function Re_theta = Drela(lambda,Tu)
    % Drela 1998

    H = (-sqrt(62500*lambda.^2+52000*lambda+3247)+250*lambda+133)/29;
    tau_dash = 2.7*tanh(Tu/2.7);
    n_crit = -8.43-2.4*log(tau_dash/100);

    Re_theta = 155+89*(0.025*tanh(10./(H-1)-5.5)+1).*n_crit.^1.25;

end

