Active Flow Control on Laminar flow over a Backward facing step

Aditya Mushyam,Josep M Bergada

doi:10.1088/1742-6596/633/1/012110

Aditya Mushyam, Josep M Bergada

Open Access

https://doi.org/10.1088/1742-6596/633/1/012110

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Abstract

In the present study, two dimensional flow over a backward-facing step in laminar flow regime with application of active flow control (AFC) technique is analysed. The aim of the present work is to gauge the effectiveness of implementing AFC to reduce drag and study its effects on flow characteristics. In order to analyse the influence of AFC on the boundary layer and the downstream vortex shedding, two different kinds of AFC techniques have been used in this study namely zero net mass flow actuators and fluidic actuators. A parametric non dimensional analysis has been carried out by varying the frequency from 0.025 to 0.1 and jet amplitude from 0.05 and 1. Four different positions of the groove were simulated; groove was respectively located at 0.024a, 0.047a, 0.072a and 0.097a, measured upstream from the right side upper edge. Three different non dimensional groove widths 0.023a, 0.048a and 0.073a were also evaluated, where a is the step height. The idea behind this study was to determine an optimal configuration to reduce the drag on the step and to suppress the vortex dissipation in the wake of the step. It was observed that when using an AFC frequency ± 10% of the vortex shedding one, was causing the maximum drag reduction. When comparing the effects of zero net mass flow actuators with the fluidic actuators, it was observed that zero net mass flow actuators were more effective.

Highlights

Among the previous research undertaken on active flow control (AFC) on backwards facing step, study carried out by Dahan et al [1] can be noted
Marrot et al [3] used a loudspeaker located downstream of the step to activate the boundary layer, that maximum effect was observed when the loudspeaker frequency was equal to the boundary layer instability mode
A similar method, consisting of two arrays of jets located on the vertical side of the step of which the upper row steadily absorbs and the lower row steadily injects, was analysed numerically in 2D by Creusé et al [4], different AFC techniques including pulsating flow were evaluated

Summary

Introduction

Among the previous research undertaken on AFC on backwards facing step, study carried out by Dahan et al [1] can be noted They performed a 2D and 3D numerical study using Reynolds number, Re=280 and 1500 respectively with both open and closed loop control. Marrot et al [3] used a loudspeaker located downstream of the step to activate the boundary layer, that maximum effect was observed when the loudspeaker frequency was equal to the boundary layer instability mode. At these conditions a small reduction of the recirculation length was obtained. The main aim of this study is to determine an optimum configuration which results in the suppression or minimization of drag on the step

Governing Equations

Numerical Strategy and Boundary Conditions:

Code Validation

Results and Discussion