• low-order modelling
• estimation
• POD
• control
• robust models

The aim is to develop and to test tools having a low computational cost for flow
simulation, estimation and control applications. The proper orthogonal decomposition
(POD) and a Galerkin projection of the equations onto the POD modes are used to
build low order models of the incompressible Navier-Stokes equations. In this work a
flow past a square cylinder is considered in two-dimensional and three-dimensional configurations.
Two blowing/suction actuators are placed on the surface of the cylinder.
Calibration techniques are applied, providing stable and rather accurate models, even
for three-dimensional wake flows with complicated patterns. A state estimation method,
involving flow measurements, is then developed for unsteady flows. Multi-dynamic calibrations
and efficient sampling techniques are applied to build models that are robust
to variations of the control parameters. A linear stability analysis by using linearized
low order models around a controlled steady state is briefly addressed. The presented
techniques are applied to the square cylinder configuration at Reynolds numbers that
range between Re = 40 and Re = 300.