Numerical study of two-dimensional near wake structure of the flow past a circular cylinder undergoing transition

1987 ◽  
Author(s):  
M. BRAZA ◽  
H. HA MINH
Keyword(s):  
Circular Cylinder ◽  
Numerical Study ◽  
Two Dimensional ◽  
Near Wake ◽  
Wake Structure ◽  
Flow Past

The flow past a rapidly rotating circular cylinder

1957 ◽  
Vol 242 (1228) ◽  
pp. 108-115 ◽  
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Present Theory ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Rotating Circular Cylinder ◽  
Flow Past ◽  
Separating Flow ◽  
Two Dimensional Flow ◽  
Uniform Stream

This paper considers the two-dimensional flow past a circular cylinder immersed in a uniform stream, when the cylinder rotates about its axis so fast that separation in suppressed. The solution of the flow in the boundary layer on the cylinder is obtained in the form of a power series in the ratio of the stream velocity to the cylinder's peripheral velocity, and expressions are deduced for the value of the circulation and the torque on the cylinder. The terms calculated explicitly are sufficient to give reliable numerical values over the whole range of rotational speeds for which the postulate of non-separating flow is justifiable. The previously accepted theory, due to Prandtl, predicted that the circulation should not exceed a certain limit, while the present theory indicates that the circulation increases indefinitely with increase of rotaional speed. Strong arguments against the older theory are put forward, but the experimental evidence available is inconclusive.

Numerical Simulation of Fluid Slip at a Hydrophobic Surface

Volume 4 ◽  
2004 ◽  
Author(s):  
Takao Fujita ◽  
Keizo Watanabe
Keyword(s):  
Boundary Condition ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Hydrophobic Surface ◽  
Friction Reduction ◽  
Water Repellent ◽  
Two Dimensional ◽  
Hydrophobic Property ◽  
Flow Past

Laminar drag reduction is achieved by using a hydrophobic surface. In this method, fluid slip is applied at the hydrophobic surface. An initial experiment to clarify for a laminar skin friction reduction was conducted using ducts with a highly water-repellent surface. The surface has a fractal-type structure with many fine grooves. Fluid slip at a hydrophobic surface has been analyzed by applying a new wet boundary condition. In this simulation, an internal flow is assumed to be a two-dimensional laminar flow in a rectangular duct and an external flow is assumed to be a two-dimensional laminar flow past a circular cylinder. The VOF technique has been used as the method for tracking gas-liquid interfaces, and the CSF model has been used as the method for modeling surface tension effects. The wet boundary condition for the hydrophobic property on the surface has been determined from the volume ratio in contact with water near the surface. The model with a stable gas-liquid interface and the experimental results of flow past a circular cylinder at Re = 250 without growing the Karman vortex street are made, and these results show that laminar drag reduction occurring due to fluid slip can be explained in this model.

The effect of base bleed on the steady separated flow past bluff objects

1969 ◽  
Vol 39 (4) ◽  
pp. 735-752 ◽  
Author(s):  
L. G. Leal ◽  
A. Acrivos
Keyword(s):  
Bluff Body ◽  
Separated Flow ◽  
Pressure Profile ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Wake Region ◽  
Near Wake ◽  
Flow Past ◽  
Modifying Effect ◽  
Base Bleed

The modifying effect of base bleed on the steady separated flow past a two-dimensional bluff body is considered. Detailed experimental results are presented for Reynolds numbers R between 50 and 250 and for bleed coefficients b in the range 0 to 0·15. The streamline pattern near the object is found to be strongly affected by small changes in the rate of bleed, with the recirculating closed wake disappearing altogether for b > 0·15. Nevertheless, the qualitative dependence on R of the physical dimensions of the near-wake region and the associated streamwise pressure profile appear to be unaffected by base bleed.

Discussion: “Flow Past a Right Circular Cylinder in a Rotating Frame” (Boyer, D. L., 1970, ASME J. Basic Eng., 92, pp. 430–435)

1970 ◽  
Vol 92 (3) ◽  
pp. 435-436
Author(s):  
S. J. Jacobs
Keyword(s):  
Circular Cylinder ◽  
Rossby Number ◽  
Rotating Frame ◽  
Two Dimensional ◽  
Parallel Plates ◽  
Extra Condition ◽  
Ekman Number ◽  
Flow Past ◽  
Number Flow ◽  
Interior Flow

An analysis of low Rossby number and low Ekman number flow between parallel plates shows that the interior flow is irrotational and two-dimensional for all Rossby numbers and Ekman numbers in the range R0≪1, E≪1. The extra condition R0≪E1/2 is not needed for this proof.

High Frequency Characteristics of the Near Wake and Vortex Past a Triangular Cylinder

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Lei Sun ◽  
Yong Huang ◽  
Xiwei Wang ◽  
Xiang Feng ◽  
Wei Xiao
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Core ◽  
High Frequency ◽  
Vortex Formation ◽  
Flame Stabilization ◽  
Near Wake ◽  
Freestream Velocity ◽  
Formation Region ◽  
Flow Past

Abstract The flow past a triangular cylinder is one of the fundamental flows and widely utilized in flame stabilization and heat transfer. In this study, the near wake and vortex characteristics of the flow past an equilateral triangular cylinder are experimentally measured by a high frequency particle image velocimetry (PIV) system at 3 kHz. The triangular cylinder is installed in a wind tunnel with Reynolds numbers ranging from 10,700 to 17,700. The Reynolds-averaged and phase-averaged methods are utilized to analyze the flow field. Based on the flow fields, the length of the vortex formation region is about 1.5 times of the length of the equilateral triangle side. The residence time of a vortex in the vortex formation region is equal to a vortex shedding period. The stream wise velocity of the vortex core center downstream the vortex formation is about 0.8 times of the freestream velocity, which is slightly larger than the value about 0.7 for the flow past a circular cylinder at the same Reynolds number. The maximum tangential velocity at the periphery of the vortex core maybe occurs slightly in advance of the vortex reaching the boundary of the vortex formation region. The normalized lengths of the recirculation zone of the triangular cylinder keep nearly unchanged and are about 1.55 to 1.9 times of those of the circular cylinder at the same Reynolds number. The normalized normal wise instead of stream wise turbulence intensity has stronger effects on the distribution of the normalized turbulent kinetic energy.

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