Examination of Hydrodynamic Forces Acting on a Group of Circular Cylinders at High Reynolds Numbers

2016 ◽  
Author(s):  
Linwei Shen ◽  
Rajeev Kumar Jaiman ◽  
Peter Francis Bernad Adaikalaraj ◽  
Vaibhav Joshi ◽  
Jungao Wang ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Hydrodynamic Forces ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Incoming Flow ◽  
Drag Coefficients ◽  
Numerical Result ◽  
High Reynolds ◽  
Engineering Practices

A group of circular cylinders exists in many engineering practices, such as offshore drilling riser system. Due to the interference between the riser main tube and auxiliary lines, the hydrodynamic forces acting on the riser system is much different from those on a single circular cylinder. It is very rare in the publication and still not certain in the determination of the forces in the drilling riser design of the industry. Particularly, it is unclear of the hydrodynamic forces when the Reynolds number is very high which is quite common in the real ocean fields. In this paper, the stationary riser system consisting of a group of six circular cylinders with unequal diameters is considered. The hydrodynamic forces acting on the main cylinder in the Reynolds number ranging from 105 to 2×106 are numerically calculated by solving the Reynolds averaged Navier-Stokes (RANS) equations. The Spalart-Allmaras RANS model is employed to account for the turbulence effect. It is found that drag coefficients are close to 1 when the incoming flow is symmetrical with respect to the configuration of the cylinders and are dramatically reduced when the incoming flow is asymmetrical. No “drag crisis”, which is a well-known phenomenon in a single cylinder case, is found in this particular range of Reynolds numbers. A detailed analysis, including the flow field and pressure distribution around the main tube, is also presented in the present work. The numerical result of the hydrodynamic forces on the main line is very helpful for the engineers to determine the drag coefficients in the practice of drilling riser system design, under the guidance of API-RP-16Q.

scholarly journals Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Nils Paul van Hinsberg
Keyword(s):  
Reynolds Number ◽  
Cross Sections ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Surface Boundary ◽  
Experimental Proof ◽  
Surface Boundary Layer ◽  
Pitch Moment ◽  
The Mean ◽  
High Reynolds

Abstract The aerodynamics of smooth and slightly rough prisms with square cross-sections and sharp edges is investigated through wind tunnel experiments. Mean and fluctuating forces, the mean pitch moment, Strouhal numbers, the mean surface pressures and the mean wake profiles in the mid-span cross-section of the prism are recorded simultaneously for Reynolds numbers between 1$$\times$$ × 10$$^{5}$$ 5 $$\le$$ ≤ Re$$_{D}$$ D $$\le$$ ≤ 1$$\times$$ × 10$$^{7}$$ 7 . For the smooth prism with $$k_s$$ k s /D = 4$$\times$$ × 10$$^{-5}$$ - 5 , tests were performed at three angles of incidence, i.e. $$\alpha$$ α = 0$$^{\circ }$$ ∘ , −22.5$$^{\circ }$$ ∘ and −45$$^{\circ }$$ ∘ , whereas only both “symmetric” angles were studied for its slightly rough counterpart with $$k_s$$ k s /D = 1$$\times$$ × 10$$^{-3}$$ - 3 . First-time experimental proof is given that, within the accuracy of the data, no significant variation with Reynolds number occurs for all mean and fluctuating aerodynamic coefficients of smooth square prisms up to Reynolds numbers as high as $$\mathcal {O}$$ O (10$$^{7}$$ 7 ). This Reynolds-number independent behaviour applies to the Strouhal number and the wake profile as well. In contrast to what is known from square prisms with rounded edges and circular cylinders, an increase in surface roughness height by a factor 25 on the current sharp-edged square prism does not lead to any notable effects on the surface boundary layer and thus on the prism’s aerodynamics. For both prisms, distinct changes in the aerostatics between the various angles of incidence are seen to take place though. Graphic abstract

scholarly journals Model-based scaling of the streamwise energy density in high-Reynolds-number turbulent channels

2013 ◽  
Vol 734 ◽  
pp. 275-316 ◽  
Author(s):  
Rashad Moarref ◽  
Ati S. Sharma ◽  
Joel A. Tropp ◽  
Beverley J. McKeon
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Low Rank ◽  
Navier Stokes ◽  
Mean Velocity ◽  
Navier Stokes Equations ◽  
Self Similar ◽  
The Mean ◽  
High Reynolds

