Added Mass and In-Line Steady Drag Coefficient of Multiple Risers

1985 ◽  
Vol 107 (1) ◽  
pp. 2-11 ◽  
Author(s):  
T. Overvik ◽  
G. Moe
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Reynolds Numbers ◽  
Added Mass ◽  
Central Cylinder ◽  
Lock In

Part of the results of an investigation with multiple rise configuration exposed to steady currents are presented. These tests were performed on smooth sectional riser models in a water flume at Reynolds numbers in the range 0.5 × 104 to 0.5 × 105. Reynolds number is based upon the diameter of the central cylinder (DC). Both the added mass, the frequency of vibration and the in-line steady drag coefficient are discussed both for vibration in the lock-in range and in the galloping mode.

Reynolds Number Effects on Hydrodynamic Coefficients for Pure In-Line and Pure Cross-Flow Forced Vortex Induced Vibrations

2009 ◽  
Author(s):  
Jamison L. Szwalek ◽  
Carl M. Larsen
Keyword(s):  
Reynolds Number ◽  
Prediction Models ◽  
Current Knowledge ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Added Mass ◽  
Hydrodynamic Coefficients ◽  
Vortex Induced Vibrations ◽  
Reynolds Number Effects ◽  
Sinusoidal Oscillations

In-line vibrations have been noted to have an important contribution to the fatigue of free spanning pipelines. Still, in-line contributions are not usually accounted for in current VIV prediction models. The present study seeks to broaden the current knowledge regarding in-line vibrations by expanding the work of Aronsen (2007) to include possible Reynolds number effects on pure in-line forced, sinusoidal oscillations for four Reynolds numbers ranging from 9,000 to 36,200. Similar tests were performed for pure cross-flow forced motion as well, mostly to confirm findings from previous research. When experimental uncertainties are accounted for, there appears to be little dependence on Reynolds number for all three hydrodynamic coefficients considered: the force in phase with velocity, the force in phase with acceleration, and the mean drag coefficient. However, trends can still be observed for the in-line added mass in the first instability region and for the transition between the two instability regions for in-line oscillations, and also between the low and high cross-flow added mass regimes. For Re = 9,000, the hydrodynamic coefficients do not appear to be stable and can be regarded as highly Reynolds number dependent.

Experimental Aerodynamic Characteristics of a Compound Wing in Ground Effect

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Saeed Jamei ◽  
Adi Maimun Abdul Malek ◽  
Shuhaimi Mansor ◽  
Nor Azwadi Che Sidik ◽  
Agoes Priyanto
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Center Of Pressure ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Ground Effect ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Ground Clearance

Wing configuration is a parameter that affects the performance of wing-in-ground effect (WIG) craft. In this study, the aerodynamic characteristics of a new compound wing were investigated during ground effect. The compound wing was divided into three parts with a rectangular wing in the middle and two reverse taper wings with anhedral angle at the sides. The sectional profile of the wing model is NACA6409. The experiments on the compound wing and the rectangular wing were carried to examine different ground clearances, angles of attack, and Reynolds numbers. The aerodynamic coefficients of the compound wing were compared with those of the rectangular wing, which had an acceptable increase in its lift coefficient at small ground clearances, and its drag coefficient decreased compared to rectangular wing at a wide range of ground clearances, angles of attack, and Reynolds numbers. Furthermore, the lift to drag ratio of the compound wing improved considerably at small ground clearances. However, this improvement decreased at higher ground clearance. The drag polar of the compound wing showed the increment of lift coefficient versus drag coefficient was higher especially at small ground clearances. The Reynolds number had a gradual effect on lift and drag coefficients and also lift to drag of both wings. Generally, the nose down pitching moment of the compound wing was found smaller, but it was greater at high angle of attack and Reynolds number for all ground clearance. The center of pressure was closer to the leading edge of the wing in contrast to the rectangular wing. However, the center of pressure of the compound wing was later to the leading edge at high ground clearance, angle of attack, and Reynolds number.

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.

