f_Haaland.m

function f = f_Haaland(D,Re,aRou)
%% Calculates the Darcy-Weisbach friction factor for pressure loss calculations
%   via explicit equation by Haaland,S.E.
%   by Tol,Hakan Ibrahim from the PhD study at Technical University of Denmark 
%   PhD Topic: District Heating in Areas with Low-Energy Houses

%% INPUTS (Scalar or Vector)
%    aRou     : Absolute roughness of pipe          [mm]
%    D        : Inner diameter of the pipe          [mm]
%    Re       : Reynolds Number                     [-]

%% Checking algorithm limitations
if Re<4000 | Re>1e8 
    error('Error: Zigrang&Sylvester algorithm is valid for a Reynold range as in 4000<Re<1e8')
end
if aRou/D<1e-6 | aRou/D>0.05  
    error('Error: Zigrang&Sylvester algorithm is valid for a relative roughness range as in 1e-6<eps/D<0.05')
end

f=(-1.8.*log10(((aRou./D)./3.7).^1.11+6.9./Re)).^-2;

end