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Experiments in Fluids

, Volume 44, Issue 2, pp 305–316 | Cite as

Investigation of a turbulent spot and a tripped turbulent boundary layer flow using time-resolved tomographic PIV

  • Andreas Schröder
  • Reinhard Geisler
  • Gerrit E. Elsinga
  • Fulvio Scarano
  • Uwe Dierksheide
Research Article

Abstract

In this feasibility study the tomographic PIV technique has been applied to time resolved PIV recordings for the study of the growth of a turbulent spot in a laminar flat plate boundary layer and to visualize the topology of coherent flow structures within a tripped turbulent flat plate boundary layer flow. The experiments are performed around (Re x )1/2 ≈ 450 in a low speed wind-tunnel using four high speed CMOS cameras operating up to 5 kHz. The volume illumination required a multiple-reflection system able to intensify light intensity within the measurement volume. This aspect is deemed essential when a high-speed tomographic PIV system is applied in air flows. The particle image recordings are used for a three dimensional tomographic reconstruction of the light intensity distribution within the illuminated volume. Each pair of reconstructed three-dimensional light distributions is analyzed by 3D spatial cross-correlation using iterative multi-grid schemes with volume-deformation, yielding a correlated time sequence of three-dimensional instantaneous velocity vector volumes. The coherent structures organization is analyzed by 3D-vorticity and -swirling-strength iso-surfaces visualization. In both flow types streaks and hairpin-like or arch vortical structures are most prominent. The data gives insight into the role of these structures for the spatio-temporal arrangement of the wall normal flow exchange mechanisms, especially of the instantaneous Reynolds stress events Q2 and Q4. A description of different self-sustainable flow organizations based on modifications of the hairpin-vortex- and streak-models is given. Two preliminary results are essential: Self-sustainability of a coherent vortical structure depends on the ability to entrain high momentum fluid, initially Q4. And, stream-wise swirl at the near-wall region of arch or hairpin-like vortices has been observed to be rare.

Keywords

Hairpin Vortex Turbulent Spot Multiplicative Algebraic Reconstruction Technique Instantaneous Velocity Vector Turbulent Boundary Layer Flow 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

t

time

Vx, Vy, Vz

instantaneous velocity components in x-, y- and z-direction

Vx, Vy, Vz

fluctuation velocity components

x, y, z

streamwise, normal and spanwise coordinates

Rex

Reynolds number based on length from plate LE

T

time-difference from excitation of spot

f

focal length

f#

aperture stop

Q1,...,Q4

Quadrants of instantaneous Reynolds stress VxVy

U

free-stream velocity

δ

boundary layer thickness (0.99 U )

λ

wave length of laser light

|rot|

magnitude of instantaneous vorticity

Abbreviations

PDF

Probability density function

RMS

Root mean square

(T)BL

(Turbulent) Boundary-layer

TE

Trailing edge

LE

Leading edge

TR

Time resolved

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Andreas Schröder
    • 1
  • Reinhard Geisler
    • 1
  • Gerrit E. Elsinga
    • 2
  • Fulvio Scarano
    • 2
  • Uwe Dierksheide
    • 3
  1. 1.Deutsches Zentrum für Luft- und RaumfahrtInstitut f. Aerodynamik und StrömungstechnikGöttingenGermany
  2. 2.Department of Aerospace EngineeringDelft University of TechnologyDelftThe Netherlands
  3. 3.La Vision GmbHGöttingenGermany

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