Free Surface RANSE Analisys Around Fixed Fully Appended

This paper presents results of Free Surface RANSE (Reynolds Average Navier Stokes Equations) simulations of the flow around a MedCup TP52. Appendages forces calculations are important to know their hydrodynamic characteristics when they work jointly. In the ETSIN towing tank, some tests had begun to measure hydrodynamics forces in each appendage that allowed evaluate the forces distribution in different conditions. StarCCM+ has been used to compute drag, lift and wave elevation. It is shown how the CFD analysis has been prepared and the results obtained in these simulations comparing experimental with numerical results and the grid influence on it. Finally, it is observed that with limited resources, reasonable good results could be obtained

Modeling of Free Surface Flows with Elastic Bodies Interactions

In this paper, a series of new fluid and structure interactions test cases with strong free surface effects are presented and computations of such flows with the Particle Finite Element Method (PFEM) (Idelsohn, Oiiate, Del Pin and Calvo, 2006) are documented. The structures object of study are elastic cantilever bars clamped inside sloshing tanks subjected ro roll motion. The possibilities of PFEM for the coupled simulation of moderately violent free surface flows interacting with elastic bodies are investigated. The problem can be described as the coupling of a sloshing flow with an easily deformable elastic body. A series of experiments designed and executed specifically for these tests are also described. The experiments comprise cases with different liquid height and liquids of different viscosity. The aim is to identify canonical benchmark problems in FSI (Fluid and Structure Interactions), including free surfaces, for future comparisons between different numerical approaches

Computational study of sail performance of a racing yacht

Es importante entender las caracteristicas del flujo y el comportamiento de las velas tanto para los navegantes como para los disenadores que quieren tener un empuje eficiente de la embarcacion. En este trabajo, se presenta la simulacion del flujo de aire alrededor de las velas, con una geometria final impuesta, y con un codigo CFD reproduciendo las medidas a escala real. El codigo numerico utilizado es un CFD viscoso basado en las ecuaciones RANS. Se han considerado tres combinaciones de velas: dos mayores y una mayor mas genova y los parametros estudiados principalmente son la sustentacion, resistencia, centro velico y el coeficiente de presion sobre las velas. Se han comparado los resultados obtenidos con datos experimentales y otros datos numericos procedentes de otros estudios. El estudio concluye que hay una buena concordancia entre los calculos numericos y los datos a escala real, mostrando la importancia de la utilizacion de estas herramientas numericas. It is important to understand flow characteristics and performance of sails for both sailors and designers who want to have an efficient thrust of yacht. In this article, the airflow around yacht sails with imposed final geometry is simulated using a CFD (Computational Fluid Dynamics) code reproducing full scale measurements. The code is a commercial viscous CFD based on Reynolds-averaged Navier-Stokes (RANS) equations. Three sets of sails are considered: two mainsails alone and one set of mainsail with jib and the parameters in study are mainly the lift, drag, center of effort and pressure coefficient over the sails. The results are compared with both experimental data and numerical computations obtained from other studies. It is concluded that there is good agreement between numerical calculations and full scale data, showing the importance of the use of numerical tools

Stability Criteria for Sailing Vessels

What do you know about sailing yacht stability? Which are the peculiarities of the stability of a sailing yacht? Is there any supposition different from those applied in conventional ships? If you have to verify the stability of your yacht, would you be sure of which criteria you should applied? The aim of this paper is to answer these questions among others. The authors assume that the readers of this paper come from varied backgrounds and experience. Some of you may not be totally familiar with these stability requirements whereas others may use them every day. It is hoped that this paper will be some enlightenment for the former and be an interesting review for the latter. In this paper the philosophy of sailing yacht stability will be presented. It will be also examined the criteria in force in countries such as Spain, United Kingdom, United States and The Netherlands among others and the assumptions upon which they are based will be highlighted. In order to clarify ideas two reference sailing yacht will be subjected to different criteria and compared their severity

Sailing Yacht Rudder Behaviour

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. Para el cálculo de las fuerzas en los apéndices es importante conocer sus características hidrodinámicas cuando trabajan conjuntamente. En el Canal de Ensayos de la ETSIN se ha iniciado una serie de ensayos para la medida separada de las fuerzas hidrodinámicas en cada apéndice que permitirá evaluar el reparto de fuerzas en diferentes condiciones de navegación así como profundizar en las interacciones entre carena, quilla y timón. El proyecto se complementa con un análisis numérico del problema con un código comercial de tipo viscoso (CFX). Benefits in a racing sailboat are considered by means of Velocity Prediction Programs (VPP) that includes the stability and aero-hydrodynamic characteristics of the boat. Appendages forces calculations are important to know their hydrodynamic characteristics when they work jointly. In the ETSIN towing tank, some tests have begun to measure hydrodynamics forces in each appendage that will allow evaluating the distribution of forces in different conditions of navigation as well as for deepening in the interactions between hull, keel and rudder. The project is complemented with a numerical analysis of the problem with a commercial viscous code (CFX)

