Three dimensional flow around a circular cylinder confined in a plane channel

Abstract

This paper presents two- and three-dimensional direct numerical simulations of the flow around a circular cylinder placed symmetrically in a plane channel. Results are presented in the Reynolds number range (based on the cylinder diameter and centerline velocity) of 10 to 390 for a blockage ratio (ratio of the cylinder diameter to the channel height) of 0.2. The aim of this work was to investigate in detail the confinement effect due to the channel’s stationary walls on the force coefficients and the associated Strouhal numbers, as well as on the generated flow regimes. Present results suggest a transition from a 2-D to a 3-D shedding flow regime between Re = 180 and Re = 210. This transition was found to be dominated by mode A and mode B three dimensional instabilities, similar to those observed in the case of an unconfined circular cylinder. This is the first time that the existence of the two modes, and of naturally occurring vortex dislocations, has been confirmed via full 3-D simulations for the case of a confined circular cylinder in a channel. A discontinuity in the variation of the Strouhal number St, and of the base pressure coefficient Cpb, with Re was also observed. This was found to be associated with the onset of mode A instability and the development of vortex dislocations, and parallels what occurs in the unconfined case, but previous studies could not confirm its existence in the confined case. Furthermore, by analyzing the mechanisms affecting the shape and evolution of these instabilities, it is demonstrated that they are significantly affected by the confinement only in the far wake.

On the transition to turbulence of a viscoplastic fluid past a confined cylinder: A numerical study

“…The channel inlet is located at a distance of L i ¼ 12:5D upstream of the circular cylinder, while the outlet is placed at L o ¼ 35:5D behind the body. These choices have been based on the previous work of Kanaris et al (2011), who repored the emergence of mode A and mode B three-dimensional wake instabilities in the transitional wake of a Newtonian fluid in the same flow configuration. A similar cylinder placement has also been used by other authors (Zisis and Mitsoulis, 2002;Mitsoulis, 2004;Tokpavi et al, 2008).…”

“…instead of periodic spanwise boundary conditions, to ensure that all of the critical physical mechanisms could be captured as accurately as possible, as recommended in Kanaris et al (2011). At the outlet a convective boundary condition is imposed,…”

“…Over the last decade there has been an increased interest in studying the confined cylinder problem, where the cylinder is placed in a plane channel (Sahin and Owens, 2004;Rehimi et al, 2008;Camarri and Giannetti, 2010;Kanaris et al, 2011). This flow configuration is not only closer to practical applications, it also allows for a more precise specification of the flow, both numerically and experimentally.…”

“…We have chosen to study the transitional regime of viscoplastic fluids in this particular configuration because the flow behavior for the viscous case is very well known. Additionally, since the required fully three-dimensional simulations are quite lengthy, the ability to leverage recently published results for the Newtonian case (Kanaris et al, 2011) is a significant consideration that we have taken into account. The main objective of this work is to study how viscoplastic effects influence transition to turbulence in the wake of a circular cylinder confined in a plane channel.…”

Assessment of Flow Interactions Between Circular Cylinders and Naca-0018 Hydrofoils at Low Reynolds Numbers

“…URANS equations were solved by applying finite volume scheme in these simulations. Kanaris et al [10] also investigated flow around circular cylinder in a plane channel by two and three-dimensional DNS method. These analyses were conducted at low Reynolds numbers and vortex shedding was captured in different cases.…”