Analysis and computation of the cross-flow past an
oscillating cylinder with two degrees of freedom
Qasem Al-Mdallal, Ph.D. Thesis, Memorial University (2004)
Abstract -
The present thesis deals with analysis and numerical simulation of a new class
of wake flows created by combined recti-linear (translational) and
rotational oscillation of a cylinder placed in a steady uniform flow. The
flow is incompressible and two-dimensional, and recti-linear and
rotational oscillations are harmonic. The instantaneous translation and
rotation start at the same moment and the development of the flow is
studied in a coordinate frame which moves with the cylinder but does not
rotate. The analysis is carried out for combined phase-locked translation
and rotation with a single frequency. The results are presented for five
set of the four dimensionless groups which characterize this flow. The
resulting vortex formation modes and synchronization (lock-on) phenomena
behind the cylinder (in the near-wake region) as well as the fluid forces
acting on the cylinder are analyzed. In addition, a series of
one-degree-of-freedom (1-DoF) forced vibration calculations are carried
out to better understand what differences result from the addition of
rotational oscillations to streamwise (in-line) or cross-stream
(transverse) motion and to see which effects a transverse-only or
in-line-only simulations miss. The numerical scheme is verified by
applying it to the special cases of uniform flow past a stationary
cylinder; a steadily rotating cylinder; a cylinder undergoing (1-DoF)
forced (recti-linear or rotational) oscillations. Exceptionally good
comparisons with previous experimental and numerical results are obtained.
Furthermore, the simulations of the start-up flow for the case of combined
(2-DoF) forced recti-linear and rotational cylinder oscillations at a
moderate Reynolds number are consistent with the results of the analytical
solution.