scholarly journals Modelling Two-Dimensional Flow Around a Circular Cylinder with Different Roughness Height

2016 ◽  
Author(s):  
Jianbo Xie ◽  
Xin Wang
Keyword(s):  
Circular Cylinder ◽  
Roughness Height ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow

Pressure Distributions and Forces on Rectangular and D-shaped Cylinders

1972 ◽  
Vol 23 (1) ◽  
pp. 1-6 ◽  
Author(s):  
B R Bostock ◽  
W A Mair
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Pressure Distribution ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Pressure Distributions ◽  
Two Dimensional Flow ◽  
Rectangular Cylinders ◽  
Shaped Section

SummaryMeasurements in two-dimensional flow on rectangular cylinders confirm earlier work of Nakaguchi et al in showing a maximum drag coefficient when the height h of the section (normal to the stream) is about 1.5 times the width d. Reattachment on the sides of the cylinder occurs only for h/d < 0.35.For cylinders of D-shaped section (Fig 1) the pressure distribution on the curved surface and the drag are considerably affected by the state of the boundary layer at separation, as for a circular cylinder. The lift is positive when the separation is turbulent and negative when it is laminar. It is found that simple empirical expressions for base pressure or drag, based on known values for the constituent half-bodies, are in general not satisfactory.

On the drag of two-dimensional flow about a circular cylinder

2004 ◽  
Vol 16 (10) ◽  
pp. 3828-3831 ◽  
Author(s):  
C.-Y. Wen ◽  
C.-L. Yeh ◽  
M.-J. Wang ◽  
C.-Y. Lin
Keyword(s):  
Circular Cylinder ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow

Axisymmetric turbulent boundary layer along a circular cylinder at constant pressure

1976 ◽  
Vol 74 (1) ◽  
pp. 113-128 ◽  
Author(s):  
Noor Afzal ◽  
R. Narasimha
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Constant Pressure ◽  
Axisymmetric Flow ◽  
Universal Constant ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Flow Experiment ◽  
Two Dimensional Flow

A constant-pressure axisymmetric turbulent boundary layer along a circular cylinder of radiusais studied at large values of the frictional Reynolds numbera+(based upona) with the boundary-layer thickness δ of ordera. Using the equations of mean motion and the method of matched asymptotic expansions, it is shown that the flow can be described by the same two limit processes (inner and outer) as are used in two-dimensional flow. The condition that the two expansions match requires the existence, at the lowest order, of a log region in the usual two-dimensional co-ordinates (u+,y+). Examination of available experimental data shows that substantial log regions do in fact exist but that the intercept is possibly not a universal constant. Similarly, the solution in the outer layer leads to a defect law of the same form as in two-dimensional flow; experiment shows that the intercept in the defect law depends on δ/a. It is concluded that, except in those extreme situations wherea+is small (in which case the boundary layer may not anyway be in a fully developed turbulent state), the simplest analysis of axisymmetric flow will be to use the two-dimensional laws with parameters that now depend ona+or δ/aas appropriate.

scholarly journals Two- and three-dimensional wake transitions of an impulsively started uniformly rolling circular cylinder

2017 ◽  
Vol 826 ◽  
pp. 32-59 ◽  
Author(s):  
F. Y. Houdroge ◽  
T. Leweke ◽  
K. Hourigan ◽  
M. C. Thompson
Keyword(s):  
Stability Analysis ◽  
Circular Cylinder ◽  
Rapid Development ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Instability Modes ◽  
Two Dimensional Flow ◽  
Lift And Drag

This paper presents the characteristics of the different stages in the evolution of the wake of a circular cylinder rolling without slipping along a wall at constant speed, acquired through numerical stability analysis and two- and three-dimensional numerical simulations. Reynolds numbers between 30 and 300 are considered. Of importance in this study is the transition to three-dimensionality from the underlying two-dimensional periodic flow and, in particular, the way that the associated transitions influence the fluid forces exerted on the cylinder and the development and the structure of the wake. It is found that the steady two-dimensional flow becomes unstable to three-dimensional perturbations at $Re_{c,3D}=37$, and that the transition to unsteady two-dimensional flow – or periodic vortex shedding – occurs at $Re_{c,2D}=88$, thus validating and refining the results of Stewart et al. (J. Fluid Mech. vol. 648, 2010, pp. 225–256). The main focus here is on Reynolds numbers beyond the transition to unsteady flow at $Re_{c,2D}=88$. From impulsive start up, the wake almost immediately undergoes transition to a periodic two-dimensional wake state, which, in turn, is three-dimensionally unstable. Thus, the previous three-dimensional stability analysis based on the two-dimensional steady flow provides only an element of the full story. Floquet analysis based on the periodic two-dimensional flow was undertaken and new three-dimensional instability modes were revealed. The results suggest that an impulsively started cylinder rolling along a surface at constant velocity for $Re\gtrsim 90$ will result in the rapid development of a periodic two-dimensional wake that will be maintained for a considerable time prior to the wake undergoing three-dimensional transition. Of interest, the mean lift and drag coefficients obtained from full three-dimensional simulations match predictions from two-dimensional simulations to within a few per cent.

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