function Re_theta = Abu_Ghannam_Shaw(lambda,Tu)
    % Abu-Ghannam and Shaw 1980

    F = zeros(size(Tu));

    for i = 1:length(F)
        if lambda(i)<=0
            F(i) = 6.91+12.75*lambda(i)+63.64*lambda(i).^2;
        else
            F(i) = 6.91+2.48*lambda(i)-12.27*lambda(i).^2;
        end
    end

    Re_theta = 163+exp(F-F.*Tu/6.91);

end

