The influence of the location of the lateral boundaries on 2D computation of
unsteady incompressible flow past a circular cylinder is investigated. The case
of Reynolds number 100 is used as a benchmark, and several quantities
characterizing the unsteady flow are obtained for a range of lateral boundary
locations. The computations are performed with two distinct finite element
formulations - space-time velocity-pressure formulation and
velocity-pressure-stress formulation. We conclude that the distance between the
cylinder and the lateral boundaries can have a significant effect on the Strouhal
number and other flow quantities. The minimum distance at which this influence
vanishes has been found to be larger than what is commonly assumed.