We studied viscoelastic turbulent flow over a backward-facing step of the expansion ratio ER = 1.5 using DNS (direct numerical simulation) at a friction Reynolds number Reτ0 of 100. We chose the Giesekus model as a viscoelastic constitutive equation, and the Weissenberg number is Wiτ0 = 10 and 20. Visualized instantaneous vortices revealing that a few vortices occur only above the recirculation regions in the viscoelastic fluid flow compared to those in the Newtonian flow. This phenomenon might be caused by the fluid viscoelasticity that would suppress the Kelvin-Helmholz vortex emanating from the step edge. The reattachment length from the step is 6.80h for the Newtonian fluid, 7.82h for Wiτ0 = 10, and 8.82h for Wiτ0 = 20, where h is the step height. In the mean velocity distributions normalized by maximum inlet velocity, we have observed no significant difference among the three fluids, except for region near the upper or bottom wall, i.e., the recirculation and recovery regions at the front and behind the reattachment point. The streamwise turbulent intensity u’rms is weaken in the recirculation region of the viscoelastic flows. In terms of v’rms, its magnitude in the recirculation region becomes largest in the case of Wiτ0 = 10, not for the Newtonian fluid flow or more viscoelastic case of Wiτ0 = 20.
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ASME/JSME/KSME 2015 Joint Fluids Engineering Conference
July 26–31, 2015
Seoul, South Korea
Conference Sponsors:
- Fluids Engineering Division
ISBN:
978-0-7918-5732-8
PROCEEDINGS PAPER
Influence of Viscoelasticity on Turbulent Flow Over a Backward-Facing Step Available to Purchase
Akito Ikegami,
Akito Ikegami
Tokyo University of Science, Noda-shi, Japan
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Takahiro Tsukahara,
Takahiro Tsukahara
Tokyo University of Science, Noda-shi, Japan
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Yasuo Kawaguchi
Yasuo Kawaguchi
Tokyo University of Science, Noda-shi, Japan
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Akito Ikegami
Tokyo University of Science, Noda-shi, Japan
Takahiro Tsukahara
Tokyo University of Science, Noda-shi, Japan
Yasuo Kawaguchi
Tokyo University of Science, Noda-shi, Japan
Paper No:
AJKFluids2015-25251, V01AT25A002; 4 pages
Published Online:
April 4, 2016
Citation
Ikegami, A, Tsukahara, T, & Kawaguchi, Y. "Influence of Viscoelasticity on Turbulent Flow Over a Backward-Facing Step." Proceedings of the ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. Volume 1A: Symposia, Part 2. Seoul, South Korea. July 26–31, 2015. V01AT25A002. ASME. https://doi.org/10.1115/AJKFluids2015-25251
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