Numerical and experimental study of appendages in racing yachts and their influence on the free surface

Las prestaciones de un velero de regatas se estiman por medio de los Programas de Predicción de Velocidad (VPP) que incluyen las características de estabilidad y modelos aero e hidrodinámico del barco. Por esta razón, es importante tener una evaluación adecuada de las fuerzas en apéndices y de su variación en diferentes condiciones de navegación, escora y deriva. Además, para el cálculo de las fuerzas en los apéndices es importante conocer sus características hidrodinámicas cuando trabajan conjuntamente en un campo fluido fuertemente modificado por la carena. Por esta razón, se han utilizado una serie de ensayos realizados en el Canal de Ensayos de la ETSIN con el objetivo de validar códigos numéricos que permiten una evaluación más rápida y focalizada en los distintos fenómenos que se producen. Dichos ensayos se han realizado de forma que pudiera medirse independientemente las fuerzas hidrodinámicas en cada apéndice, lo que permitirá evaluar el reparto de fuerzas en diferentes condiciones de navegación para poder profundizar en las interacciones entre carena, quilla y timón. Las técnicas numéricas permiten capturar detalles que difícilmente se pueden visualizar en ensayos experimentales. En este sentido, se han probado las últimas técnicas utilizadas en los últimos workshops y se ha enfocado el estudio a un nuevo método con el objetivo de mostrar una metodologia más rápida que pueda servir a la industria para este tipo de aproximación al problema. ABSTRACT The performances of a racing sailboat are estimated by means of the speed prediction programs (VPP), which include the ship stability characteristics and the aero and hydrodynamic models. For this reason, it is important to have an adequate evaluation of the forces in appendices and its variation in different sailing conditions, heel and leeway Moreover, for the analysis of the forces in the appendices, it is important to know their hydrodynamic characteristics when they work together in a fluid field strongly modified by the canoe body. For this reason, several tests have been done in the ETSIN towing tank with the aim to validate numeric codes that allowing faster analysis and they permit to focus on the different phenomena that occur there. Such tests have been done in a way that the hydrodynamic forces in each appendage could be measured independently allowing assessing the distribution of forces in different sailing conditions to be able to deepen the interactions between the canoe body, the keel and the rudder. Numerical techniques allow capturing details that can hardly be displayed in experimental tests. In this sense, the latest techniques used in the recent workshops have been reviewed and the study has been focused to propose a new model with the aim to show a new faster methodology which serves the industry for this type of approach to the problem.

