Numerical investigation of flow over a finite wall-mounted circular cylinder at low Reynolds numbers for various aspect ratios

Three-dimensional simulations of flow over and heat transfer from a finite wall-mounted circular cylinder have been conducted for different Reynolds numbers (Re = 1 – 100) and aspect ratios (AR=1–8) at Pr= 0.7, where flow remains steady for most of Re and AR considered. It was found that the computational domain size strongly affects the results, especially at low AR and Re. Thus, for very low Re , where the viscous effects are more dominant, it needs to be employed a more extensive domain size. In contrast, the sensitivity to the domain size decreases with increasing Re and AR. It was also deduced that the drag coefficients decrease by increasing Re for all aspect ratios examined. Furthermore, with the increase of AR but with the same Re , the drag coefficients increase. Some unsteady simulations were also carried out for higher Re in the range of Re= 100–200 for AR= 3–8 to find the critical Reynolds numbers of the onset of vortex shedding (Re_cr). It is found that the Re_cr decreases from 195 ± 5–65 ± 5 by increasing AR from 3 to 8, or flow becomes unsteady in lower Re for higher AR. Furthermore, the flow structure has been examined for various Re and AR. Different types of vortices, including tip (TV), base (BV), and horseshoe (HV) vortices, as well as Kármán vortex shedding (VS), are observed for a specific range of Re and AR. It is found that contrary to cases with high Re, the aforementioned vortices do not form for all Re (1−100) and AR (1−8) examined.