Numerical Study of the Flow-Induced Vibration of Two Equal-Diameter Cylinders in Tandem With Varying the Mass Ratio

2014 ◽  
Author(s):  
M. Mobassher Tofa ◽  
Adi Maimun ◽  
Yasser M. Ahmed ◽  
Saeed Jamie
Keyword(s):  
Shear Stress ◽  
Circular Cylinder ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Flow Regime ◽  
Turbulence Model ◽  
Numerical Study ◽  
Mass Ratio ◽  
Flow Induced Vibration ◽  
Two Degree Of Freedom

Mass ratio is an important parameter that influences the vortex-induced vibration of circular cylinder, especially for a two degree of freedom system. Numerical simulations have been performed for two equal-diameter cylinders with different mass ratios in tandem arrangement which are subjected to uniform flows in subcritical flow regime. The distances between the upstream and downstream cylinders were three and four times of the cylinder diameter. The purpose of this study is to investigate the effect of upstream cylinder’s mass ratio on the vibration of downstream cylinder. The shear stress transport detached eddy turbulence model has been used for simulating the turbulent flow around the two cylinders. The numerical results of a single cylinder subjected to 2DOF vibration have been compared with the experimental results available for such cases to validate the present study.

scholarly journals A preliminary study of the pressure and shear stress on a plane surface beneath a circular cylinder in turbulent flow fields

2017 ◽  
Vol 14 (1) ◽  
pp. 9-24
Author(s):  
Jian-Chen Cai ◽  
Jie Pan ◽  
Shi-Ju E ◽  
Wei-Dong Jiao ◽  
Dong-Yun Wang
Keyword(s):  
Shear Stress ◽  
Circular Cylinder ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Plane Surface ◽  
Pressure Fluctuations ◽  
Flow Fields ◽  
Ocean Engineering ◽  
Cylinder Diameter

This paper studies the fluctuating forces on a plane surface beneath a circular cylinder in the subcritical flow regime using two-dimensional computational fluid dynamics (CFD). The turbulent flow fields were calculated via numerical solutions of the Navier–Stokes (N–S) equations without a turbulence model (laminar flow computation), large eddy simulation (LES), and Reynolds-Averaged N-S equations (RANS) approach with the shear-stress transport (SST) turbulence model. The primary goal is to evaluate the performance of 2-D turbulence simulation with different approaches and to have preliminary knowledge of the forces on the plane which is important in studying scours and flow-induced vibration in ocean engineering. Results show that although a coarse mesh scheme can only obtain potential flows, the laminar approach with high mesh resolution can adequately simulate turbulent flows at moderate Reynolds numbers. Spatially, the fluctuating forces on the plane surface due to the flow are significant within three times the cylinder diameter in the downstream, and within one cylinder diameter in the upstream of the cylinder. The pressure fluctuations are approximately two orders of magnitude larger than the shear stress fluctuations. In the frequency domain, the fluctuating forces are significant under twice the vortex-shedding frequency. Within one cylinder diameter in the downstream and upstream regions of the cylinder, the pressure fluctuations on the plane surface are well correlated, while the shear stress is not so well correlated.

A Numerical Study of Heat Transfer and Flow Structure in Channels With Miniature V Rib-Dimple Hybrid Structure on One Wall

2018 ◽  
Author(s):  
Peng Zhang ◽  
Yu Rao ◽  
Yanlin Li
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Hybrid Structure ◽  
Transfer Enhancement ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Flow Mixing

This paper presents a numerical study on turbulent flow and heat transfer in the channels with a novel hybrid cooling structure with miniature V-shaped ribs and dimples on one wall. The heat transfer characteristics, pressure loss and turbulent flow structures in the channels with the rib-dimples with three different rib heights of 0.6 mm, 1.0 mm and 1.5 mm are obtained for the Reynolds numbers ranging from 18,700 to 60,000 by numerical simulations, which are also compared with counterpart of a pure dimpled and pure V ribbed channel. The results show that the overall Nusselt numbers of the V rib-dimple channel with the rib height of 1.5 mm is up to 70% higher than that of the channels with pure dimples. The numerical simulations show that the arrangement of the miniature V rib upstream each dimple induces complex secondary flow near the wall and generates downwashing vortices, which intensifies the flow mixing and turbulent kinetic energy in the dimple, resulting in significant improvement in heat transfer enhancement and uniformness.

scholarly journals Effect of Prandtl number on heat transfer characteristics in an axisymmetric sudden expansion: A numerical study

