Efficient computation of natural convection in a concentric annulus between an outer square cylinder and an inner circular cylinder

2002 ◽  
Vol 38 (5) ◽  
pp. 429-445 ◽  
Author(s):  
C. Shu ◽  
Y. D. Zhu
Keyword(s):  
Natural Convection ◽  
Circular Cylinder ◽  
Efficient Computation ◽  
Square Cylinder ◽  
Concentric Annulus

Patterns of Natural Convection Around a Square Cylinder Placed Concentrically in a Horizontal Circular Cylinder

1983 ◽  
Vol 105 (2) ◽  
pp. 273-280 ◽  
Author(s):  
K. S. Chang ◽  
Y. H. Won ◽  
C. H. Cho
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Circular Cylinder ◽  
Convection Heat Transfer ◽  
Boundary Layer Separation ◽  
Flow Speed ◽  
Low Flow ◽  
Square Cylinder ◽  
Aspect Ratios ◽  
Irregular Enclosure

The Galerkin finite element method was used to analyze the natural convection heat transfer in an irregular enclosure made by two isothermal concentric horizontal cylinders: the inner square cylinder and the outer circular cylinder. Two different aspect ratios, A/R = 0.2 and 0.4, are considered for two possible symmetric attitudes of the inner square cylinder. For the case of aspect ratio 0.4, experimental verification has also been made by obtaining field temperature measurement and streamline visualization. It is found that there is no boundary layer separation past the sharp edges of the inner cylinder in the range of Rayleigh numbers less than 105, although this phenomenon plays a negative role in the local and overall heat transfer. Above the upper horizontal surface of the inner square cylinder, a well-defined symmetric plume is found despite its low flow speed and temperature gradient. For the geometry of stand-on-edge position of the inner cylinder, vortex cores exist in the enclosure in quadruple for Ra≤5.0×104 and A/R = 0.4, and in double for other cases including A/R = 0.2.

scholarly journals Dynamical effect of the total strain induced by the coherent motion on local isotropy in a wake

2013 ◽  
Vol 720 ◽  
pp. 393-423 ◽  
Author(s):  
F. Thiesset ◽  
L. Danaila ◽  
R. A. Antonia
Keyword(s):  
Circular Cylinder ◽  
Large Scale ◽  
Bluff Body ◽  
Initial Conditions ◽  
Scale Up ◽  
Wake Flow ◽  
Total Strain ◽  
Coherent Motion ◽  
Square Cylinder ◽  
Local Isotropy

AbstractWe assess the extent to which local isotropy (LI) holds in a wake flow for different initial conditions, which may be geometrical (the shape of the bluff body which creates the wake) and hydrodynamical (the Reynolds number), as a function of the dynamical effects of the large-scale forcing (the mean strain, $ \overline{S} $, combined with the strain induced by the coherent motion, $\tilde {S} $). LI is appraised through either classical kinematic tests or phenomenological approaches. In this respect, we reanalyse existing LI criteria and formulate a new isotropy criterion based on the ratio between the turbulence strain intensity and the total strain ($ \overline{S} + \tilde {S} $). These criteria involve either time-averaged or phase-averaged quantities, thus providing a deeper insight into the dynamical aspect of these flows. They are tested using hot wire data in the intermediate wake of five types of obstacles (a circular cylinder, a square cylinder, a screen cylinder, a normal plate and a screen strip). We show that in the presence of an organized motion, isotropy is not an adequate assumption for the large scales but may be satisfied over a range of scales extending from the smallest dissipative scale up to a scale which depends on the total strain rate that characterizes the flow. The local value of this scale depends on the particular nature of the wake and the phase of the coherent motion. The square cylinder wake is the closest to isotropy whereas the least locally isotropic flow is the screen strip wake. For locations away from the axis, the study is restricted to the circular cylinder only and reveals that LI holds at scales smaller than those that apply at the wake centreline. Arguments based on self-similarity show that in the far wake, the strength of the coherent motion decays at the same rate as that of the turbulent motion. This implies the persistence of the same degree of anisotropy far downstream, independently of the scale at which anisotropy is tested.

Heat transfer from a circular cylinder by acoustic streaming

1967 ◽  
Vol 30 (2) ◽  
pp. 337-355 ◽  
Author(s):  
Peter D. Richardson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Natural Convection ◽  
Circular Cylinder ◽  
Prandtl Number ◽  
Acoustic Streaming ◽  
Mean Flow ◽  
Wide Range ◽  
Transverse Oscillations ◽  
Streaming Flow

An analysis is described for convection from a circular cylinder subjected to transverse oscillations relative to the fluid in which it is immersed. The analysis is based upon use of the acoustic streaming flow field. It is assumed that the frequency involved is sufficiently small that the acoustic wavelength in the fluid is much larger than the cylinder diameter, and that there is no externally imposed mean flow across or along the cylinder. Solutions are presented which are appropriate for a wide range of Prandtl number, and the cases of small and of large streaming Reynolds number are distinguished. The analysis compares favourably with experiments when the influence of natural convection is small.

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