arXiv subjects

Mahmood Mousavi

Publications and source records attributed to Mahmood Mousavi.

3 recordsLinked to original sources

arXiv2026

Viscoelastic Droplet Impact on Surfaces with Sharp Wettability Contrast: Coupled Influence of Relaxation Time and Surface Tension

The impact dynamics of viscoelastic droplets on solid surfaces play a critical role in numerous applications, including inkjet printing, spray coating, and microfluidics, where precise control of spreading, retraction, and rebound is essential. This numerical study investigates the coupled influence of fluid viscoelasticity, modeled via the Oldroyd-B constitutive equation, and gravitational-capillary balance on droplet behavior upon impact onto surfaces featuring sharp hybrid wettability. Employing a high-fidelity three-dimensional OpenFOAM-based solver that integrates the volume-of-fluid method, log-conformation formulation for improved numerical stability, and a velocity-dependent dynamic contact angle model, we simulated a 2 cm-diameter droplet impacting at 4 m/s across a range of relaxation times and surface tensions. Results demonstrate that increasing the relaxation time from 0.02 s to 0.12 s enhances elastic energy storage, leading to up to 12.9% larger maximum spreading diameters (from 24.97 mm to 28.09-28.17 mm) and a 16.6% reduction in minimum droplet height across uniform and hybrid surfaces. In contrast, increasing surface tension from 0.05 N/m to 0.15 N/m suppresses maximum spreading by about 1.1% (from 27.21 mm to 26.90 mm) while increasing minimum height by 3.3% (from 2.12 mm to 2.20 mm). On hybrid surfaces with static contact angles of 0{\deg} and 160{\deg}, the sharp wettability contrast induces pronounced asymmetric spreading and directional fluid migration toward the hydrophilic region, ultimately producing distinctive dustpan- and shoe-like equilibrium morphologies. Variations in surface tension, which simultaneously modulate the Weber and E\"otv\"os numbers, reveal that stronger capillary forces suppress radial expansion while enhancing curvature-driven recoil and redistributing viscoelastic stresses.

physics.flu-dyn↗

arXiv2025

Physics-Informed Neural Networks in Clean Combustion: A Pathway to Sustainable Aerospace Propulsion

Achieving clean combustion systems is crucial in terms of solving environmental impacts, decarbonization needs and sustainability matters. Traditional combustion modeling techniques via computational fluid dynamics with accurate chemical kinetics face obstacles in computational cost and accurate representation of turbulence-chemistry interactions. Physically Informed Neural Networks (PINNs) as a new framework, merges physical laws with data-driven learning and shows great potential as an alternative methodology. By directly integrating conservation equations into their training process, PINNs achieve accurate mesh-free modeling of complex combustion phenomena despite having limited data sets. This review examines how this approach applies to clean combustion systems while focusing on their impact in aerospace applications including flame dynamics, turbulent combustion, emission prediction, and instability management in propulsion systems. Next-generation aerospace engines rely on PINNs to reduce computational costs while increasing predictive performance and enabling real-time control methods. This analysis concludes by exploring current barriers and future paths, while demonstrating how PINNs can revolutionize sustainable and efficient combustion technologies in aerospace propulsion systems.

physics.flu-dyn↗

arXiv2025

Wall Wettability Control of Cavitation Patterns and Stability

This study investigates the role of wall wettability, characterized by the wall contact angle (WCA), in controlling cavitation dynamics and stability around a Clark Y hydrofoil. High-fidelity Large Eddy Simulations (LES) coupled with a dynamic contact angle model were employed within the OpenFOAM framework to explore WCAs ranging from hydrophilic ($0^\circ$) to superhydrophobic ($160^\circ$) under distinct cavitation numbers ($\sigma = 1.6$, $0.8$, and $0.4$), representing incipient, cloud, and supercavitation regimes, respectively. The results show that increasing WCA consistently promotes earlier cavitation inception, thicker cavity development, and greater flow unsteadiness. For $\sigma = 1.6$, higher WCAs led to smaller, detached vapor bubbles and localized pressure fluctuations. At $\sigma = 0.8$, superhydrophobic surfaces caused more extensive vapor structures, intensified shedding dynamics, and stronger pressure fluctuations. For $\sigma = 0.4$, high WCAs facilitated stable, wall-adhered cavities that suppressed re-entrant jet activity and reduced unsteady loading. These findings demonstrate that surface wettability serves as an effective passive control mechanism for tailoring cavitation behavior and optimizing flow stability in engineering applications.

physics.flu-dyn↗