# Flow over periodic hills: an experimental study

Flow over periodic hills: an experimental study Two-dimensional flow over periodically arranged hills was investigated experimentally in a water channel. Two-dimensional particle image velocimetry (PIV) and one-dimensional laser Doppler anemometry (LDA) measurements were undertaken at four Reynolds numbers ( $$\text{5,600} \le Re \le \text{37,000}$$ ). Two-dimensional PIV field measurements were thoroughly validated by means of point-by-point 1D LDA measurements at certain positions of the flow. A detailed study of the periodicity and the homogeneity was undertaken, which demonstrates that the flow can be regarded as two-dimensional and periodic for $$Re \ge \text{10,000}$$ . We found a decreasing reattachment length with increasing Reynolds number. This is connected to a higher momentum in the near-wall zone close to flow separation which comes from the velocity speed up above the obstacle. This leads to a velocity overshoot directly above the hill crest which increases with Reynolds number as the inner layer depth decreases. The flow speed up above that layer is independent of the Reynolds number which supports the assumption of inviscid flow disturbance in the outer layer usually made in asymptotic theory for flow over small hills. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

# Flow over periodic hills: an experimental study

, Volume 51 (1) – Feb 11, 2011
23 pages

/lp/springer_journal/flow-over-periodic-hills-an-experimental-study-pmD4Sh0BCO
Publisher
Springer-Verlag
Subject
Engineering; Fluid- and Aerodynamics; Engineering Fluid Dynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-011-1045-y
Publisher site
See Article on Publisher Site

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