Developments in the IMS VPP Formulations

1999 ◽  
Author(s):  
Andrew Claughton
Keyword(s):  
Aerodynamic Force ◽  
Wind Tunnel Test ◽  
Force Model ◽  
Added Resistance ◽  
Detailed Model ◽  
Prediction Program ◽  
Construction Methods ◽  
Force Modeling ◽  
Velocity Prediction ◽  
Lift And Drag

The paper describes the improvements made to the aerodynamic and hydrodynamic force models of the Offshore Racing Council (ORC) International Measurement System (IMS) sailing yacht velocity prediction program (VPP) since 1990. The paper explains the mechanisms of the force modeling used in the IMS VPP to provide a framework within which the modifications and revisions to the VPP are described. The major revisions fall into three categories. 1) The hydrodynamic model, where a revised formulation for residuary resistance and characteristic length has been introduced, which includes modifications to both the residuary and viscous resistance components. Revisions to the drag due to heel and induced drag formulations are described that more accurately reflect the behavior observed from towing tank tests. 2) The added resistance in waves module was introduced to assist with the equitable handicapping of diverse bull types and construction methods, which affect the behavior of sailing yachts in waves. The mechanism by which the sea state is charaterised and the added resistance calculated is described. 3) The aerodynamic force model, which derives complete rig lift and drag coefficients from standard sail types is described. The behavior of the VPP force model is compared with wind tunnel test results, and the recent additions of coefficient sets for a range of different sail types is described. Finally the components of a more detailed model of hull and rig windage are outlined.

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.

Modeling IACC Sail Forces by Combining Measurements with CFD

1993 ◽  
Author(s):  
Jerome H. Milgram ◽  
Donald B. Peters ◽  
D. Noah Eckhouse
Keyword(s):  
Scale Model ◽  
Force Model ◽  
Actual Performance ◽  
Force Coefficients ◽  
Prediction Program ◽  
Induced Drag ◽  
Load Cells ◽  
Velocity Prediction ◽  
America’S Cup ◽  
Parasitic Components

A sailing dynamometer with a 42% scale model of an International America's Cup Class rig is used to measure sail forces and moments in actual sailing conditions. The sailing dynamometer is a 35-foot boat containing an internal frame connected to the hull by six load cells configured to measure all the forces and moments between the frame and the hull. All sailing rig components are attached to the frame, so that the sail forces are measured. Sail shapes in use are determined by computer-interfaced video. Computational fluid dynamics performed on the measured shapes provides the induced drag. This allows the measured drag to be decomposed into induced and form-and-parasitic components, which is necessary for generating a mathematical sail force model for a velocity prediction program (VPP). It is shown that VPP results using these new sail force coefficients are in better agreement with actual performance than are VPP results based on traditional sail force coefficients.

Changes to Sail Aerodynamics in the IMS Rule

2003 ◽  
Author(s):  
Jim Teeters ◽  
Robert Ranzenbach ◽  
Martyn Prince
Keyword(s):  
Wind Tunnel ◽  
Reverse Engineering ◽  
Measurement System ◽  
Wind Tunnel Test ◽  
Prediction Program ◽  
Aerodynamic Model ◽  
Velocity Prediction ◽  
International Measurement

US Sailing, the Offshore Racing Council (ORC), the Glenn L. Martin Wind Tunnel (GLMWT), Quantum Sail Design Group (QSDG), the Wolfson Unit and North Sails have collaborated on a series of wind tunnel test programs to investigate the performance of both upwind and offwind sails. These programs were initiated in response to perceived inequities in the ratings of boats of various rig designs sailing under the International Measurement System (IMS). Observations of on-the-water performance have lead to the conclusion that there are biases within the rule with respect to rig planform design. Specifically, it has been concluded that large spinnakers are penalized so that a fractional rig, with its small spinnaker, is favored when sailing offwind, that there are un-rated benefits to a masthead rig upwind, and that there are errors in the relative handicapping of overlapping and non-overlapping jibs. The IMS Rule uses a Velocity Prediction Program (VPP) in which sail forces are represented by algorithms that are based on a combination of science and reverse engineering from the measured sailing performance of real boats. The results of investigations at both GLMWT and Wolfson have been used to modify this IMS aerodynamic model, thereby reducing the pre-existing biases.

scholarly journals Multi-Fidelity Surrogate Models for VPP Aerodynamic Input Data

