Unsteady Aerodynamics Of Upwind Sailing And Tacking
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Unsteady Aerodynamics Of Upwind Sailing And Tacking
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Author : Frederik C. Gerhardt
language : en
Publisher:
Release Date : 2011
Unsteady Aerodynamics Of Upwind Sailing And Tacking written by Frederik C. Gerhardt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Sailboats categories.
Predicting unsteady sailing yacht performance is of significant current interest to racing syndicates and yacht designers alike because it is anticipated that optimising boats for dynamic conditions will lead to large performance gains. Such optimisations are usually carried out with the aid of Dynamic Velocity Prediction Programs (DVPPs). These programs require knowledge about the behaviour of the sails in unsteady flow. To this end Part A of this work looks at the simplified unsteady aerodynamics of a yacht that sails upwind in waves. Unsteady thin aerofoil theory is extended to the case of two interacting aerofoils representing the headsail and mainsail. The developed novel method is analytical in nature and is based on representing the sail bound vorticity distributions and the unsteady vortex wakes by planar vortex sheets. The theory is successfully validated against data from the literature and pressure distributions from wind tunnel tests. An application of the theory to the case of an International America's Cup Class yacht that pitches in waves reveals that the time-varying components of the aerodynamic forces are small and that only very little energy can be extracted from the unsteady flow about the sails and converted into thrust. Part B looks at the aerodynamics of a yacht that tacks. Since today's DVPPs usually suffer from a lack of available data on the behaviour of the sail forces at very low apparent wind angles a series of quasi-steady experiments was carried out. Test results for different tacking scenarios (headsail flogging or backed) are presented in a form that facilitates incorporation into a DVPP. The quasi-steady approach used in the wind tunnel tests does not account for unsteady effects like the aerodynamic inertia due to the 'added mass' of the sails. The added inertia of a sail can, however, be estimated by 'strip theory'. Using expressions from the literature and experimental results it is found that such a strip theory over-estimates the added inertia of a mainsail by about 20%because it neglects the three-dimensional flow around the head and the foot of the sails. Using the DVPP FS Equilibrium the influence of added sail inertia on the tacking behaviour of a yacht is studied and it is found that added sail inertia has a small but noticeable influence on tacking performance.
Unsteady Aerodynamics Of Sailing Maneuvers And Kinetic Techniques
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Author : Riley R. Schutt
language : en
Publisher:
Release Date : 2017
Unsteady Aerodynamics Of Sailing Maneuvers And Kinetic Techniques written by Riley R. Schutt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Small sailboat kinetics are significantly affected by bodyweight motions of the sailor. Highly dynamic motions of the boat lead to unsteady aerodynamics around the sail. These unsteady flows are studied using a two-part approach. First, on-the-water tests in a modified Laser sailboat capture the motion of the boat and sail. Subsequently, these characteristic motions are the basis for towing tank experiments exploring fundamental 2D flows around representative sail sections. The “Sail-Flicking”, “S-Turn”, and “Roll-Tacking” kinetic techniques are explored in depth. Each technique is used by racing sailors to improve the performance during specific portions of a race and are most effective in select wind conditions. Sail Flicking consists of repeated small amplitude sail pulses which increase straight-line speed in upwind and cross-wind sailing. In the 2D case, a vortex pair is shed during each individual “flick”. The benefit in driving force is maximized at apparent wind angles near 45°. Sail Flicking effectiveness scales with the non-dimensional parameters reduced frequency and heave-to-chord ratio, making the technique most effective in light wind. The S-Turning technique uses coordinated turns, rolls, and sail adjustments while sailing downwind. It is named after the boat's “S” shaped path through the water. On-the-water tests show a measurable increase in downwind Velocity Made Good, VMG, while laboratory experiments indicate constructive interaction between the sail and vortices shed during each motion period. Sailboats tack back and forth to make progress into the wind. During a Roll-Tack, sailors allow the boat to reach a high heel angle during the turn. An aggressive bodyweight shift then rolls the boat upright, sweeping the sail through the air and increasing driving force. On-the-water tests show that Roll-Tacking in light wind increases windward VMG relative to straight-line sailing and relative to tacks which do not roll the boat. 2D laboratory experiments representing a slice of the sail show the formation of a strong vortex pair associated with a six fold increase in driving force. ...
An Experimental Investigation Of Full Scale Sail Aerodynamics Using Pressures Shapes And Forces
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Author : Dario Motta
language : en
Publisher:
Release Date : 2015
An Experimental Investigation Of Full Scale Sail Aerodynamics Using Pressures Shapes And Forces written by Dario Motta and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with Aerodynamic measurements categories.
