Viscous effects assessment through nonlinear lifting-line theory

Abstract:

An existing extension to the classic Prandtl’s Lifting-Line theory is assessed for viscous effects. The method incorporates two preeminent differences from the original formulation: (i) a nonlinearization of the constitutive equations and (ii) the incorporation of viscosity through the use of bi-dimensional aerodynamic data from XFOIL. Three cases were tested to verify and validate the tool; both convergence study and comparison with another numerical method and experimental data are presented. In general, the lift coefficient is in good agreement for small angles of attack and, as it increases, this quantity deviates from one method to the other. Moreover, for the straight wing, the stall occurs at different angles of attack. In terms of drag, the coefficient agrees well for the straight wing, while it doesn’t for the elliptical one. Nevertheless, the agreement is worst at small angles for both cases. A 45-degree sweptback wing is also evaluated, and the convergence analysis indicates that the proposed formulation is not suitable. Finally, the formulation seems to be powerful as a preliminary wing design tool, given the necessary improvement suggestions made.


Reference:
CHREIM, José Rodolfo; DANTAS, João Lucas Dozzi; BURR, Karl Peter; PIMENTA, Marcos de Mattos. Viscous effects assessment through nonlinear lifting-line theory. In: INTERNATIONAL CONGRESS OF MECHANICAL ENGINEERING, 24th., 2017, Curitiba. Anais… 10 p.

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