2007 ◽  
Vol 11 (4) ◽  
pp. 171-178
Author(s):  
Khalid Alammar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Study ◽  
Sudden Expansion ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Simulated Effect

Using the standard k-e turbulence model, an incompressible, axisymmetric turbulent flow with a sudden expansion was simulated. Effect of Prandtl number on heat transfer characteristics downstream of the expansion was investigated. The simulation revealed circulation downstream of the expansion. A secondary circulation (corner eddy) was also predicted. Reattachment was predicted at approximately 10 step heights. Corresponding to Prandtl number of 7.0, a peak Nusselt number 13 times the fully-developed value was predicted. The ratio of peak to fully-developed Nusselt number was shown to decrease with decreasing Prandtl number. Location of maximum Nusselt number was insensitive to Prandtl number.

Fluid-Structure Interaction Modeling of a Subsea Jumper Pipe

2014 ◽  
Author(s):  
Mohammad A. Elyyan ◽  
Yeong-Yan Perng ◽  
Mai Doan
Keyword(s):  
Multiphase Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Fluid Structure Interaction ◽  
Flow Experience ◽  
Flow Induced Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Start Up ◽  
Interaction Modeling

Flow-induced vibration (FIV) is one of the main reasons for subsea piping failure, where subsea pipes, which typically carry multiphase flow, experience large fluctuating forces. These fluctuating forces can induce severe vibrations leading to premature piping failure. This paper presents a transient numerical study of a typical subsea M-shape jumper pipe that is carrying a gas-liquid multiphase flow subject to a slug frequency of 4.4 Hz, starting from rest to include the start-up effect as part of the study. 3-D numerical simulations were used to capture the fluid-structure interaction (FSI) and estimate pipe deformations due to fluctuating hydrodynamic forces. In this paper, two FSI approaches were used to compute the pipe deformations, two-way coupled and one-way decoupled. Analysis of the results showed that decoupled (one-way) FSI approach overestimated the peak pipe deformation by about 100%, and showed faster decay of fluctuations than coupled (two-way) FSI analysis. The assessment of resonant risk due to FIV is also discussed.

Numerical study of turbulent flow over an S-shaped hydrofoil

2008 ◽  
Vol 222 (9) ◽  
pp. 1717-1734 ◽  
Author(s):  
T Micha Prem Kumar ◽  
Dhiman Chatterjee
Keyword(s):  
Shear Stress ◽  
Turbulent Flow ◽  
Flow Separation ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Pressure Gradients ◽  
Convex Surfaces ◽  
Shear Stress Transport ◽  
Formidable Challenge

In this paper, a numerical study of turbulent flow over the S-shaped hydrofoil at 0° angle of attack has been reported. Here, the flow takes place over concave and convex surfaces and is accompanied by the favourable and adverse pressure gradients and flow separation. Modelling such a flow poses a formidable challenge. In the present work four turbulence models, namely, k–∊ realizable, k–ω shear stress transport

scholarly journals Numerical Study on the Characteristics of Pressure Fluctuations in an Axial-Flow Water Pump

2014 ◽  
Vol 6 ◽  
pp. 565061 ◽  
Author(s):  
Zhi-Jun Shuai ◽  
Wan-You Li ◽  
Xiang-Yuan Zhang ◽  
Chen-Xing Jiang ◽  
Feng-Chen Li
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Axial Flow ◽  
Rotation Frequency ◽  
Dominant Frequency ◽  
Water Pump ◽  
Flow Induced Vibration ◽  
Impeller Blade

Flow induced vibration due to the dynamics of rotor-stator interaction in an axial-flow pump is one of the most damaging vibration sources to the pump components, attached pipelines, and equipment. Three-dimensional unsteady numerical simulations were conducted on the complex turbulent flow field in an axial-flow water pump, in order to investigate the flow induced vibration problem. The shear stress transport (SST) k-ω model was employed in the numerical simulations. The fast Fourier transform technique was adopted to process the obtained fluctuating pressure signals. The characteristics of pressure fluctuations acting on the impeller were then investigated. The spectra of pressure fluctuations were predicted. The dominant frequencies at the locations of impeller inlet, impeller outlet, and impeller blade surface are all 198 Hz (4 times of the rotation frequency 49.5 Hz), which indicates that the dominant frequency is in good agreement with the blade passing frequency (BPF). The first BPF dominates the frequency spectrum for all monitoring locations inside the pump.

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