Abstract
The stall behavior of an empennage is a crucial and conditioning factor for its design. Thus, the preliminary design of empennages requires a fast low-order method which reliably computes the stall behavior and which must be sensitive to the design parameters (taper, sweep, dihedral, airfoil, etc.). Handbook or semi-empirical methods typically have a narrow scope and low fidelity, so a more general and unbiased method is desired. This paper presents a nonlinear vortex lattice method (VLM) for the stall prediction of generic fuselage-empennage configurations which is able to compute complete aerodynamic polars up to and beyond stall. The method is a generalized form of the van Dam algorithm, which couples the potential VLM solution with 2.5D viscous data. A novel method for computing 2.5D polars from 2D polars is presented, which extends the traditional infinite swept wing theory to finite wings, relying minimally on empirical data. The method has been compared to CFD and WTT results, showing a satisfactory degree of accuracy for the preliminary design of empennages.
Highlights
The core of the methodology is a vortex lattice method coupled with viscous aerodynamic polars
It may be observed that the present method has the proper sensitivity to the wing sweep
The present method has been implemented as a Python library with a simple user interface which enables the user to generate wing and fuselage geometries, read 2D input polars from XFOIL, MSES and Tau2D, and compute complete 3-dimensional lift curves
Summary
The core of the methodology is a vortex lattice method coupled with viscous aerodynamic polars. This is achieved with a generalized version of the α-method presented by van Dam [1]. The viscous coupling algorithm is presented, under the assumption that the section polars are available. This project has been supported entirely by the Clean Sky 2 program
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