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Geraldo de Freitas Maciel, Jean Paul Vila, Gilbert Martinet & Geraldine Girard
INSA/TOULOUSE, MIP/CNRS, Complexe Scientifique de Rangueil - 31077 Toulouse cedex 4,
E-mail : maciel@gmm.insa-tlse.fr, vila@gmm.insa-tlse.fr
The purpose of this paper is first to determine the criteria for the occurrence of discontinuous roll waves in the non-Newtonian fluids such as debris and dense snow avalanche flows. These are periodic waves separated by hydraulic jumps. Using shallow water equations applied to a Bingham fluid, a flow down an inclined infinite plane is considered. The conditions for the development of such instabilities are discussed to justify the field observations of such waves in these geophysical flows. Special attention is given to the Froude and the Reynolds numbers. The influences of the wavenumber and the fluid cohesion are also adressed. We limited to present the mathematical development of the phenomenon and a few numerical results which should be appreciated by engineers. The numerical model was elaborated using a finite volume technique and the Godunov -VanLeer (2nd order ) scheme was applied.
Keywords: shallow water equations, Bingham fluid, roll waves, numerical simulations
equações de água rasa, fluido de Bingham, "roll waves", simulações numéricas
COB507 Lift Force of a Cylinder in a Reversing Flow – Measurements and Modeling
Elyas Ferreira de Medeiros, Maurício Pazini Brandão, and Richard W. Miksad
Instituto de Aeronáutica e Espaço - Centro Técnico Aeroespacial - IAE - CTA
12228-904 - São José dos Campos, Brasil, E-mail: elyasfm@intervale.com, pazini@aer.ita.cta.br, and rwmiksad@virginia.edu
Reduced measurements and a semi-empirical equation are presented for the hydrodynamic lift of a circular cylinder in a harmonically oscillating flow. Characteristic loading features associated with vortex shedding and wake returns are clearly shown from the experimental data. The relationship between the flow near the cylinder and the lift is well represented by a model-equation based on added-mass and circulation concepts. This study may help efforts aimed at a better understanding and modeling of the transverse force induced by oscillatory flows on submerged bodies.
Keywords: Hydrodynamic lift, reversing flow, vortex shedding, lift on cylinder.
COB726 application of a sailing yacht velocity prediction program to A monotype and an oceanic sailboat
Mardel Bongiovanni de Conti
Rodrigo César Franceschini de Oliveira
Departamento de Engenharia Naval e Oceânica - EPUSP
Av. Prof. Mello Moraes, 2231 - São Paulo (SP) - CEP 05508-900 - E-mail: mbdconti@usp.br
This paper analyses the steady-state performance of an oceanic yacht cruiser and of a monotype sailboat. The first one is here considered with three sails, namely the main, the jib and the spinnaker, and the last one just with a main sail. True wind incidence angle is varied from 0 to 180 degrees. Three wind velocity amplitudes are considered: 9, 15 and 20 knots. The boat velocity and the leeway and heel angles are determined by solution of three non-linear equations. Two of these equations express magnitude equality and phase opposition between aerodynamic and hydrodynamic forces, and the third expresses equilibrium of heel moments. Suggestions for the first guess of the boat velocity, leeway and heel are made, in order to initialize the solution of the non-linear system. Some discussion about the shadow zone, the heel angles on close-hauled, the spinnaker rising effect and the true wind magnitude effect is presented.
Keywords: Naval Architecture, Yacht Design, Sail Propulsion, Sail Boat Performance
COB1515 Particle Weighted schemes for Conservation laws. Recent developments and Applications.
J.P. Vila
Mathématiques pour l'Industrie et la Physique, UMR 5640, CNRS-UPS-INSA, Département de Génie Mathématique,
INSA, Complexe Scientifique de Rangueil, 31077 Toulouse Cedex 4, France, email vila@mip.ups-tlse.fr
In the last ten years new Particle Weighted methods for Partial Differential Equations have been introduced. There is a lot of applications in the field of Fluid dynamic, and we must quote Vortex and Vortex like methods for inviscid Euler equations and Navier Stokes equations. PIC (Particle in Cell) methods are also well known in the field of compressible gas dynamic. Together with Vortex methods they use a specific numerical or semi-analytical methods to compute differential terms such as pressure terms:
- Green kernels for Vortex methods
- particle grid coupling for PIC methods.
Keywords: Particle weighted, partial differential equations, vortex methods, PIC methods.