17-03-2014, 10:10 PM
Abstract—Incompressible flow around a pair of circular
cylinders in various staggered arrangements with heated
upstream cylinder is investigated in this study. Three
dimensional direct numerical simulation (DNS) has been
performed with spatial discretization based on the spectral/hp
element method with the Reynolds numbers of 200 and the
Richardson numbers are varied from 0.05 to 2.0. The
longitudinal separation to cylinders diameter ratio is set to 2.5
and 5.0 with transverse separation to cylinders diameter ratio
is fixed at 1.0. The investigation focuses on the effects of
buoyancy as well as cylinders placement on both flow
structures and local heat transfer characteristics of both
cylinders.
Keywords-Direct numerical simulation; Mixed Convection;
Staggerred cylinders
I. INTRODUCTION
Two staggered cylinders flows have been subject of
interest to engineering and scientific community relevance to
fluid mechanics because the flows can represent many
important physical phenomena, such as flow interference,
complicated vortex shedding and transition. Besides, they
also express complicated behavior of mass and energy
transfer which include:
• Wake interference: One of the cylinders is partially or
completely submerged in the wake of the other, and
• Proximity interference: The two cylinders are located
close to one another, but neither is submerged in the wake of
the other.
Both types of interferences apparently yield complicated
flow structures as well as highly complex wake vortex
dynamics. The heat transfer characteristics of the cylinders
usually depend on a given interference regime resulted from
cylinders placements. The recent investigation of the three
dimensional instability of staggered and tandem cylinders
wake can be found in [1] and [2] where the explanation of
interference phenomenon and its interaction with the three
dimensional vertical structure, the effects of threedimensionality
and cylinder spacing are proposed. The
influence of buoyancy on flow behaviors of isolated cylinder
and tandem cylinder in laminar flow regime have been
reported by [5] stating that the buoyancy-driven convection
induced dramatically changes to vortex shedding and
temperature distribution patterns. There are very few studies
on the heat transfer mechanism of staggered cylinders
especially when effects of the buoyancy becomes more
important or relatively comparable to those from forced
convection process.
In present study, we aim to investigate the effects of
buoyancy on both three-dimensional structures of the flow
as well as heat transfer characteristics of a pair of cylinders
placed in staggered arrangements at Re = 200 where
secondary instability of the two dimensional vortex street of
single cylinder appears. The investigation is done via direct
numerical simulation (DNS) approach. Here, we have carried
out numerical studies on both types of interferences.
Specifically, for proximity interference, we focus on the
biased gap flow and reattachment regimes which exhibit
suppression of three dimensionality. The paper is organized
as follows. In next section, we describe the details of the
simulation and analysis methods used in the current
investigation. Then, we present the results with some
discussions. Finally, we close the paper with summary of the
investigation.
cylinders in various staggered arrangements with heated
upstream cylinder is investigated in this study. Three
dimensional direct numerical simulation (DNS) has been
performed with spatial discretization based on the spectral/hp
element method with the Reynolds numbers of 200 and the
Richardson numbers are varied from 0.05 to 2.0. The
longitudinal separation to cylinders diameter ratio is set to 2.5
and 5.0 with transverse separation to cylinders diameter ratio
is fixed at 1.0. The investigation focuses on the effects of
buoyancy as well as cylinders placement on both flow
structures and local heat transfer characteristics of both
cylinders.
Keywords-Direct numerical simulation; Mixed Convection;
Staggerred cylinders
I. INTRODUCTION
Two staggered cylinders flows have been subject of
interest to engineering and scientific community relevance to
fluid mechanics because the flows can represent many
important physical phenomena, such as flow interference,
complicated vortex shedding and transition. Besides, they
also express complicated behavior of mass and energy
transfer which include:
• Wake interference: One of the cylinders is partially or
completely submerged in the wake of the other, and
• Proximity interference: The two cylinders are located
close to one another, but neither is submerged in the wake of
the other.
Both types of interferences apparently yield complicated
flow structures as well as highly complex wake vortex
dynamics. The heat transfer characteristics of the cylinders
usually depend on a given interference regime resulted from
cylinders placements. The recent investigation of the three
dimensional instability of staggered and tandem cylinders
wake can be found in [1] and [2] where the explanation of
interference phenomenon and its interaction with the three
dimensional vertical structure, the effects of threedimensionality
and cylinder spacing are proposed. The
influence of buoyancy on flow behaviors of isolated cylinder
and tandem cylinder in laminar flow regime have been
reported by [5] stating that the buoyancy-driven convection
induced dramatically changes to vortex shedding and
temperature distribution patterns. There are very few studies
on the heat transfer mechanism of staggered cylinders
especially when effects of the buoyancy becomes more
important or relatively comparable to those from forced
convection process.
In present study, we aim to investigate the effects of
buoyancy on both three-dimensional structures of the flow
as well as heat transfer characteristics of a pair of cylinders
placed in staggered arrangements at Re = 200 where
secondary instability of the two dimensional vortex street of
single cylinder appears. The investigation is done via direct
numerical simulation (DNS) approach. Here, we have carried
out numerical studies on both types of interferences.
Specifically, for proximity interference, we focus on the
biased gap flow and reattachment regimes which exhibit
suppression of three dimensionality. The paper is organized
as follows. In next section, we describe the details of the
simulation and analysis methods used in the current
investigation. Then, we present the results with some
discussions. Finally, we close the paper with summary of the
investigation.