AbstractWe study the Reynolds-number scaling and the geometric self-similarity of a gain-based, low-rank approximation to turbulent channel flows, determined by the resolvent formulation of McKeon & Sharma (J. Fluid Mech., vol. 658, 2010, pp. 336–382), in order to obtain a description of the streamwise turbulence intensity from direct consideration of the Navier–Stokes equations. Under this formulation, the velocity field is decomposed into propagating waves (with single streamwise and spanwise wavelengths and wave speed) whose wall-normal shapes are determined from the principal singular function of the corresponding resolvent operator. Using the accepted scalings of the mean velocity in wall-bounded turbulent flows, we establish that the resolvent operator admits three classes of wave parameters that induce universal behaviour with Reynolds number in the low-rank model, and which are consistent with scalings proposed throughout the wall turbulence literature. In addition, it is shown that a necessary condition for geometrically self-similar resolvent modes is the presence of a logarithmic turbulent mean velocity. Under the practical assumption that the mean velocity consists of a logarithmic region, we identify the scalings that constitute hierarchies of self-similar modes that are parameterized by the critical wall-normal location where the speed of the mode equals the local turbulent mean velocity. For the rank-1 model subject to broadband forcing, the integrated streamwise energy density takes a universal form which is consistent with the dominant near-wall turbulent motions. When the shape of the forcing is optimized to enforce matching with results from direct numerical simulations at low turbulent Reynolds numbers, further similarity appears. Representation of these weight functions using similarity laws enables prediction of the Reynolds number and wall-normal variations of the streamwise energy intensity at high Reynolds numbers (${Re}_{\tau } \approx 1{0}^{3} {\unicode{x2013}} 1{0}^{10} $). Results from this low-rank model of the Navier–Stokes equations compare favourably with experimental results in the literature.

scholarly journals Numerical investigations of flow around subsea covers at high Reynolds numbers

2021 ◽  
Vol 1201 (1) ◽  
pp. 012013
Author(s):  
G Yin ◽  
Y Zhang ◽  
M C Ong
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Layer Flow ◽  
High Reynolds

Abstract Two-dimensional (2D) numerical simulations of flow over wall-mounted rectangular and trapezoidal ribs subjected to a turbulent boundary layer flow with the normalized boundary layer thickness of δ/D = 0.73,1.96,2.52 (D is the height of the ribs) have been carried out by using the Reynolds-averaged Navier-Stokes (RANS) equations combined with the k – ω SST (Shear Stress Transport) turbulence model. The angles of the two side slopes of trapezoidal rib varies from 0° to 60°. The Reynolds number based on the free-stream velocity U ∞ and D are 1 × 106 and 2 × 106. The results obtained from the present numerical simulations are in good agreement with the published experimental data. Furthermore, the effects of the angle of the two side slopes of the trapezoidal ribs, the Reynolds number and the boundary layer thickness on the hydrodynamic quantities are discussed.

Vortex Formation for Different Geometry of Cavities Using High Reynolds Number

2014 ◽  
Vol 699 ◽  
pp. 416-421
Author(s):  
Mohd Noor Asril Saadun ◽  
Muhammad Zulhakim Sharudin ◽  
Nor Azwadi Che Sidik ◽  
Mohd Hafidzal Mohd Hanafi
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Contaminant Removal ◽  
Navier Stokes Equations ◽  
High Reynolds

A preliminary study of Computational Fluid Dynamics (CFD) on the effect of high Reynolds numbers in the cavity has been carried out. Two dimensional model analysis of the flow characteristics were conducted using the numerical solution of Navier-Stokes equations based on the finite difference method. The flow characteristics in the cavity and the driven flow were modeled via turbulence equation modelling. This paper focuses on the effects of different high Reynolds number on the flow pattern of contaminant removal in the cavity. Different types of geometry and aspect ratio of the geometry were used as the parameters of the cavity in this study. Based on visualization of flows between each model with the different parameters used, the results of a comparison analysis focusing on the behavior of the flow were reported.

scholarly journals Velocity and temperature derivatives in high-Reynolds-number turbulent flows in the atmospheric surface layer. Part 1. Facilities, methods and some general results

2007 ◽  
Vol 589 ◽  
pp. 57-81 ◽  
Author(s):  
G. GULITSKI ◽  
M. KHOLMYANSKY ◽  
W. KINZELBACH ◽  
B. LÜTHI ◽  
A. TSINOBER ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Surface Layer ◽  
Turbulent Flows ◽  
Atmospheric Surface Layer ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Taylor Hypothesis ◽  
High Reynolds

This is a report on a field experiment in an atmospheric surface layer at heights between 0.8 and 10m with the Taylor micro-scale Reynolds number in the range Reλ = 1.6−6.6 ×103. Explicit information is obtained on the full set of velocity and temperature derivatives both spatial and temporal, i.e. no use of Taylor hypothesis is made. The report consists of three parts. Part 1 is devoted to the description of facilities, methods and some general results. Certain results are similar to those reported before and give us confidence in both old and new data, since this is the first repetition of this kind of experiment at better data quality. Other results were not obtained before, the typical example being the so-called tear-drop R-Q plot and several others. Part 2 concerns accelerations and related matters. Part 3 is devoted to issues concerning temperature, with the emphasis on joint statistics of temperature and velocity derivatives. The results obtained in this work are similar to those obtained in experiments in laboratory turbulent grid flow and in direct numerical simulations of Navier–Stokes equations at much smaller Reynolds numbers Reλ ~ 102, and this similarity is not only qualitative, but to a large extent quantitative. This is true of such basic processes as enstrophy and strain production, geometrical statistics, the role of concentrated vorticity and strain, reduction of nonlinearity and non-local effects. The present experiments went far beyond the previous ones in two main respects. (i) All the data were obtained without invoking the Taylor hypothesis, and therefore a variety of results on fluid particle accelerations became possible. (ii) Simultaneous measurements of temperature and its gradients with the emphasis on joint statistics of temperature and velocity derivatives. These are reported in Parts 2 and 3.

