The ongoing development of low order methods providing fast estimations of aerodynamic loading ar... more The ongoing development of low order methods providing fast estimations of aerodynamic loading are essential for pre-dimensioning and optimization of wings and fins. The aim of this study is to present an efficient 3D Non-Linear Lifting-Line Method enhanced by an artificial viscosity correction, able to give reliable results for post-stall regime, where conventional lifting-line methods usually fail. In the present method, the lifting-line governing equation is solved by a Newton-Raphson algorithm, with an analytical Jacobian matrix. An artificial viscosity term has been added to the governing equation, in order to regularize the solution for post-stall regime. A unique parameter was defined to control the amount of artificial viscosity introduced in the governing equation. The investigations focus on the influence of the amount of artificial viscosity on the regularization of the final solution. The perturbation generated by the artificial viscosity on the governing equation is also analyzed. The method has been validated and evaluated with linear and non-linear test cases, from analytical and experimental data from the literature. It was shown that there is an optimal amount of artificial viscosity leading to a converged solution, for post-stall regime, associated with smooth circulations along the wing span, coherent 3D lift coefficients, and low deviations from the initial governing equation. When the amount of artificial viscosity increases beyond this optimal value, the solution deteriorates. The optimal value of the parameter controlling the amount of artificial viscosity has been found to be practically insensitive to the angle of attack, and to the wing discretization.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 15, 2020
A Design Of Experiment method was applied combined with a performance prediction program to asses... more A Design Of Experiment method was applied combined with a performance prediction program to assess the influence of four design parameters on the propulsive capacity of kites used as auxiliary propulsion for merchant vessels. Those parameters are the lift coefficient, the lift to drag ratio or drag angle, the maximal load bearable by the kite and the ratio of the tether length on the square root of the kite area. These parameters are independent from the kite area and, therefore, they could be used with various kite ranges and types. The maximum wing load parameter is the one that shows the most influence on the propulsive force. Over 50% of the gains obtained through this study are directly attributable to it. Then the ratio of the tether length on the square root of the kite area comes as the second greatest influence factor for true wind angles above 70°. While the drag angle is more influential for the narrower angles. In fact, the most substantial gains are made upwind.
Breizh Spirit, a Reliable Boat for Crossing the Atlantic Ocean
To meet the Microtransat challenge, ENSTA Bretagne chose to realize several sailing robots. The f... more To meet the Microtransat challenge, ENSTA Bretagne chose to realize several sailing robots. The first, having served as a test platform, allowed us to develop two new boats, one for research and one for the Atlantic crossing. The different tests in the bay of Brest allowed us to improve the reliability of systems on our sailboat. Various studies have been
Breizh Spirit, un voilier autonome à travers l'Atlantique
National audienceTo meet the Microtransat challenge, ENSTA Bretagne chose to realize several sail... more National audienceTo meet the Microtransat challenge, ENSTA Bretagne chose to realize several sailing robots. The first, having served as a test platform, allowed us to develop two new boats, one for research and one for the Atlantic crossing. The different tests in the bay of Brest allowed us to improve the reliability of systems on our sailboat. Various studies have been conducted to improve reliability of sailboats both mechanically and electronically. This tests allowed us to test different concepts on the three Breizh Spirit boats. The results are very positive and we can now say that we have a boat able to resist to strong storms, to follow a predifined route, to supply its own energy and to navigate in sea waves. From the experience acquired from Breizh Spirit 1, we hope we will be able to cross the Atlantic Ocean
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In this work, a hardware-in-the-loop (HIL) simulator is designed to diagnose the behavior of an a... more In this work, a hardware-in-the-loop (HIL) simulator is designed to diagnose the behavior of an autonomous sailboat as it navigates between waypoints. At its core, the HIL simulator includes the sailboat pilot on an embedded system. The sensor data input to the embedded system is fed by a navigation simulator that takes into account the different forces on the sailboat due to the wind, waves and current conditions. The HIL simulator is then tested for a navigation route from sea trials published in 2014, and the behavior of the automated pilot is compared to its behavior when the vessel is driven by a crew. As demonstrated, the automated system can outperform the man-operated vessel. The tool is also used to diagnose weaknesses in the sailboat autopilot algorithm that can be improved in the future.
International audienceThis paper presents sea trials on a 6-meter boat specifically designed for ... more International audienceThis paper presents sea trials on a 6-meter boat specifically designed for kite propulsion. The kite control is automatic or manual, dynamic or static, depending on the point of sailing. The measurement system records boat motion and loads generated by the kite. A particular attention was payed for wind measurement with several fixed and mobile locations directly on the kiteboat or in the vicinity. A fine modelling shows thata classical power low is not satisfactory to describe the wind at kite location. 5-minute measurement phase were systematically recorded. At the end, 101 runs were conducted. Data are processed with the phase-averaging method in order to produce reliable results. First results are presented
Estimation par la méthode de ligne portante de l'effet d'un virage sur la finesse : application aux cerfs-volants de traction pour la propulsion auxiliaire des navires
Comparaison d'une méthode de ligne portante 3D non linéaire avec des simulations RANSE 3D
International audienceAs a part of the design and operation of kites as auxiliary propulsion of v... more International audienceAs a part of the design and operation of kites as auxiliary propulsion of vessels, it is necessary to be able to quickly estimate the aerodynamic efforts along various trajectories. A 3D non-linear model based on the lifting line of Prandtl has been developed for this purpose. It allows these rapid calculations for wings with any laws for the dihedral angle, the twist, and the sweep angle, along the span, and for a general flight kinematic taking into account translation velocities and rotation rates. This model has been verified by comparison with 3D simulations performed with a Navier-Stokes solver. It gives satisfactory results in incidence and sideslip, with gaps of about 4% for forecasts lift. Special attention has been paid to the estimation of the accuracy of the provided numerical results.Dans le cadre de la conception et de l'exploitation de cerfs-volants pour la propulsion auxiliaire de navires, il est nécessaire de pouvoir simuler rapidement les ...
Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2017
GSEA Design developed a fluid structure method (FSI) suitable for early design stage of appendage... more GSEA Design developed a fluid structure method (FSI) suitable for early design stage of appendage with complex shapes dedicated to the America's Cup flying catamarans. The aerodynamic loading and the boat weight are counteracted by the appendages and mainly the dagger-board. Consequently, the appendage structural design is very critical. Based on a 3D lifting line and a modified beam element method, the GSEA Design FSI method takes less than one minute to compute. An illustrating example on a L-shape appendage shows that the FSI results compared to a non-FSI results can be particularly different at the elbow. Thanks to the short computational time of the method, multi-objective optimizations can be performed. For instance, a second illustrating example shows the optimization of the appendage weight and stiffness.
AbstractThis year, we launched MicroTransat Project in our school to prepare the next year transa... more AbstractThis year, we launched MicroTransat Project in our school to prepare the next year transat-lantic race. In this article we will talk about the solutions in mechanics, electronics, sailing strategies and simulation that we developed for our autonomous robotic boat. As for the mechanics, the hull is home-made using mainly glass ber mat bound together with a resin binder. As for the electronics, we tried to use off-the-shelf components as much as possible to ensure the maintainability of the system. In order to test the sailing algorithm we are using a simulator made with SCILAB. Index TermsAutonomous, Sailing boat,
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