How to find the actual value of d,b,t and D in the maximum value of sac?

close all
clear all
clc
% Constants
c   = 340;                        % Speed of sound
rho = 1.204;                      % Air Density
n   = 1.825e-5;                   % dynamics viscosity
w   = 3000*pi;                    
% Loop
for d=1:1:10
    for t=50:10:200
        for b=10:10:200
            for D=10:10:800
                sac(d,t,b,D)  = (4*(32*n.*(t*10^-4)/((78.5*(d*10^-4).^2/(b*10^-4).^2)*rho*c*(d*10^-4).^2))*((sqrt(1+((d*10^-4)*sqrt(w*rho/(4*n)).^2/32)))+((sqrt(2)/32)*(d*10^-4)*sqrt(w*rho/(4*n))*(d*10^-4)./(t*10^-4))))./(((1+(32*n.*(t*10^-4)/((78.5*(d*10^-4).^2/(b*10^-4).^2)*rho*c*(d*10^-4).^2))*((sqrt(1+((d*10^-4)*sqrt(w*rho/(4*n)).^2/32)))+((sqrt(2)/32)*(d*10^-4)*sqrt(w*rho/(4*n))*(d*10^-4)./(t*10^-4)))).^2)+((w.*(t*10^-4))/((78.5*(d*10^-4).^2/(b*10^-4).^2)*c).*(1+(1./(sqrt(3^2+(((d*10^-4)*sqrt(w*rho/(4*n)).^2)/2))))+(0.85*((d*10^-4)./(t*10^-4))))-cot(w*(D*10^-4)/c)).^2);
            end
        end
    end
end
M = max(sac(:));

Answer 1

[Torsten]

close all
clear all
clc
% Constants
c   = 340;                        % Speed of sound
rho = 1.204;                      % Air Density
n   = 1.825e-5;                   % dynamics viscosity
w   = 3000*pi;                    
% Loop
sacmax = -Inf;
indmax = zeros(1,4);
for d=1:1:10
    for t=50:10:200
        for b=10:10:200
            for D=10:10:800
                sac  = (4*(32*n.*(t*10^-4)/((78.5*(d*10^-4).^2/(b*10^-4).^2)*rho*c*(d*10^-4).^2))*((sqrt(1+((d*10^-4)*sqrt(w*rho/(4*n)).^2/32)))+((sqrt(2)/32)*(d*10^-4)*sqrt(w*rho/(4*n))*(d*10^-4)./(t*10^-4))))./(((1+(32*n.*(t*10^-4)/((78.5*(d*10^-4).^2/(b*10^-4).^2)*rho*c*(d*10^-4).^2))*((sqrt(1+((d*10^-4)*sqrt(w*rho/(4*n)).^2/32)))+((sqrt(2)/32)*(d*10^-4)*sqrt(w*rho/(4*n))*(d*10^-4)./(t*10^-4)))).^2)+((w.*(t*10^-4))/((78.5*(d*10^-4).^2/(b*10^-4).^2)*c).*(1+(1./(sqrt(3^2+(((d*10^-4)*sqrt(w*rho/(4*n)).^2)/2))))+(0.85*((d*10^-4)./(t*10^-4))))-cot(w*(D*10^-4)/c)).^2);
                if sac > sacmax
                    sacmax = sac;
                    indmax = [d,t,b,D];
                end
            end
        end
    end
end
sacmax

sacmax = 1.0000

indmax

indmax = 1×4

4 80 20 540