Using DBD plasma actuators as flow and heat transfer controller over a backward-facing step: CFD approach

The study of flow control and heat transfer enhancement in case of a backward-facing step (BFS) has consistently attracted interest, primarily due to the complexities associated with flow separation phenomena. This numerical study was conducted to investigate the capability of a DBD plasma actuator as an active flow control device for regulating flow and enhancing heat transfer in a BFS channel. To achieve this objective, the influence of key parameters, including two distinct actuator positions, Reynolds number, applied voltage, and actuation frequency, on the reattachment length and heat transfer was evaluated. Results show that the use of a DBD actuator enhances heat transfer by 377% relative to the BFS without a DBD actuator, corresponding to a 4.77 fold increase in heat transfer efficiency. Notably, the application of the plasma actuator in the BFS configuration offers a unique advantage by simultaneously reducing pressure drop and enhancing heat transfer, in contrast to conventional flow control methods that typically increase pressure losses. This finding highlights that the application of DBD in a BFS flow can significantly enhance heat transfer and, as a primary practical implication, facilitate the development of more compact and efficient thermal devices. Additionally, it was observed that when the Reynolds number and applied voltage increase, the average Nusselt number can be raised by 16.75% and 31.22%, respectively. Furthermore, among the two investigated actuator positions, positioning on the step surface is identified as the more effective location for the DBD actuator in a BFS configuration.