ı want to calculate the flow variable by the specified input by user. for example when ı take l/d=1 and S=0.20 on the chart and then ı read by hand its almost 4.10. but when ı calculate with my code it gives different result. can you help me?

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matlab coder 2020-12-22

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https://ww2.mathworks.cn/matlabcentral/answers/700030-i-want-to-calculate-the-flow-variable-by-the-specified-input-by-user-for-example-when-i-take-l-d-1

评论： Alan Stevens 2020-12-23

D=input('enter a value of diameter:');
L=input('enter a value of length:');
if L/D==1
    % for l/d=1 performance parameters
    S=[0 0.00474 0.0188 0.0446 0.121 0.264 0.631 1.33 inf];
    % the corresponding vector for the volumetric oil-flow rate, Q/ (RcnL)
    Qc_1=[0 4.82 4.74 4.62 4.33 3.99 3.59 3.37 pi];
    fQR = csapi( S, Qc_1 );
    % suppose ı took Sc=0.20 from the chart
    Sc=0.20;
    Qc = fnval(fQR, Sc);
end

ı want to calculate the flow variable by the specified input by user. for example when ı take l/d=1 and S=0.20 on the chart and then ı read by hand its almost 4.10. but when ı calculate with my code it gives different result. can you help me? where is my mistake? and how can ı wite a code for the calculate flow variable for the user specified S

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Answer 1

Alan Stevens 2020-12-22

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Use interp1, but get rid of inf (and possibly use more points!)

>> S=[0 0.00474 0.0188 0.0446 0.121 0.264 0.631 1.33 6]; 
>> Qc_1=[0 4.82 4.74 4.62 4.33 3.99 3.59 3.37 3.2];
>> Q = interp1(S,Qc_1,0.2)
Q =
    4.1422

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matlab coder 2020-12-22

but ı use the tabular form of these values. and there is inf there. what can use if ı have inf? and also as ı shown below for some parameters there is no value on the table. they just put (-). ı dont know what should ı write for this kind of notation when ı try to create a corresponding matrix.

Alan Stevens 2020-12-23