How to Plot for multiple values of a variable

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Saumya Nagar 17BME0447
回答： Star Strider 2021-4-9
I am new to MATLAB and need to plot for three different numerical values of G and plot the result on a single plot. Is there an easy way to do it by putting a loop, if yes, can you please let me know how should I write it. Thanks in advance!
The code is given below
clc; clf
clear all;
format short;
syms M;
syms G;
G = input('Enter the value of Gamma of the gas used (for monoatomic=1.66, for diatomic=1.4) : ' );
%Need to plot for different values of G (1.4,1.66, 1.8);
Molecular_Weight=input('Enter the molecular weight of the gas used in grams/mole (for air=28.97): ' );
%Molecular_Weight=28.97;
R=8314.46261815324/Molecular_Weight;
Throat_Diameter=2.8;
Throat_Area=3.14159265.*(10.^(-6)).*((Throat_Diameter).^2)/4;
Exit_Diameter=5.76;
Exit_Area_inMeter=3.14159265.*(10.^(-6)).*((Exit_Diameter).^2)/4;
Diverging_Length= input('Enter the length of diverging section in mm: ' );
DFT=[1:1:Diverging_Length];
M_Local=zeros([1 numel(DFT)]);
for d=1:numel(DFT)
Distance_from_throat=DFT(d);
Section_Diameter=Throat_Diameter+((Exit_Diameter-Throat_Diameter).*Distance_from_throat)/Diverging_Length;
Section_Area=3.14159265.*(10.^(-6)).*((Section_Diameter).^2)/4;
ARatio=Section_Area/Throat_Area;
problem.objective = @(M) (1/M.^2).*(((2+(G-1).*M.^2)/(G+1)).^((G+1)/(G-1)))-ARatio.^2; % Objective function
problem.solver = 'fzero'; % Find the zero
problem.options = optimset(@fzero); % Default options
% Solve supersonic root
problem.x0 = [1+1e-6 50]; % Supersonic solver bounds
M_Local(d) = fzero(problem); % Solve for supersonic M
end
plot(DFT,M_Local);
title('Distance from Throat vs Mach Number');
xlabel('Distance from Throat (in mm)');
ylabel('Mach Number');
hold on

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回答（1 个）

Star Strider
Star Strider 2021-4-9
It would likely be easiest to define ‘G’ as a vector:
Gv = [1.4,1.66, 1.8];
and then add an additional loop for it:
for k = 1:numel(Gv)
G = Gv(k);
for d=1:numel(DFT)
Distance_from_throat=DFT(d);
Section_Diameter=Throat_Diameter+((Exit_Diameter-Throat_Diameter).*Distance_from_throat)/Diverging_Length;
Section_Area=3.14159265.*(10.^(-6)).*((Section_Diameter).^2)/4;
ARatio=Section_Area/Throat_Area;
problem.objective = @(M) (1/M.^2).*(((2+(G-1).*M.^2)/(G+1)).^((G+1)/(G-1)))-ARatio.^2; % Objective function
problem.solver = 'fzero'; % Find the zero
problem.options = optimset(@fzero); % Default options
% Solve supersonic root
problem.x0 = [1+1e-6 50]; % Supersonic solver bounds
M_Local(d,k) = fzero(problem); % Solve for supersonic M
end
end
plot(DFT,M_Local);
title('Distance from Throat vs Mach Number');
xlabel('Distance from Throat (in mm)');
ylabel('Mach Number');
legend(compose('G = %.2f',Gv), 'Location','best')for k = 1:numel(Gv)
G = Gv(k);
for d=1:numel(DFT)
Distance_from_throat=DFT(d);
Section_Diameter=Throat_Diameter+((Exit_Diameter-Throat_Diameter).*Distance_from_throat)/Diverging_Length;
Section_Area=3.14159265.*(10.^(-6)).*((Section_Diameter).^2)/4;
ARatio=Section_Area/Throat_Area;
problem.objective = @(M) (1/M.^2).*(((2+(G-1).*M.^2)/(G+1)).^((G+1)/(G-1)))-ARatio.^2; % Objective function
problem.solver = 'fzero'; % Find the zero
problem.options = optimset(@fzero); % Default options
% Solve supersonic root
problem.x0 = [1+1e-6 50]; % Supersonic solver bounds
M_Local(d,k) = fzero(problem); % Solve for supersonic M
end
end
plot(DFT,M_Local);
title('Distance from Throat vs Mach Number');
xlabel('Distance from Throat (in mm)');
ylabel('Mach Number');
legend(compose('G = %.2f',Gv), 'Location','best')
.

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