1998 Fiscal Year Final Research Report Summary
Research on Unsteadiness of Separated Turbulent Shear Layer
| Project/Area Number |
08405061
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Aerospace engineering
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| Research Institution | THE UNIVERSITY OF TOKYO |
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Principal Investigator |
SUNADA Yasuto The University of Tokyo, School of Engineering, Research Assistant, 大学院・工学系研究科, 助手 (50216488)
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| Co-Investigator(Kenkyū-buntansha) |
RINOIE Ken-ichi The University of Tokyo, School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (20175037)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Separated Shear Layer / Turbulence / Unsteadiness |
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| Research Abstract |
The turbulent separated and reattaching flow formed over a backward facing step has been measured to investigate the unsteady phenomenon of the flow. Upstream of the reattachment point, the power spectrum analysis of the velocity fluctuation indicated the dominant frequency is shilling towards lower frequency, which is thought to be caused by the vortex pairing inside the shear layer. The velocity fluctuation with higher frequency and with larger amplitude is periodically observed at the shear layer edge near the reattachment point. When this fluctuation is observed, the smoke wire visualization picture showed that there is a kind of large smoke cluster downstream of the reattachment point.
Further wind tunnel measurements were done [or the separated and reattaching flow formed over backward facing step. Turbulent energy and turbulent normal stress balances were estimated from the measured data of mean velocities, Reynolds stresses and turbulent triple products. The main objective of the experiments is to analyze the turbulent structure inside the reattaching shear layer, including the reverse flow, in detail. The results indicated different turbulent structures in three classified regions of the backward facing step flow, i.e. the dead air, reverse flow and separated shear layer regions. In the reverse flow region, the transverse diffusion by turbulence in the turbulent energy balance equation is positive. The production term by shear stress, the transverse diffusion term by turbulence, and the advection term similarly help to balance the dissipation term in the same region. Classified Reynolds stress that are u positive and v negative contribute the most to the generation of Reynolds shear stress in this region.
Numerical simulation using two-equation turbulence model has also been done for the backward-facing step flow. Results were compared with the experimental results.
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Research Products
(6 results)