Sail aerodynamics is an active field of study in the research community. The basic behaviour of sails in steady conditions is well known due to numerical computations and wind tunnel testing, but there are several unanswered questions about the sail aerodynamics in actual, dynamic, sailing conditions. The unsteady aerodynamics of upwind sails has been addressed very few times in the past, both by numerical and experimental methods, and there is still a lack of knowledge on the unsteady aerodynamics of downwind sails. At the present time only full-scale testing can give some of the answers to the questions of what is really happening to downwind sails on the water. This project aims at improving the understanding of the unsteady aerodynamics of downwind sails at full-scale. This is done by measuring instantaneous pressures and sail shapes at full-scale, and combining them to obtain the aerodynamic forces developed from the sails. The measuring system, developed at the University of Auckland and named FEPV (`Force Evaluation via Pressures and VSPARS'), is validated for both upwind and downwind sailing by comparing its predictions with wind tunnel measurements carried out at the Twisted Flow Wind Tunnel of the University of Auckland. The steady aerodynamics of upwind and downwind sails at full-scale are investigated, at first, in this project, by averaging the measured pressures, sail shapes and yacht motions over chosen recording times. The averaged differential pressure distributions across the sail sections are compared with the expected and measured pressure fields from the literature. The calculated aerodynamic forces are compared with wind tunnel measurements, and a good agreement is found. The unsteady aerodynamics of downwind sails is then investigated by combining the knowledge of the instantaneous values of the differential pressures across the sails, of the sail shapes and of the aerodynamic forces. The results of two different tests, carried out on a J80 and a Stewart 34 class yachts respectively, are presented in this thesis. In either case, the yacht is equipped with an asymmetric spinnaker and it is found that, even in relatively steady wind conditions and limited yacht motions, the spinnaker has a very dynamic behaviour. The periodic folding and filling of the spinnaker luff influences the differential pressure distributions, in particular near the luff , and the aerodynamic forces, which have large variations from their average values during the recording time. The recovery of the sail shape is found to produce very large suctions near the luff and an increase in the drive force that would not be otherwise achieved.
The Aero And Hydromechanics Of Keel Yachts
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Author : J.W. Slooff
language : en
Publisher: Springer
Release Date : 2015-04-25
The Aero And Hydromechanics Of Keel Yachts written by J.W. Slooff and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-04-25 with Technology & Engineering categories.
How and why does sail boat performance depend on the configuration and trim of boat and sails? This book provides the yachtsman with answers in a relatively straightforward account of the physical mechanisms of sailing. It presents an accessible overview of the fluid dynamic aspects of sailing and sailing technology, addressing both aeromechanics and hydromechanics. Readers are provided with the basic principles of physics and general mechanics that will assist their understanding of the fluid mechanics of sailing yachts. Rich appendices cover not only in-depth,mathematical-physical treatments and derivations for those wishing to explore further, but also helpful summaries of basic mathematical notions for those wishing to refresh their knowledge. This work explores keel yachts, specifically single-masted mono-hulls with ‘fore-and-aft’, Bermuda-rigged sails. However, much of it is applicable to other types of sailing vessels such as multi-hulls, yachts with multiple masts, windsurf boards and the like. Yachtsmen, yacht designers and professionals of sailing technology will all find something of interest in this work which provides explanations of the mechanics of sailing in a way that is scientifically justified, whilst remaining appealing to those wishing to use their knowledge on-board a sailing vessel. For some years I’m teaching a course on “Sailing Yacht Design” in the master class of yacht design. Actually, I’ve found your book the best one about physics of a sailing yacht I’ve ever read. Edward Canepa, assistant professor in Fluid Machinery at the University of Genova (Italy) ...very impressed, no wonder it took so long. It is “everything I ever wanted to know about sailing but was afraid to ask” ! Frank Woodward, former computational fluid dynamicist at the Boeing Company and Analytical Methods Inc., and a cruising yachtsman
Aero Hydrodynamics And The Performance Of Sailing Yachts
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Author : Fabio Fossati
language : en
Publisher: A&C Black
Release Date : 2009-12-18
Aero Hydrodynamics And The Performance Of Sailing Yachts written by Fabio Fossati and has been published by A&C Black this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-12-18 with Sports & Recreation categories.
A groundbreaking technical analysis of yacht design based on cutting edge research in the field of aero-hydrodynamics.
Yacht Racing The Aerodynamics Of Sails And Racing Tactics
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Author : Manfred Curry
language : en
Publisher: Read Books Ltd
Release Date : 2012-12-21
Yacht Racing The Aerodynamics Of Sails And Racing Tactics written by Manfred Curry and has been published by Read Books Ltd this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-21 with Sports & Recreation categories.
A guide for racing yachtsman that is as useful today as when it was first published. Teaching the fundamentals of the start line, beating to windward, rounding a mark, wind abeam, before the wind. This book is a wonderful collection of anecdotes, tactics and case studies. Many of the earliest books, particularly those dating back to the 1900s and before, are now extremely scarce and increasingly expensive. We are republishing these classic works in affordable, high quality, modern editions, using the original text and artwork.
Sailing Aerodynamics
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Author : John Morwood
language : en
Publisher:
Release Date : 1962
Sailing Aerodynamics written by John Morwood and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1962 with Aerodynamics categories.
Aero Hydrodynamics Of Sailing
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Author : Czesław A. Marchaj
language : en
Publisher:
Release Date : 1988
Aero Hydrodynamics Of Sailing written by Czesław A. Marchaj and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with Sailboats categories.
Sail Performance
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Author : Czesław A. Marchaj
language : en
Publisher: International Marine/Ragged Mountain Press
Release Date : 2003
Sail Performance written by Czesław A. Marchaj and has been published by International Marine/Ragged Mountain Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Sports & Recreation categories.
Based upon on Marchaj's Sailing Theory and Practice, this volume explains the many developments in sail performance that have taken place. The author explains the factors that affect sail power and why certain rigs have superior power and efficiency.
Upwind Sail Aerodynamics
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Author : Dejan Nožak
language : en
Publisher:
Release Date : 2013
Upwind Sail Aerodynamics written by Dejan Nožak and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.