Solving for multiple solutions and plotting them

Question

Benneth Perez 2021-10-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1571718-solving-for-multiple-solutions-and-plotting-them

编辑： Benneth Perez 2021-10-26

Hello,

By choosing one value to theta2 I'm able to solve for one solution of beta and then use it to calculate P2.

What Id like to do is solve for multiple solutions of beta and then use those to find the correstpoing P2 (pressure 2).I tried making theta2 an array but it does not work.

Once thats complete I want to plot all angles and the correspoinding pressure 2(P2).

The code works if i just set theta 2 to some interger but when i want to make it an array to solve for many Beta which i need to solve for P2s i get an error. HELP

clc
clear all
format short g
M1 = 3;
P1 = 1;
theta2 = 1:1:20;
gamma = 1.4;
phi = 4.8;
syms beta2  
tantheta2 = tand(theta2);
x = 2*cotd(beta2)*((M1^2*((sind(beta2))^2)-1));
y = M1^2*(gamma+cosd(2*beta2))+2;
eqn2 = x/y;
b0=1;
result2 = vpasolve(tantheta2 == eqn2, beta2,b0);
beta2 = vpa(result2);
Mn1 = M1*sind(beta2);% Eqn 4.7 from Anderson's
p2p1 = 1+((2*gamma)/(gamma+1))*(Mn1^2-1);% Eqn 4.9 from Anderson's
Mn2sq = (Mn1^2+(2/(gamma-1)))/((2*gamma/(gamma-1))*Mn1^2-1);% Eqn 4.10 from Anderson's
Mn2 = sqrt(Mn2sq);
M2 = Mn2/sind(beta2-theta2);
P2 = p2p1*P1;

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Answer 1

Sulaymon Eshkabilov 2021-10-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1571718-solving-for-multiple-solutions-and-plotting-them#answer_816503

编辑：Sulaymon Eshkabilov 2021-10-26

在 MATLAB Online 中打开

Here is the corrected code:

clc; clearvars
format short g
M1 = 3;
P1 = 1;
theta2 = 1:1:20;
gamma = 1.4;
phi = 4.8;
syms beta2  
tantheta2 = tand(theta2);
x = 2*cotd(beta2)*((M1^2*((sind(beta2)).^2)-1));
y = M1^2*(gamma+cosd(2*beta2))+2;
eqn2 = x/y;
b0=1;
for ii=1:numel(theta2)
    T = tantheta2(ii); 
    clearvars result2 
    syms beta2
result2 = vpasolve(T== eqn2, beta2,b0);
beta2   = vpa(result2);
Mn1     = M1*sind(beta2);                                              % Eqn 4.7 from Anderson's
p2p1    = 1+((2*gamma)/(gamma+1))*(Mn1^2-1); % Eqn 4.9 from Anderson's
Mn2sq= (Mn1^2+(2/(gamma-1)))/((2*gamma/(gamma-1))*Mn1^2-1);% Eqn 4.10 from Anderson's
Mn2 = sqrt(Mn2sq);
M2 = Mn2/sind(beta2-theta2(ii));
P2 = p2p1*P1;
P2_ALL{ii}=P2;
end

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Benneth Perez 2021-10-26

编辑：Benneth Perez 2021-10-26

在 MATLAB Online 中打开

This seems to work how ever all the solutions are symbolics and I want to be able to plot them?

I'm guessing if I wanted to make a plot of changing theta angles vs p2 i would do something likes this? However, this is not working and I'm guessing its bc P2_All are symbolic solutions?

plot(theta2,P2_ALL)

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