Multiphase flows are ubiquitous in nature and in engineering processes. Examples of multiphase flows include atomization and sprays in agriculture, propulsion, and printers; phase change and heat transfer in energy devices; Rayleigh-Taylor and Richtmyer–Meshkov instabilities in inertial confinement fusion and supernova; emulsions in chemical industries; and bubble cavitation and acoustics in lithotripsy, marine propellers, and sound suppression system during rocket liftoff. However, there are various challenges in numerical modeling of multiphase flows. In this talk, I’ll highlight these challenges and present a novel diffuse-interface model and numerical methods for robust simulations of compressible multiphase flows.
I’ll first present an accurate conservative diffuse-interface/phase-field (ACDI) method for modeling interfaces. This method conserves the mass of each of the phases and results in bounded transport of the volume fraction while maintaining the interface thickness on the order of only one-to-two grid points. I’ll present results from the canonical test cases, showing the improvement in the accuracy of interface shape and surface tension forces over the commonly used second-order conservative phase-field method. The capability of the ACDI model to maintain such sharp interfaces without the need for any special geometric treatment, unlike the sharp-interface methods, makes it a highly attractive interface-capturing method for accurate simulations of multiphase flows at an affordable cost.
Next, for the simulation of compressible multiphase flows, a five-equation model that consists of transport equations for the volume fraction, the mass of each phase, momentum, and total energy is used. Starting from this baseline five-equation model, I’ll present modifications to the model in such a way that the resulting system of equations can be discretized using a non-dissipative central scheme that is suitable for the simulation of turbulent flows and acoustics. The resulting model is conservative, scalable, and maintains a constant interface thickness throughout the simulation. Furthermore, for stable and accurate numerical simulations of compressible flows, particularly at high Reynolds numbers (Re), it is known that a discrete entropy condition needs to be satisfied in addition to the discrete conservation of kinetic energy. I’ll present a numerical flux formulation for the five-equation model that satisfies this condition (a KEEP scheme) and show that this formulation results in stable numerical simulations of compressible turbulent multiphase flows at high Re.
Finally, I’ll briefly highlight some of the related research efforts on modeling atomization and phase change, particle-laden flows, multi-material systems, and ice accretion and aerodynamics.
About the Speaker
Suhas S. Jain is a postdoctoral fellow at the Center for Turbulence Research, Stanford University, working with Prof. Parviz Moin. Suhas graduated with an M.S. and Ph.D. in mechanical Engineering from Stanford University in December 2021. Prior to his graduate studies, he was a researcher at the Institute of Fluid Dynamics at Helmholtz-Zentrum Dresden-Rossendorf, Germany (2014-15), and a project assistant at the Multiphase Flow Simulations Lab at the Indian Institute of Science, India (2015-16). He received his bachelor’s in mechanical engineering from National Institute of Technology Karnataka, India in 2014. During his graduate studies, Suhas was a Franklin P. and Caroline M. Johnson Stanford Graduate Fellow, and a recipient of the American Physical Society (APS) Gallery of Fluid Motion award in 2018 and the National Overseas Scholarship in 2019. He also received the APS Forum for Early Career Scientists mini award in 2022. His research interests include computational modeling of multiphase flows; particle-laden flows; compressible turbulent flows; external aerodynamics; fluid-structure interaction; and high-performance computing for applications in sustainable energy, propulsion, aerospace design, and climate change.
Host: Professor Arne Pearlstein