prediction program this work develops an on-water system capably of measuring the applied hiking moment due to the sailor’s pose and compares this with the resultant dinghy motion. The sailor’s kinematics are captured using a network of inertial motion sensors (IMS) synchronized to a video camera and dinghy motion sensor. The hiking moment is evaluated using a ‘stick man’ body representation with the mass and inertial terms associated with the main body segments appropriately scaled for the representative sailor. The accuracy of the pose capture is validated using laboratory based pose measurements. The completed work will provide a platform to model how sailor generated forces interact with the sailboat to affect boat speed. This will be used alongside realistic modelling of the wind and wave loadings to extend an existing time-domain dynamic velocity prediction program (DVPP). The results are demonstrated using a single handed Laser and demonstrate an acceptable level of accuracy.

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.

Sailboat Hydrodynamic Drag Source Prediction and Performance Assessment

1991 ◽  
Author(s):  
Charles W. Boppe
Keyword(s):  
Flow Simulation ◽  
Surface Friction ◽  
Approximate Model ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Drag ◽  
Important Place ◽  
Drag Forces ◽  
Induced Drag ◽  
Velocity Prediction ◽  
And Performance

Velocity Prediction Programs used for sailboat hull, sail, and keel sizing trades, have found an important place in the designer's toolbox. Sail designers now recognize the benefits of applying aerodynamic panel methods. In addition, the 1983 and 1987 America's Cup competitions have drawn attention to use of computerized flow simulation methods for improving hydrodynamic performance. This paper highlights characteristics of methods capable of predicting sailboat hydrodynamic drag forces. Taken together the resistance components predicted include appendage surface friction drag, configuration and lift-induced drag, and configuration trim drag. All of the computer programs discussed in this paper were originally developed for aircraft aerodynamic applications. Since each method is based on some approximate model of real world flow physics, the need to establish a simulation experience base is emphasized and illustrated. VPP polar diagrams are used to link drag source benefits and penalties to sailboat performance. Micro-computer execution times are provided because the methods described operate in machines commonly found in the naval architect’s office.

scholarly journals Development of a 6-DOF Dynamic Velocity Prediction Program for offshore racing yachts

2020 ◽  
Vol 212 ◽  
pp. 107668
Author(s):  
Paul Kerdraon ◽  
Boris Horel ◽  
Patrick Bot ◽  
Adrien Letourneur ◽  
David Le Touzé
Keyword(s):  
Prediction Program ◽  
Dynamic Velocity ◽  
Velocity Prediction

The Application of VPPs to Practical Sailing Problems

1987 ◽  
Author(s):  
Kart L. Kirkman
Keyword(s):  
Prediction Program ◽  
Widespread Acceptance ◽  
Velocity Prediction ◽  
Do So

The velocity prediction program, VPP, appeared on the yachting scene about ten years ago and it now dominates design and sailing. Originally implemented as a handicapping tool under the Measurement Handicap System, now accepted internationally as IMS, it has seen widespread acceptance for many other uses, from design to tuning and racing. This capability means that it is productive, even necessary, for the typical sailor interested in good performance to understand how to apply a VPP to his activities. To do so requires an appreciation of how a VPP functions and how it is applied to practical sailing problems, such as sail selection or tactics. The paper presents a review of VPP fundamentals and then treats the following applications: - Sail selection and strategy for offshore yachts. - Tuning and optimization of all boats. It is the goal of the paper to impart a working understand­ing of the VPP to many sailors so that they can take advantage of the technology in their normal activities.