Análisis y optimización de la resistencia de interferencia en multicascos

Esta tesis presenta un estudio de la resistencia de interferencia en multicascos, término que engloba las variaciones en la resistencia al avance debidas a la interacción entre cascos. Su característica más notable es que puede ser tanto positiva como negativa, contribuyendo favorablemente en este último caso a la reducción de la resistencia total. Su análisis permanece como un área activa dentro de la comunidad hidrodinámica, si bien se ha detectado una significativa falta de información experimental sobre el flujo entre cascos. En primer lugar se incluye una caracterización de los fenómenos de interferencia, evaluando su impacto en las diferentes componentes de la resistencia al avance. Al igual que la resistencia total, su predicción requiere el uso de técnicas experimentales o numéricas al ser inviable su solución analítica. Ambos procedimientos han sido considerados en esta tesis. El análisis experimental de la resistencia de interferencia supone el núcleo central del trabajo realizado. Se han ensayado dos geometrías diferentes, un catamarán de servicio comercial PESBO junto con un catamarán compuesto por dos Serie 60 (S60) en paralelo. Los ensayos se han llevado a cabo en dos canales de experiencias, CEHINAV y CEHIPAR, midiéndose resistencia al avance, asiento y trimados dinámicos, y cortes de olas en la zona entre cascos. Mención especial a estos últimos, dado que a pesar de ser en la zona central donde ocurren los principales efectos de interferencia, no se encontró información previa publicada en la literatura. Su medición requirió la fabricación de un sistema de soporte especifico para las probetas de medición. Por otro lado, aunque el Serie 60 es una geometría bien conocida en la comunidad hidrodinámica, a conocimiento del autor su comportamiento como multicasco no había sido aun caracterizado experimentalmente. Los bastidores de unión se fabricaron de forma que permitieran variar la separación entre cascos. Además, los multicascos son en general embarcaciones de alta velocidad mostrando asientos y trimados dinámicos significativos. Para cuantificar su efecto en la resistencia total y de interferencia se construyo un sistema de fijación del modelo al carro que los restringiera, posibilitando comparar los resultados en esta condición con los del modelo libre. Como resultado, se han obtenido resultados experimentales de las dos geometrías estudiadas con múltiples separaciones, incluyendo un solo casco, y con modelo fijo y libre. Una de las principales utilidades de los resultados experimentales es servir como referencia para validar modelos de predicción. Como primera aplicación, los datos experimentales obtenidos con el catamarán S60 se han contrastado con las predicciones numéricas de Yeung et al. (2004). El análisis numérico de la resistencia de interferencia se completa con la realización de simulaciones numéricas utilizando dos códigos substancialmente diferentes: Tdynlin y CD--‐Adapco Star--‐CCM+. Los cortes de olas obtenidos en las simulaciones se comparan con los valores experimentales, mostrándose además los campos de presiones y velocidades calculados sobre el casco. La principal aportación de esta tesis es una extensa caracterización experimental de los fenómenos de interferencia, con la intención de servir de referencia para futuros estudios con multicascos. El análisis de los resultados permite comprender mejor el impacto que la interacción entre cascos, así como las variaciones dinámicas de las condiciones de navegación, tienen en las diferentes componentes de la resistencia. Por otro lado, permite apreciar la dependencia de la resistencia de interferencia con la velocidad y separación entre cascos, de cara a su utilización como parámetro de diseño. ABSTRACT This thesis presents a study of the interference resistance in multihulls, which comprises all the variations in the ship resistance due to the interaction between hulls. Its most remarkable characteristic is that it can be positive or negative, contributing in the second case to the reduction of the total ship resistance. Its study remains an active area in the hydrodynamic community, although there is a significant lack of published experimental data regarding the flow between hulls. First of all, the interference phenomena are characterized, evaluating the impact in the different components of the ship resistance. Similar to the total resistance, their prediction requires experimental or numerical techniques, as no analytic solutions are known. Both procedures have been considered in this thesis. The experimental analysis of the interference resistance is the core of the work done. Two different geometries have been tested, a commercial catamaran PESBO and a catamaran composed by two parallel Series 60 (S60). The tests have been carried out in two towing tanks, CEHINAV and CEHIPAR, measuring ship resistance, dynamic sinkage and trim, and wave cuts in--‐between the hulls. Special mention to the wave cuts, as no previous published information was found regarding this zone, even if it is where the main interference effects happen. Their measurement required building a support tripod for the probes, specifically designed for this experimental campaign. In addition, although the Series 60 is a well known hull for experimental and computational analyses, to the author’s knowledge its behavior as a multihull had not yet been experimentally described. The connection frames between the hulls were built so they allowed adjusting the hull spacing. Furthermore, multihulls are usually high--‐speed vessels, acquiring significant dynamic sinkage and trim. To quantify the effect of these dynamic variations of the interference resistance, a clamping system was developed to fixed the model and compare the results with the free model condition. Thus, experimental results have been obtained for various hull separations with the two geometries analyzed, including a single hull, and with free and fixed model. One of the main applications of experimental results is to serve as a reference to validate prediction models. As a first step, the obtained experimental data with the catamaran S60 have been compared with the numerical predictions of Yeung et al. (2004). The numerical analysis of the interference resistance is completed with the inclusion of numerical simulations using two codes substantially different: Tdynlin and CD--‐Adapco Star--‐CCM+. The wave cuts obtained from the simulations are compared with the experimental ones, showing also the pressure and velocity fields over the hulls. The main contribution of this thesis is an extensive experimental characterization of the interference phenomena, aiming to serve as reference for future studies about multihulls. The analysis of the results provides insights into the impact that the interaction between hulls, as well as the dynamic variations of the sailing conditions, have in the different components of the ship resistance. Moreover, it allows us to observe the dependence of the interference resistance on the velocity and hull spacing, useful towards its use as a design parameter.

