the maximum difference bewteen lines from a loop and plot

Hello everyone!

Please, could you help me with a code

In my code, I'm plotting power and drag versus velocity. So, I need to calculate at which speed the maximum difference between two lines occur and the maximum difference between powers and drags. So, for example in figure 1, I need to calculate the value of maximum difference between orange and blue lines, and at which speed it occurs

My code is:

clear all; close all

W_takeoff = 10000;
W_landing=6000;
S = 20;
AR = 5;
cd0 = 0.02;
k = 1/pi/AR;
RC=0.51;
clalpha = 2*pi;
amin=2;
astall=12;
rho=1;
ct=0.001;
figure(1);hold on; xlabel('V');ylabel('D')
figure(2);hold on; xlabel('V');ylabel('D')
figure(3);hold on; xlabel('V');ylabel('P')
figure(4);hold on; xlabel('V');ylabel('P')
figure(5);hold on; xlabel('\alpha');ylabel('c_l/c_d^2')
    i=0;
    for alpha = amin:0.25:astall
        i=i+1;
        cl(i) = clalpha * alpha * pi/180;
        V_takeoff(i) = sqrt(2*W_takeoff/rho/S/cl(i));
        V_landing(i) = sqrt(2*W_landing/rho/S/cl(i));
        cd(i) = cd0 + k * cl(i) * cl(i);
        D_takeoff(i) = 0.5 * rho * V_takeoff(i) * V_takeoff(i) * S * cd(i);
        D_landing(i) = 0.5 * rho * V_landing(i) * V_landing(i) * S * cd(i);
        p_takeoff(i) = D_takeoff(i)*V_takeoff(i);
        p_landing(i) = D_landing(i)*V_landing(i);
        P_takeoff(i)=20000+500*V_takeoff(i);
        T_takeoff(i)=20000/V_takeoff(i)+500;
        P_landing(i)=20000+500*V_landing(i);
        T_landing(i)=20000/V_landing(i)+500;
        cl_cd2(i)=cl(i)/(cd(i)*cd(i));
        ang(i)=alpha;
    end  
    figure(1); plot(V_takeoff,D_takeoff)
    hold on 
    plot(V_takeoff,T_takeoff)
    title(['Takeoff'])
    figure(2); plot(V_landing,D_landing)
    hold on 
    plot(V_landing,T_landing)
    title(['Landing'])
    figure(3); plot(V_takeoff,p_takeoff)
    hold on 
    plot(V_takeoff,P_takeoff)
    title(['Takeoff'])
    figure(4); plot(V_landing,p_landing)
    hold on 
    plot(V_landing,P_landing)
    title(['Landing'])

Answer 1

[Mathieu NOE]

hello

see updated code below

clear all; close all
W_takeoff = 10000;
W_landing=6000;
S = 20;
AR = 5;
cd0 = 0.02;
k = 1/pi/AR;
RC=0.51;
clalpha = 2*pi;
amin=2;
astall=12;
rho=1;
ct=0.001;

i=0;
    for alpha = amin:0.25:astall
        i=i+1;
        cl(i) = clalpha * alpha * pi/180;
        V_takeoff(i) = sqrt(2*W_takeoff/rho/S/cl(i));
        V_landing(i) = sqrt(2*W_landing/rho/S/cl(i));
        cd(i) = cd0 + k * cl(i) * cl(i);
        D_takeoff(i) = 0.5 * rho * V_takeoff(i) * V_takeoff(i) * S * cd(i);
        D_landing(i) = 0.5 * rho * V_landing(i) * V_landing(i) * S * cd(i);
        p_takeoff(i) = D_takeoff(i)*V_takeoff(i);
        p_landing(i) = D_landing(i)*V_landing(i);
        P_takeoff(i)=20000+500*V_takeoff(i);
        T_takeoff(i)=20000/V_takeoff(i)+500;
        P_landing(i)=20000+500*V_landing(i);
        T_landing(i)=20000/V_landing(i)+500;
        cl_cd2(i)=cl(i)/(cd(i)*cd(i));
        ang(i)=alpha;
    end  
    
    figure(1); 
    [max_delta,idelta] = max(abs(D_takeoff-T_takeoff));
    
    plot(V_takeoff,D_takeoff,V_takeoff,T_takeoff,...
        V_takeoff(idelta),D_takeoff(idelta),'dk',V_takeoff(idelta),T_takeoff(idelta),'dk')
    hold on
    plot([V_takeoff(idelta) V_takeoff(idelta)],[D_takeoff(idelta) T_takeoff(idelta)],'k--');
    title(['Takeoff'])
    xlabel('V');ylabel('D')

    
    figure(2); plot(V_landing,D_landing,V_landing,T_landing)
    title(['Landing'])
    xlabel('V');ylabel('D')

    
    figure(3); plot(V_takeoff,p_takeoff,V_takeoff,P_takeoff)
    title(['Takeoff'])
    xlabel('V');ylabel('P')

    
    figure(4); plot(V_landing,p_landing,V_landing,P_landing)
    title(['Landing'])
    xlabel('V');ylabel('P')

Answer 2

[Antoni Garcia-Herreros]

maxdiff=max(abs(p_takeoff-P_takeoff)); % Value of the maximum difference 
i=find(abs(p_takeoff-P_takeoff)==maxdiff); % Index at which the maximum difference occurs