iteration

Question

mohamed saber 2011-11-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21065-iteration

plz .... why there is no answer in this iteration when i use this input by order :

30 , .01 ,1 1000 ,18,.02 ,1.2 ,1200, 2 , .05 , .75 , 1400

clear , clc 
fprintf('            \n <<< this program calculate Q in three branched pipes from three tanks >>> \n %12.5f ')
fprintf (' \n 1- Data for highest tank \n %12.5f')
% Data for highest tank
E1=input ('\n Enter tank_ energy (m) :  ');
f1=input (' Enter pipe_friction coefficient (m) :  ');
d1=input (' Enter pipe_diameter (m) :  ');
l1=input (' Enter pipe_length (m) : ');
fprintf (' \n 2- Data for intermediate tank \n %12.5f ')
% Data for intermediate tank
E2=input ('\n Enter tank_ energy (m) :  ');
f2=input (' Enter pipe_friction coefficient (m) :  ');
d2=input (' Enter pipe_diameter (m) :  ');
l2=input (' Enter pipe_length (m) : ');
fprintf (' \n 3- Data for lower tank \n %12.5f ')
% Data for lower tank
E3=input ('\n Enter tank_ energy (m) :  ');
f3=input (' Enter pipe_friction coefficient (m) :  ');
d3=input (' Enter pipe_diameter (m) :  ');
l3=input (' Enter pipe_length (m) : ');
% resistance calculation
R1=(.8*f1*l1)/(9.8*d1^5); % 1st pipe resistance
R2=(.8*f2*l2)/(9.8*d2^5); % 2nd pipe resistance
R3=(.8*f3*l3)/(9.8*d3^5); % 3rd pipe resistance
% junction's energy assumption (Ej)
Ej=(E1+E3)/2;   %  E1 <Ej< E3
% Q calculation
Q1=((abs(E1-Ej))/(R1))^.5;
Q2=((abs(E2-Ej))/(R2))^.5;  
Q3=((abs(E3-Ej))/(R3))^.5;
% Q enter to j is +ve , Q out from j is -ve
if E2<Ej   % Q in 2nd pipe is -ve
      dQ=Q1-Q2-Q3; % applying sign law
elseif E2>Ej % Q in 2nd pipe is +ve
     dQ=Q1+Q2-Q3; % applying sign law  
  end
if dQ>0  % if dQ +ve ... increase Ej
       iter=0;
      while abs(dQ)>.0001    % tolerrance
       Ej=Ej+.001;   % increase Ej
       iter=iter+1;   % no of try & error
        q1=((abs(E1-Ej))/(R1))^.5;
        q2=((abs(E2-Ej))/(R2))^.5;  
        q3=((abs(E3-Ej))/(R3))^.5;
        if Ej>E2
            dQ=q1-q2-q3;
        else 
            dQ=q1+q2+q3;
        end 
      end
      fprintf('\n Q at 1st pipe(m^3/s)= %12.5f\n ',q1)
      fprintf('\n Q at 2nd pipe(m^3/s)= %12.5f\n ',q2)
      fprintf('\n Q at 3rd pipe(m^3/s)= %12.5f\n ',q3)
      fprintf('\n Energy at junction(m)= %12.5f\n ',Ej)
      fprintf('\n no.of iteration= %12.5f\n',iter)
elseif dQ<0;  % if dQ +ve ... decrease Ej
      iter=0;
      while abs(dQ)>.0001    % tolerrance
       Ej=Ej-.001;   % decrease Ej
       iter=iter+1;   % no of try & error
        q1=((abs(E1-Ej))/(R1))^.5;
        q2=((abs(E2-Ej))/(R2))^.5;  
        q3=((abs(E3-Ej))/(R3))^.5;
        if Ej>E2
            dQ=q1-q2-q3;
        else 
            dQ=q1+q2+q3;
        end 
      end
        fprintf('\n Q at 1st pipe(m^3/s)= %12.5f\n ',q1)
      fprintf('\n Q at 2nd pipe(m^3/s)= %12.5f\n ',q2)
      fprintf('\n Q at 3rd pipe(m^3/s)= %12.5f\n ',q3)
      fprintf('\n Energy at junction(m^3/s)= %12.5f\n ',Ej)
      fprintf('\n no.of iteration(m^3/s)= %12.5f\n',iter)
  end

generally , the program run well when (E1+E3)/2 >E2 but it doesn't run when (E1+E3)/2 >E2

please , help me

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Answer 1

Jan 2011-11-13

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21065-iteration#answer_27808

You can use the debugger to check, what's going on: Open the file in the editor, set a breakpoint after the input commands and step through the program line by line.

Working with the debugger is more efficient than asking the forum.