Flow behavior downstream of two side-by-side circular cylinders in shallow water

2016 ◽  
Vol 94 (10) ◽  
pp. 975-981
Author(s):  
Mustafa Atakan Akar ◽  
Burcu Oguz ◽  
Huseyin Akilli ◽  
Besir Sahin
Keyword(s):  
Shallow Water ◽  
Large Scale ◽  
Flow Behavior ◽  
Circular Cylinders ◽  
Small Scale ◽  
Piv Method ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
The Right ◽  
Bistable Flow

Investigations of bistable flow structure past a pair of cylinders positioned side-by-side in shallow water is conducted experimentally applying dye observation and the particle image velocimetry (PIV) method. For the gap ratio of G/D = 1.25, the jet-like flow between cylinders deflects asymmetrical flow structures forming a large-scale wake as well as a small-scale wake downstream of cylinders. The small vortices around the right cylinder get closer to each other forming a larger vortex in the large-scale wake region, which leads the jet-like flow to changeover side to side. The small frequency (f = 0.352 Hz) associated with frequency of vortex shedding of cylinder with wider wake and the higher frequency (f = 0.793 Hz) which depicts the smaller wakes frequency.

Flow Behavior Behind Two Side-by-Side Circular Cylinders With Unequal Diameters

2010 ◽  
Author(s):  
Yangyang Gao ◽  
Dingyong Yu ◽  
Soon Keat Tan ◽  
Xikun Wang ◽  
Zhiyong Hao
Keyword(s):  
Average Velocity ◽  
Particle Image ◽  
Flow Behavior ◽  
Water Channel ◽  
Open Water ◽  
Circular Cylinders ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
Pitch Ratio ◽  
Wake Modes

In this study, flow behavior behind two side-by-side circular cylinders with unequal diameters, was investigated by using the technique of particle-image-velocimetry (PIV). The experiments were conducted in a re-circulating open water channel within the subcritical Reynolds number regime and a center-to-center pitch ratio T/D range of 1.2 to 3.6. Instantaneous and average velocity patterns, vorticity and Reynolds stress contours acquired with the PIV were used to analyze the flow behavior behind the two cylinders. The effects of the gap ratio and Re on vortex shedding were studied. The results showed that three flow patterns including the asymmetric biased flow, symmetric biased flow and two wake modes with different scales for different gap ratios respectively were observed.

scholarly journals Shallow Water Magnetohydrodynamics in Plasma Astrophysics. Waves, Turbulence, and Zonal Flows

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 314 ◽  
Author(s):  
Arakel Petrosyan ◽  
Dmitry Klimachkov ◽  
Maria Fedotova ◽  
Timofey Zinyakov
Keyword(s):  
Shallow Water ◽  
Large Scale ◽  
Fundamental Problem ◽  
Flow Behavior ◽  
Magnetohydrodynamic Equations ◽  
Plasma Astrophysics ◽  
Wave Interactions ◽  
Zonal Flows ◽  
New Applications ◽  
The Universe

The purpose of plasma astrophysics is the study and description of the flow of rotating plasma in order to understand the evolution of various objects in the universe, from stars and planetary systems to galaxies and galaxy clusters. A number of new applications and observations have appeared in recent years and actualized the problem of studying large-scale magnetohydrodynamic flows, such as a thin layer under the convective zone of the sun (solar tachocline), propagation of accreting matter in neutron stars, accretion disks in astrophysics, dynamics of neutron star atmospheres, and magnetoactive atmospheres of exoplanets tidally locked with their host star. The article aims to discuss a fundamental problem in the description and study of multiscale astrophysical plasma flows by studying its general properties characterizing different objects in the universe. We are dealing with the development of geophysical hydrodynamic ideas concerning substantial differences in plasma flow behavior due to the presence of magnetic fields and stratification. We discuss shallow water magnetohydrodynamic equations (one-layer and two-layer models) and two-dimensional magnetohydrodynamic equations as a basis for studying large-scale flows in plasma astrophysics. We discuss the novel set of equations in the external magnetic field. The following topics will be addressed: Linear theory of magneto-Rossby waves, three-wave interactions and related parametric instabilities, zonal flows, and turbulence.

