Numerical investigation of the effect of dielectric barrier discharge plasma actuator-induced momentum jet parameters on flow control of an oscillating wind turbine airfoil

A strong micro heat engine that can be used in the untethered state is essential for next-generation microrobotics. Here, we propose a rapid swimmer using explosive boiling due to electrical discharge in water. Specifically, we demonstrate that the water-repellent swimmer that has an aluminum discharge antenna in the rear part can swim with the maximum velocity of ∼14 cm/s on the water surface like a water strider between a pair of parallel electrodes in a shallow water pool by applying direct current high-voltage pulses repeatedly. Moreover, by the video observation with high speed (960 fps), we found that an asymmetrical wave was generated immediately after the discharge, and it propelled the swimmer. Our findings should contribute to next-generation microrobots in the future.

Rapid swimmer using explosive boiling due to electrical discharge in water

Sugioka,

Arai

2023

Data-driven reduced-order modeling for nonlinear aerodynamics using an autoencoder neural network

Moni,

Yao,

Malekmohamadi

2024

The design of commercial air transportation vehicles heavily relies on understanding and modeling fluid flows, which pose computational challenges due to their complexity and high degrees of freedom. To overcome these challenges, we propose a novel approach based on machine learning (ML) to construct reduced-order models (ROMs) using an autoencoder neural network coupled with a discrete empirical interpolation method (DEIM). This methodology combines the interpolation of nonlinear functions identified based on selected interpolation points using DEIM with an ML-based clustering algorithm that provides accurate predictions by spanning a low-dimensional subspace at a significantly lower computational cost. In this study, we demonstrate the effectiveness of our approach by the calculation of transonic flows over the National Advisory Committee of Aeronautics 0012 airfoil and the National Aeronautics and Space Administration Common Research Model wing. All the results confirm that the ROM captures high-dimensional parameter variations efficiently and accurately in transonic regimes, in which the nonlinearities are induced by shock waves, demonstrating the feasibility of the ROM for nonlinear aerodynamics problems with varying flow conditions.

Self-starting and performance improvement of a Darrieus type wind turbine using the plasma actuator

Zare Chavoshi,

Ebrahimi

2024

Although the popularity of Darrieus-type vertical axis wind turbines is growing for small-scale electricity generation, these turbines have severe challenges in self-starting. This paper proposes a flow control method, namely, the plasma actuator, to solve the self-starting problem besides enhancing the turbine performance. The Darrieus turbine is numerically investigated using a pressure-based finite volume method to solve the unsteady Reynolds-averaged Navier–Stokes and the γ–Reθt transitional model equations. Simulation of the blade rotation is performed using the sliding mesh technique accompanied by the turbine equation of motion to enable the blade rotational degree of freedom. Furthermore, the body forces associated with the plasma actuator are determined by calibrating the Shyy plasma model parameters. The plasma actuator is assessed at both the constant and free rotational speeds. The constant rotational speed results in plasma off condition show negative torque generation for tip speed ratios lower than 1.5, known as the origin of turbine self-starting challenges. The plasma actuator improves the negative torque by 128% in the tip speed ratio of 0.5 and turns it positive. Also, at larger tip speed ratios, it reduces the negative torque generation and enhances the turbine power production by up to 260%. Furthermore, the plasma actuator in free rotational speed improves the tip speed ratio increment by up to 8%, reducing the total time of turbine self-starting.