Calculate the difference between minimum values of a parabola and straight line (from a plot)
1 visualizzazione (ultimi 30 giorni)
Mostra commenti meno recenti
Alina Abdikadyr
il 10 Feb 2023
Commentato: Les Beckham
il 10 Feb 2023
Hello everyone, please could you help me with a code.
How I can calculate the values from a plot? I need the difference between straight line (P) and between the minimum value of a parabola (P) for each curve.
So, for example in this curve, the difference between the straight blue curve and the first parabola, then the next straight line and green parabola and so on.
My code is:
clear all; close all
W = 60000;
S = 28.2;
AR=7;
cd0 = 0.02;
k = 0.04;
RC=0.51;
clalpha = 2*pi;
Psl=741000;
hv=0:1:10;
cdminp=4*cd0;
clminp=sqrt(3*cd0/k);
Vmin=sqrt(2*W/(1.225*28.2*clminp));
D=0.5*1.225*Vmin^2*S*cdminp;
Pminreq=D*Vmin;
deltaPgiven=RC*W;
figure(1);hold on; xlabel('V');ylabel('P')
hv=0:1:10;
for k1 = 1:numel(hv)
h = hv(k1);
i=0;
for alpha = 1:0.25:15
i=i+1;
rho(i)=1.225*exp(-h/10.4);
cl(i) = clalpha * alpha * pi/180;
V(i) = sqrt(2*W/rho(i)/S/cl(i));
L(i) = 0.5 * rho(i) * V(i) * V(i) * S * cl(i);
cd(i) = cd0 + k * cl(i) * cl(i);
D(i) = 0.5 * rho(i) * V(i) * V(i) * S * cd(i);
clcd(i) = cl(i)/cd(i);
p(i) = D(i)*V(i);
Ph(i)=Psl*(rho(i)/1.225).^0.75;
end
figure(1); plot(V,p)
hold on
plot(V,Ph);
end
0 Commenti
Risposta accettata
Les Beckham
il 10 Feb 2023
Modificato: Les Beckham
il 10 Feb 2023
Maybe this?
W = 60000;
S = 28.2;
AR=7;
cd0 = 0.02;
k = 0.04;
RC=0.51;
clalpha = 2*pi;
Psl=741000;
hv=0:1:10;
cdminp=4*cd0;
clminp=sqrt(3*cd0/k);
Vmin=sqrt(2*W/(1.225*28.2*clminp));
D=0.5*1.225*Vmin^2*S*cdminp;
Pminreq=D*Vmin;
deltaPgiven=RC*W;
figure(1);hold on; xlabel('V');ylabel('P')
hv=0:1:10;
for k1 = 1:numel(hv)
h = hv(k1);
i=0;
for alpha = 1:0.25:15
i=i+1;
rho(i)=1.225*exp(-h/10.4);
cl(i) = clalpha * alpha * pi/180;
V(i) = sqrt(2*W/rho(i)/S/cl(i));
L(i) = 0.5 * rho(i) * V(i) * V(i) * S * cl(i);
cd(i) = cd0 + k * cl(i) * cl(i);
D(i) = 0.5 * rho(i) * V(i) * V(i) * S * cd(i);
clcd(i) = cl(i)/cd(i);
p(i) = D(i)*V(i);
Ph(i)=Psl*(rho(i)/1.225).^0.75;
end
figure(1); plot(V,p)
hold on
plot(V,Ph);
[pmin, imin] = min(p); % find the min p
deltas(k1) = Ph(1) - pmin; % calculate the difference
tolerance = 5000; % or whatever you want
if (abs(deltas(k1) - 300000) < tolerance)
fprintf('delta = %8.1f at h = %4.1f, rho = %.5f, V = %.2f, Ph = %.1f, p = %.1f\n', ...
deltas(k1), h, rho(imin), V(imin), Ph(imin), p(imin))
end
end
legend(compose('h = %.1f', hv), 'location', 'northwest')
grid on
8 Commenti
Les Beckham
il 10 Feb 2023
It just represents how close to 300000 the delta has to be to make the code print the results. Adjust as desired.
Più risposte (1)
Torsten
il 10 Feb 2023
Modificato: Torsten
il 10 Feb 2023
syms h V W S rho cd0 k cl Psl
eqn = V == sqrt(2*W/rho/S/cl);
cl = solve(eqn,cl);
cd = cd0 + k * cl^2;
D = 0.5 * rho * V * V * S * cd;
p = D*V;
Vmin = solve(diff(p,V)==0,V);
pmin = subs(p,V,Vmin);
Ph = Psl*(rho/1.225)^0.75;
hnum = 0:0.01:10;
Wnum = 60000;
Snum = 28.2;
rhonum = 1.225*exp(-hnum/10.4);
cd0num = 0.02;
knum = 0.04;
Pslnum = 741000;
for i = 1:numel(hnum)
Phnum(i) = double(subs(Ph,[rho Psl],[rhonum(i),Pslnum]));
pm = double(subs(pmin,[W S rho cd0 k],[Wnum Snum rhonum(i) cd0num,knum]));
pminnum(i) = pm(end);
deltaP(i) = Phnum(i)-pminnum(i);
end
format long
deltaP.'
idx = deltaP > 2.8e5 & deltaP < 3.2e5; % select those deltaP with 2.8e5 <= deltaP < = 3.2e5
[hnum(idx).' deltaP(idx).'] % Show these values together with the corresponding h values
Vedere anche
Categorie
Scopri di più su Text Data Preparation in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!