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Transition and control in rotating-disk boundary-layer

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HAL Id: hal-00632327

https://hal.archives-ouvertes.fr/hal-00632327

Submitted on 14 Oct 2011

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Transition and control in rotating-disk boundary-layer

Muhammad Ehtisham Siddiqui, Benoît Pier, Mukund Vasudevan, Julian F.

Scott, Carlo Cossu, Alexandre Azouzi, Christian Nicot, Roger Michelet

To cite this version:

Muhammad Ehtisham Siddiqui, Benoît Pier, Mukund Vasudevan, Julian F. Scott, Carlo Cossu, et al..

Transition and control in rotating-disk boundary-layer. Euromech Fluid Mechanics Conference 8, Sep

2010, Bad Reichenhall, Germany. �hal-00632327�

(2)

Transition and control in rotating-disk boundary-layer

M. E. SIDDIQUI

, B. PIER

, MUKUND V.

, J. SCOTT

, C. COSSU

, A. AZOUZI

, C. NICOT

, R. MICHELET

The flow due an infinite disk rotating in otherwise still fluid has served as the archetypical configuration for the study of three-dimensional boundary layers and is known to display a sharp transition from laminar to turbulent flow at a nondimen- sional critical radiusR≃510. Using linear stability analysis, this location was found by Lingwood1 to precisely coincide with the onset of local absolute instability. More recently2, a fully nonlinear analysis and a secondary stability analysis have further contributed to the understanding of the complex dynamics prevailing near the tran- sition radius. An open-loop control strategy3 has been theoretically shown4 to be applicable in this context. The aim is to delay onset of secondary perturbations, and thus transition, by a controlled modification of the primary nonlinear state.

The present experimental investigation has been undertaken to confirm these pre- dictions and to test the practical applicability of the control method.

The experimental arrangement consists of a 50 cm diameter glass disk that is ro- tated at constant angular speeds, up to 1500 rpm. Control is applied via a set of needles, evenly distributed on a cylinder placed above the disk. The forcing parame- ters are adjusted and optimized by changing the number of needles and the rotation rate of the cylinder (which can be varied independently of the disk rotation rate). A second technique, using microstructured roughness elements on the disk surface, is also currently being implemented.

The flow features, with and without control, are characterized by time-resolved local hot-wire measurements. The influence of the different control parameters and forcing strategies will be discussed and compared with theoretical predictions.

Laboratoire de m´ecanique des fluides et d’acoustique; CNRS—Universit´e de Lyon ; ´Ecole centrale de Lyon ; 36 avenue Guy-de-Collongue ; F-69134 ´Ecully cedex.

Institut de m´ecanique des fluides de Toulouse ; CNRS—Universit´e de Toulouse ; all´ee Camille- Soula ; F-31400 Toulouse.

1Lingwood,J. Fluid Mech. 299, 17–33 (1995).

2Pier,J. Fluid Mech.487, 315–343 (2003).

3Pier,Proc. R. Soc. Lond. A459, 1105–1115 (2003).

4Pier,J. Eng. Math.57, 237–251 (2007).

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