Oscillating Flow About Smooth and Rough Cylinders

1987 ◽  
Vol 109 (4) ◽  
pp. 307-313 ◽  
Author(s):  
Turgut Sarpkaya
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Coherence Length ◽  
Lift Force ◽  
Diameter Ratio ◽  
Oscillating Flow ◽  
Force Coefficients ◽  
Smooth Cylinder ◽  
Cylinder Drag ◽  
Length To Diameter Ratio

The lift, drag, and inertia coefficients and the first ten harmonics of the lift force have been determined through the use of four smooth, four sand-roughened, and one marine-roughened cylinders. The length-to-diameter ratio of the smooth and sand-roughened cylinders was kept constant (L/D = 2) in order to determine the effect of coherence length on the force coefficients. The Keulegan-Carpenter number ranged from about 1 to 60 and the Reynolds number from about 2500 to 800,000. The results have shown that (i) the smooth cylinder data agree quite well with those presented by Sarpkaya [1, 2] and Rodenbusch and Gutierrez [3]; (ii) the drag and inertia coefficients for rough cylinders (k/D = 1/50) become independent of β (= D2/vT) or of the Reynolds number (Re = UmD/v) for β larger than about 4000; (iii) the rough-cylinder data agree quite well within those reported by Sarpkaya [2] and show that the effect of roughness is indeed very profound; and (iv) the rough-cylinder drag-coefficient data of Rodenbusch and Gutierrez [3] are somewhat larger than those obtained in the present investigation.

Simulation of Flow Around a Cube at Moderate Reynolds Numbers Using the Lattice Boltzmann Method

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Majid Hassan Khan ◽  
Atul Sharma ◽  
Amit Agrawal
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lattice Boltzmann Method ◽  
Steady Flow ◽  
Flow Regime ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Side Force ◽  
Force Coefficients ◽  
Boltzmann Method

Abstract This article reports flow behavior around a suspended cube obtained using three-dimensional (3D) lattice Boltzmann method (LBM)-based simulations. The Reynolds number (Re) range covered is from 84 to 770. Four different flow regimes are noted based on the flow structure in this range of Re: steady axisymmetric (84 ≤ Re ≤ 200), steady nonaxisymmetric (215 ≤ Re ≤ 250), unsteady nonaxisymmetric in one plane and axisymmetric in the other plane (276 ≤ Re ≤ 300), and unsteady nonaxisymmetric in streamwise orthogonal planes (339 ≤ Re ≤ 770). Recirculation length and drag coefficient follow inverse trend in the steady flow regime. The unsteady flow regime shows hairpin vortices for Re ≤ 300 and then it becomes structureless. The nature of force coefficients has been examined at various Reynolds numbers. Temporal behavior of force coefficients is presented along with phase dependence of side force coefficients. The drag coefficient decreases with increase in Reynolds number in the steady flow regime and the side force coefficients are in phase. Drag coefficients are compared with established correlations for flow around a cube and a sphere. The side force coefficients are perfectly correlated at Re = 215 and they are anticorrelated at Re = 250. At higher Reynolds numbers, side force coefficients are highly uncorrelated. This work adds to the existing understanding of flow around a cube reported earlier at low and moderate Re and extends it further to unsteady regime at higher Re.

A Series Pressure Drop Representation for Flow Through Orifice Tubes

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
T. A. Jankowski ◽  
E. N. Schmierer ◽  
F. C. Prenger ◽  
S. P. Ashworth
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Simple Model ◽  
Pressure Drop ◽  
Diameter Ratio ◽  
Pressure Drops ◽  
In Series ◽  
Orifice Flow ◽  
Flow Through ◽  
Length To Diameter Ratio

A simple model is developed here to predict the pressure drop and discharge coefficient for incompressible flow through orifices with length-to-diameter ratio greater than zero (orifice tubes) over wide ranges of Reynolds number. The pressure drop for flow through orifice tubes is represented as two pressure drops in series; namely, a pressure drop for flow through a sharp-edged orifice in series with a pressure drop for developing flow in a straight length of tube. Both of these pressure drop terms are represented in the model using generally accepted correlations and experimental data for developing flows and sharp-edged orifice flow. We show agreement between this simple model and our numerical analysis of laminar orifice flow with length-to-diameter ratio up to 15 and for Reynolds number up to 150. Agreement is also shown between the series pressure drop representation and experimental data over wider ranges of Reynolds number. Not only is the present work useful as a design correlation for equipment relying on flow through orifice tubes but it helps to explain some of the difficulties that previous authors have encountered when comparing experimental observation and available theories.

