arXiv subjects

Abbas Ebrahimi

Publications and source records attributed to Abbas Ebrahimi.

3 recordsLinked to original sources

arXiv2025

The effect of non-uniformity density structure on the molecular cloud-cores magnetic braking in the ideal MHD framework

The phenomenon of magnetic braking is one of the significant physical effects of the magnetic field in rotating molecular clouds. The physical characteristics of the core can affect on the core rotation rate. and one of the important parameter is the core density structure. According to observation, by regarding the power-law density distribution, $r^{-p}$, for molecular cloud cores, using smoothed particle hydrodynamics simulation, the results show that the increasing of density steepness (i.e., larger $p$) leads to the intensity of the toroidal components of the magnetic field and as a result larger $B_{\phi}$-components lead to more transfer of angular momentum to the outward. Thus, results show that the magnetic braking being stronger with increasing density slope in non-uniform molecular core. For example, the rotation of the system can approximately decrease by fifty percent from $p=0.2$ to $p=1.8$ for a non-uniform system.

astro-ph.GA↗

arXiv2025

Integrated Multiphysics Modeling of a Piezoelectric Micropump

This paper presents an integrated multiphysics simulation approach of piezoelectric micropumps. Micropumps and micro blowers are essential devices in various cutting-edge industries like laboratory equipment, medical devices, and fuel cells. A piezoelectric micropump involves complex physics including microfluidics, flow-structure interaction, electricity, and piezoelectric material. Hence, a comprehensive analysis of the interactions between different physical phenomena, would be essential for the effective design and optimization of these micropumps. Prior studies on piezoelectric micropump were mainly focused on isolated physical aspects of these pumps, such as piezoelectric mechanics, fluid dynamics, electrical properties, and also fluid-structure Interactions. The present paper fills this gap by integrating these aspects into a holistic simulation and design approach, introducing a new methodology for micropump analysis. Advanced simulation and design tools like COMSOL and SolidWorks were employed in accordance. A brief review of piezoelectric materials, and an exploration of different types of micropumps and their operating principles is discussed. Also, a comparison of various piezoelectric materials, including their properties and applications is investigated. Further, the paper discusses the simulation process of the micropumps, using COMSOL software, and presents an in-depth analysis of the simulation results. This structured approach provides a comprehensive understanding of piezoelectric micropumps, from theoretical underpinnings to practical design considerations. ..

physics.flu-dyn↗

arXiv2025

Model Predictive and Reinforcement Learning Methods for Active Flow Control of an Airfoil with Dual-point Excitation of Plasma Actuators

This study investigates the effectiveness of Model Predictive Control (MPC) and Reinforcement Learning (RL) for active flow control over a NACA 4412 airfoil near static stall at Reynolds number 4*10^5. By systematically evaluating these strategies, the research addresses a critical gap in optimizing excitation frequency and improving response time in flow control. The work contributes to understanding RL adaptability and performance versus MPC in aerodynamic flow separation control. Numerical simulations of the Reynolds Averaged Navier-Stokes equations with the Scale-Adaptive Simulation turbulence model are used. Dielectric Barrier Discharge plasma actuators in dual-point excitation mode control flow separation. The study evaluates adaptive MPC, temporal difference RL (TDRL), and deep Q-learning (DQL) for optimizing excitation frequency and expediting stabilization. An integrated signal processing DQL approach is also examined. Adaptive MPC achieved Cl = 1.60 at 110 Hz but struggled near physical limits. RL optimized excitation frequencies, reaching Cl = 1.62 in under 2.5 s at 100 or 200 Hz. The study presents a novel RL - MPC comparison for active flow control with DBD actuators, contrasting with prior work focusing on MPC or RL alone. Using an online learning framework, RL methods dynamically adapt to real-time conditions. Evaluating adaptive MPC and RL together in this setup yields new insights into comparative performance in dynamic environments.

physics.flu-dyn↗