Michael Z. Podowski

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This paper investigates the change in contact angle of droplets of fluid containing dispersed nanoparticles (nanofluid) functionalized with thioglycolic acid molecules as a function of the concentration and size of nanoparticles, and the quality and composition of the substrate material. Bismuth telluride nanoparticles with an average size ranging from 2.5(More)
The purpose of this paper is to present a consistent theoretical concept that can explain the various physical phenomena associated with the effect of droplet size on contact angle for droplets on solid surfaces, and with the geometry of the liquid/gas/solid contact line in general. Two droplet geometries have been considered: uniformly elongated droplets(More)
Due to the high effectiveness of direct steam condensation, it is being considered for use as a passive safety system in the design of a next generation 1400 MWe PWR, the APR1400. In order to gain an understanding of the physical principles governing direct condensation in a high speed steam jet, two independent models have been developed, cross compared,(More)
The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases,(More)
Nonlinear stability analysis has been performed for differential integral equations describing nuclear reactor dynamics. New stability criteria in bounded domains of initial perturbations have been established for a large class of reactor models with both linear and nonlinear reactivity feedbacks. Also, relationships have been studied between the magnitude(More)
The objective of this work has been to study the mechanisms governing flow and phase distributions in developing gas/liquid two phase flows in general, and the evolution of different size bubbles in an adiabatic vertical pipe in particular. Flow regimes from bubbly to churn-turbulent have been accounted for. The main emphasis of the work has been on the(More)
The state-of-the-art multiphase fluid dynamics code, NPHASE-CMFD, performs multiphase flow simulations in complex domains nonlinearly implicitly and in parallel, which is a challenging environment for the linear solver. The present work illustrates how the Portable, Extensible Toolkit for Scientific Computation (PETSc) and scalable Algebraic Multigrid AMG(More)
DNS simulations of two-phase turbulent bubbly channel flow at Res = 180 (Reynolds number based on friction velocity and channel half-width) were performed using a stabilized finite element method (FEM) and a level set approach to track the air/water interfaces. Fully developed turbulent single-phase solutions obtained previously using the same stabilized(More)
Core degradation phenomena in PHEBUS FPT-3 experiment has been simulated by using COMPASS code, which has been under developing in Korea to simulate severe accident scenario. In the test section of PHEBUS FPT-3 experiment, a fuel assembly consisting of 20 fuel rods and 1 control rod with a height of 1m has been installed within a surrounding in-vessel(More)