Linear Force Coefficients for Squeeze-Film Dampers

1983 ◽  
Vol 105 (3) ◽  
pp. 326-334 ◽  
Author(s):  
A. Z. Szeri ◽  
A. A. Raimondi ◽  
A. Giron-Duarte
Keyword(s):  
Reynolds Number ◽  
Diameter Ratio ◽  
Linear Velocity ◽  
Squeeze Film ◽  
Viscous Damper ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Squeeze Film Dampers ◽  
Linear Force

This paper presents a simplifed analysis of viscous squeeze-film damper behavior. It makes use of the notation of averaged inertia and calculates linear velocity and inertia coeffcients. These coefficients are shown to be accurate at practical values of the length/diameter ratio and the gap Reynolds number of the viscous damper.

scholarly journals Turbulent Swirling Flow in Short Cylindrical Chambers

1993 ◽  
Vol 115 (3) ◽  
pp. 444-451 ◽  
Author(s):  
A. Riahi ◽  
P. G. Hill
Keyword(s):  
Reynolds Number ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Cylindrical Chamber ◽  
Transient Conditions ◽  
Chamber Length ◽  
Smooth Disk ◽  
Length To Diameter Ratio

Turbulent swirling flow in a short closed cylindrical chamber has been measured with laser Doppler anemometry. The swirl was generated by a rotating roughened disk and measured during steady and transient conditions with a smooth disk. The velocity and turbulence fields were found to be strongly dependent on swirl Reynolds numbers (in the range 0.3 × 106 < ΩR2/v < 0.6 × 106) and on chamber length-to-diameter ratio (in the range 0.1 ≤ L/D ≤ 0.5). With a roughened disk the flow was nearly independent of Reynolds number though still strongly dependent on chamber length-to-diameter ratio.

scholarly journals Simulation of Gas Flow Over a Micro Cylinder

2009 ◽  
Author(s):  
Yuan Hu ◽  
Quanhua Sun ◽  
Jing Fan
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Drag Coefficient ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Low Reynolds Number ◽  
Pressure Drag ◽  
Low Reynolds ◽  
Rarefied Gas Effect ◽  
Gas Effect

Gas flow over a micro cylinder is simulated using both a compressible Navier-Stokes solver and a hybrid continuum/particle approach. The micro cylinder flow has low Reynolds number because of the small length scale and the low speed, which also indicates that the rarefied gas effect exists in the flow. A cylinder having a diameter of 20 microns is simulated under several flow conditions where the Reynolds number ranges from 2 to 50 and the Mach number varies from 0.1 to 0.8. It is found that the low Reynolds number flow can be compressible even when the Mach number is less than 0.3, and the drag coefficient of the cylinder increases when the Reynolds number decreases. The compressible effect will increase the pressure drag coefficient although the friction coefficient remains nearly unchanged. The rarefied gas effect will reduce both the friction and pressure drag coefficients, and the vortex in the flow may be shrunk or even disappear.

Optimized growth of high length-to-diameter ratio Lu2O3 single crystal fibers by the LHPG method

CrystEngComm ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 1657-1662
Author(s):  
Na Zhang ◽  
Yuqing Yin ◽  
Jian Zhang ◽  
Tao Wang ◽  
Siyuan Wang ◽  
...  
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
High Power ◽  
Diameter Ratio ◽  
Solid State Lasers ◽  
Crystal Fibers ◽  
High Length ◽  
Length To Diameter Ratio

Lu2O3 crystals have attracted intense attention due to their great potential in the field of high power solid-state lasers.

EXPERIMENTAL STUDY ON FLAME PROPAGATION IN A STRAIGHT PIPE

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Siti Zubaidah Sulaiman ◽  
Rafiziana Md Kasmani ◽  
A. Mustafa
Keyword(s):  
Experimental Study ◽  
Flame Propagation ◽  
Experimental Work ◽  
Diameter Ratio ◽  
Straight Pipe ◽  
Pipe Length ◽  
Operating Condition ◽  
Consistent Trend ◽  
Length To Diameter Ratio

Flame propagation in a closed pipe with diameter 0.1 m and 5.1 m long, as well as length to diameter ratio (L/D) of 51, was studied experimentally. Hydrogen/air, acetylene/air and methane/air with stoichiometric concentration were used to observe the trend of flame propagation throughout the pipe. Experimental work was carried out at operating condition: pressure 1 atm and temperature 273 K. Results showed that all fuels are having a consistent trend of flame propagation in one-half of the total pipe length in which the acceleration is due to the piston-like effect. Beyond the point, fuel reactivity and tulip phenomenon were considered to lead the flame being quenched and decrease the overpressures drastically. The maximum overpressure for all fuels are approximately 1.5, 7, 8.5 barg for methane, hydrogen, and acetylene indicating that acetylene explosion is more severe. 

Roller Skewing Behavior in Roller Bearings

1982 ◽  
Vol 104 (3) ◽  
pp. 311-320
Author(s):  
L. J. Nypan
Keyword(s):  
Diameter Ratio ◽  
Radial Load ◽  
Outer Race ◽  
Roller Bearings ◽  
Length To Diameter Ratio

Measurements of roller skewing of a 1.15 length to diameter ratio roller in 118 mm bore roller bearings of 0.18 and 0.21 mm (0.0073 and 0.0083 in.) clearance operating with a 4450 N (1000 lb) radial load at shaft speeds of 4000, 8000, and 12,000 rpm with outer race misalignment of 0, 0.5, and −0.5 deg are reported.

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