Linear stability analysis of a boundary layer with rotating wall-normal cylindrical roughness elements

Wu, Yongxiang; Axtmann, Gabriel; Rist, Ulrich

doi:10.1017/jfm.2021.146

Cited by 4 publications

(22 citation statements)

References 47 publications

(77 reference statements)

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“…(2014) and Wu et al. (2021) as well. However, it should be noted that in the roughness region () the term dominates the energy production for cases with .…”

Section: Controlled Transitionmentioning

confidence: 84%

“…In Wu et al. (2021), two sets of boundary-layer flows with rotating cylindrical roughness elements, i.e. co-rotating and counter-rotating cylinder pairs, are investigated by linear stability theory.…”

Section: Methodsmentioning

confidence: 99%

“…The above governing equations are implemented and solved with the open source OpenFOAM solver icoSfdFoam (Wu et al. 2021), which solves the incompressible Navier–Stokes equations using the pressure-implicit with splitting of operators algorithm. The unsteady terms of the governing equations are discretised with an implicit backwards scheme.…”

Section: Methodsmentioning

confidence: 99%

“…A more detailed discussion of the generation of this vortical system can be found in Wu et al. (2021).

Figure 3.Vortex visualisation for isolated roughness element (, , ) by means of , coloured by streamwise velocity .…”

Section: Laminar Base Flowsmentioning

confidence: 99%

“…A crescent of high shear stress region around the DIV (identified by the -criterion of Meyer 2003) is noticeable, where inflectional points of the velocity profile are located and consequently inviscid inflectional instability could be expected (Wu et al. 2021).…”

Section: Laminar Base Flowsmentioning

confidence: 99%

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Transition mechanisms in a boundary layer controlled by rotating wall-normal cylindrical roughness elements

Römer²,

Axtmann³

et al. 2022

J. Fluid Mech.

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The transition to turbulence induced by counter-rotating wall-normal rotating cylindrical roughness pairs immersed within a laminar boundary layer on a flat plate is investigated with direct numerical simulations, dynamic mode decomposition (DMD) and perturbation kinetic energy (PKE) analysis. As long as the cylinder stub is rotating, the wake contains a steady dominating inner vortex (DIV) surrounded by a secondary inner vortex. Its circumferential velocity accelerates the fluid on one side of the cylinder and decelerates it on the other side. With low rotation speed, the perturbation is initiated by a combination of elliptical and centrifugal instabilities in the near wake. At medium rotation speeds, Taylor–Couette-like streamwise vortices are generated on the decelerated side, resulting in a protruding reverse-flow zone. Results from DMD analysis and corresponding PKE analysis reveal the unstable nature of the deceleration region and the wake. At the largest rotation speed investigated, the onset of perturbations is directly located on the decelerated side of the cylinder stubs, where a deceleration mechanism feeds the instability. In the near wake, the mechanism gradually changes to a pure centrifugal instability when the rotation speed increases. In the far wake, both elliptical and centrifugal instabilities fade away, and the streaky flow featuring a vigorous DIV is then only subject to inviscid inflectional instability.

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“…(2014) and Wu et al. (2021) as well. However, it should be noted that in the roughness region () the term dominates the energy production for cases with .…”

Section: Controlled Transitionmentioning

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…A more detailed discussion of the generation of this vortical system can be found in Wu et al. (2021).

Figure 3.Vortex visualisation for isolated roughness element (, , ) by means of , coloured by streamwise velocity .…”

Section: Laminar Base Flowsmentioning

confidence: 99%

Section: Laminar Base Flowsmentioning

confidence: 99%

See 3 more Smart Citations

Transition mechanisms in a boundary layer controlled by rotating wall-normal cylindrical roughness elements

Römer²,

Axtmann³

et al. 2022

J. Fluid Mech.

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Direct Numerical Simulation of Counter-Rotating Cylindrical Roughness Pairs for Laminar Flow Control

Wu,

Wenzel,

Rist

2023

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Delay of laminar–turbulent transition by counter-rotating cylindrical roughness elements in a laminar flat plate boundary layer

Römer

Schulz

et al. 2023

Exp Fluids

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Delaying laminar–turbulent transition in boundary layers is of great interest since the skin-friction coefficient can be reduced by up to one order of magnitude. In this experimental research, it is shown that counter-rotating cylindrical roughness elements are able to delay transition under realistic flow conditions. Evidence is given by the intermittency, evaluated from hot-film measurements in a laminar water channel. An increase in rotation speed results in a delay of transition of up to $${6.5}{\%}$$ 6.5 % in the center of the plate. This trend can be explained by the streaks amplified by the rotating cylinders, resulting in a damping of the fluctuation amplitude in the boundary layer. The advantage of this method is that the transition delay can be actively controlled with conventional cylindrical roughness elements. Graphical abstract

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Linear stability analysis of a boundary layer with rotating wall-normal cylindrical roughness elements

Abstract: Abstract

Cited by 4 publications

References 47 publications

Transition mechanisms in a boundary layer controlled by rotating wall-normal cylindrical roughness elements

Transition mechanisms in a boundary layer controlled by rotating wall-normal cylindrical roughness elements

Direct Numerical Simulation of Counter-Rotating Cylindrical Roughness Pairs for Laminar Flow Control

Delay of laminar–turbulent transition by counter-rotating cylindrical roughness elements in a laminar flat plate boundary layer

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