Reynolds Number and Geometry Effects on Quasi-Steadiness of Heaving Rectangular Cylinders

An experimental investigation is conducted to examine the quasi-steady (QS) behavior of a transversely oscillating rectangular cylinder. The study is conducted at Reynolds numbers based on cylinder thickness of [Formula: see text] and 7500, below the range [Formula: see text] predominantly investigated in literature. In this low [Formula: see text] range, we showed recently that using a sharp-corner rectangular cylinder revealed a hitherto unreported [Formula: see text] effect on the reduced velocity [Formula: see text] threshold required for QS behavior. The goals of the present work are to confirm the findings of the recent study using substantially more data and to extend the work to a geometry with fully round corners. Measurements of the transverse force coefficient are carried out on static as well as oscillating cylinders. The results support our recent findings, showing an increase in the [Formula: see text] value required to reach the QS limit with decreasing [Formula: see text] ([Formula: see text] is the reduced velocity of vortex shedding). However, an [Formula: see text] independent threshold could be identified using [Formula: see text] instead of [Formula: see text]. The new parameter also provides a more compatible characterization of approaching the QS limit for both the sharp- and round-corner cylinders. The non-QS behavior observed in the load data is supported by boundary-layer-resolved measurements using molecular tagging velocimetry.