BES AVBP - Hands-on Course at INPT-ENSEEIHT

This hands-on course BES (Bureaux d'Etudes Spécialisées) on AVBP is held in the winter term of the ENSEEIHT Engineering School which belongs to the Institut National Polytechnique de Toulouse. The course is optional for final year master students in 'Option Mécanique de Fluides Numérique' (CFD). The entire course has 8-9 sessions and was held for the first time in 1996/1997 by T. Schönfeld and I. d'Ast (both of CERFACS).
In the first part of this course a brief introduction to the code and the pre- and postprocessing tools is given. For this standard test cases like the NACA0012 profile or the channel with bump are executed. The second part of the course is devoted to little project to be defined by the students. Such a project comprises mesh generation, setting up of boundary conditions, etc. , execution of AVBP and interpretation of results. Below are shown a collection of results for these different configurations obtained by the students. All geometries are limited to two dimensions in order to simplify the mesh generation task and to save computing expenses. The computational grids were generated with the delaundo tool of J.D. Müller.
Note, these figures do not show results that are fully converged ! Time is fairly limited for the students the goal of this course is more to teach a global idea of what CFD is rather than tuning results ! Hence often improved computational grids or run parameters would be required to improve solution quality.

Syllabus du BES AVBP en francais:
Le BES AVBP a pour but de familiariser les étudiants avec l'utilisation d'un code parallèle de mécanique des fluides dans un cycle complet de calcul. Le logiciel utilisé est le code parallèle AVBP developpé au CERFACS, qui résout les equations de Navier-Stokes compressibles tridimensionnelles sur des maillages non structurés. Les trois étapes d'un cycle standard de calcul en mécanique des fluides (le pré-traitement des données, l'exécution du code de calcul et le post-traitement des résultats) sont abordées.
Le BES est decomposé en deux parties: la première est consacrée à l'introduction des logiciels et surtout l'utilisation du code AVBP incluant les notions de parallélisme. Cette partie se termine par le calcul de cas tests de référence bien documentés, comme par exemple un profil d'aile NACA. Dans la deuxième partie, les élèves doivent définir un petit projet de leur choix. Cette géometrie est alors maillée, les conditions aux limites sont à définir ainsi qu'éventuellement une solution initiale. Les premiers calculs sur cette configuration montrent les défauts du maillage initial, des paramètres de calculs, etc. Les élèves apprennent à régler tous les paramètres afin d'obtenir une solution correcte et à interpréter ces résultats.

Results obtained by the students in winter term 1997/98

Supersonic vehicle (Alexandre Castellini):
The configuration of a car running at supersonic speed on a solid ground is a challenging task. The freestream Mach number is 1.02 and thus just above the sonic barrier which results in a shock wave below the vehicle which bounds between the ground and the vehicle. The 2-D simulation of course does not allow to model the wheels ! Several approximations to the geometry were necessary, especially the correct design of the rear part has shown to be difficult.

Velocity vectors colored by the Mach number.

Computational grid composed of triangles

Interaction of boat sails (Olivier Beon and Olivier Rocher):
In this study the interaction of the foc and the main sail of racing sailing boat is investigated. The freestream Mach number is 0.1 which corresponds to a fairly high speed of around 30 m/s or 50 Kns ! However, simulations at lower Mach numbers would be in the range of incompressible flows and hence not realistic with AVBP. This parametric study allowed to study the influence between the two sails, the influence of the sail inclination and the flow detachment on the sail surface. The profiles of the sails were approximated the modified NACA0012 profiles !

Interaction of wing profiles (Guillaume Galateau):
In the project the influence of the main profile on the flow past the tail stabilizer is investigated. Two NACA0012 profiles are scaled in size and rotated in order to do a qualitative parametrical study on the flow field depending on their relative position and inclination.

Mach number shading for freestream Mach=0.85 and 8 degrees incidence for both main wing and tail.
Left figure: total velocity for freestream Mach=1.4, figure to the right: freestream Mach=0.85 and 2 degrees incidence for both main wing and tail

Inlet of a combustion chamber (Jean-Philippe Légier):
The unsteady flow through the inlet of a simplified gas-turbine combustion chamber is studied. The inlet is composed of three inlets for air (in the middle) and fuel (outer sections). The flow is laminar at Re=16.000. In this initial work only the correct boundary conditions and the influence of the mesh are investigated, no chemistry is taken into account. The entire project is continued in the frame of a 5 month trainee (DEA) with the aim to study ignition and flame stabilization in the chamber using a chemistry model.

Pressure distribution.

Iso-vorticity shading.

Car engine valve flow (Thierry Soulères):
In this study the internal flow around a valve of a car piston engine is simulated. The work aims to determine the pressure loss which is to be minimized. This kind of configuration is typically fully turbulent, unsteady and three-dimensional whereas the project is limited to 2-D laminar and stationary flows ... The inlet freestream Mach number is 0.1 which results in Mach=0.6 at the narrowest section of the piston. The Reynold number based on the inlet diameter is Re=120.000. More text and figures under preparation ...

Last update by T. Schönfeld: April 3, 1998