the maximum difference bewteen lines from a loop and plot

Question

Alina Abdikadyr 2023-3-28

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1936804-the-maximum-difference-bewteen-lines-from-a-loop-and-plot

回答： Mathieu NOE 2023-3-28

采纳的回答： Mathieu NOE

在 MATLAB Online 中打开

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'])

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Answer 1

Mathieu NOE 2023-3-28

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1936804-the-maximum-difference-bewteen-lines-from-a-loop-and-plot#answer_1202989

在 MATLAB Online 中打开

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')

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Answer 2

Antoni Garcia-Herreros 2023-3-28

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1936804-the-maximum-difference-bewteen-lines-from-a-loop-and-plot#answer_1202974

在 MATLAB Online 中打开

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