The Drag on Spheres and Cylinders in a Stream of Dust-Laden Air

1959 ◽  
Vol 26 (4) ◽  
pp. 584-586
Author(s):  
Thomas Gillespie ◽  
A. W. Gunter
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Kinetic Energy ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Reynolds Numbers ◽  
Dust Concentration ◽  
Phase System ◽  
Two Phase ◽  
Coefficient Versus

Abstract A system has been developed for measuring the drag on small spheres and cylinders in a stream of dust-laden air. The drag was found to be proportional to the kinetic energy of the air plus the kinetic energy of the dust, and to be independent of particle size for particles having diameters in the range of 50 to 400μ. The well-known drag-coefficient versus Reynolds-number plots are the same for dust-free and dust-laden air provided the drag coefficient is calculated using the density of the two-phase system and the Reynolds numbers are calculated using the density of air alone. This suggests that the dust has little effect on the flow pattern. The results indicate that an instrument utilizing the drag principle to measure dust concentration could be developed.

CFD Analysis of Drag Coefficient of a Parachute in a Steady and Turbulent Condition in Various Reynolds Numbers

2009 ◽  
Author(s):  
Muhammad Javad Izadi ◽  
Mazyar Dawoodian
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Aerospace Industry ◽  
Reynolds Numbers ◽  
Cfd Analysis ◽  
Drag Coefficients ◽  
Turbulent Condition ◽  
General Variation

Study of parachutes is very important in aerospace industry. In this research, the effect of various Reynolds numbers on a parachute with a vent and without a vent at the top on drag coefficient in a steady and turbulent condition is studied. After a complete research on an efficient grid study, the drag coefficients are calculated numerically. The Reynolds number is varied from 78000 to 3900000 (1 m/s to 50 m/s). It is found that, for a parachute without a vent at the top, as the Reynolds number is increased from 78000 to 800000, the drag coefficient is decreased from about 2.5 to 1.4, and then as the Reynolds number is increased to 1500000, the drag coefficient increased to about 1.62 and it stayed constant for higher Reynolds number up to 3900000. As the vent ratio of the parachute is increased from zero to 5 percent of the parachute inlet diameter, the drag coefficient increased and for further increase of the vent ratio diameter, the drag coefficient decreased, but the general variation of drag coefficient was the same as of same parachute with no vent.

Aerodynamic study of corrugated skins for morphing wing applications

2010 ◽  
Vol 114 (1154) ◽  
pp. 237-244 ◽  
Author(s):  
C. Thill ◽  
J. D. Downsborough ◽  
S. J. Lai ◽  
I. P. Bond ◽  
D. P. Jones
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Smooth Surface ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Potential Solution ◽  
Morphing Wing ◽  
Lift Curve ◽  
Length Changes ◽  
Wing Skin

AbstractCorrugated structures offer a potential solution for morphing wing skin applications due to their anisotropic behaviour that allows chordwise camber and length changes. Aerofoils with corrugated skins in the aft 1/3 of the chordwise section have been studied experimentally and computationally using various corrugation shapes and forms (sinusoidal, trapezoidal and triangular) at different Reynolds numbers. The study showed that the aerodynamic performance is highly dependent on corrugation amplitude, wavelength, gradient (combination of amplitude and wavelength) and Reynolds number. Evidence is given highlighting that penalties for having a non-smooth surface in the aft 1/3 of the chordwise section of an aerofoil can be eliminated for the lift curve slope and minimised for the zero lift drag coefficient.

A Numerical Study on Motion of a Sphere Coated With a Thin Liquid Film at Intermediate Reynolds Numbers

1997 ◽  
Vol 119 (2) ◽  
pp. 397-403 ◽  
Author(s):  
S. Kawano ◽  
H. Hashimoto
Keyword(s):  
Reynolds Number ◽  
Liquid Film ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Numerical Study ◽  
Thin Liquid Film ◽  
Strong Dependence ◽  
Reynolds Numbers ◽  
Rigid Sphere ◽  
Flow Past A Sphere

The steady viscous flow past a sphere coated with a thin liquid film at low and intermediate Reynolds numbers (Re ≤ 200) was investigated numerically. The influences of fluid physical properties, film thickness, and Reynolds number on the flow pattern were clarified. Temperature field around the compound drop was also analyzed. The strong dependence of flow pattern on the characteristics of heat transfer was recognized. The empirical equation of the drag coefficient for the compound drop was proposed. Furthermore, the explicit adaptability of the drag coefficient equation for a gas bubble, a liquid drop, and a rigid, sphere in the range of Reynolds number Re ≤ 1000 was confirmed.