scholarly journals The flow induced by a rotationally oscillating and translating circular cylinder

2000 ◽  
Vol 407 ◽  
pp. 123-144 ◽  
Author(s):  
S. C. R. DENNIS ◽  
P. NGUYEN ◽  
SERPIL KOCABIYIK
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Interesting Phenomenon ◽  
Navier Stokes Equations ◽  
Drag Coefficients ◽  
Small Times ◽  
High Reynolds ◽  
Lift And Drag

The temporal development of two-dimensional viscous incompressible flow induced by an impulsively started circular cylinder which performs time-dependent rotational oscillations about its axis and translates at right angles to this axis is investigated. The investigation is based on the solutions of the unsteady Navier–Stokes equations. A series expansion for small times is developed. The Navier–Stokes equations are also integrated by a spectral–finite difference method for moderate values of time for both moderate and high Reynolds numbers. The numerical method is checked with the results of the analytical solution. The effects of the Reynolds number and of the forcing Strouhal number S on the laminar asymmetric flow structure in the near-wake region are studied. The lift and drag coefficients are also extracted from numerical results. An interesting phenomenon has been observed both in the flow patterns and in the behaviour of drag coefficients for S = π/2 at Reynolds number R = 500 and is discussed. For comparison purposes the start-up flow is determined numerically at a low Reynolds number and is found to be in good agreement with previous experimental predictions.

3D Simulation of Vortex Shedding Past Tapered Circular Cylinders in Subcritical Reynolds Numbers

2012 ◽  
Author(s):  
V. Tamimi ◽  
M. Zeinoddini ◽  
A. Bakhtiari ◽  
M. Golestani
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
High Reynolds

In this paper results from simulating the vortex shedding phenomena behind a fixed tapered circular cylinder, at relatively high Reynolds numbers, are reported. Ansys-CFX computational fluid dynamics model, based on solving three-dimensional (3D) incompressible transient Navier Stokes equations, is employed for this purpose. The geometries applied in the models resemble those used in wind tunnel experiments by other researchers. The taper slope along the cylinder span is uniform with a tangent of 24:1. The diameter at mid-span of the cylinder equals to 0.0389 m. The Reynolds number (based on the mid-span diameter) is around 29,000. The computational model has first been calibrated against experiments for uniform 3D cylinders as well as results from a Direct Numerical Simulation of turbulent wake with vortex shedding past a uniform circular cylinder, as obtained by other researchers. The main flow characteristics for tapered cylinders such as vortex dislocations and splitting, cellular vortex shedding, oblique vortex shedding and the variation of the vorticity patterns along the tapered cylinder could be obtained from the simulations.

scholarly journals RANS Simulations of Flow Past an DU-91-W2-250 Airfoil at High Reynolds Number

2018 ◽  
Vol 44 ◽  
pp. 00150
Author(s):  
Krzysztof Rogowski ◽  
Martin O.L. Hansen
Keyword(s):  
Reynolds Number ◽  
Navier Stokes ◽  
Transient Model ◽  
Drag Coefficients ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Rans Simulations ◽  
High Reynolds ◽  
Lift And Drag ◽  
Good Agreement

This paper presents numerical results of the DU-91-W2-250 airfoil. Reynolds-averaged Navier–Stokes (RANS) simulations of the 2D profile are performed employing the Transient SST turbulence model. The airfoil was investigated for the Reynolds number of 6 106. Lift and drag coefficients are compared with the experimental data from LM Low Speed Wind Tunnel (LSWT). The results of lift and drag coefficients obtained using the SST Transient model are in a good agreement in comparison with the experiment in the angle of attack range from -10° to 10°. The static pressure distributions calculated by the SST Transition model are also in good agreement with the experiment.

Numerical Prediction of the Hydrodynamic Loads and Vortex-Induced Vibrations of Offshore Structures

2000 ◽  
Vol 122 (4) ◽  
pp. 289-293 ◽  
Author(s):  
Karl W. Schulz ◽  
Yannis Kallinderis
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Structural Response ◽  
Reynolds Numbers ◽  
Offshore Structures ◽  
Navier Stokes ◽  
High Reynolds Numbers ◽  
Vortex Induced Vibrations ◽  
Flow Algorithm ◽  
High Reynolds

An incompressible Navier-Stokes flow algorithm is coupled with an elastic body structural response to numerically investigate the hydrodynamics of several relevant offshore applications. These applications include the effects of surface roughness on a bare cylinder and the study of vortex-induced vibrations (VIV) for a cylinder at high Reynolds numbers. The Reynolds number for the roughness cases was Re=4×106, while the Reynolds number for the VIV cases ranged from 2.25×105⩽Re⩽4.75×105. Additional VIV cases were also performed for two common suppression devices: strakes and fairings. The results from both the roughness and bare cylinder VIV applications were compared to experimental data in order to further validate the numerical scheme and illustrate the effectiveness of applying Navier-Stokes technologies to offshore applications. [S0892-7219(00)00604-X]

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