arXiv subjects

Diba Behnoudfar

Publications and source records attributed to Diba Behnoudfar.

3 recordsLinked to original sources

arXiv2026

Uncertainty quantification of reacting fluids interacting with porous media using a hybrid physics-based and data-driven approach

Accurately simulating coupled physical processes under uncertainty is essential for reliable modeling and design in performance-critical applications such as combustion systems. Ablative heat shield design, as a specific example of this class, involves modeling multi-physics interactions between reacting flows and a porous material. Repeatedly evaluating these models to quantify parametric uncertainties would be prohibitively computationally expensive. In this work, we combine physics-based modeling using a single-domain approach with data-driven reduced-order modeling to quantify uncertainty via the operator inference method. The detailed physics-based simulations reproduce the measured surface temperature of an object exposed to high-enthalpy flow in a plasma wind tunnel experiment within 5%. We further use the model to demonstrate the effect of complex flow situations on the dynamic interactions between the porous heat shield material and the surrounding gas. The parametric reduced-order model, built on physics-based simulation data, successfully captures variations in quantities of interest resulting from changes in the permeability and heat transfer coefficient of the porous material in two separate studies: solid-fuel combustion with emission of buoyant reacting plumes in quiescent air, and ablation in a wind tunnel.

physics.comp-ph↗

arXiv2025

Autoencoder-based Dimensionality Reduction for Accelerating the Solution of Nonlinear Time-Dependent PDEs: Transport in Porous Media with Reactions

Physics-based models often involve large systems of parametrized partial differential equations, where design parameters control various properties. However, high-fidelity simulations of such systems on large domains or with high grid resolution can be computationally expensive for the accurate evaluation of a large number of parameters. Reduced-order modeling has emerged as a solution to reduce the dimensionality of such problems. This work focuses on a nonlinear compression technique using a convolutional autoencoder for accelerating the solution of transport in porous media problems. The model demonstrates successful training, achieving a mean square error (MSE) on the order of \num{1e-3} for the validation data. For an unseen parameter set, the model exhibits mixed performance; it achieves acceptable accuracy for larger time steps but shows lower performance for earlier times. This issue could potentially be resolved by fine-tuning the network architecture.

physics.comp-ph↗

arXiv2024

A single-domain approach for modeling flow in and around porous media applied to buoyant reacting plume formation and ignition

Many processes involve mixed porous-solid fluid domains where fluid flow, heat transfer, and chemical reactions interact over disparate length scales, such as the combustion of multi-species solid fuels. Although many studies have concentrated on detailed physics within the fluid or porous phase, few consider both phases, in part due to the challenge in determining suitable boundary conditions between the regions, particularly in turbulent flows where eddies might penetrate the pores. Here, we apply a single-domain approach that eliminates the need for boundary conditions at the interface, and simulate scenarios involving porous solids and a surrounding fluid. Similar to large eddy simulation, the method averages properties over a small spatial volume -- but over the entire domain. We focus on ignition and related interfacial phenomena. After verifying and validating the model, we examine the emission of buoyant reacting plumes from the surface of a heated solid and the near-field flow dynamics. The results indicate flow instabilities similar to Rayleigh--Taylor and Kelvin--Helmholtz phenomena. A combination of viscous and baroclinic torques triggers vorticity generation near the interface and its growth in the surrounding fluid region. Furthermore, we explore the effect of interface morphology, finding that geometrical characteristics such as asymmetry or gap size can alter ignition time and location, or even suppress it. Asymmetry-induced oscillations initially cause negative heat fluxes, which prevent the temperature from reaching the critical level necessary to trigger ignition. These behaviors could significantly influence the mixing of oxidizer and fuel, ignition processes, and fire propagation.

physics.flu-dyn↗