Why does this function always gets solved at the initial point even though I keep on trying for different initial guess ? What is wrong with my fsolve ? Any kind of help will be appreciated

Jaunty Jose

2018 1 23

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更新时间：2021 8 20

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if true
  % Bubble formation in highly viscous liquids
% Model: Ramakrishnan, Kumar, Kuloor 1970

% taking place under constant flow condition.

%first Stage v_fb % final bubble is v_fin % two separate functions are used for each:

    function [v_finRam,v_rate,v_fbRam,v_secRam] = mainRamakrishnafb ()  
   v_fbRam = zeros(100,1);
    v_secRam = zeros(100,1);
   v_rate = zeros(100,1);
   v_finRam = zeros(100,1);
   A = zeros(100,1);
   B = zeros(100,1);
   C = zeros(100,1);
   E = zeros(100,1);
   g= 9.81;
        sig= 0.072;
        D_or= 2e-03;           % Orifice Diameter 
        denliq= 1000;
        vis= 8.9e-4;      %Dynamic Viscosity of the liquid (Pa.s)r
        dengas= 1.225;
        theta= 70*(pi/180);
   options = optimoptions('fsolve','TolX',1e-15);
     options = optimoptions(options,'TolFun',1e-15);
   %for i=1:15
  %v_rate(i) = 1e-6+(i-1)*5e-6;  % Volumetric Flow Rate
  for i=1:100;
  v_rate(i) = 1e-6+(i-1)*1e-6;
  v_fbRam(i) = fsolve(@(x)Ramakrishna(x,v_rate(i)),1e-6); % force balance bzbble volume = v_fb 
   end

Qcrit = (pi*((16/(3*(g^2)))^(1/6))*((sig*(D_or/2)/denliq)^(5/6)))*10^6;

plot (v_rate,v_fbRam,'Marker','o')

    function F1 = Ramakrishna(x,v_rate)
       g= 9.81;
        sig= 0.072;
        D_or= 2e-03;           % Orifice Diameter 
        denliq= 1000;
        vis= 8.9e-4;      %Dynamic Viscosity of the liquid (Pa.s)r
        dengas= 1.225;
        theta= 70*(pi/180);         % The contact angle
        F1 = ((11*v_rate^2)/((192*pi)*(((3)/(4*pi))^(2/3))*g))+(((3*vis*v_rate)*(x^(1/3)))/(2*((3)/4*pi)^(2/3)*g*denliq))+((((pi*D_or*sig*cos(theta))/(denliq*g)))*(x^(2/3)))- x^(5/3);
end
  end
  end