2021 ◽  
Vol 6 (01) ◽  
pp. 21-43
Author(s):  
Tanya Peart ◽  
Nicolas Aubin ◽  
Stefano Nava ◽  
John Cater ◽  
Stuart Norris
Keyword(s):  
Aerodynamic Force ◽  
Computational Cost ◽  
Computational Effort ◽  
Force Coefficient ◽  
Cfd Models ◽  
Research Activities ◽  
Velocity Prediction ◽  
Computational Fluid Dynamics Cfd ◽  
Lift And Drag ◽  
Force Data

Predicting the performance of a sail design is important for optimising the performance of a yacht, and Velocity Prediction Programs (VPPs) are commonly used for this purpose. The aerodynamic force data for a VPP is often calculated using Computational Fluid Dynamics (CFD) models, but these can be computationally expensive. A full VPP analysis for sail design is therefore usually restricted to high-budget design projects or research activities and is not practical for many industry projects. This work presents a method to reduce the computational cost of creating lift and drag force coefficient curves for input into a VPP using both multi-fidelity kriging surrogate modelling and data from existing sail designs. This method is shown to reduce the number of CFD simulations required for a desired accuracy when compared to a single-fidelity model. A maximum reduction in the required computational effort of 57% was achieved for model-scale symmetric spinnaker sails. For the same number of simulations, the accuracy of the model predictions was improved by up to 72% for scale-symmetric spinnaker sails, and 90% for asymmetric spinnakers.

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.

Analytical cutting force modelling of micro-slot grinding considering tool-workpiece interactions on both primary and secondary tool surfaces

2021 ◽  
pp. 1-43
Author(s):  
Ashwani Pratap ◽  
Karali Patra
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
Orthogonal Cutting ◽  
Surface Interactions ◽  
Surface Interaction ◽  
Edge Density ◽  
Force Model ◽  
Height Distribution ◽  
Force Modeling ◽  
Tool Surface

Abstract This work presents an analytical cutting force modeling for micro-slot grinding. Contribution of the work lies in the consideration of both primary and secondary tool surface interactions with the work surface as compared to the previous works where only primary tool surface interaction was considered during cutting force modeling. Tool secondary surface interaction with workpiece is divided into two parts: cutting/ ploughing by abrasive grits present in exterior margin of the secondary tool surface and sliding/adhesion by abrasive grits in the inner margins of the secondary tool surface. Orthogonal cutting force model and indentation based fracture model is considered for cutting by both the abrasives of primary tool surface and the abrasives of exterior margin on the secondary surface. Asperity level sliding and adhesion model is adopted to solve the interaction between the workpiece and the interior margin abrasives of secondary tool surface. Experimental measurement of polycrystalline diamond tool surface topography is carried out and surface data is processed with image processing tools to determine the tool surface statistics viz., cutting edge density, grit height distribution and abrasive grit geometrical measures. Micro-slot grinding experiments are carried out on BK7 glass at varying feed rate and axial depths of cut to validate the simulated cutting forces. Simulated cutting forces considering both primary and secondary tool surface interactions are found to be much closer to the experimental cutting forces as compared to the simulated cutting forces considering only primary tool surface interaction.

An Investigation to Added Mass Force on the Wing of Insect Inspired from a Rigid Sphere Model

2012 ◽  
Vol 476-478 ◽  
pp. 2485-2488
Author(s):  
Mei Jun Hu ◽  
Xing Yao Yan ◽  
Jin Yao Yan
Keyword(s):  
Insect Flight ◽  
Aerodynamic Force ◽  
Mass Effect ◽  
Added Mass ◽  
Rigid Sphere ◽  
Force Model ◽  
Mass Force ◽  
Real Time Control ◽  
Wing Model ◽  
Force Peak

There is a force peak at the beginning of each stroke during the insect flight, this force peak contributes a lot to the total aerodynamic force. To build a man made insect inspired man-made micro aero vehicle, this force need to be considered in the aero force model, and this model should as simple as possible in order to be used in feedback real-time control. Here we presented a simplified model to take the medium added mass effect of the wing into account. Simulated results show a high force peak at the beginning of each stroke and are quite similar to the measured forces on the physical wing model which were carried out by Dickinson et.al.

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 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.

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.

Sign in / Sign up

Export Citation Format

Share Document