Numerical simulation of the effect of wave form and sudden transverse displacement on vortex shedding from a circular cylinder

1997 ◽  
Author(s):  
J. Meneghini ◽  
Cesareo Siqueira ◽  
P. Bearman ◽  
J. Meneghini ◽  
Cesareo Siqueira ◽  
...  
Author(s):  
S. Nagaya ◽  
R. E. Baddour

CFD simulations of crossflows around a 2-D circular cylinder and the resulting vortex shedding from the cylinder are conducted in the present study. The capability of the CFD solver for vortex shedding simulation from a circular cylinder is validated in terms of the induced drag and lifting forces and associated Strouhal numbers computations. The validations are done for uniform horizontal fluid flows at various Reynolds numbers in the range 103 to 5×105. Crossflows around the circular cylinder beneath a free surface are also simulated in order to investigate the characteristics of the interaction between vortex shedding and a free surface at Reynolds number 5×105. The influence of the presence of the free surface on the vortex shedding due to the cylinder is discussed.


Author(s):  
Antoine Placzek ◽  
Jean-Franc¸ois Sigrist ◽  
Aziz Hamdouni

The numerical simulation of the flow past a circular cylinder forced to oscillate transversely to the incident stream is presented here for a fixed Reynolds number equal to 100. The 2D Navier-Stokes equations are solved with a classical Finite Volume Method with an industrial CFD code which has been coupled with a user subroutine to obtain an explicit staggered procedure providing the cylinder displacement. A preliminary work is conducted in order to check the computation of the wake characteristics for Reynolds numbers smaller than 150. The Strouhal frequency fS, the lift and drag coefficients CL and CD are thus controlled among other parameters. The simulations are then performed with forced oscillations f0 for different frequency rations F = f0/fS in [0.50–1.50] and an amplitude A varying between 0.25 and 1.25. The wake characteristics are analysed using the time series of the fluctuating aerodynamic coefficients and their FFT. The frequency content is then linked to the shape of the phase portrait and to the vortex shedding mode. By choosing interesting couples (A,F), different vortex shedding modes have been observed, which are similar to those of the Williamson-Roshko map.


Author(s):  
Jean-Franc¸ois Sigrist ◽  
Cyrille Allery ◽  
Claudine Beghein

The present paper is the sequel of a previously published study which is concerned with the numerical simulation of vortex-induced-vibration (VIV) on an elastically supported rigid circular cylinder in a fluid cross-flow (A. Placzek, J.F. Sigrist, A. Hamdouni; Numerical Simulation of Vortex Shedding Past a Circular Cylinder at Low Reynolds Number with Finite Volume Technique. Part I: Forced Oscillations, Part II: Flow Induced Vibrations; Pressure Vessel and Piping, San Antonio, 22–26 July 2007). Such a problem has been thoroughly studied over the past years, both from the experimental and numerical points of view, because of its theoretical and practical interest in the understanding on flow-induced vibration problems. In this context, the present paper aims at exposing a numerical study based on a fully coupled fluid-structure simulation. The numerical technique is based on a finite volume discretisation of the fluid flow equations together with i) a re-meshing algorithm to account for the cylinder motion ii) a projection subroutine to compute the forces induced by the fluid on the cylinder and iii) a coupling procedure to describe the energy exchanges between the fluid flow and solid motion. The study is restricted to moderate Reynolds numbers (Re∼2.000–10.000) and is performed with an industrial CFD code. Numerical results are compared with existing literature on the subject, both in terms of cylinder amplitude motion and fluid vortex shedding modes. Ongoing numerical studies with different numerical techniques, such as ROM (Reduced Order Models)-based methods, will complete the approach and will be published in next PVP conference. These numerical simulations are proposed for code validation purposes prior to industrial applications in tube bundle configuration.


2007 ◽  
Vol 594 ◽  
pp. 463-491 ◽  
Author(s):  
T. K. PRASANTH ◽  
S. MITTAL

Results are presented for a numerical simulation of vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m* = 10) in the laminar flow regime (60 < Re < 200). The natural structural frequency of the oscillator, fN, matches the vortex shedding frequency for a stationary cylinder at Re = 100. This corresponds to fND2/ν = 16.6, where D is the diameter of the cylinder and ν the coefficient of viscosity of the fluid. A stabilized space–time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. Unlike at high Re, where the cylinder response is known to be associated with three branches, at low Re only two branches are identified: ‘initial’ and ‘lower’. For a blockage of 2.5% and less the onset of synchronization, in the lower Re range, is accompanied by an intermittent switching between two modes with vortex shedding occurring at different frequencies. With higher blockage the jump from the initial to lower branch is hysteretic. Results from free vibrations are compared to the data from experiments for forced vibrations reported earlier. Excellent agreement is observed for the critical amplitude required for the onset of synchronization. The comparison brings out the possibility of hysteresis in forced vibrations. The phase difference between the lift force and transverse displacement shows a jump of almost 180° at, approximately, the middle of the synchronization region. This jump is not hysteretic and it is not associated with any radical change in the vortex shedding pattern. Instead, it is caused by changes in the location and value of the maximum suction on the lower and upper surface of the cylinder. This is observed clearly by comparing the time-averaged flow for a vibrating cylinder for different Re. While the mean flow for Re beyond the phase jump is similar to that for a stationary cylinder, it is associated with a pair of counter-rotating vortices in the near wake for Re prior to the phase jump. The phase jump appears to be one of the mechanisms of the oscillator to self-limit its vibration amplitude.


2011 ◽  
Vol 255-260 ◽  
pp. 942-946
Author(s):  
Hua Bai ◽  
Jia Wu Li

The hydrodynamic characteristics of a circular cylinder in two-dimensional unsteady uniform cross flow was simulated numerically by the laminar model with the reasonable mesh used the method of fluent. The focus of this numerical simulation was to research the characteristics of pressure distribution, drag coefficient and lift coefficient, and the Strouhal number was calculated at Reynolds-numbers value of 200. The results agree well with experimental data and other numerical results according to the reference. In order to study the control measures of the flow over a circular cylinder, the different baffles inserted at various locations downstream of the cylinder have been compared. The results shows that the vortex shedding of flow over a circular cylinder could be well controlled by place the baffle at a right position of the downstream medial axis of the cylinder, which could reduce drag and resist vibration.


1999 ◽  
Vol 42 (18) ◽  
pp. 3495-3507 ◽  
Author(s):  
B.S. Varaprasad Patnaik ◽  
P.A. Aswatha Narayana ◽  
K.N. Seetharamu

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