Vortex Damping Outflow Forcing in Multiphase Flows with Sharp Interfacial Jumps

Core Concepts

Introducing a damping outflow forcing mechanism improves stability in multiphase flow simulations with sharp interfacial jumps.

Abstract

A study introduces a damping outflow forcing mechanism to stabilize multiphase flows with sharp interfacial jumps. Inadequate treatment of jumps at the outlet can lead to undesirable fluid disturbances. The forcing term acts as a damping mechanism to control vortices generated by droplets/bubbles. It is designed to enforce stability in the numerical solution and can be applied to simulate various multiphase flow problems. The study demonstrates its applicability in pool and flow boiling scenarios, addressing challenges posed by bubble-induced vortices during evaporation and condensation at the outflow boundary. Computational experiments using Flash-X software show promising results for three-dimensional simulations on supercomputing platforms.

Stats

These flows are dominated by low Weber numbers and a sharp jump in pressure, velocity, and temperature. Validation and verification cases are chosen to quantify accuracy and stability of the proposed method. Computational experiments are performed using Flash-X, an open-source software instrument for fluid dynamics simulations. The formulation is implemented for a sharp interface ghost fluid method (GFM) but can be extended to other methods with minor modifications. Parameters such as density ratios, viscosity ratios, Reynolds numbers, Prandtl numbers, Stefan numbers, Froude numbers, and Weber numbers are provided for different scenarios.

Quotes

"The forcing term acts as a damping mechanism to control vortices that are generated by droplet/bubbles in multiphase flows." "To mitigate these disturbances, we introduce a forcing term that can be applied to incompressible Navier-Stokes equations." "Outflow boundaries play an important role in multiphase fluid dynamics simulations involving transition between liquid and vapor phases."

Key Insights Distilled From

A Vortex Damping Outflow Forcing for Multiphase Flows with Sharp Interfacial Jumps

by Akash Dhruv at arxiv.org 03-19-2024

https://arxiv.org/pdf/2306.10174.pdf

Deeper Inquiries

How does the introduction of artificial condensation affect the overall quality of numerical simulations over time

The introduction of artificial condensation in numerical simulations can have both positive and negative effects on the overall quality of the results over time. On one hand, artificial condensation can help mitigate multiphase instabilities at the boundary by ensuring that only the liquid phase exists at the outflow boundary. This can prevent non-physical backflows and stabilize the simulation, especially in scenarios involving phase transitions like boiling. However, on the other hand, artificial condensation introduces a non-physical artifact into the simulation which may not accurately represent real-world phenomena. This can lead to discrepancies between simulated results and actual physical behavior over time as these artifacts accumulate.

What are the implications of choosing different buffer region lengths on the accuracy of the outflow forcing mechanism

The choice of different buffer region lengths in implementing outflow forcing mechanisms has significant implications for the accuracy of simulations. The buffer region length determines how far into the computational domain the effects of forcing are applied near an outflow boundary. A shorter buffer region length may not adequately dampen fluctuations or vortices generated at boundaries, leading to instabilities within computational domains. Conversely, a longer buffer region length may excessively dampen flow features or introduce inaccuracies due to overcorrection. By selecting an optimal buffer region length based on factors such as capillary flow conditions and disturbance sizes exiting from computational domains, researchers can strike a balance between stabilizing flows near boundaries without introducing excessive damping that could affect solution accuracy.

How do advancements in traction boundary conditions impact stability in multiphase flow simulations

Advancements in traction boundary conditions play a crucial role in enhancing stability in multiphase flow simulations by providing more accurate representations of fluid dynamics at boundaries where different phases interact. By improving formulations for traction forces derived from weak forms of governing equations like Navier-Stokes equations, researchers can better model complex interactions between phases while maintaining mass conservation and mitigating pressure fluctuations. These advancements enable more robust modeling of multiphase flows with sharp interfacial jumps or phase transitions where traditional boundary conditions might be insufficient to capture intricate behaviors accurately. By incorporating sophisticated traction boundary conditions into numerical solvers for multiphase flows, researchers can achieve higher fidelity simulations that closely mirror real-world phenomena while ensuring stability and reliability in their results.