Pressure calculation loop error
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I have to calculate the pressure at different altitudes. I have the code that calculate all of the variables to go into my pressure calculation and all of those run fine and seem to produce the values that I am looking for but when I try to run the pressure loop it says the sides have different values. Can anyone tell me where I am going wrong?
This is what I have so far:
clc;
clear all;
p(1)=1.013e5;
r=287; %Jules/kg*K
dz=200;
% =================== Gravity Calculations ============================
alt=0:200:50000;
Re=6.37e6;
g0=9.80665;
i=1:length(alt);
g=g0*((Re^2)./((alt(i)+Re).^2));
% =================== Temperature Calculations ============================
for i=1:length(alt)
if alt(i)<=11000
t(i)=((-71.5/11000).*alt(i)+15)+273;
elseif 11000<alt(i) && alt(i)<=20100
t(i)=(-56.5)+273;
elseif 20100<alt(i) && alt(i)<=32200
t(i)=((12/12100).*alt(i)-76.434)+273;
elseif 32200<alt(i) && alt(i)<=47300
t(i)=((42/15100).*alt(i)-134.063)+273;
else
t(i)=(-2.5)+273;
end
x=g./(r*t(i));
end
for i=1:length(alt)
p(i+1)=p(i).*((1/2)*x.*dz)+(1-(1/2)*x.*dz);
end
5 个评论
Geoff Hayes
2020-6-26
John - x is a 1x251 array, so the line of code
p(i+1)=p(i).*((1/2)*x.*dz)+(1-(1/2)*x.*dz);
is trying to assign a 1x251 array on the right-hand side to the 1x1 scalar on the left-hand side. Is this what you want, or do you mean to use the ith element of x in the calculation. SImilarly, in your for loop, you have
x=g./(r*t(i));
where g is the 1x251 array. Do you mean for x to be a 1x251 array where each element of this array changes on every iteration? Or should this be
x(i) = g(i)./(r*t(i));
?
KSSV
2020-6-26
You should replace the last loop to this:
for i=1:length(alt)-1
p(i+1)=p(i).*((1/2)*x(i)*dz)+(1-(1/2)*x(i)*dz);
end
John Woods
2020-6-26
KSSV
2020-6-26
If you replace the loop with the given..I am not getting any error.....your error is becuse you are using x, replace ot with x(i).
John Woods
2020-6-26
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2020-6-26
2020-6-26
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