Tg. Zaki et al., NUMERICAL AND EXPERIMENTAL INVESTIGATION OF FLOW PAST A FREELY ROTATABLE SQUARE CYLINDER, Journal of fluids and structures, 8(6), 1994, pp. 555-582
This work deals with the response of a square cylinder free to rotate
in a uniform flow. The two-dimensional, incompressible, time-dependent
Navier-Stokes equation for flow around a fixed-cylinder are numerical
ly solved for Reynolds numbers up to 250. The static rotational stabil
ity of the cylinder is analysed by considering moments around the fixe
d cylinder at different angles to the flow. The separation pattern and
resulting wake are also investigated. Experiments are conducted on fi
xed and freely rotatable cylinders in the range of Reynolds number fro
m 1,000 to 10,000. Variation of shedding frequency with cylinder orien
tation is determined for the fixed cylinder. The rotatable cylinder sh
ows four distinct regimes of motion: a stable position where the cylin
der side surfaces are parallel to the flow, periodic oscillations abou
t this position, rotation with reversal of direction, and autorotation
. Some of the dynamics of the freely rotatable cylinder can be modelle
d by a nonlinear, second-order differential equation. Numerical soluti
ons of this simplified equation are compared qualitatively with experi
mental results.