Notebook on geometry, geography, astronomy, and navigation, ca. 1714-1718

This heavily illustrated notebook contains entries on the following topics: geometrical definitions and axioms, geographical and astronomical definitions, compasses, plain sailing, parallel sailing, and Mercator's sailing. It also contains pages designated for notes on "Currents, Lee Way, & Variation," but these pages have been left blank. The back cover contains calculations which appear to relate to charting a course from Jamaica to "Lizzard."

Notebook on geography, navigation, mensuration, and other subjects, ca. 1723-1743

This heavily illustrated notebook contains entries on the following topics, among others: geography; mensuration; navigation and the history of navigation; "the use of Gunter's Scale in plain sailing;" compasses; quadrants and their use; "the refraction of the stars observed by the famous Tycho Brahe;" the latitude and longitude of coasts in America, Europe, and Africa; oceans and islands; mountains and "burning mountains" (volcanoes); rivers and lakes; forests and deserts; maps and sea charts; and the uses of geometry and other measurements by carpenters, joiners, painters, glaziers, masons, and bricklayers. Many pages contain navigational problems and their detailed solutions, as well as chronologies of global exploration and lists of all known rivers, mountains, and other geographic features across the world, many with vivid descriptions. The last pages of the notebook contain entries made in December of 1743 regarding celestial measurements Prince took in Stratford, Connecticut, where he was staying with his brother.

Student mathematical notebook of Thomas Noyes, 1793

This sewn volume contains Noyes’ mathematical exercises in geometry; trigonometry; surveying; measurement of heights and distances; plain, oblique, parallel, middle latitude, and mercator sailing; and dialing. Many of the exercises are illustrated by carefully hand-drawn diagrams, including a mariners’ compass and moon dials.

Student mathematical notebook of William Emerson Faulkner, 1795

Leather hardcover notebook with unruled pages containing the handwritten mathematical exercises of William Emerson Faulkner, begun in 1795 while he was an undergraduate at Harvard College. The volume contains rules, definitions, problems, drawings, and tables on geometry, trigonometry, surveying, calculating distances, sailing, and dialing. Some of the exercises are illustrated by unrefined hand-drawn diagrams, including some of buildings and trees.

Student mathematical notebook of William Tudor, 1795

Notebook containing the handwritten mathematical exercises of William Tudor, kept in 1795 while he was an undergraduate at Harvard College. The volume contains rules, definitions, problems, drawings, and tables on geometry, trigonometry, surveying, calculating distances, sailing, and dialing. Some of the exercises are illustrated with hand-drawn diagrams. The Menusration of Heights and Distances section contains color drawings of buildings and trees, and some have been altered with notes in different hands and with humorous additions. For instance, a drawing of a tower was drawn into a figure titled “Egyptian Mummy.” Some of the images are identified: “A rude sketch of the Middlesex canal,” Genl Warren’s monument on Bunker Hill,” “Noddles Island,” “the fields of Elysium,” and the “Roxbury Canal.” The annotations and additional drawings are unattributed.

Letter from Henry Higginson to William Tudor,

One letter from the Boston merchant in England regarding experiments in ship construction and Frederic Tudor’s ideas on designing sailing vessels to transport ice.

Letters from Thomas James Maling to William Tudor,

Two letters regarding peace negotiations in Buenos Aires and politics in Europe, and two letters from Maling’s wife regarding accommodations she was seeking in Lima and news regarding various sailing vessels.

Letters from Stanhope Prevost to William Tudor,

Five letters regarding his investment in the Chanca silver mine, equipment needed, and his and Tudor’s partners in the venture, including Llaveria, Maling, and Miralles. Also includes personal news and information regarding the movements of certain sailing vessels.

Letters from John Hubbard Church to William Jenks, 1795-1798

John Hubbard Church wrote these twelve letters to his friend and classmate William Jenks between 1795 and 1798. Church wrote the letters from Boston, Rutland, Cambridge, and Chatham in Massachusetts and from Somers, Connecticut; they were sent to Jenks in Cambridge and Boston, where for a time he worked as an usher in Mr. Vinall's school and Mr. Webb's school. Church's letters touch on various subjects, ranging from his increased interest in theology and his theological studies under Charles Backus to his seasickness during a sailing voyage to Cape Cod. Church also informs Jenks of what he is reading, including works by John Locke, P. Brydone, James Beattie, John Gillies, Plutarch, and Alexander Pope. He describes his work teaching that children of the Sears family in Chatham, Massachusetts, where he appears to have spent a significant amount of time between 1795 and 1797. Church's letters are at times very personal, and he often expresses great affection for Jenks and their friendship.