The effect of the Mast on Sail Performance

In this study, the airflow around a yacht sail with imposed final geometry is simulated using a CFD (Computational Fluid Dynamics) code reproducing full scale measurements. The code is a commercial viscous CFD based on Reynolds-Averaged Navier-Stokes (RANS) equations. The purpose of this article is to consider the effect of the mast on the performance of a sail. This research is related to a previously and published investigation written by the first author. That research was based on the aerodynamics of sails alone due to the lack of knowledge in regards to the geometry of the mast. The contribution of this new research is the calculation of how the mast affects sail performance using a recently acquired software. Furthermore, a methodology for the study of sails has been developed using this last software. The pressure coefficient on the sail, driving and side forces are computed among other variables.. The results are compared with both reference data obtained by full scale measurements. It is concluded that there is good agreement between the current results and the reference data

Aportaciones sobre la implantación del Plan Bolonia. Un giro copernicano para los alumnos

La implantación del Sistema del denominado Plan Bolonia no sólo representa un reto para el profesorado sino también para el alumnado, acostumbrado a seguir la clase de lejos, participar poco en ella y darse un atracón de estudiar los días previos al examen. Un sistema basado en la asistencia a clase de forma activa, haciendo ejercicios y trabajos en grupo asiduamente, representa para muchos de nuestros alumnos un giro copernicano. En este trabajo se presenta el seguimiento de una cierta evaluación continua en una asignatura que aunque está situada en 2º curso es específica de los estudios que nos ocupa de la Ingeniería Naval, lo que podría dar lugar a pensar un cierto interés o al menos motivación por parte del alumno. Una vez planteada la metodología de la evaluación continua, se analizan la participación de los alumnos, su asistencia a clase, la evolución de los abandonos y la influencia de este sistema en los resultados académicos. Los resultados pondrán de manifiesto las dificultades que la implantación del Plan Bolonia tiene entre el alumnado acostumbrado a otros esquemas de funcionamiento

Becarios de grado en un grupo de investigación: Una experiencia de 20 años y 200 estudiantes.

Este artículo está dedicado a documentar la experiencia que al respecto de la figura del becario de grado con cargo a proyectos hemos tenido en el Grupo de Investigación del Canal de Ensayos Hidrodinámicos de la Escuela Técnica Superior de Ingenieros Navales de la Universidad Politécnica de Madrid (UPM). Se trata por tanto de describir las particularidades del proceso de selección, formación y evolución laboral de los becarios que nuestro grupo viene gestionando. El becario es una pieza angular que debe ser manejada con extraordinario cuidado para que el progreso de un grupo de investigación sea el adecuado. Nuestros planteamientos a este respecto han sido contrastados con los resultados de una encuesta que hemos realizado sobre antiguos becarios de nuestro grup

Shallow convolutional network excel for classifying motor imagery EEG in BCI applications

Many studies applying Brain-Computer Interfaces (BCIs) based on Motor Imagery (MI) tasks for rehabilitation have demonstrated the important role of detecting the Event-Related Desynchronization (ERD) to recognize the user’s motor intention. Nowadays, the development of MI-based BCI approaches without or with very few calibration stages session-by-session for different days or weeks is still an open and emergent scope. In this work, a new scheme is proposed by applying Convolutional Neural Networks (CNN) for MI classification, using an end-to-end Shallow architecture that contains two convolutional layers for temporal and spatial feature extraction. We hypothesize that a BCI designed for capturing event-related desynchronization/synchronization (ERD/ERS) at the CNN input, with an adequate network design, may enhance the MI classification with fewer calibration stages. The proposed system using the same architecture was tested on three public datasets through multiple experiments, including both subject-specific and non-subject-specific training. Comparable and also superior results with respect to the state-of-the-art were obtained. On subjects whose EEG data were never used in the training process, our scheme also achieved promising results with respect to existing non-subject-specific BCIs, which shows greater progress in facilitating clinical applications

Reducción de la resistencia al avance de un buque mediante la aplicación de pinturas especiales al casco

La crisis económica, el impacto medioambiental y el consumo continuado de los combustibles fósiles propician cualquier iniciativa que conlleve un ahorro de energía. En el mundo de los buques, uno de los objetivos ha sido siempre el alcanzar un casco hidrodinámicamente óptimo que con un mínimo de potencia proporcione la velocidad deseada. Esta resistencia al avance se debe esencialmente a dos razones: a la fricción entre el agua y el casco del buque y a la generación de olas debido a la presencia de la interfase aireagua. El presente trabajo recoge las labores llevadas a cabo para evaluar la posibilidad de minimizar la resistencia debida a la fricción mediante la aplicación de pinturas especiales al casco del buque. El análisis se ha aplicado a un buque de cooperación en materia de pesca que ha sido estudiado hidrodinámicamente en el Canal de Ensayos Hidrodinámicos de la E.T.S.I. Navales. Para el estudio de la reducción de la resistencia de fricción se han ensayado dos planchas con una superficie mojada equivalente al modelo utilizado en los ensayos hidrodinámicos con dos tipos diferentes de pintura. También se han llevado a cabo cálculos numéricos con un código comercial de tipo viscoso con la posibilidad de evaluar la rugosidad. Se pretende también con ello proceder a la validación de dicho código para la consideración de la rugosidad