Computational Analysis of Active and Passive Flow Control for Backward Facing Step

The internal steady and unsteady flows with a frequency and amplitude are examined through a backward facing step (expansion ratio 2), for low Reynolds numbers (Re=400, Re=800), using the immersed boundary method. A lower part of the backward facing step is oscillating with the same frequency as the...

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Bibliographic Details
Published in:Computation 2022-01, Vol.10 (1), p.12
Main Authors: Moulinos, Iosif, Manopoulos, Christos, Tsangaris, Sokrates
Format: Article
Language:English
Subjects:
active and passive flow control
Active control
Amplitudes
backward facing step
Backward facing steps
Boundary conditions
curvilinear immersed boundary method
elastic membrane
External pressure
Finite volume method
Flow control
Flow separation
Flow velocity
Fluid flow
Fluid-structure interaction
Membranes
oscillating surface
Reversed flow
Reynolds number
Separation
Unsteady flow
Wall flow
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Summary:The internal steady and unsteady flows with a frequency and amplitude are examined through a backward facing step (expansion ratio 2), for low Reynolds numbers (Re=400, Re=800), using the immersed boundary method. A lower part of the backward facing step is oscillating with the same frequency as the unsteady flow. The effect of the frequency, the amplitude, and the length of this oscillation is investigated. By suitable active control regulation, the recirculation lengths are reduced, and, for a percentage of the time period, no upper wall, negative velocity, region occurs. Moreover, substituting the prescriptively moving surface by a pressure responsive homogeneous membrane, the fluid–structure interaction is examined. We show that, by selecting proper values for the membrane parameters, such as membrane tension and applied external pressure, the upper wall flow separation bubble vanishes, while the lower one diminishes significantly in both the steady and the unsteady cases. Furthermore, for the time varying case, the length fluctuation of the lower wall reversed flow region is fairly contracted. The findings of the study have applications at the control of confined and external flows where separation occurs.
ISSN:2079-3197
2079-3197
DOI:10.3390/computation10010012