Looping for a specified number of iteration

clc
clear all

%-------------------------------------------------------------------------%
% Specify the variable %
oil_SAE = 10; 
Temp_in = 85;          % Sump Temperature (°C)
d       = 0.15;        % Shaft Journal Diameter (Meter, m) 
r       = (d/2);       % Shaft Journal Radius (Meter, m)
N       = (166.69/60); % Shaft Speed (revolution per second,rps)
W       = 9000;        % Radial Load (Newton, N)
L       = 0.3;         % Bearing Length (Meter, m)
c       = 0.000026;     % Bearing clearance (Meter,m)

%-------------------------------------------------------------------------%
% Calculate the variable %

C_ratio     = r/c;        % Clearance ratio
P           = W/(d*L);    % Nominal Pressure (Pascal)
Slenderness = L/d  ;      % Bearing Aspect Ratio

%-------------------------------------------------------------------------%
% Viscosity - Temperature Chart

Temperature    = xlsread ('MFT','viscosity-temperature chart','A4:A30');

if oil_SAE     == 10
    V0          = 0.1089*10^(-3);
    b           = 1157.5 ;
elseif oil_SAE == 20
    V0          = 0.0937*10^(-3);
    b           = 1271.6;
elseif oil_SAE == 30
    V0          = 0.0971*10^(-3);
    b           = 1360.0;
elseif oil_SAE == 40
    V0          = 0.0827*10^(-3);
    b           = 1474.4;
elseif oil_SAE == 50
    V0          = 0.1171*10^(-3);
    b           = 1509.6;
elseif oil_SAE == 60
    V0          = 0.1288*10^(-3);
    b           = 1564.0;
end

%-------------------------------------------------------------------------%
% Calculation to find average temperature and viscosity %

Tf = Temp_in + 3;                  % Assumed Average Temperature (°C)
V  = V0*exp (b/((1.8*Tf)+127));    % Viscosity (Pa.s)
S  = (C_ratio)^2*((V*N)/P);        % Sommerfeld Number

if Slenderness      == 1
     delta_T        = (0.349109 + (6.00940*S)+(0.047467*(S^2)))*(P*(10^-6))/0.120;     % Temperature Rise(°C) at l/d=1
 elseif Slenderness == 1/2
     delta_T        = (0.394552 + (6.392527*S)-(0.036013*(S^2)))*(P*(10^-6))/0.120;    % Temperature Rise(°C) at l/d=1/2
 elseif Slenderness == 1/4
     delta_T        = 0.933828 + (6.437512*S)- (0.011048*(S^2))*(P*(10^-6))/0.120;     % Temperature Rise(°C) at l/d=1/4
else 
     delta_T        = ((33405*(S)^6)-(51557*(S)^5)+(30669*(S)^4)-(8871.9*(S)^3)+(1297.4*(S)^2)-(85.088*(S))+2.6111)*(P*(10^-6))/0.120; % Temperature Rise(°C) at l/d=Infinity
end

T_average  = Temp_in + (delta_T/2); % Average temperature (°C)

iter=0;
while iter <= 5 && abs (Tf-T_average)>0.001
    
    iter = iter + 1;
    delta = (Tf-T_average)/2;
    Tf    = Tf-delta;
    
    V  = V0*exp (b/((1.8*Tf)+127));   % Viscosity (Pa.s)
    S  = (C_ratio)^2*((V*N)/P);       % Sommerfeld Number
    
    if Slenderness  == 1
     delta_T        = (0.349109 + (6.00940*S)+(0.047467*(S^2)))*(P*(10^-6))/0.120;     % Temperature Rise(°C) at l/d=1
    elseif Slenderness == 1/2
     delta_T        = (0.394552 + (6.392527*S)-(0.036013*(S^2)))*(P*(10^-6))/0.120;    % Temperature Rise(°C) at l/d=1/2
    elseif Slenderness == 1/4
     delta_T        = 0.933828 + (6.437512*S)- (0.011048*(S^2))*(P*(10^-6))/0.120;     % Temperature Rise(°C) at l/d=1/4
    else 
     delta_T        = ((33405*(S)^6)-(51557*(S)^5)+(30669*(S)^4)-(8871.9*(S)^3)+(1297.4*(S)^2)-(85.088*(S))+2.6111)*(P*(10^-6))/0.120; % Temperature Rise(°C) at l/d=Infinity
end
    
    T_average  = Temp_in + (delta_T/2); % Average temperature (°C)
   
    disp ('Table for iteration');disp ('         c          Tf          V               S         deltaT        T average ');
    format shortG
    disp ([c',Tf', V',S',delta_T', T_average'])
    
end

** I want to loop the iteration as long as Tf-T_average is not in negative value and also not more than 0.001 which is 0 for 5th iteration. If the 5th iteration this is still not satisfied, then I want to increase the c where c=c+0.000001 for the next iteration until Tf-T_average=0. Please help me.Thanks

Answer 1

[ag]

Hi Siti,

To incorporate the described logic, you can modify the code as shown below:

% Initialize the iteration counter
iter = 0;

% Start a loop that continues until the difference between Tf and T_average is small enough
while abs(Tf - T_average) > 0.001
    % Increment the iteration counter
    iter = iter + 1;
    
    % Place your main calculation logic here

    % Check every 5 iterations 
    if (mod(iter, 5) == 0)
        if(Tf - T_average) != 0)
            % if the convergence condition is not met increament c
            c = c + 0.000001;
        else
            % if the convergence condition is met, break out of the loop
            break
        end
    end
end

Please note, that if the breaking condition is not met the loop will continue running forever, so please ensure that the convergence condition is met after certain iterations.

Hope this helps!