@inproceedings{8609205,
  abstract     = {{Vortex streets occur in a tightly packed cylinder array subjected to axial flow, a geometry similar to the tube bundle array encountered in heat exchangers in general and in nuclear reactor cores specifically. These vortices lead to quasi-periodic pressure fluctuations, possibly causing the tubes to vibrate, which in turn causes fretting and fatigue damage. In this paper, the pressure fluctuations are analyzed with Computational Fluid Dynamics (CFD). Firstly, Large-Eddy Simulations are performed on a single cylinder geometry with periodic boundary conditions. It is shown that the amplitude and the location of the maximal pressure fluctuations can be derived from these calculations. These simulations indicate that the amplitude of the instability is dependent on the cylinder spacing and is strongest when the pitch-over-diameter ratio equals 1.03. The circumferential position of the maximal pressure fluctuations also depends on the cylinder spacing. However, modelling the flow with LES is computationally intensive and therefore it is subsequently investigated whether the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach is also able to model the characteristics of the flow instability. It is shown that the Kelvin-Helmholtz instability is clearly captured with the URANS simulations, both in velocity fluctuations in the flow as in the wall pressure profile, but there is a quantitative difference between the LES and URANS calculations. Finally, URANS calculations are performed on a 3-by-3 square array to analyze the effect of the periodic boundary conditions around the single cylinder geometry that was used previously. It is concluded that the cross-flow velocity in an intercylinder gap is similar, but a slightly more irregular pattern is found for the 3-by-3 array. The root mean square value of the cross-flow velocity is 2.4 percent point larger in the 3-by-3 array compared to the single cylinder case.}},
  author       = {{De Moerloose, Laurent and Verzelen, Bart and Dolfen, Henri and De Ridder, Jeroen and Degroote, Joris}},
  booktitle    = {{SESAME Final International Workshop, Proceedings}},
  keywords     = {{CFD,LES,URANS,flow-induced vibrations,tube bundle}},
  language     = {{eng}},
  location     = {{Petten (NL)}},
  pages        = {{9}},
  title        = {{Analysis of the Kelvin-Helmholtz instability in a square cylinder array subjected to axial flow with LES and URANS}},
  url          = {{http://sesame-h2020.eu/apply-now-for-sesame-final-international-workshop/}},
  year         = {{2019}},
}