SEMINAR - New Insight on Flow Development and Two-dimensionality of Turbulent Channel Flows, by Dr. Hassan Nagib, Mechanical, Materials, and Aerospace Engineering, Illinois Institute of Technology

Education - Colloquium - WPI Only

Thursday, April 25, 2013
2:00 PM-3:00 PM

Higgins Laboratories

The experimental conditions required for a turbulent channel flow to be considered fully-developed and nominally
two-dimensional remain a challenging objective. Oil film interferometry (OFI) and static pressure measurements
were carried out over the range 200 < Re_tau < 800 in an adjustable-geometry channel flow facility. Three-dimensional
effects were studied by considering different aspect ratio (AR) configurations, and also by fixing the AR and
modifying the hydraulic diameter Dh of the section. The conditions at the centerplane of the channel were characterized
through the local skin friction from the OFI and the centerline velocity at three different streamwise locations, as
well as the wall shear based on the streamwise global pressure gradient. The skin friction obtained from the pressure
gradient overestimated the local shear measurements obtained from the OFI, and did not reproduce the same AR-dependence
observed with OFI. Differences between the local and global techniques were also reflected in the flow development.
Development length of high-aspect-ratio channels scales with the hydraulic diameter of the section, and is around 200
channel full-heights H, much larger than the values of around 100−150 H previously reported in the literature. Results
of a complementary study aimed at characterizing three-dimensional effects present in turbulent duct flows (side-wall
boundary layers and secondary motions) by means of DNSs are also presented.

Suggested Audiences: College

Phone: 508-831-5236

Last Modified: January 28, 2013 at 11:58 AM

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