Find Critical Mach number graphically
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Hey,
I have to plot two curves to find the critical mach number in matlab. Very rusty at Matlab (been a few years). For the first curve I have to plot the Critical Pressure coefficient value vs. the Critical Mach number and the other curve is the Pressure coefficient (calculated with the minimum pressure coefficient at low speed) vs object mach number
my code thus far is:
Cpo = -0.65; Mcr = linspace(1,8,20); Minfin = linspace(0,1,20);
Ccrit = (2/(1.4*Mcr.^2))*(((((2+(.4*Mcr.^2))/2.4))^3.5)-1); Cp = Cpo/(sqrt(1-Minfin.^2));
plot(Mcr,Ccrit) plot(Minfin,Cp) grid
and I keep getting an error in the Ccrit and Cp lines. Any help is appreciated thanks
7 Comments
Brian B
on 12 Feb 2013
You've probably figured it out by now, but you need to change use
Ccrit = (2./(1.4*Mcr.^2)) ...*(((((2+(.4*Mcr.^2))/2.4)).^3.5)-1);
% ^ ^
% | |
% Note the periods before the "/" and before the "^".
You will need to make a similar change to the equation for Cp.
Answers (3)
Teja Muppirala
on 12 Feb 2013
You probably just need to change "/" to "./"
Remember, the dot indicates elementwise operations.
This works:
1./[1 2 3]
This does not:
1/[1 2 3]
0 Comments
Youssef Khmou
on 12 Feb 2013
hi Kyle : try this :
Cpo = -0.65;
Mcr = linspace(1,8,20);
Minfin = linspace(0,1,20);
Ccrit = (2./(1.4*Mcr.^2)).*(((((2+(.4*Mcr.^2))./2.4)).^3.5)-1);
%keyboard,
Cp = Cpo./(sqrt(1-Minfin.^2));
figure,
plot(Mcr,Ccrit),xlabel('Critical Mach number'), ylabel('Critical Pressure coefficient value')
figure,grid
plot(Minfin,Cp,'r'), xlabel('object mach number'), ylabel(' Pressure coefficient' );grid
1 Comment
Youssef Khmou
on 12 Feb 2013
The erro exist only in power operator "^" you have to use element-wise ".^" .
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