Estimation of the divergence characteristics of a jet transport aircraft wing using numerical method.

Abstract The goal of the present paper work is to demonstrate the use of numerical matrix iteration technique to obtain the divergence speed of a jet transport aircraft wing by employing aerodynamic strip theory. Aerodynamics strip theory is employed to obtain the divergence speeds for a finite (Three Dimensional) wing and for an infinite (Two dimensional) wing by matrix iteration technique. The aircraft wing is divided in to a number of Multhopp’s stations. The elastic property of the wing of a typical jet transport is considered for this analysis. Assuming a straight elastic axis, the matrix of torsional influence coefficients associated with Multhopp’s stations has been computed. A MATLAB code is used to iterate the matrix to arrive at the required convergent approximate solution. The solution converges about after ten iterations of the matrix. It is observed that torsional divergence speed estimated on the basis of strip theory without finite span correction is about 18% lower than the divergence speed estimated on the basis of strip theory with finite span correction. Two-dimensional torsional divergence analysis based on strip theory yields conservative torsional divergence speed. A tentative increase of 20 % in torsional stiffness resulted in about 15.5 percent increase in torsional divergence speed of a three-dimensional wing. This shows that divergence speed of a wing is directly proportional to the square root of torsional stiffness. This corroborates the result obtained for a two-dimensional wing. The result of the findings will be mandatory to high performance modern airplane designers for aeroelastic analysis.