[Paper Review] Implicit Large Eddy Simulation of Cavitation in Micro Channel Flows

Stefan Hickel, M. Mihatsch+1 more|arXiv (Cornell University)|Jan 25, 2014

Computational Fluid Dynamics and AerodynamicsEngineering17 references21 citations

TL;DR

This study presents an implicit large eddy simulation (LES) framework for compressible two-phase flows to model cavitation in microchannel flows with step-like restrictions, using a barotropic equation of state and equilibrium-based phase change. The method resolves compressible wave dynamics and shear-layer turbulence, accurately capturing complex cavitating flow structures validated against experimental data from Iben et al. (2010).

ABSTRACT

We present a numerical method for Large Eddy Simulations (LES) of compressible two-phase flows. The method is validated for the flow in a micro channel with a step-like restriction. This setup is representative for typical cavitating multi-phase flows in fuel injectors and follows an experimental study of Iben et al., 2010. While a diesel-like test fuel was used in the experiment, we solve the compressible Navier-Stokes equations with a barotropic equation of state for water and vapor and a simple phase-change model based on equilibrium assumptions. Our LES resolve all wave dynamics in the compressible fluid and the turbulence production in shear layers.

Motivation & Objective

• To develop a numerical framework for simulating cavitating flows in microchannels relevant to fuel injectors.
• To address the challenge of modeling compressible two-phase flows with phase change under turbulent shear layers.
• To validate the LES approach against experimental data from Iben et al. (2010) involving diesel-like fuel and water-vapor mixtures.
• To assess the capability of implicit LES to capture unsteady cavitation dynamics and wave propagation in confined geometries.
• To evaluate the performance of a barotropic equation of state and equilibrium-based phase-change model in predicting cavitating flow features.

Proposed method

• Solves the compressible Navier-Stokes equations with a finite-volume discretization and implicit time integration.
• Employs a barotropic equation of state to model the thermodynamic behavior of water and vapor phases.
• Applies an equilibrium-based phase-change model to simulate liquid-vapor transitions without solving transport equations for mass transfer.
• Uses an implicit large eddy simulation approach to resolve large-scale turbulent structures and compressible wave dynamics directly.
• Implements a high-order numerical scheme to ensure accuracy in resolving sharp gradients and discontinuities in cavitating flows.
• Validates the simulation setup against experimental data from Iben et al. (2010) for a microchannel with a step-like restriction.

Experimental results

Research questions

• RQ1 Can implicit LES accurately capture unsteady cavitation dynamics in microchannel flows with geometric constraints?
• RQ2 How well does the barotropic equation of state represent the thermodynamic behavior of water-vapor mixtures in cavitating flows?
• RQ3 To what extent does the equilibrium-based phase-change model reproduce experimental cavitation patterns?
• RQ4 How do compressible wave dynamics and turbulent shear-layer instabilities interact in cavitating microflows?
• RQ5 What is the predictive capability of the implicit LES framework for complex two-phase flow features in fuel injector-like geometries?

Key findings

• The implicit LES framework successfully resolves compressible wave dynamics and unsteady turbulence in shear layers, even in the presence of strong phase transitions.
• The simulation captures the formation, growth, and collapse of vapor cavities in the microchannel, matching key features observed in the experiment by Iben et al. (2010).
• The barotropic equation of state provides a stable and accurate representation of the liquid-vapor mixture behavior under high-pressure gradients.
• The equilibrium-based phase-change model enables realistic prediction of cavitation inception and evolution without explicit mass transfer modeling.
• The method reproduces complex flow structures such as vortex shedding and shock-like wave propagation associated with cavitating flows.
• The agreement with experimental data confirms the robustness and predictive capability of the implicit LES approach for cavitating microchannel flows.