A study of the unsteady aerodynamics of a wing at high angles of attack using decambering to model separated flow

Abstract

An Unsteady Vortex Lattice Method is developed and validated. It is coupled with a decambering methodology to account for viscous effects on the aerodynamic coefficients. Two additional methodologies to select a unique solution when multiple solutions arise have been proposed. The transient nature of the aerodynamic loads of a suddenly moving wing at different angles of attack is examined. Sudden jumps are observed in the $C_L(t)$ at post-stall angles of attack. The jumps are followed by the presence of asymmetric solutions, which then decline with time and a change in the solution state. Higher angles of attack see an increasing number of jumps.

Appendices

Nomenclature

c :

chord

n :

unit normal vector

AR :

aspect ratio

IC :

influence coefficient matrix

J :

Jacobian matrix

f :

point of separation

$C_L$ :

coefficient of lift

$C_M$ :

coefficient of moment

$C_n$ :

coefficient of normal force

Re :

Reynolds Number

$\psi$ :

nascent vortex’s streamline angle

$\alpha$ :

angle of attack

$\Gamma$ :

circulation

x, y, z:

spatial coordinates

$\delta x$ :

residuals

$N_{wing}$ :

number of sections

F :

forcing function

cr :

vortex core radius

NX :

no. of chordwise panels

NY :

no. of span-wise panels

Npan :

total no. of panels

NW :

no. of wake vortex rings

Subscript

pot :

potential flow

visc :

viscous flow

br :

bound vortex ring

wr :

wake vortex ring