The wake characteristics and hydrodynamic forces of a near-wall circular cylinder with the splitter plate

Abstract

Flow around a near-wall circular cylinder with the splitter plate is numerically performed at Reynolds number of 500, with the objective of investigating the wake characteristics and hydrodynamic forces. Five gap ratios [Formula: see text] and [Formula: see text] (G is the gap between the lower surface of the cylinder and the wall, D is the diameter of the cylinder) are selected, and the splitter plate length [Formula: see text] ranges from 0 to [Formula: see text]. The flow characteristics of an isolated cylinder with the splitter plate are investigated first for comparison, and four wake flow modes are observed, which include 2S mode ([Formula: see text]), P+S mode ([Formula: see text]), 2S+S mode ([Formula: see text]) and 2P mode ([Formula: see text]). As [Formula: see text] increases from 0 to [Formula: see text], the mean drag coefficient ([Formula: see text]) is decreased, and there is a slight increase of [Formula: see text] for [Formula: see text]. In addition, the cases of [Formula: see text] and [Formula: see text] produce a very significant reduction of drag, and the [Formula: see text] is reduced by as much as [Formula: see text] and [Formula: see text], respectively. The wake characteristics and hydrodynamic forces of a near-wall cylinder with the splitter plate are investigated in detail, and five wake regimes are observed, which include the wake vortex merging regime I, merged vortex attaching regime II, steady flow regime III, wall shear layer elongation regime IV and upper shear layer attaching regime V. For [Formula: see text], the wake vortex shedding is suppressed. For [Formula: see text], the Strouhal number (St) is decreased as [Formula: see text] increases from 0 to 1.0, and there is an increase of St at [Formula: see text]. At [Formula: see text], the St of the near-wall cylinder is larger than that of the isolated cylinder, and the increase in St is affected by the deflected gap flow. What is more, the hydrodynamic characteristics are affected by the wall. For [Formula: see text], the variations of [Formula: see text] with [Formula: see text] are similar to that of the isolated cylinder. It is found that the cases of [Formula: see text] and [Formula: see text] still produce a significant reduction of drag for [Formula: see text], and the [Formula: see text] is increased for all cases of [Formula: see text] as [Formula: see text] increases.