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Published in:
2006 | OriginalPaper | Chapter
Experimental and Numerical Investigations of Flow Separation and Transition to Turbulence in an Axisymmetric Diffuser
Authors : L. Hoefener, W. Nitsche, A. Carnarius, F. Thiele
Published in: New Results in Numerical and Experimental Fluid Mechanics V
Publisher: Springer Berlin Heidelberg
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Flow separation and transition to turbulence in a smooth axisymmetric diffuser at
Re
D
1, ≈ 7800 were investigated both numerically and experimentally.
The inlet flow is an incompletely developed laminar pipe flow with a typical boundary layer thickness (δ
99
/
D
1
≈ 0.3). The smooth diffuser contour causes a pressure-induced laminar separation. Due to the inflection point within the shear layer, instabilities cause a transition of the separated laminar flow. Further downstream, the flow reattaches turbulent and recovers slowly to a turbulent equilibrium boundary layer. Periodic disturbances are introduced upstream of the separation point in order to control the breakdown of the separated shear layer. In the present study, two different perturbation modes are tested experimentally and compared in detail with numerical investigations.