Simple wing: Drag coefficient decreases with negative deflection values

[ybeyer]

Instead of increasing the drag coefficient, it decreases by negative deflection values.

Have a look at the code at L90

For testing, run the following command (-10-deg deflection):

alpha_M         = [-pi/2:0.05:pi/2]';
beta_M          = 0;
eta             = [-10]'*pi/180;
figure
for i = 1:length(eta)
C_D = simpleWingGetCd( wing, alpha_M*[1,1], beta_M*[1,1], eta(i)*[1,1] );
plot( alpha_M, C_D )
hold on
end
xlabel('\alpha_M, rad'), ylabel('C_D'), grid on;

and then this (0-deg deflection):

alpha_M         = [-pi/2:0.05:pi/2]';
beta_M          = 0;
eta             = [0]'*pi/180;
figure
for i = 1:length(eta)
C_D = simpleWingGetCd( wing, alpha_M*[1,1], beta_M*[1,1], eta(i)*[1,1] );
plot( alpha_M, C_D )
hold on
end
xlabel('\alpha_M, rad'), ylabel('C_D'), grid on;

You will see a decrease in the drag coefficient compared to a zero angle of attack.