PROJECT ASSIGNMENT

Project Assignment

Project Assignment

1 page milestone

Designing a light-powered aircraft or a sailplane has become easier than in the past due to an increasing number of numerical codes available along with a high level of precision attained with the recent and modern experimental techniques. In spite of all that, using tools developed by third parties, surely leads to difficulties or inability to handle particular cases that will inevitably appear during the design phase of a new aircraft.

This is particularly true in view of the fact that to perform a successful new design this has to be competitive and very well done and the best way to be sure is that this can be accomplished by developing or adapting proprietary codes and techniques to the specific case under consideration. Obviously, it is almost impossible to develop or to own a number of codes or experimental facilities capable to cover all types of design, but if we restrict our investigations to a limited category of aircraft, we will try to show that this can be done in a relatively easy way.

In particular, we will deal with propeller-driven aircraft or with sailplanes and we will show that for this category of aircraft both general (conceptual) and detailed design can be accomplished using a combination of experimental and numerical techniques, all of them being developed in house at our department during the last year. Other authors have developed numerical tools to help the designer to rapidly verify the effect of modifying some geometric or aerodynamic parameters on the final designed aircraft.

Introduction

Not only most of these tools are non-modifiable, but they also deal with low angles of attack, giving only a rough estimation of the maximum lift coefficient of the whole aircraft. The numerical tools presented in this paper try to overcome these limitations and we will highlight the necessity of their integration to obtain a complete design process, including the possibility to virtually fly the aircraft that is being designed.

Numerical 2D codes

Analysis

As far as airfoil analysis is concerned, it is since 1990 that viscous/inviscid interaction codes are being developed . The inviscid part is treated using panel methods and the viscous part is modeled through integral boundary layer equations (laminar and turbulent) written in direct and inverse form. The actual version of the code (named TBVOR) valid for subsonic flow is capable to predict all viscous (mono and multi-component) airfoil characteristics.

The code is based on viscous/inviscid interaction and is capable of evaluating airfoil aerodynamic coefficients also when strong interactions are present on the airfoil such as laminar separation bubbles and large areas of turbulent separation. The code has been developed mainly to predict airfoil characteristics in stall and also in post-stall conditions, adding an inviscid point vortex at the airfoil-trailing edge to model the vorticity present in the wake at high angles of attack and with large separated areas.

Design

Based on the same 2D flow solver, DESAIRF is a two-dimensional design code that employs conjugate search methods to ...