Turbulent spots in a channel: large-scale flow and self-sustainability

2013 ◽  
Vol 731 ◽  
Author(s):  
Grégoire Lemoult ◽  
Jean-Luc Aider ◽  
José Eduardo Wesfreid
Keyword(s):  
Large Scale ◽  
Large Time ◽  
Rectangular Channel ◽  
Small Scale ◽  
Turbulent Spot ◽  
Time Resolved ◽  
Image Velocimetry ◽  
Streamwise Streaks ◽  
Large Scale Flow ◽  
Scale Motion

AbstractUsing a large-time-resolved particle image velocimetry field of view, a developing turbulent spot is followed in space and time in a rectangular channel flow for more than 100 advective time units. We show that the flow can be decomposed into a large-scale motion consisting of an asymmetric quadrupole centred on the spot and a small-scale part consisting of streamwise streaks. From the temporal evolution of the energy of the streamwise and spanwise velocity perturbations, it is suggested that a self-sustaining process can occur in a turbulent spot above a given Reynolds number.

Establishment of Testing Methodology for Forge Welded Tubular Products

2012 ◽  
Author(s):  
Ganesan S. Marimuthu ◽  
Per Thomas Moe ◽  
Bjarne Salberg ◽  
Jan Inge Audestad
Keyword(s):  
Material Flow ◽  
Large Scale ◽  
Flow Behavior ◽  
Treatment Options ◽  
Full Scale ◽  
International Standards ◽  
Small Scale ◽  
Test Plan ◽  
Welding Machine

A state-of-the-art small-scale solid state forge welding machine has been fabricated for checking weldability by Shielded Active Gas Forge Welding (SAG-FW) of tubular products applicable predominantly for, but not limited to offshore Industries. Effective, fast and inexpensive welding and testing of joints make this small-scale method suitable for evaluating weldability of a material before starting regular qualification and fabrication in a full-scale welding machine normally located in spool base or offshore. The small-scale machine provides a complete package for pre-qualification studies, including assessment of welding conditions, material flow behavior, heat treatment options. However, there are considerable challenges relating to application of international standards of testing as well as interpretation and use of results in the context of large-scale welding. In this paper results from small-scale welding and weld characterization of an API 5L X65 quality are presented. First, a detailed test plan for analyzing the weld is outlined. This procedure is subsequently applied for checking the welds to be produced in the full-scale machine. Short-comings in using the small-scale process as well as the possible remedies are discussed in detail.

Influence of Wall Proximity and Free Surface on Wake of Two Side-by-Side Circular Cylinders: PIV Measurement and POD Analysis

2010 ◽  
Author(s):  
S. S. Paul
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Circular Cylinders ◽  
Particle Image Velocimetry Technique ◽  
Large Scale Structures ◽  
Turbulent Statistics ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Pitch Ratio ◽  
Pod Analysis

The paper reports on an experimental study of turbulent flow around a pair of circular cylinders with a pitch ratio of two. The cylinders were located in the vicinity of a plane wall, in a uniform stream, and adjacent to a free surface in an open channel. The Reynolds number based on depth of flow and fresstream velocity was 30300 while the Froude number was 0.3. A particle image velocimetry technique was used to conduct detailed velocity measurements around and in the near wake region of the cylinder pairs, from which contours and profiles of the mean velocities and turbulent statistics were obtained and discussed. The proper orthogonal decomposition was then applied to provide an insight into the structure of the flow. Reconstruction of the fluctuating velocity components for various numbers of modes were also shown to investigate the role of large-scale structures.

scholarly journals Experimental Investigation of Flow Structures Around side-by-side Yawed Cylinders in Shallow Water

2019 ◽  
Vol 2 (3) ◽  
pp. 1138-1151
Author(s):  
Ebubekir Kütük ◽  
Umutcan Olmuş ◽  
Tahir Durhasan ◽  
Hüseyin Akıllı
Keyword(s):  
Shear Stress ◽  
Shallow Water ◽  
Vector Fields ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Flow Structures ◽  
Piv Technique ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
Yaw Angle

The aim of this experimental study is to investigate the flow behaviour around two equally yawed side-by-side cylinders in shallow water. Time averaged velocity vector fields, Reynolds shear stress distrubutions and streamline patterns were obtained using Particle Image Velocimetry (PIV) technique. The gap ratio between the cylinders were in the range of G/D=0.25-1.25 with an increment of 0.25 where G is the distance between the cylinders and D is the cylinder diameter. Five different yaw angles of cylinders were employed during the experiment. The results showed that the yaw angle, α had an important effect on the flow structures of the downstream of the cylinders. Reynolds shear stress and vortex structures were decreased, the intensity of the jet like flow were significantly attenuated for the gap ratios of G/D=0.25, 0.50 and 0.75.

