How to Form Continuous Curve Plot
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I have the following code. At the end, I issue the plot command. The resulting figure shows hundreds of discrete points along the plot. Is there someway to tell Matlab to connect those points to form a continuous curve, simply so the end product looks more like a curve instead of many tiny little dots?
I'm new, so please provide answers in simple terms with clear explanation, since I'm trying to learn and get a better understanding.
Thanks,
M Ridzon
%Define ratio of specific heats
gamma=1.4;
%Define gas constant
R=287; %(J/Kg/K)
%Define reservoir properties
P_Res=500; %(kPa)
T_Res=500; %(Kelvin)
%Define nozzle exit area
NozArea=50; %(cm^2)
%Find pressure ratio when nozzle exit plane becomes choked.
P_Ch=((1+((gamma-1)./2).*((1.0).^2)).^(gamma./(gamma-1))).^-1;
%From critical pressure ratio, find actual back pressure which causes choke
P_Crit=P_Res.*P_Ch; %(kPa)
%Find density of fluid in reservoir
rho_Res=P_Res.*1000./R./T_Res;
%***********************************
%Calculate m-dot for choked case
%***********************************
%Find temperature of air exiting nozzle
T_Exit_Ch=T_Res./(1+((gamma-1)./2).*((1.0).^2)); %(K)
%Find speed of sound for the given temperature
a_Exit_Ch=(gamma.*R.*T_Exit_Ch).^0.5; %(m/s)
%Find fluid density from equation of state
rho_Exit_Ch=(P_Crit.*10.^3)./R./T_Exit_Ch; %(kg/m^3)
%Find m-dot
m_dot_Ch=rho_Exit_Ch*a_Exit_Ch*NozArea*((1/100)^2); %(kg/s)
%***********************************
%Begin FOR loop
%***********************************
for i=0:P_Res/500:P_Res
if i<=P_Crit
m_dot=m_dot_Ch;
else
%Find mach speed of fluid exiting nozzle
M=((2./(gamma-1)).*((P_Res./i).^((gamma-1)./gamma)-1)).^0.5;
%Find temperature of air exiting nozzle
T_Exit_Norm=T_Res./(1+((gamma-1)./2).*(M.^2)); %(K)
%Find density of air exiting nozzle
rho_Exit_Norm=rho_Res./((1+((gamma-1)./2).*(M.^2)).^(1./(gamma-1))); %(kg/m^3)
%Find speed of sound for the given temperature
a_Exit_Norm=(gamma.*R.*T_Exit_Norm).^0.5; %(m/s)
%Find exit velocity
V_Exit_Norm=M.*a_Exit_Norm; %(m/s)
%Find m-dot
m_dot=rho_Exit_Norm*V_Exit_Norm*NozArea*((1/100)^2); %(kg/s)
end
P_Ratio=i./P_Res;
plot(P_Ratio,m_dot,'Color','k');
hold on %Hold plotting until the conclusion
end
title('Ratio of Back Pressure to Reservoir Pressure vs. Mach Number')
xlabel('Pb / Pr')
ylabel('Mach Number')
hold off
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採用された回答
Star Strider
2015 年 3 月 11 日
Create ‘i’ as a vector, and then subscript it and your variables where necessary:
%***********************************
%Begin FOR loop
%***********************************
i=0:P_Res/5000:P_Res;
for k1 = 1:length(i)
if i(k1)<=P_Crit
m_dot(k1)=m_dot_Ch;
else
%Find mach speed of fluid exiting nozzle
M=((2./(gamma-1)).*((P_Res./i(k1)).^((gamma-1)./gamma)-1)).^0.5;
%Find temperature of air exiting nozzle
T_Exit_Norm=T_Res./(1+((gamma-1)./2).*(M.^2)); %(K)
%Find density of air exiting nozzle
rho_Exit_Norm=rho_Res./((1+((gamma-1)./2).*(M.^2)).^(1./(gamma-1))); %(kg/m^3)
%Find speed of sound for the given temperature
a_Exit_Norm=(gamma.*R.*T_Exit_Norm).^0.5; %(m/s)
%Find exit velocity
V_Exit_Norm=M.*a_Exit_Norm; %(m/s)
%Find m-dot
m_dot(k1)=rho_Exit_Norm*V_Exit_Norm*NozArea*((1/100)^2); %(kg/s)
end
P_Ratio(k1)=i(k1)./P_Res;
end
plot(P_Ratio,m_dot,'Color','k');
hold on %Hold plotting until the conclusion
title('Ratio of Back Pressure to Reservoir Pressure vs. Mach Number')
xlabel('Pb / Pr')
ylabel('Mach Number')
hold off
Every instance of ‘i’ in your original code should now be ‘i(k1)’. Check this in the event I missed any.
Also, it’s best not to use ‘i’ or ‘j’ as variables, including loop counters, because MATLAB uses them as its imaginary operators. Using them otherwise causes confusion.
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