Direct Numerical Simulations of Flow Past an Array of Distributed Roughness Elements

2006 ◽  
Author(s):  
Donald Rizzetta ◽  
Miguel Visbal
Keyword(s):  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Flow Past ◽  
Roughness Elements

scholarly journals Investigation of the roughness-induced transition: global stability analyses and direct numerical simulations

2014 ◽  
Vol 760 ◽  
pp. 175-211 ◽  
Author(s):  
Jean-Christophe Loiseau ◽  
Jean-Christophe Robinet ◽  
Stefania Cherubini ◽  
Emmanuel Leriche
Keyword(s):  
Aspect Ratio ◽  
Global Stability ◽  
Numerical Simulations ◽  
Shear Layer ◽  
Roughness Element ◽  
Three Dimensional ◽  
Direct Numerical Simulations ◽  
Low Speed ◽  
Stability Analyses ◽  
Roughness Elements

AbstractThe linear global instability and resulting transition to turbulence induced by an isolated cylindrical roughness element of height $h$ and diameter $d$ immersed within an incompressible boundary layer flow along a flat plate is investigated using the joint application of direct numerical simulations and fully three-dimensional global stability analyses. For the range of parameters investigated, base flow computations show that the roughness element induces a wake composed of a central low-speed region surrounded by a three-dimensional shear layer and a pair of low- and high-speed streaks on each of its sides. Results from the global stability analyses highlight the unstable nature of the central low-speed region and its crucial importance in the laminar–turbulent transition process. It is able to sustain two different global instabilities: a sinuous and a varicose one. Each of these globally unstable modes is related to a different physical mechanism. While the varicose mode has its root in the instability of the whole three-dimensional shear layer surrounding the central low-speed region, the sinuous instability turns out to be similar to the von Kármán instability in the two-dimensional cylinder wake and has its root in the lateral shear layers of the separated zone. The aspect ratio of the roughness element plays a key role on the selection of the dominant instability: whereas the flow over thin cylindrical roughness elements transitions due to a sinuous instability of the near-wake region, for larger roughness elements the varicose instability of the central low-speed region turns out to be the dominant one. Direct numerical simulations of the flow past an aspect ratio ${\it\eta}=1$ (with ${\it\eta}=d/h$) roughness element sustaining only the sinuous instability have revealed that the bifurcation occurring in this particular case is supercritical. Finally, comparison of the transition thresholds predicted by global linear stability analyses with the von Doenhoff–Braslow transition diagram provides qualitatively good agreement.

Direct numerical simulations on the flow past a thin square plate

2021 ◽  
Vol 33 (3) ◽  
pp. 034128
Author(s):  
Yakun Zhao ◽  
Song Gao ◽  
Xiantao Zhang ◽  
Xiaoxian Guo ◽  
Xin Li ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Flow Past ◽  
Square Plate

Direct numerical simulations of tonal noise generated by laminar flow past airfoils

2009 ◽  
Vol 320 (4-5) ◽  
pp. 838-858 ◽  
Author(s):  
R.D. Sandberg ◽  
L.E. Jones ◽  
N.D. Sandham ◽  
P.F. Joseph
Keyword(s):  
Laminar Flow ◽  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Tonal Noise ◽  
Flow Past

Direct numerical simulations on the flow past an inclined circular disk

2017 ◽  
Vol 72 ◽  
pp. 152-168 ◽  
Author(s):  
Xinliang Tian ◽  
Zhihuan Hu ◽  
Haining Lu ◽  
Jianmin Yang
Keyword(s):  
Numerical Simulations ◽  
Circular Disk ◽  
Direct Numerical Simulations ◽  
Flow Past

scholarly journals Control of laminar breakdown in a supersonic boundary layer employing streaks

2021 ◽  
Vol 932 ◽  
Author(s):  
Simon Kneer ◽  
Zhengfei Guo ◽  
Markus J. Kloker
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Point Source ◽  
Numerical Simulations ◽  
Supersonic Boundary Layer ◽  
Direct Numerical Simulations ◽  
Roughness Elements ◽  
Controlling Mechanism ◽  
Laminar Flow Control

In this study direct numerical simulations are employed to investigate the effects of various parameters on the laminar-flow-control capabilities of narrowly spaced streaks in a supersonic boundary layer at Mach $2.0$ . Previous work by Sharma et al. (J. Fluid Mech., vol. 873, 2019, pp. 1072–1089) has found these streak modes, excited by a spanwise blowing-and-suction strip, to be highly effective at delaying pure oblique-type breakdown. In the present work it is shown that spectrum-enriching subharmonic modes, relevant with increasing running-length Reynolds number, do not destroy the controlling mechanism, and also a complex breakdown scenario, triggered by a multi-frequency point source, is found to be effectively controlled. Moreover, the control-streak excitation by roughness elements is compared in detail with the blowing-and-suction method, revealing relevant differing features.

Insights into the physics of dominating frequency modes for flow past a stationary sphere: Direct numerical simulations

2019 ◽  
Vol 31 (4) ◽  
pp. 045108 ◽  
Author(s):  
Shashank S. Tiwari ◽  
Shivkumar Bale ◽  
Ashwin W. Patwardhan ◽  
Krishnaswamy Nandakumar ◽  
Jyeshtharaj B. Joshi
Keyword(s):  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Flow Past

Direct Numerical Simulations of the Flow Past a Cylinder Moving With Sinusoidal and Nonsinusoidal Profiles

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Osama A. Marzouk
Keyword(s):  
Numerical Simulations ◽  
Mechanical Energy ◽  
Harmonic Oscillation ◽  
Maximum Energy ◽  
Mean Value ◽  
Displacement Function ◽  
Direct Numerical Simulations ◽  
Flow Past ◽  
Flow Past A Cylinder ◽  
Lift And Drag

We perform direct numerical simulations of the flow past a circular cylinder undergoing a one-degree-of-freedom transverse oscillation. The displacement follows a sine function raised to an arbitrary integer power ranging from 1 to 8. When the displacement power is above 2, we have multifrequency oscillation, and the number of Fourier components in the oscillation increases with the power, but they are either odd or even multiples of the input (argument) frequency of the displacement function. We study the responses of the nondimensional lift and drag under these different oscillation profiles and the transfer of nondimensional mechanical energy due to the oscillation, and their trends as the power (hence the number of Fourier components in the oscillation) increases. For odd powers, the energy is transferred to the cylinder; whereas for even powers, it is transferred to the flow. A unity power (harmonic oscillation) corresponds to the maximum energy transfer to the cylinder, which can explain the occurrence of this profile in the case when the cylinder is free to oscillate due to the vortex-induced vibration (VIV) phenomenon. The lift exhibits a mean value only with even powers above 2. The results show that the lift is driven to a large extent by the acceleration of the oscillation rather than its velocity. This should be considered when modeling the fluid-structure coupling in reduced-order VIV models.

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