Low Reynolds Number Flow Computations of a Sphere With Slip

2005 ◽  
Author(s):  
O. Pulat ◽  
R. N. Parthasarathy
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Reynolds Numbers ◽  
Water Medium ◽  
Reynolds Number Flow ◽  
Drag Forces ◽  
Falling Sphere ◽  
Number Flow ◽  
High Reynolds ◽  
Flow Past A Sphere

A computational fluid dynamics package (FLUENT) was used to simulate the conditions of a falling sphere through a water medium with a zero shear stress condition (full slip) for Reynolds numbers in the range. Comparisons of the results were made with simulations of the flow past a sphere with no slip. Specific differences were observed in the drag coefficient, drag forces, axial velocity, radial velocity, and wake characteristics. A significant reduction in the drag coefficient was observed with the presence of slip on the surface. With a decrease in the Reynolds number the decreases in the wake structure became negligible, however, the differences in drag coefficient became significant. At high Reynolds numbers, the wake was skewed towards the rear of the sphere, under the full slip condition.

Flow past a flat plate at low Reynolds numbers

1958 ◽  
Vol 3 (4) ◽  
pp. 329-343 ◽  
Author(s):  
E. Janssen
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Flat Plate ◽  
Truncation Error ◽  
Reynolds Numbers ◽  
Experimental Result ◽  
Total Drag ◽  
Low Reynolds Numbers ◽  
Flow Past ◽  
The Difference

The flow past a flat plate at Reynolds numbers in the range 0·1 to 10·0 is investigated by an analogue method. The solution gives the stream function and the vorticity in the flow field surrounding the plate. From these are obtained the local coefficient of friction, the pressure distribution along the plate, and the total drag coefficient. The drag coefficient approaches the analytical values of Haaser (1950) and of Tomotika & Aoi (1953) as the Reynolds number decreases toward 0·1. The drag coefficient approaches the Blasius solution as the Reynolds number increases. At Reynolds number 10·0 the drag coefficient is still above the Blasius value, but is below the value obtained experimentally by Janour (1951). The difference from the experimental result is attributed for the most part to truncation error.

Vortical patterns behind a tapered cylinder oscillating transversely to a uniform flow

1998 ◽  
Vol 363 ◽  
pp. 79-96 ◽  
Author(s):  
A. H. TECHET ◽  
F. S. HOVER ◽  
M. S. TRIANTAFYLLOU
Keyword(s):  
Reynolds Number ◽  
Transverse Direction ◽  
Single Mode ◽  
Reynolds Numbers ◽  
Single Frequency ◽  
Forward Speed ◽  
Hybrid Mode ◽  
Threshold Amplitude ◽  
Lock In ◽  
Vortex Split

Visualization studies of the flow behind an oscillating tapered cylinder are performed at Reynolds numbers from 400 to 1500. The cylinder has taper ratio 40[ratio ]1 and is moving at constant forward speed U while being forced to oscillate harmonically in the transverse direction. It is shown that within the lock-in region and above a threshold amplitude, no cells form and, instead, a single frequency of response dominates the entire span. Within certain frequency ranges a single mode dominates in the wake, consisting of shedding along the entire span of either two vortices per cycle (‘2S’ mode), or four vortices per cycle (‘2P’ mode); but within specific parametric ranges a hybrid mode is observed, consisting of a ‘2S’ pattern along the part of the span with the larger diameter and a ‘2P’ pattern along the part of the span with the smaller diameter. A distinct vortex split connects the two patterns which are phase-locked and have the same frequency. The hybrid mode is periodic, unlike vortex dislocations, and the location of the vortex split remains stable and repeatable, within one to two diameters, depending on the amplitude and frequency of oscillation and the Reynolds number.

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