  A novel method to estimate unsteady aerodynamic force coefficients from
pointwise velocity measurements is presented. The methodology is based on a
resolvent-based reduced-order model which requires the mean flow to obtain
physical flow structures and pointwise measurement to calibrate their
amplitudes. A computationally-affordable time-stepping methodology to obtain
resolvent modes in non-trivial flow domains is introduced and compared to
previous existing matrix-free and matrix-forming strategies. The technique is
applied to the unsteady flow around an inclined square cylinder at low Reynolds
number. The potential of the methodology is demonstrated through good agreement
between the fluctuating pressure distribution on the cylinder and the temporal
evolution of the unsteady lift and drag coefficients predicted by the model and
those computed by direct numerical simulation.
