Test cell

Experiments have been performed in a vertical open-loop airflow system. The crosssection of the active portion of the test cell (to be called the test section) is with an overall length of 2 m. The active length of the test section where wake measurements have been carried out is 0:3 m. A contraction ratio of 10:1 ahead of the test section has been used. Prisms of square cross-section (3-4 mm edge) have been used for experiments as square cylinders. They are made either of Plexiglas or brass and carefully machined for sharp edges. Each cylinder is mounted horizontally with its axis perpendicular to the flow direction. It is supported along the two side walls for fixed cylinder experiments and mounted on actuators for oscillating cylinder experiments.

Fig 3.9: Picture of the PIV setup used for the present experiments

Two different ratios (also called aspect ratios) of 16 and 28 have been utilized in the experiments. The two aspect ratios were realized depending on the alignment of the cylinder axis with respect to test section. The corresponding blockage ratios are 0:03 and 0:06 respectively. With reference to Figure 3.8.the - axis is vertical and aligned with the mean flow direction. The - axis coincides with the cylinder axis and the - axis is perpendicular to both and .