the wallturb joined experiment to assess the large scale

Wallturb Workshop Lille – April 21-23 2009

The WALLTURB joined experiment to assess the large scale structures in a high Reynolds

number turbulent boundary layer.

J. Delville*, P. Braud*, S. Coudert**, J.M Foucaut**,C. Fourment*, W.K. George***, P.B.V. Johansson***, J. Kostas**, F. Mehdi***, A. Royer*, M. Stanislas**,M. Tutkun***

* LEA Poitiers (France)

** LML Lille (France)

*** TU-Chalmers Gottenborg (Sweden)


… to assess the large scale structures in a high Reynolds number turbulent boundary layer.

• Investigate the spatial and temporal structure of the near wall region.

• Interaction between inner and outer flow

• More than single-point statistics

• Use state-of-the-art techniques to study the dynamics in a volume of the boundary layer.

4 PIV systems 8 cameras ; 143 Hot wires

Synchronised measurements

…… a Joined Adventure a Joined Adventure ……


• Large turbulent boundary layer ~ 300 mm.

Can easily reach small distance from the wall: up to y+ ~ 10

• Flat plate: Zero Pressure Gradient (ZPG)

Two Reynolds numbers :

Reθ = 10 000 ( Ue = 5 m/s ; Uτ ~ 0.2 m/s )Reθ = 20 000 ( Ue = 10 m/s ; Uτ ~ 0.4 m/s )

• Bump: Adverse Pressure Gradient (APG)

One Reynolds numbers :

Reθ = 20 000 ( Ue = 10m/s ; Uτ = 0.25 m/s )

…… Flow Configurations Flow Configurations ……


The LML Wind TunnelThe LML Wind Tunnel

~20m long … Boundary Layer Thickness at test section: ~30cm

Test section: 1x2 m²


143143 HotHot--WiresWires


Rake of 143Rake of 143 HotHot--WiresWires

y+ = 1 @ 40 μm at U∞ = 10 m/s

y+ = 1 @ 80 μm at U∞ = 5 m/s

Wire #1 @ 0.3mm y+~4 (Reθ=10 000)y+~7.5 (Reθ=20 000)

μ


HotHot--wirewire setup and setup and anemometersanemometers

Anemometers

• 30 kHz sampling rate (Microstar dap5400a 16 bit A/D)

• Separate S/H circuits on the anemometer boards


• 2 stereo PIV systems to record on 30 x 30 cm² in the YZ plane 1 cm upstream of the wires plane ( & )

• 1 stereo PIV system to record on 10 x 15 cm² in the XY plane of symmetry ( )

• 143 hot wires distributed on 30 x 30 cm² ( )

PIV Setup PIV Setup 1: 1: HWR + XY &YZHWR + XY &YZ


• 1 high repetition PIV system to record in the XZ plane 3 kHz at Re = 20,000 ; y+ = 100 ; FoV: 4.5x4.5 cm²1.5 kHz at Re = 10,000 ; y+ = 50 ; FoV: 6.5x6.5 cm²

• 143 hot wires distributed on 30x30 cm²

PIV Setup PIV Setup 2 : 2 : HWR + XZHWR + XZ


• PIV: separation of light sheets by using polarisation filters

• Effective position of HW probes

• Calibration of HW probes

• Synchronisation HW sampling – PIV

• Flow blockage effect

…… Technical features Technical features ……


Data Base for the ZPGData Base for the ZPGTurbulent Boundary LayerTurbulent Boundary Layer

Total : 56543Total : 23210620HWR10 0005

29431 block of 1.96 sHWR + XZ10 00051100x401100HWR + XZ10 0005

9600600HWR + XY &YZ10 0005

Total : 60480Total : 23140613HWR20 00010

68801 block of 2.29 sHWR + XZ20 000101100x401100HWR + XZ20 00010

9600600HWR + XY &YZ20 00010

N° of PIV records

N° of HWR blocks (6 sec.)configurationRθUe m/s


Instantaneous Snaphots:Instantaneous Snaphots:Setup 1: Setup 1: HWR + XY &YZHWR + XY &YZ

With HWR With HWR


Time history:Time history:Setup 2 : Setup 2 : HWR + XZHWR + XZ

Ue=10m/sReθ = 20 000 Uτ ~ 0.4 m/s y+ = 100

Sampling rate: 3kHzField of View: 4.5x4.5 cm²

X+

Z+


What What the HW rake can the HW rake can see, compared with PIVsee, compared with PIV

• HW distribution and sample record lengths provide a very large field of view, by using Taylor’s hypothesis

• Example (FP 10m/s): spatial correlations for a reference probe located @ y~0.015δ : color plots: PIV ; lines: HW


Bump ExperimentBump Experiment

Shape of the bump is designed by Dassault Aviation to generate APG representative of airfoil at high angle of attack.

An equivalent Data Base has been

created for the APG configuration


SummarySummary

• Complicated but well documented experiment: Stereoscopic PIV; High Repetition PIV; Rake of 143 hot wires.

• Combination of time resolution (HW & HR PIV) and of spatial resolution (PIV)

• Covers at the same time small inner scales and large outer scales

• Covers very long temporal integral scales

• All raw data are now available : http://lmlm6-62.univ-lille1.fr/db/

• Some non exhaustive results will be presented during this workshop

• This work has been performed under the WALLTURB project. WALLTURB (A European synergy for the assessment of wall turbulence) is funded by the CEC under the 6th framework program (CONTRACT No: AST4-CT-2005-516008).

the wallturb joined experiment to assess the large scale

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