11:40   Flow Control Applications Effect of nozzle brim shape on the flow characteristics in a rectangular container injected air from a slit nozzle Takahiro Kiwata, Kojiro Arima, Yasuharu Kawamura, Hiroaki Uchida, Kuniaki Toyoda Abstract: Planar jets are used in various applications, such as drying, heating, cooling, and dust removal. In particular, the flow injected into a container has been reported by many researchers because it is used for heating in the container manufacturing process. The authors have investigated the effect of nozzle offset distance on the behavior of planar jets injected into a rectangular container through experiments and numerical analysis. Although the planar nozzle, which was close to the container wall, did not allow the jet oscillation, the planar jet reached the bottom of the container. The present paper describes the results of the effect of the shape of the nozzle exit brim, which is installed at the nozzle exit, on the flow characteristics in a rectangular container were experimentally investigated using the particle image velocimetry (PIV) system. It is found that the long horizontal plate of the nozzle brim and the long vertical plate of the L-shaped nozzle brim are effective to attach a slit jet on the wall due to the Coanda effect, and the planar jet reaches near the bottom of the container. Experimental Design and Implementation of a Single-Step Deep Reinforcement Learning-Based Tollmien-Schlichting Wave Controller Sergio Garcia Villasol, Babak Mohammadikalakoo, Marios Kotsonis, Nguyen Anh Khoa Doan Abstract: Controlling the laminar-turbulent transition is essential for reducing skin friction drag, as aerodynamic drag is closely linked to the extent of laminar flow over aerodynamic surfaces. By attenuating the early growth of Tollmien-Schlichting (TS) waves, it is possible to delay transition on unswept wings in low freestream, low turbulence flows. However, controlling TS waves is challenging and requires complex control laws that could be supported by AI-driven optimization methods. This experimental research explores single-step deep reinforcement learning (SDRL) algorithms to control TS waves on a flat plate, using dielectric barrier discharge (DBD) plasma actuators as a real-time active flow control (AFC) system and microphones to monitor the evolution of the waves. In order to complement the pressure measurements, particle image velocimetry (PIV) is also utilized to evaluate the performance of the controller. The experimental campaign is conducted at the anechoic vertical wind tunnel (i.e. A-Tunnel) of the Low Speed Wind Tunnel Laboratory of Delft University of Technology. Active control of energy-containing scales in grid-generated turbulence via plasma forcing Nicolas Bernard, 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.

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