Added Resistance in Seaways and its Impact on Yacht Performance

2007 ◽  
Author(s):  
Kai Graf ◽  
Marcus Pelz ◽  
Volker Bertram ◽  
H. Söding
Keyword(s):  
Strong Impact ◽  
Wave Spectra ◽  
Linear Extensions ◽  
Added Resistance ◽  
Optimum Length ◽  
Prediction Program ◽  
Strip Theory ◽  
Velocity Prediction ◽  
Added Resistance In Waves ◽  
Response Amplitude Operators

A method for the prediction of seakeeping behaviour of sailing yachts has been developed. It is based on linear strip theory with some non-linear extensions. The method is capable to take into account heeling and yawing yacht hulls, yacht appendages and sails. The yacht's response amplitude operators (RAO) and added resistance in waves can be predicted for harmonic waves as well as for natural wave spectra. The method is used to study added resistance in seaways for ACC-V5 yachts of varying beam. Results are used for further VPP investigations. The AVPP velocity prediction program is used to study optimum length to beam ratio of the yachts depending on wind velocity and upwind to downwind weighting. This investigation is carried out for flat water conditions as well as for two typical wave spectra. The results show that taking into account added resistance in seaways has a strong impact on predicted performance of the yacht.

scholarly journals Rowing VPP(Velocity Prediction Program)

2003 ◽  
Vol 2003 (194) ◽  
pp. 67-73
Author(s):  
Hiroshi Kobayashi ◽  
Takeshi Kinoshita
Keyword(s):  
Prediction Program ◽  
Velocity Prediction

scholarly journals Flow Simulation And Performance Analysis Of Centrifugal Compressor Using Cfd_Tool

2021 ◽  
Vol 23 (11) ◽  
pp. 693-703
Author(s):  
Tesfaye Barza ◽  
◽  
G. Lakshmikanth ◽  
Keyword(s):  
Performance Analysis ◽  
Pressure Distribution ◽  
Turbulence Model ◽  
Centrifugal Compressor ◽  
Flow Simulation ◽  
Internal Flow ◽  
Design System ◽  
Turbulent Fluid Flow ◽  
Compressor Impeller ◽  
And Performance

This paper is concerned the flow simulation and performance analysis of the Centrifugal Compressor Using CFD – Tool. The complex internal flow of centrifugal compressor can be well analyzed, and the unique design system needs to be developed. It should be early to use the interface and also flexible for input and output. A 3-D flow simulation of turbulent – fluid flow is presented to visualize the flow pattern in-terms of velocity, streamline and pressure distribution on the blade surface are graphically interpreted. The standard K- e turbulence model and the simple model algorithm were chosen for turbulence model and pressure distribution well determined. The simulation was steady Heat transfer and moving reference frame was used to consider the impeller interaction under high resolution. Furthermore, A computational Fluid Dynamics (CFD) 3-D simulation is done to analyze the impeller head and efficiency required of centrifugal compressor. The impeller is rotated for a constant revolution and mass flow rate, in this study initially the geometry of centrifugal compressor impeller is created by an ANSYS Vista CCD, and the Blade modeller done by Bladegen, Finally, CFD analysis was performed in ANSYS CFX using the ANSYS Turbo grid meshing tool. According to the analysis, as the number of impeller blades increases, so does the value of the head and power imparted, as well as the impeller’s efficiency.

Scoring IMS Regattas - An Empirical Study of Alternative Methods

1995 ◽  
Author(s):  
John W. Cane
Keyword(s):  
Empirical Study ◽  
Measurement System ◽  
Alternative Methods ◽  
Prediction Program ◽  
Data Points ◽  
Velocity Prediction ◽  
International Measurement

The International Measurement System (IMS) uses a computerized velocity prediction program (VPP) to calculate the performance of a meas­ured hull and rig in winds from six to twenty knots, at any sailing angle. A regatta is scored by comparing a yacht's performance with pre­dictions of the VPP. The winner is the yacht whose performance, relative to its VPP predic­tions, is the best, compared to all other yachts in its class or division. This paper discusses different methods of malc­ing the comparison and accounting for various factors in the race such as wind shifts and cur­rent on the course. Decisions made by race man­agers and/or developers of scoring programs can significantly impact results. Illustrative examples show the effects that these decisions can have. In 1994 the number of data points available for use in scoring yachts in custom courses doubled. Alternative ways of using these data are illus­trated by application to a sample regatta.

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