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Session: Flow Control Applications
Session starts: Tuesday 04 November, 11:40
Presentation starts: 12:20
Room: Commission roon 2

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Nicolas Bernard ( University of Poitiers)
Tom Fridlender ()
Sylvain Grosse ()
Eric Moreau ()
Jean-Paul Bonnet ()

Abstract:
Among the various turbulent regimes, homogeneous isotropic turbulence (HIT) stands as a canonical framework to investigate fundamental aspects of turbulence without the complexity induced by mean flows, boundary layers, or directional biases. HIT is characterized by statistical uniformity in space (homogeneity) and the absence of preferential direction (isotropy), particularly at small scales. Although it is an idealization rarely encountered in natural or industrial settings, it serves as a critical benchmark for theory, modeling, and simulation [1]. In this configuration, turbulence is typically generated using a grid or obstacle placed upstream of the measurement region, allowing the flow to evolve toward a state where inertial interactions dominate and viscous effects are confined to the smallest scales. While HIT is commonly associated with the absence of long-lived coherent structures, recent studies have highlighted the intermittent emergence of large-scale motions or correlated patterns, even in nominally isotropic flows [2]. Understanding the formation, persistence, or enhancement of such coherent structures in HIT offers a novel perspective on how energy is distributed and sustained in turbulent flows. From a fundamental point of view, this challenges the classical view of homogeneous turbulence as structureless and purely stochastic. Moreover, if these structures can be selectively amplified or sustained—through active control strategies such as plasma forcing—it may open new avenues for manipulating turbulent dynamics without altering the flow’s statistical isotropy. In this study, active flow control is achieved using a Dielectric Barrier Discharge (DBD) plasma actuator—a wall-mounted, non-intrusive device that operates at atmospheric pressure and introduces small, localized perturbations via a weak ionic wind [3]. Despite the low momentum input, the actuation can interact with existing flow instabilities, particularly by enhancing shear layer development and promoting the emergence of coherent structures [4]. This approach enables targeted modulation of the flow without imposing global forcing, thereby preserving the statistical properties of nearly homogeneous isotropic turbulence. Within this framework, the present work examines whether large-scale structures can be actively sustained in grid-generated turbulence through plasma-based actuation.