scholarly journals Energy Separation and Base Pressure in the Wake of a Circular Cylinder

2002 ◽  
Author(s):  
Jonathan Ackerman ◽  
John Gostelow ◽  
Aldo Rona ◽  
William Carscallen
Keyword(s):  
Circular Cylinder ◽  
Base Pressure ◽  
Energy Separation

Simulation of Low-Reynolds Number Flow Around a Circular Cylinder Following a Slender Elliptical Path

2013 ◽  
Author(s):  
László Baranyi
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Amplitude Ratio ◽  
Oscillation Amplitude ◽  
Base Pressure ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Lock In

Two-dimensional flow around a circular cylinder forced to follow an elliptical path at low Reynolds numbers is investigated numerically using a thoroughly tested in-house code based on the finite difference method. Time-mean (TM) and rms values of lift, drag and base pressure coefficients are investigated within the lock-in region against the transverse oscillation amplitude for Reynolds number Re = 150 at frequency ratios of 0.8, 0.9 and 1.0 while the ratio of in-line and transverse cylinder oscillation amplitudes is kept at six different values yielding slender elliptical cylinder paths. The objective of the paper is to investigate the effect of the shape of the path, or amplitude ratio, on force coefficients. Findings show that for the cases investigated the rms of lift and TM of drag and base pressure are hardly affected by the amplitude ratio, while its effects are pronounced on the TM of lift and rms of drag and base pressure.

Flow Characteristics of a Bluff Body Cut From a Circular Cylinder

1997 ◽  
Vol 119 (2) ◽  
pp. 453-454 ◽  
Author(s):  
S. Aiba ◽  
H. Watanabe
Keyword(s):  
Circular Cylinder ◽  
Drag Coefficient ◽  
Flow Velocity ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Angular Position ◽  
Flow Characteristics ◽  
Uniform Flow ◽  
Base Pressure ◽  
Singular Flow

This is a report on an investigation of the flow characteristics of a bluff body cut from a circular cylinder. The volume removed from the cylinder is equal to d/2(1 − cos θs), where d and θs are the diameter and the angular position (in the case of a circular cylinder, θs, = 0 deg), respectively. θs, ranged from 0 deg to 72.5 deg and Re (based on d and the upstream uniform flow velocity U∞) from 2.0 × 104 to 3.5 × 104. It is found that a singular flow around the cylinder occurs at around θs = 53 deg when Re > 2.5 × 104, and the base pressure coefficient (−Cpb,) and the drag coefficient CD take small values compared with those for otherθs.

Energy Separation and Acoustic Interaction in Flow Across a Circular Cylinder

2001 ◽  
Vol 123 (4) ◽  
pp. 682-687 ◽  
Author(s):  
R. J. Goldstein ◽  
Boyong He
Keyword(s):  
Wind Tunnel ◽  
Circular Cylinder ◽  
Stagnation Point ◽  
Energy Separation ◽  
Acoustic Measurements ◽  
Velocity Measurements ◽  
Acoustic Interaction ◽  
Strong Energy ◽  
Separation Mechanisms ◽  
Rear Stagnation Point

Energy separation in a flow around an adiabatic circular cylinder is investigated using a surface-mounted thermocouple. Energy separation mechanisms in different regions around the cylinder are discussed. Velocity measurements near the rear stagnation point and acoustic measurements indicate that shedding vortices and the wind tunnel intrinsic resonant acoustics can strengthen each other when their frequencies match producing strong energy separation.

The effects of wake splitter plates on the flow past a circular cylinder in the range 104

1973 ◽  
Vol 61 (1) ◽  
pp. 187-198 ◽  
Author(s):  
C. J. Apelt ◽  
G. S. West ◽  
Albin A. Szewczyk
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Measurement Techniques ◽  
Base Pressure ◽  
Visualization Technique ◽  
Pressure Distributions ◽  
Splitter Plates ◽  
Flow Past ◽  
Careful Measurement

Experiments were carried out using models having L/D [les ] 2 and the resulting pressure distributions and vortex shedding characteristics are presented. A simple visualization technique which provides explanations of some of the measured results is described. It is concluded that splitter planes reduce the drag markedly by stabilizing the separation points and produce a wake narrower than that for a plain cylinder, raise the base pressure by as much as 50% and affect the Strouhal number to a lesser degree. Careful measurement techniques have enabled these effects to be presented accurately.

The Relationship Between Energy Separation and Base Drag in Turbine Blade Wakes

2013 ◽  
Author(s):  
J. P. Gostelow ◽  
W. E. Carscallen ◽  
M. Kurosaka ◽  
A. Mahallati
Keyword(s):  
Vortex Shedding ◽  
Large Scale ◽  
Base Pressure ◽  
Energy Separation ◽  
Bluff Bodies ◽  
Number Range ◽  
Pressure Losses ◽  
Central Regions ◽  
Total Temperature ◽  
High Base

During annular cascade testing of a highly-loaded turbine stage of aggressive design, the nozzle blading experienced a redistribution of the downstream total temperature field. In this ostensibly adiabatic arrangement, the central regions of the vane wakes exhibited a significant decrease in total temperature and their edges showed an unexpected increase. To resolve these anomalous results and obtain detailed information over the Mach number range, the mid-span section of the nozzle was tested in a large scale transonic planar cascade. At high subsonic speeds, vortex shedding created energy redistribution in the wake. This was measured using an 80 kHz bandwidth temperature probe, making it possible to investigate wake total temperature fluctuations in addition to fluctuations in total pressure, and hence entropy. ‘Hot spots’ of increased total temperature were found to be located at the edge of the wake and ‘cold spots’ of decreased total temperature were located close to the wake center line. The results from the turbine cascade were consistent with the phenomenon of energy separation behind bluff bodies. High base pressure losses were observed and were also related to the vortex shedding. The blade had a thick trailing edge and the high base pressure loss condition coincided with the peak of energy separation in the wake. The analysis indicates that in the subsonic speed range the phenomena of energy separation and of base pressure deficit are inextricably linked to, and are caused by, vortex shedding. A strategy for minimizing the related adverse impacts on performance is outlined.

Direct STEM ADF imaging of gold on silicon (111)

1989 ◽  
Vol 47 ◽  
pp. 472-473
Author(s):  
P. Xu ◽  
E. J. Kirkland ◽  
J. Silcox
Keyword(s):  
Film Growth ◽  
Heavy Atom ◽  
High Vacuum ◽  
Dark Field ◽  
Thin Metal Film ◽  
Base Pressure ◽  
Ultra High Vacuum ◽  
Specimen Preparation ◽  
Dark Field Imaging ◽  
Wide Range

Many studies of thin metal film growth and the formation of metal-semiconductor contacts have been performed using a wide range of experimental methods. STEM annular dark field imaging could be an important complement since it may allow direct imaging of a single heavy atom on a thin silicon substrate. This would enable studies of the local atomic arrangements and defects in the initial stage of metal silicide formation.Preliminary experiments were performed in an ultra-high vacuum VG HB501A STEM with a base pressure of 1 × 10-10 mbar. An antechamber directly attached to the microscope for specimen preparation has a base pressure of 2×l0-10 mbar. A thin single crystal membrane was fabricated by anodic etching and subsequent reactive etching. The specimen was cleaned by the Shiraki method and had a very thin oxide layer left on the surface. 5 Å of gold was deposited on the specimen at room temperature from a tungsten filament coil monitored by a quartz crystal monitor.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

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