On minimum aspect ratio for duct flow facilities and the role of side walls in generating secondary flows

Vinuesa R, Schlatter P, Nagib HM (2015)

Publication Type: Journal article

Publication year: 2015

Journal

Journal of Turbulence Taylor & Francis

Book Volume: 16

Pages Range: 588-606

Journal Issue: 6

DOI: 10.1080/14685248.2014.996716

Abstract

To the surprise of some of our colleagues, we recently recommended aspect ratios of at least 24 (instead of accepted values over last few decades ranging from 5 to 12) to minimise effects of side walls in turbulent duct flow experiments, in order to approximate the two-dimensional channel flow. Here we compile available results from hydraulics and civil engineering literature, where this was already documented in the 1980s. This is of great importance due to the large amount of computational studies (mainly direct numerical simulations, DNSs) for spanwise-periodic turbulent channel flows, and the extreme complexity of constructing a fully developed duct flow facility with aspect ratio of 24 for high Reynolds numbers with adequate probe resolution. Results from this non-traditional literature for the turbulence community are compared to our recent database of DNS of turbulent duct flows with aspect ratios ranging from 1 to 18 at Reτ, c values of 180 and 330, leading to very good agreement between their experimental and our computational results at these low Reynolds numbers. The DNS results also reveal the complexity of a multitude of streamwise vortical structures in addition to the secondary corner flows (which extend up to z ≃ 5h). These time-dependent and meandering streamwise structures are located at the core of the duct and scale with its half-height. Comparisons of these structures with the vortical motions found in spanwise-periodic channels reveal similitudes in their time-averages and the same rate of decay of their mean kinetic energy ∼ TA-1, with TA being the averaging time. However, differences between the two flows are identified and ideas for their future analysis are proposed.

Authors with CRIS profile

Philipp Schlatter

Involved external institutions

Royal Institute of Technology / Kungliga Tekniska Högskolan (KTH) SE Sweden (SE) Indian Institute of Technology (IIT) Gandhinagar IN India (IN)

How to cite

APA:

Vinuesa, R., Schlatter, P., & Nagib, H.M. (2015). On minimum aspect ratio for duct flow facilities and the role of side walls in generating secondary flows. Journal of Turbulence, 16(6), 588-606. https://doi.org/10.1080/14685248.2014.996716

MLA:

Vinuesa, Ricardo, Philipp Schlatter, and Hassan M. Nagib. "On minimum aspect ratio for duct flow facilities and the role of side walls in generating secondary flows." Journal of Turbulence 16.6 (2015): 588-606.

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