Shetland Islands, United Kingdom, Nautical Chart, 1788 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: A new hydrographical survey of the islands of Shetland : with many improvements and additions, and the sailing directions, by Captn. Thomas Preston. It was printed for Robert Sayer, chartseller No. 63 Fleet Street 1st. Jany., 1788. Scale [ca. 1:419,830].The image inside the map neatline is georeferenced to the surface of the earth and fit to the European Datum 1950, Universal Transverse Mercator (UTM) Zone 30N projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as rocks, channels, points, ports, coves, islands, anchorage points, and more. Includes also selected land features such as towns and villages, drainage, selected buildings, and more. Relief shown by hachures; depths shown by soundings. Includes also profile views, navigational notes, and insets: Directions for Valey Sound -- The Isles of Feroe. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.

Nantucket Island and eastern Martha's Vineyard, Massachusetts, Nautical Chart, 1776 (Image 2 of 2) (Raster Image)

This layer is a georeferenced raster image of the untitled, historic nautical chart: [Nantucket Island and the eastern end of Martha's Vineyard] (sheet originally published in 1776). The map is [sheet 14] from the Atlantic Neptune atlas Vol. 3 : Charts of the coast and harbors of New England, from surveys taken by Samuel Holland and published by J.F.W. Des Barres, 1781. Scale [ca. 1:54,000]. This layer is image 2 of 2 total images of the two sheet source map, representing the western portion of the map. Covers the eastern portion of Martha's Vineyard and a portion of Nantucket Sound. The image is georeferenced to the surface of the earth and fit to the 'World Mercator' (WGS 84) projected coordinate system. All map collar information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, or other information associated with the principal map. This map shows coastal features such as harbors, inlets, rocks, channels, points, coves, shoals, islands, and more. Includes also selected land features such as cities and towns. Relief is shown by hachures; depths by soundings and shading. Includes sailing notes. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection. The entire Atlantic Neptune atlas Vol. 3 : Charts of the coast and harbors of New England has been scanned and georeferenced as part of this selection.

Nantucket Island and eastern Martha's Vineyard, Massachusetts, Nautical Chart, 1776 (Image 1 of 2) (Raster Image)

This layer is a georeferenced raster image of the untitled, historic nautical chart: [Nantucket Island and the eastern end of Martha's Vineyard] (sheet originally published in 1776). The map is [sheet 13] from the Atlantic Neptune atlas Vol. 3 : Charts of the coast and harbors of New England, from surveys taken by Samuel Holland and published by J.F.W. Des Barres, 1781. Scale [ca. 1:54,000]. This layer is image 1 of 2 total images of the two sheet source map, representing the eastern portion of the map. Cover Nantucket Island, Massachusetts and surroundings. The image is georeferenced to the surface of the earth and fit to the 'World Mercator' (WGS 84) projected coordinate system. All map collar information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, or other information associated with the principal map. This map shows coastal features such as harbors, inlets, rocks, channels, points, coves, shoals, islands, and more. Includes also selected land features such as cities and towns. Relief is shown by hachures; depths by soundings and shading. Includes sailing notes. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection. The entire Atlantic Neptune atlas Vol. 3 : Charts of the coast and harbors of New England has been scanned and georeferenced as part of this selection.

New York Bay and Harbor, 1776 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the entrance of Hudson's River, from Sandy Hook to New York : with the banks, depths of water, sailing-marks, & ca. It was printed for Robt. Sayer & John Bennett, sea chart & map-sellers ... 1st June 1776. Scale [ca. 1:70,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM) Zone 18N NAD83 projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows coastal features such as lighthouses, rocks, channels, points, coves, islands, and more. Depths shown by soundings and shading. Relief shown by hachures. Includes notes. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.