Viscous Free-Surface Flow Past Twin Vertical Cylinders

2003 ◽  
Author(s):  
Tong Chen ◽  
Allen T. Chwang
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Circular Cylinders ◽  
Small Scale ◽  
The Finite Element Method ◽  
Suction Force ◽  
Large Scale Vortex ◽  
Vertical Cylinders

The laminar flow behaviors around two vertical circular cylinders (in a tandem arrangement) that pierce a free surface are investigated by the finite element method in this paper. The computational results exhibit two major free-surface effects: the presence of a free surface allows the occurrence of small-scale Kelvin-Helmholtz instabilities, but suppresses the onset of large-scale vortex alternating behavior. It is also found that the vorticity will expand in a necklace shape adjacent to the free surface. The second cylinder may experience a persisting suction force due to “trapped” vortices in the gap between the two cylinders, which may not happen in the absence of a free surface.

Small-angle scattering behavior of thread-like and film-like systems

2016 ◽  
Vol 49 (1) ◽  
pp. 260-276 ◽  
Author(s):  
Salvino Ciccariello ◽  
Pietro Riello ◽  
Alvise Benedetti
Keyword(s):  
Small Angle ◽  
Large Scale ◽  
Probability Function ◽  
Structural Parameters ◽  
Small Angle Scattering ◽  
Constant Thickness ◽  
Small Scale ◽  
Linear Segment ◽  
Angle Scattering ◽  
The Right

Film-like and thread-like systems are, respectively, defined by the property that one of the constituting homogenous phases has a constant thickness (δ) or a constant normal cross section (of largest chord δ). The stick probability function of this phase, in the limit δ → 0, naturally leads to the definition of the correlation function (CF) of a surface or of a curve. This CF closely approximates the generating stick probability function in the range of distances larger than δ. The surface and the curve CFs, respectively, behave as 1/rand as 1/r2asrapproaches zero. This result implies that the relevant small-angle scattering intensities behave as {\cal P}_{{\cal S}}/q^2 or as {\cal P}_{{\cal C}}/q in the intermediate range of the scattering vector magnitude (q) and as {\cal P}/q^4 in the outermostqrange. Similarly to {\cal P}, pre-factors {\cal P}_{{\cal S}} and {\cal P}_{{\cal C}} simply depend on some structural parameters. Depending on the scale resolution it may happen that a given sample looks thread like at large scale, film like at small scale and particulate at a finer scale. An explicit example is reported. As a practical illustration of the above results, the surface and the curve CFs of some simple geometrical shapes have been explicitly evaluated. In particular, the CF of the right circular cylinder is evaluated. Its limits, as the height or the diameter the cylinder approaches zero, are shown to coincide with the CFs of a circle and of a linear segment, respectively.

Bridging the Nano-gap: From Scientific Discovery to Real World Products

2009 ◽  
Vol 1209 ◽  
Author(s):  
Partha Sarathi Dutta
Keyword(s):  
Large Scale ◽  
Scientific Discovery ◽  
High Volume ◽  
Small Scale ◽  
Global Business ◽  
Personal Learning ◽  
Start Up ◽  
Business Entities ◽  
Value Add ◽  
The Right

AbstractGoing from a small scale laboratory invention or discovery to a large scale application is not a trivial task and incorporating them into a product for a viable business is even more difficult. As technologies approach final products and applications, the number of criteria it must meet increases exponentially. Economics of the manufacturing process, environmental issues, intellectual property management, etc. needs to be assessed and monitored carefully. Bridging the gap from research to business not only needs multi-disciplinary understanding of the various aspects of the technology, but also how and what it could potentially enable or replace in current technologies and how to go about it through partnerships with global business entities. Especially with new materials, such as nano-scale materials, technology push needs to be rigorous and often the end results are uncertain. One needs to start from a large number of end user applications and narrow down to 1-2 high value-add or high volume opportunities. This process also requires constant development of the existing products to meet the exact needs for the high opportunity end markets. Timing for such efforts is crucial and the resources needed for such activities are often under-estimated by small start-up firms. Even for materials with well understood end products and established markets, significant market pull requires huge investments in product reliability demonstrations, cost of manufacturing, etc. Innovation, flexibility, change, educated risk, adaptability, focus and excellence are all key drivers and necessary ingredients for a successful and sustainable start-up venture. While scientific and engineering innovations are absolutely necessary, the metric for success for any business is revenue generation. Finding the right mechanisms for closing this gap (so-called the valley of death) is where the innovations of entrepreneurs lies. In this paper, I will share some of my personal learning experiences through the start-up company Applied Nanoworks Inc., (now Auterra Inc.).

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