Issue with correct Fanno parameter when using flowfanno function.

Question

Kirin Kawamoto 2024-10-1

0
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https://ww2.mathworks.cn/matlabcentral/answers/2156620-issue-with-correct-fanno-parameter-when-using-flowfanno-function

回答： Alan Stevens 2024-10-1

I am trying to solve the following problem fanno line flow problem (for context):

"Air flows into a constant area, insulated square duct at M = 0.6, static pressure of 10.0 psia, and static temperature of 500 °R. The duct length is 8.0 ft, duct diameter is 1.0 ft, and cf = 0.004. Determine the Mach number, static pressure, static temperature, and total pressure ratio Pt.2/Pt.1."

Here is my code:

M1 = 0.6;
P1 = 10;
T1 = 500;
L12 = 8;
D = 1;
cf = 0.004;
y=1.4;
[~,T1oTs,P1oPs,~,~,P01oP0s,fanno1] = flowfanno(y,M1);
fanno2 = fanno1 - cf*L12 / D;
[M2,T2oTs,P2oPs,~,~,P02oP0s,~] = flowfanno(y,fanno2,'fannosub');
P2 = P2oPs * (1/P1oPs) * P1;
T2 = T2oTs * (1/T1oTs) * T1;
Pt2 = P02oP0s*(1/P01oP0s);

In the documentation, it describes that the Fanno parameter is

. When I use this equation to calculate the Fanno parameter at the end of the duct, I get a mach number M2 = 0.6083. However, the solution for the problem (provided by my class) is M2 = 0.6368. The only way I get M2 = 0.6368 is if I use the Fanno parameter equation describe by my textbook and my class:

. Am I doing something wrong with my calculations, my code, or is my class solution to this problem just inccorect? Any help is appreciated.